TWI876858B - An optical sensing device - Google Patents

Abstract

This disclosure discloses an optical sensing device. The device includes a carrier body; a first light-emitting device disposed on the carrier body; and a light-receiving device including a group III-V semiconductor material disposed on the carrier body, including a light-receiving surface having an area, wherein the light-receiving device is capable of receiving a first received wavelength having a largest external quantum efficiency so the ratio of the largest external quantum efficiency to the area is≧13 (%/mm ²).

Description

Optical sensing module

The present invention relates to a structural design of an optical sensing module, and more particularly to a non-invasive optical sensing module for measuring physiological signals in blood.

With the fast pace of modern life, people are increasingly eager to monitor various indicators of physical health at any time. On the one hand, it can be used for early detection and early treatment of diseases, and on the other hand, it can also be used to monitor physical conditions during exercise.

Various physiological signals, such as heart rate, blood oxygen, blood sugar, blood pressure, etc., can be detected by placing a non-invasive reflective optical sensing module close to the skin surface, so that the measurement light of a specific wavelength can be irradiated on the skin. The measurement light penetrates the skin to the cells and blood vessels in the body. After partial absorption, partial scattering, and reflection, the optical sensing module can receive the returned measurement light. By measuring and analyzing the intensity of the returned light signal, physiological indicators with health significance can be obtained. However, when the human body is moving or exercising, the relative position or distance between the optical sensing module and the skin will constantly change, which will cause the signal to be unstable and produce inaccurate results. Therefore, if the light receiving element in the optical sensing module has the characteristics of high detection limit and high signal-to-noise ratio, the accuracy and stability of the physiological signals obtained by the optical sensing module can be enhanced.

The present invention discloses an optical sensing module with high signal-to-noise ratio and high detection limit.

An embodiment of the present invention discloses an optical sensing module, comprising a carrier, a light emitting element, and a light receiving element. The light emitting element is located on the carrier. The light receiving element is located on the carrier and comprises a III-V semiconductor material. The light receiving element has a light absorbing surface, a receiving band, and a non-receiving band with a wavelength greater than the receiving band. The ratio of the maximum quantum efficiency of the light receiving element in the receiving band to the area of the light absorbing surface is ≥ 13 (%/ ^mm2 ).

The following embodiments will be accompanied by drawings to illustrate the concept of the present invention. In the drawings or descriptions, similar or identical parts use the same reference numerals, and in the drawings, the shape, thickness or height of the components can be enlarged or reduced within a reasonable range. The various embodiments listed in the present invention are only used to illustrate the present invention and are not used to limit the scope of the present invention. Any obvious modifications or changes made to the present invention do not deviate from the spirit and scope of the present invention.

FIG. 1A shows a top view of an optical sensing module 100 in an embodiment of the present invention. The optical sensing module 100 includes a carrier 120, a light receiving element 131, a first light emitting element 111, and a second light emitting element 112. The carrier 120 includes a housing 121, baffles 122, 123 for separating a first space 124, a second space 125, and a third space 126. The first space 124 is surrounded by the housing 121 and the baffles 122; the third space 126 is surrounded by the housing 121 and the baffles 123; the second space 125 is located between the first space 124 and the third space 126, and is surrounded by the baffles 122, 123, and the housing 121. The light receiving element 131 is located in the second space 125, the first light emitting element 111 is located in the first space 124, and the second light emitting element 112 is located in the third space 126. The first light emitting element 111 and the second light emitting element 112 are arranged on the left and right sides of the light receiving element 131 symmetrically. The distance between the light receiving element 131 and the first light emitting element 111 or/and the second light emitting element 112 should be as close as possible. When the optical sensing module is irradiated close to the skin in order to measure physiological signals, the light receiving element 131 is more likely to only receive the signal reflected back by the first light emitting element 111 and the second light emitting element 112 irradiating the skin. The interval G between the light receiving element 131 and the first light emitting element 111 or the second light emitting element 112 is less than or equal to 1 mm. The area of the light receiving element 131 is larger than that of the light emitting elements 111 and 112. FIG. 1A shows that the light receiving element 131, the first light emitting element 111, and the second light emitting element 112 are all square in shape. The size of the light receiving element is ≤100milÎ100mil, for example, 100milÎ100mil, 80milÎ80mil, 61milÎ105mil, 61milÎ81mil, 47milÎ105mil, 60milÎ60mil, 50milÎ50mil, 45milÎ45mil, 40milÎ40mil. In another embodiment, the size of the light receiving element is ≤80milÎ80mil. The size of the light emitting element is less than 25milÎ25mil, for example, 20milÎ20mil, 18milÎ18mil, 16milÎ16mil, 14milÎ11mil, 8milÎ8mil.

The light receiving element 131 and the light emitting elements 111 and 112 are respectively located in separate and isolated spaces. Therefore, it is possible to avoid the light emitted by the light emitting elements 111 and 112 being directly absorbed by the light receiving element 131, thereby preventing direct interference (crosstalk) between the light emitting elements 111 and 112 and the light receiving element 131, thereby affecting the accuracy of the measurement.

FIG. 1B shows a top view of an optical sensing module 101 in another embodiment of the present invention. Like the optical sensing module 100, the optical sensing module 101 includes a carrier 120, a light receiving element 131, a first light emitting element 111, and a second light emitting element 112. The carrier 120 includes a housing 121, baffles 122 and 123 for separating a first space 124, a second space 125, and a third space 126. The light receiving element 131 is located in the second space 125, the first light emitting element 111 is located in the first space 124, and the second light emitting element 112 is located in the third space 126. The light receiving element 131 is rectangular in shape, and the first light emitting element 111 and the second light emitting element 112 are square in shape. The first light emitting element 111 and the second light emitting element 112 are disposed on the left and right sides of the light receiving element 131 symmetrically in the long direction.

FIG. 1C shows a top view of an optical sensing module 102 in another embodiment of the present invention. Like the optical sensing module 100, the optical sensing module 102 includes a carrier 120, a light receiving element 131, a first light emitting element 111, and a second light emitting element 112. The carrier 120 includes a housing 121, baffles 122 and 123 for separating a first space 124, a second space 125, and a third space 126. The light receiving element 131 is located in the second space 125, the first light emitting element 111 is located in the first space 124, and the second light emitting element 112 is located in the third space 126. The light receiving element 131 is rectangular in shape, and the first light emitting element 111 and the second light emitting element 112 are square in shape. The first light emitting element 111 and the second light emitting element 112 are disposed on the left and right sides of the light receiving element 131 in the short side direction, and may be mirror-symmetrical with respect to the light receiving element 131 .

The outer shell 121 of the carrier 120 and the baffles 122 and 123 may include polymers or resins, such as thermoplastic plastics or thermosetting plastics. Thermoplastic plastics include PPA (polyphthalamide), PCT (polycyclohexylenedimethylene terephthalate), ABS (acrylonitrile butadiene styrene), polyetheretherketone (PEEK), or other suitable materials. Thermosetting plastics include EMC (epoxy molding compound), SMC (silicone molding compound), or other suitable materials. Optionally, the materials of the outer shell and the baffles may also include opaque materials for blocking light to further reduce interference of light emitting elements and light receiving elements. The opaque material may include light absorbing materials or reflective materials.

The color of the light-absorbing material is preferably dark, which is not easy to reflect light, such as black, brown, gray, or other dark colors. The light-absorbing material can be Bismaleimide Triazine Resin (BT), and the surface is formed with a material that can block visible light, such as black ink (BT is light yellow), metal, resin, or graphite. The metal material can be chromium or nickel. The resin can be Polyimide (PI) or acrylic as the main body, and then the light-absorbing material, such as carbon, titanium oxide, etc., or a dark pigment is dispersed in the resin. The light-absorbing material can also include a mixture of a matrix and a light-absorbing substance. The matrix can be a silicone-based matrix or an epoxy-based matrix. Light absorbing materials may include carbon, titanium oxide, or dark pigments.

The reflective material includes a mixture of a matrix and a high reflectivity material. The matrix may be a silicone-based matrix or an epoxy-based matrix. The high reflectivity material may include titanium dioxide, silicon dioxide, aluminum oxide, K ₂ TiO ₃ , ZrO ₂ , ZnS, ZnO, or MgO.

FIG. 2A shows a schematic diagram of an optical sensing module 103 disposed in a wearable device 1, such as a watch. The optical sensing module 103 is disposed at the center of the wearable device 1. The optical sensing module is similar to the aforementioned optical sensing modules 100, 101, and 102. The carrier 120 includes a first space 124, a second space 125, and a third space 126. The second space 125 is located between the first space 124 and the third space 126. The first space 124 includes three light emitting elements 111, 112, and 113 arranged in a straight line. The third space 126 includes three light emitting elements 114, 115, and 116 arranged in a straight line. The second space 125 includes a light receiving element 131. The first space 124, the second space 125, and the third space 126 are arranged in a straight line along a first direction (up and down direction). The light emitting elements 111, 112, 113 in the first space 124 are arranged in a straight line along the second direction (left-right direction). The light emitting elements 114, 115, 116 in the third space 126 are arranged in a straight line along the second direction (left-right direction). The first direction is different from the second direction and is perpendicular to each other.

FIG. 2B shows a schematic diagram of an optical sensing module 104 disposed in a wearable device 1, such as a watch. The optical sensing module 104 is disposed at the center or near the center of the wearable device 1. The optical sensing module 104 is similar to the optical sensing module 103. The carrier 120 includes a first space 124, a second space 125, a third space 126, and a fourth space 127. The second space 125 is located between the first space 124 and the third space 126. The first space 124 includes three light emitting elements 111, 112, and 113 arranged in a straight line. The third space 126 includes three light emitting elements 114, 115, and 116 arranged in a straight line. The second space 125 includes a light receiving element 131. The first space 124, the second space 125, and the third space 126 are arranged in a straight line along the first direction (up and down direction). The light emitting elements 111, 112, 113 in the first space 124 are arranged in a straight line along the second direction (left and right direction). The light emitting elements 114, 115, 116 in the third space 126 are arranged in a straight line along the second direction (left and right direction). The first direction is different from the second direction, for example, the first direction and the second direction are perpendicular to each other or not parallel to each other. The fourth space 127 is located on the same side of the first space 124, the second space 125, and the third space 126, and is arranged along the second direction (left and right direction) with the second space 125. The fourth space 127 includes a light emitting element 117, which emits a wavelength greater than that of the light emitting elements 111 to 116. For example, the light emitting elements 111-116 emit green light in a wavelength band, and the light emitting element 117 emits red light or infrared light in a wavelength band. The light emitting element 117 has a square or rectangular appearance, and its area is larger than that of the light emitting elements 111-116.

The light receiving element of the present invention can be a photodiode, which has a photoelectric conversion efficiency greater than or equal to a preset value, and is used to convert the received light energy into electrical energy or photocurrent. Its composition includes semiconductor materials, especially semiconductor materials of the III-V group, such as: InGaP that can be used to receive a band of 350 to 700 nm, GaAs that can be used to receive a band of 350 to 870 nm, and InGaAs that can be used to receive a band greater than 870 nm. For example, the receivable band of the light receiving element 131 is the green light band of 500 to 580 nm.

The light emitting element described in the present invention can be a light emitting diode (LED) or a laser diode (LD). The light emitting diode can be a chip with a single diode or a chip with an array diode (a light emitting diode that can operate at a high voltage). For example, the light emitting elements 111 to 116 are light emitting diodes that can be used to emit light with a wavelength between 480 and 600 nm.

The receiving band described in the present invention refers to the band of light emitted by the light emitting element in the optical sensing module, for example: the green light band with a wavelength between 500 nm and 580 nm, the red light band with a wavelength between 610 nm and 700 nm, and/or the infrared light band with a wavelength between 700 nm and 1700 nm. The light emitting band of the light emitting element is selected according to the physiological signal to be measured, for example: the green light band can be used to detect heart rate and blood pressure, the red light band can be used to detect blood oxygen, and the infrared light band can be used to detect blood oxygen, blood sugar, and blood lipids. The light receiving element has a photoelectric conversion efficiency greater than or equal to a preset value in the receiving band, which is sufficient to absorb the light signal incident on the object to be measured and then reflected back by the corresponding light emitting element. The non-receiving band is a band outside the receiving band, and may include a band greater than the receiving band and/or a band less than the receiving band. In one embodiment, the receiving band is a green light band, for example, the wavelength is between 500 nm and 580 nm, and the non-receiving band is a band other than green light, for example, less than 500 nm and/or greater than 580 nm. In another embodiment, the receiving band is a red light band, for example, 610 nm to 700 nm, and the non-receiving band is a band other than red light, for example, less than 610 nm and/or greater than 700 nm. In another embodiment, the receiving band is an infrared light band, for example, 700 nm to 1700 nm, and the non-receiving band is outside the infrared light band, for example, less than 700 nm and/or greater than 1700 nm. In another embodiment, a receiving band including at least two colors of light can be used to measure multiple physiological signals, for example, a receiving band including green light and red light, or a receiving band including red light and infrared light, or a receiving band including green light, red light, and infrared light.

Figures 3A to 3M show partial schematic diagrams of an optical sensing module in an embodiment of the present invention. Figure 3A is a partial cross-sectional view of the optical sensing module 200, which includes a carrier 220, a light emitting element 211, and a light receiving element 231. The optical sensing module 200 can be a part of the aforementioned optical sensing modules 100, 101, and 102. The carrier 220 includes a first baffle 221, a second baffle 222, a third baffle 223, and a carrier 224. The light emitting element 211 and the light receiving element 231 can be flip-chip chips, face-mounted horizontal chips, or face-mounted vertical chips, and are located on the carrier 224 and electrically connected to the circuit connection structure (not shown) on the carrier 224. The light emitting element 211 is located in the space 225 between the first baffle 221 and the second baffle 222, and the light receiving element 231 is located in the space 226 between the second baffle 222 and the third baffle 223. The light emitting element 211 and the first baffle 221 and the second baffle 222 are each at a distance greater than 0, and the light receiving element 231 and the second baffle 222 and the third baffle 223 are each at a distance greater than 0. Specifically, the light emitting element 211 has a first side surface 212 and a first baffle 221 with a distance greater than 0, and a second side surface 213 and a second baffle 222 with a distance greater than 0; the light receiving element 231 has a first side surface 232 and a second baffle 222 with a distance greater than 0, and a second side surface 233 and a third baffle 223 with a distance greater than 0. The baffles 221, 222, 223 and the carrier 224 are substantially perpendicular to each other.

The baffles 221, 222, and 223 include opaque materials that can be used to block light. The opaque materials may include light-absorbing materials or reflective materials that are not easy to reflect light. For detailed descriptions of the materials, please refer to the descriptions in the aforementioned relevant paragraphs. The carrier 224 may be a printed circuit board, an organic material, an inorganic material, or a flexible or bendable material. Organic materials may include phenolic resins, glass fibers, epoxy resins, polyimide, or dimaleimide-triazine resin (BT). Inorganic materials may include aluminum or ceramic materials. Flexible or bendable materials may include PET, PI (polyimide), HPVDF (polyvinylidene fluoride), or ETFE (ethylene-tetrafluoroethylene).

The sidewalls of the optical sensing module facing the light receiving element 231 may also include light absorbing materials. Therefore, the background noise light incident on the baffles 222 and 223 to generate reflection and scattering and enter the light receiving element 231 can be reduced. As shown in FIG. 3B, a partial cross-sectional view of the optical sensing module 201 is similar to the optical sensing module 200, including a carrier 220, a light emitting element 211, and a light receiving element 231. The carrier 220 includes a first baffle 221, a second baffle 222, a third baffle 223, and a carrier 224. The light emitting element 211 and the light receiving element 231 are located on the carrier 224. The light emitting element 211 is located in the space 225 between the first baffle 221 and the second baffle 222, and the light receiving element 231 is located in the space 226 between the second baffle 222 and the third baffle 223. The inner surface of the second baffle 222 facing the light receiving element 231 includes a light absorbing layer 241, and the inner surface of the third baffle 223 facing the light receiving element 231 includes a light absorbing layer 242. Therefore, the light receiving element 231 is disposed in the space 226 of the carrier 220 and is surrounded by the light absorbing layers 241 and 242. In another embodiment, the surface of the carrier 224 located in the space 226 that is not covered by the light receiving element 231 also includes a light absorbing layer, which can reduce the background noise light reflected and/or scattered by the carrier 224 and entering the light receiving element 231. In another embodiment, each surface of the baffles 221, 222, and 223 includes a light absorbing layer. It is worth noting that only the detailed description of the partial cross-sectional view of the optical sensing module 201 is described here. In the three-dimensional structure, the baffles not shown facing the light receiving element 231, like the second baffles 222 and the third baffles 223, have an inner surface that includes a light absorbing layer. Therefore, in the three-dimensional structure, the inner surfaces of the baffles surrounding the light receiving element 231 all include a light absorbing layer.

The baffle in the optical sensing module is in the space 225 facing the light emitting element 211, and may also include a light reflective material to increase the light intensity. FIG. 3C shows a partial cross-sectional view of the optical sensing module 202, which, like the optical sensing module 200, includes a carrier 220, a light emitting element 211, and a light receiving element 231. The carrier 220 includes a first baffle 221, a second baffle 222, a third baffle 223, and a carrier 224. The light emitting element 211 and the light receiving element 231 are located on the carrier 224. The light emitting element 211 is located in the space 225 between the first baffle 221 and the second baffle 222, and the light receiving element 231 is located in the space 226 between the second baffle 222 and the third baffle 223. The inner surface of the first baffle 221 facing the light emitting element 211 includes a reflective layer 243, and the inner surface of the second baffle 222 facing the light emitting element 211 includes a reflective layer 244. Therefore, the light emitting element 211 is disposed in the space 225 of the carrier 220 and is surrounded by the reflective layers 243 and 244. In another embodiment, the surface of the carrier 224 located in the space 225 that is not covered by the light emitting element 211 also includes a reflective layer, which can reflect or scatter the light incident on the carrier 224 so that it leaves the space 225 and is emitted upward. In another embodiment, only a portion of the baffles surrounding the light emitting element 211 has a reflective layer, so that the light emitted by the light emitting element 211 when leaving the space 225 is an asymmetric light type. For example, only the inner surface of the first baffle 221 includes a reflective layer 243, and the inner surface of the second baffle 222 facing the light emitting element 211 does not include a reflective layer. Therefore, when the light emitted by the light emitting element 211 leaves the space 225, the path of the light will be more biased towards the direction of the light receiving element 231. In another embodiment, each surface of the baffles 221, 222, and 223 includes a reflective layer. It is worth noting that only the detailed description of the partial cross-sectional view of the optical sensing module 202 is described here. In the three-dimensional structure, the baffles not shown facing the light emitting element 211, like the first baffle 221 and the second baffle 222, have an inner surface including a reflective layer. Therefore, in the three-dimensional structure, the inner surfaces of the baffles surrounding the light emitting element 211 all include a reflective layer.

The side wall of the optical sensing module facing the light emitting element 211 can be a slope to increase the extraction of light. The side wall of the optical sensing module facing the light receiving element 231 can also be a slope to increase the light receiving area and the amount of light received. As shown in FIG. 3D, a partial cross-sectional view of the optical sensing module 203, similar to the optical sensing module 200, includes a carrier 220, a light emitting element 211, and a light receiving element 231. The carrier 220 includes a first baffle 221, a second baffle 222, a third baffle 223, and a carrier 224. The light emitting element 211 and the light receiving element 231 are located on the carrier 224. The light emitting element 211 is located in a space 225 between the first baffle 221 and the second baffle 222, and the light receiving element 231 is located in a space 226 between the second baffle 222 and the third baffle 223. The inner surface 227 of the first baffle 221 facing the light emitting element 211 is not perpendicular to the carrier 224, and has a first tilt angle θ ₁ less than 90 degrees relative to the carrier 224. The inner surface 228 of the second baffle 222 facing the light emitting element 211 is not perpendicular to the carrier 224, and has a second tilt angle θ ₂ less than 90 degrees relative to the carrier 224. Therefore, the space 225 for accommodating the light emitting element 211 has a shape that is wide at the top and narrow at the bottom in a cross-sectional view. In detail, the width of the space 225 gradually widens in a direction away from the carrier board 224. In this embodiment, the first tilt angle _θ1 is substantially equal to the second tilt angle _θ2 . In another embodiment, the first tilt angle θ1 is not equal to the second tilt angle _θ2 , for example, the first tilt angle _θ1 is greater than the second tilt angle _θ2 (the center of the light pattern above the light emitting element 211 is more likely to be biased toward the first baffle 221), or the first tilt angle _θ1 is less than the second tilt angle _θ2 (the center of the light pattern above the light emitting element 211 is more likely to be biased toward the right side). The inner surface 229 of the second baffle 222 facing the light receiving element 231 is not perpendicular to the carrier 224, and has an inclination angle less than 90 degrees relative to the carrier 224. The inner surface 230 of the third baffle 223 facing the light receiving element 231 is not perpendicular to the carrier 224, and has an inclination angle less than 90 degrees relative to the carrier 224. Therefore, the space 226 for accommodating the light receiving element 231 has a shape that is wide at the top and narrow at the bottom in a cross-sectional view. In detail, the width of the space 226 gradually widens in the direction away from the carrier 224. The baffles 221, 222, and 223 include opaque materials, which may include light-absorbing materials or reflective materials. For detailed description of materials, please refer to the description of the above-mentioned relevant paragraphs. It is worth noting that only the detailed description of the partial cross-sectional view of the optical sensing module 203 is described here. In the three-dimensional structure, the unshown baffle facing the light emitting element 211 has an inner surface with respect to the carrier 224, like the first baffle 221 and the second baffle 222. The unshown baffle facing the light receiving element 231 has an inner surface with respect to the carrier 224, like the second baffle 222 and the third baffle 223.

The above-mentioned embodiment makes an appropriate flexible combination according to the photoelectric characteristics of the light emitting element 211 and the light receiving element 231 according to the environment in which the photo sensor is used. In addition to the inclined surface of the baffle, a reflective layer and a light absorbing layer can also be formed on the inclined surface of the baffle. As shown in FIG. 3E, a partial cross-sectional view of the optical sensing module 204 is similar to the optical sensing module 203, including a carrier 220, a light emitting element 211, and a light receiving element 231. The carrier 220 includes a first baffle 221, a second baffle 222, a third baffle 223, and a carrier 224. The light emitting element 211 and the light receiving element 231 are located on the carrier 224. The light emitting element 211 is located in the space 225 between the first baffle 221 and the second baffle 222, and the light receiving element 231 is located in the space 226 between the second baffle 222 and the third baffle 223. The inner surface 227 of the first baffle 221 facing the light emitting element 211 has an inclination angle relative to the carrier 224, and has a reflective layer 243. The inner surface 228 of the second baffle 222 facing the light emitting element 211 has an inclination angle relative to the carrier 224, and has a reflective layer 244. Therefore, the space 225 for accommodating the light emitting element 211 has a shape that is wide at the top and narrow at the bottom in a cross-sectional view. The inner surface 229 of the second baffle 222 facing the light receiving element 231 has an inclination angle relative to the carrier 224, and includes a light absorbing layer 241. The inner surface 230 of the third baffle 223 facing the light receiving element 231 has an inclination angle relative to the carrier 224, and includes a light absorbing layer 242. Therefore, the space 226 for accommodating the light receiving element 231 has a shape that is wide at the top and narrow at the bottom in a cross-sectional view. In another embodiment, the surface of the carrier 224 located in the space 226 that is not covered by the light receiving element 231 also includes a light absorbing layer, which can reduce the background noise light incident on the carrier 224 and entering the light receiving element 231 through reflection and scattering of the carrier 224. The surface of the carrier 224 located in the space 225 that is not covered by the light emitting element 211 also includes a reflective layer, which can reflect or scatter the light incident on the carrier 224 so that the light leaves the space 225 and is emitted upward.

In the above embodiments, due to the difference in manufacturing process, the baffle and the reflective layer can be a material formed in one piece, and the baffle and the light absorbing layer can be a material formed in one piece. As shown in FIG. 3F, a partial cross-sectional view of the optical sensing module 205 is shown, which, like the optical sensing module 200, includes a carrier 220, a light emitting element 211, and a light receiving element 231. The carrier 220 includes a first baffle 221, a second baffle 222, a third baffle 223, and a carrier 224. The light emitting element 211 and the light receiving element 231 are located on the carrier 224. The light emitting element 211 is located in the space 225 between the first baffle 221 and the second baffle 222, and the light receiving element 231 is located in the space 226 between the second baffle 222 and the third baffle 223. The first outer surface 2211 of the first baffle 221 is the outermost surface of the optical sensing module 205, and the inner surface 2212 faces the light emitting element 211. The first baffle 221 is a reflective material, including a mixture of a matrix and a high reflectivity substance. The matrix can be a silicone-based matrix or an epoxy-based matrix. The high reflectivity substance can include titanium dioxide, silicon dioxide, aluminum oxide, K ₂ TiO ₃ , ZrO ₂ , ZnS, ZnO, or MgO. Therefore, the reflection coefficients of the inner and outer surfaces of the first barrier wall 221 are equal. The first inner surface 2221 of the second barrier wall 222 and the inner surface 2231 of the third barrier wall 223 both face the light receiving element 231. The second inner surface 2222 of the second barrier wall 222 faces the light emitting element 211, and the second outer surface 2232 of the third barrier wall 223 can face another light receiving element or light emitting element in the optical sensing module (not shown). The second barrier wall 222 and the third barrier wall 223 are light absorbing materials that are not easy to reflect light. The color of the light absorbing material is preferably a dark color that is not easy to reflect light, such as black, brown, gray, or other dark colors. The light-absorbing material may include Bismaleimide Triazine Resin (BT), and the surface may be formed with a material that can block visible light, such as black ink (BT is light yellow), metal, resin or graphite. The metal material may be chromium or nickel. The resin may be Polyimide (PI) or Acrylate as the main body, and then light-absorbing materials such as carbon, titanium oxide, or dark pigments are dispersed in the resin. The light-absorbing material may also include a mixture of a matrix and a light-absorbing substance. The matrix may be a silicone-based matrix or an epoxy-based matrix. The light-absorbing substance may include carbon, titanium oxide, or dark pigments. Specifically, in the optical sensing module 205, the first side surface 212 of the light emitting element 211 faces the first baffle 221 having a reflective material, and the second side surface 213 of the light emitting element 211 faces the second baffle 222 having a light absorbing material that is not easy to reflect light. The first side surface 232 of the light receiving element 231 faces the second baffle 222 having a light absorbing material that is not easy to reflect light, and the second side surface 233 of the light receiving element 231 faces the third baffle 223 having a light absorbing material that is not easy to reflect light.

The outer surface of the baffle in the optical sensing module 205 facing the light emitting element and the light receiving element can be an inclined surface. As shown in FIG. 3G, which is a partial cross-sectional view of the optical sensing module 206, the first outer surface 2211 of the first baffle 221 is the outermost surface of the optical sensing module 206, and the inner surface 2212 faces the light emitting element 211 and has an inclination angle of not equal to 90 degrees relative to the carrier 224. The first outer surface 2211 is substantially perpendicular to the carrier 224. In other words, the angle of the first outer surface 2211 relative to the carrier 224 is different from the angle of the inner surface 2212 relative to the carrier 224. The first baffle 221 includes a reflective material, and the material can refer to the aforementioned relevant paragraphs. The first inner surface 2221 of the second barrier wall 222 and the inner surface 2231 of the third barrier wall 223 both face the light receiving element 231. The second inner surface 2222 of the second barrier wall 222 faces the light emitting element 211, and the second outer surface 2232 of the third barrier wall 223 can face another light receiving element or light emitting element in the optical sensing module (not shown). The second barrier wall 222 and the third barrier wall 223 are light absorbing materials that are less likely to reflect light, and the materials can refer to the above-mentioned relevant paragraphs. The first inner surface 2221 and the inner surface 2212 of the second barrier wall 222 have an inclination angle of not equal to 90 degrees relative to the carrier 224. Therefore, in a cross-sectional view, the second baffle 222 has a shape that is narrow at the top and wide at the bottom (trapezoid), and the space 225 presents a shape that is wide at the top and narrow at the bottom (inverted trapezoid), and the space 226 also presents a shape that is wide at the top and narrow at the bottom. The inner surface 2231 of the third baffle 223 has an inclination angle of not equal to 90 degrees relative to the carrier 224, and the second outer surface 2232 of the third baffle 223 is substantially perpendicular to the carrier 224. In another embodiment, the second outer surface 2232 of the third baffle 223 has an inclination angle of not equal to 90 degrees relative to the carrier 224.

Figures 3H to 3I show the top view of the optical sensing module when the first baffle 221 includes a reflective material. As shown in Figure 3H, the optical sensing module 206A includes a first outermost baffle 251, a second baffle 222, a third baffle 223, a second outermost baffle 252, a third outermost baffle 253, and a fourth outermost baffle 254. The first outermost baffle 251, the second baffle 222, the third baffle 223, and the second outermost baffle 252 are arranged in a parallel array in the transverse direction. The third outermost baffle 253 and the fourth outermost baffle 254 are arranged in a parallel array in the vertical direction. The third outermost barrier wall 253 is perpendicular to the first outermost barrier wall 251, the second barrier wall 222, the third barrier wall 223, and the second outermost barrier wall 252, and is connected to the first outermost barrier wall 251, the second barrier wall 222, the third barrier wall 223, and the second outermost barrier wall 252. The fourth outermost barrier wall 254 is perpendicular to the first outermost barrier wall 251, the second barrier wall 222, the third barrier wall 223, and the second outermost barrier wall 252, and is connected to the first outermost barrier wall 251, the second barrier wall 222, the third barrier wall 223, and the second outermost barrier wall 252. The first outermost wall 251, the second outermost wall 222, the third outermost wall 253, and the fourth outermost wall 254 together form a space 225 for accommodating the light emitting element 211. The second outermost wall 222, the third outermost wall 223, the third outermost wall 253, and the fourth outermost wall 254 together form a space 226 for accommodating the light receiving element 231. The third outermost wall 223, the second outermost wall 252, the third outermost wall 253, and the fourth outermost wall 254 together form a space 227' for accommodating the light emitting element 214. The first outermost wall 251 and the second outermost wall 252 reflect the material. The second baffle 222, the third baffle 223, the third outermost baffle 253, and the fourth outermost baffle 254 are light-absorbing materials that are less reflective. The description of the reflective material and the light-absorbing material can refer to the above paragraphs.

In the top view, the uppermost outer surface of the optical sensing module 206A has a middle portion 2531, a left end portion 2511, and a right end portion 2521, and the middle portion 2531 is located between the left end portion 2511 and the right end portion 2521. The left end portion 2511 is the uppermost surface of the first outermost baffle 251, and the right end portion 2521 is the uppermost surface of the second outermost baffle 252. The middle portion 2531 of the uppermost outer surface includes a light-absorbing material that does not reflect light, and the left and right end portions 2511 and 2521 include a reflective material. The lowermost outer surface of the optical sensing module 206A has a middle portion 2541, a left end portion 2512, and a right end portion 2522, and the middle portion 2541 is located between the left end portion 2512 and the right end portion 2522. The left end portion 2512 is the bottom surface of the first outermost baffle 251, and the right end portion 2522 is the bottom surface of the second outermost baffle 252. The middle portion 2541 of the bottom outermost surface includes a light-absorbing material that does not reflect light, and the left and right end portions 2512 and 2522 include reflective materials. The rightmost outer surface 2523 of the optical sensing module 206A is the outer surface of the second outermost baffle 252, and therefore, the rightmost outer surface 2523 only includes reflective materials. The leftmost outer surface 2513 of the optical sensing module 206A is the outer surface of the first outermost baffle 251, and therefore, the leftmost outer surface 2513 only includes reflective materials.

FIG. 3I is a top view of an optical sensing module in another embodiment of the present invention when the first baffle 221 includes a reflective material. Similar to the optical sensing module 206A, the optical sensing module 206B includes a first outermost baffle 251, a second baffle 222, a third baffle 223, a second outermost baffle 252, a third outermost baffle 253, and a fourth outermost baffle 254. The first outermost baffle 251, the second baffle 222, the third baffle 223, and the second outermost baffle 252 are arranged in a parallel array in the transverse direction. The third outermost barrier wall 253 and the fourth outermost barrier wall 254 are arranged in a parallel array in the vertical direction. The third outermost barrier wall 253 is perpendicular to the first outermost barrier wall 251, the second barrier wall 222, the third barrier wall 223, and the second outermost barrier wall 252, and is connected to the first outermost barrier wall 251, the second barrier wall 222, the third barrier wall 223, and the second outermost barrier wall 252. The fourth outermost barrier wall 254 is perpendicular to the first outermost barrier wall 251, the second barrier wall 222, the third barrier wall 223, and the second outermost barrier wall 252, and is connected to the first outermost barrier wall 251, the second barrier wall 222, the third barrier wall 223, and the second outermost barrier wall 252. The first outermost barrier wall 251, the second barrier wall 252, the third outermost barrier wall 253, and the fourth outermost barrier wall 254 together form a space 225 for accommodating the light emitting element 211. The second baffle 222, the third baffle 223, the third outermost baffle 253, and the fourth outermost baffle 254 together form a space 226 for accommodating the light receiving element 231. The third baffle 223, the second outermost baffle 252, the third outermost baffle 253, and the fourth outermost baffle 254 together form a space 227' for accommodating the light emitting element 214. The first outermost baffle 251 and the second outermost baffle 252 are reflective materials. The second baffle 222, the third baffle 223, the third outermost baffle 253, and the fourth outermost baffle 254 are light-absorbing materials that are not easy to reflect light. The description of the reflective material and the light-absorbing material that is not easy to reflect light can refer to the description of the above paragraph.

In the top view, the uppermost outer surface 2534 of the optical sensing module 206B is the uppermost surface 2534 of the third outermost baffle 253, and therefore, the uppermost outer surface 2534 only includes a light-absorbing material that is not easy to reflect light. The lowermost outer surface 2544 is the lowermost surface 2544 of the fourth outermost baffle 254, and therefore, the lowermost outer surface 2544 only includes a light-absorbing material that is not easy to reflect light. The rightmost outer surface of the optical sensing module 206B has a middle portion 2524, an upper portion 2532, and a lower portion 2542, and the middle portion 2524 is located between the upper portion 2532 and the lower portion 2542. The upper portion 2532 is the rightmost surface of the third outermost baffle 253, and the lower portion 2542 is the rightmost surface of the fourth outermost baffle 254. The middle portion 2524 of the rightmost outer surface includes a reflective material, and the upper and lower end portions 2532 and 2542 include light-absorbing materials that are not easy to reflect light. The leftmost outer surface of the optical sensing module 206B has a middle portion 2514, an upper portion 2533, and a lower end portion 2543, and the middle portion 2514 is located between the upper portion 2533 and the lower portion 2543. The upper portion 2533 is the leftmost surface of the third outermost baffle 253, and the lower portion 2543 is the leftmost surface of the fourth outermost baffle 254. The middle portion 2514 of the leftmost outer surface includes a reflective material, and the upper and lower end portions 2533 and 2543 include light-absorbing materials that are not easy to reflect light.

In the optical sensing module of Figures 3H to 3I, since only the two outermost walls are made of different materials from the other walls, in the manufacturing process, light-absorbing materials that are not easy to reflect light can be used to form all the walls, and then the entire surface facing the light-emitting element can be cut with a tool to remove the position of the wall, and then the reflective material can be filled in. This process is simple and easy to manufacture.

FIG. 3J is a partial cross-sectional schematic diagram of an optical sensing module in another embodiment of the present invention. The optical sensing module 207A is similar to the optical sensing module 205, and the baffle and the reflective layer are formed of a material integrally formed, or/and the baffle and the light-absorbing layer that is not easy to reflect light are formed of a material integrally formed. The optical sensing module 207A includes a carrier 220, a light emitting element 211, and a light receiving element 231. The carrier 220 includes a first baffle 221, a second baffle 222, a third baffle 223, and a carrier 224. The light emitting element 211 and the light receiving element 231 are located on the carrier 224. The light emitting element 211 is located in the space 225 between the first baffle 221 and the second baffle 222, and the light receiving element 231 is located in the space 226 between the second baffle 222 and the third baffle 223. The first outer surface 2211 of the first baffle 221 is the outermost surface of the optical sensing module 207A, and the inner surface 2212 faces the light emitting element 211. The first baffle 221 is a reflective material, so the reflection coefficients of the inner and outer surfaces of the first baffle 221 are equal. The second baffle 222 includes a first portion 2223 and a second portion 2224 adjacent to each other. The outer surface of the first portion 2223 is the second inner surface 2222 of the second baffle, facing the light emitting element 211. The outer surface of the second part is the first inner surface 2221 of the second baffle, facing the light receiving element 231. The first part 2223 is a reflective material, and the second part 2224 is a light absorbing material that is not easy to reflect light. Therefore, the reflection coefficients of the two opposite outer surfaces of the second baffle 222 are different. The second outer surface 2232 of the third baffle 223 can face another light receiving element or a light emitting element (not shown) in the optical sensing module. If the second outer surface 2232 faces another light receiving element, the third baffle 223 is a light absorbing material that is not easy to reflect light. If the second outer surface 2232 faces another light emitting element, as shown in Figure 3F, the third baffle 223, like the second baffle 222, includes a first part 2233 and a second part 2234 that are adjacent to each other. The outer surface of the first part 2233 is the inner surface 2231 of the third barrier wall 223, facing the light receiving element 231. The outer surface of the second part 2234 is the second outer surface 2232 of the third barrier wall 223, facing the other light emitting element (not shown) in the optical sensing module. The first part 2233 is a light absorbing material that is not easy to reflect light, and the second part 2234 is a reflective material. Therefore, the reflection coefficients of the two opposite outer surfaces of the third barrier wall 223 are different.

FIG. 3K is a top view of an optical sensing module in an embodiment of the present invention, similar to the sensing module 207A in FIG. 3J. As shown in FIG. 3K, the optical sensing module 207B includes a first barrier wall structure 255 forming a space 225 for accommodating the light emitting element 211, a second barrier wall structure 256 forming a space 226 for accommodating the light receiving element 231, and a third barrier wall structure 257 forming a space 227' for accommodating the light emitting element 214. The first barrier wall structure 255 includes a reflective material and surrounds the light emitting element 211. The second barrier wall structure 256 includes a light absorbing material that is not easy to reflect light and surrounds the light receiving element 231. The third barrier wall structure 257 includes a reflective material and surrounds the light emitting element 214. A side 2551 of the first wall structure 255 close to the second wall structure 256 is adjacent to a side 2561 of the second wall structure 256 close to the first wall structure 255. A side 2562 of the second wall structure 256 close to the third wall structure 257 is adjacent to a side 2571 of the third wall structure 257 close to the second wall structure 256.

In the top view, the uppermost outer surface of the optical sensing module 207B has a middle portion 2563, a left end portion 2552, and a right end portion 2572, and the middle portion 2563 is located between the left end portion 2552 and the right end portion 2572. The left end portion 2552 is the upper surface of the first barrier wall structure 255, and the right end portion 2572 is the upper surface of the third barrier wall structure 257. The middle portion 2563 of the uppermost outer surface includes a light-absorbing material that is not easy to reflect light, and the left and right end portions 2552 and 2572 include a reflective material. The lowermost outer surface of the optical sensing module 207B has a middle portion 2564, a left end portion 2553, and a right end portion 2573, and the middle portion 2564 is located between the left end portion 2553 and the right end portion 2573. The left end portion 2553 is the lower surface of the first barrier structure 255, and the right end portion 2573 is the lower surface of the third barrier structure 257. The middle portion 2564 of the lowermost outer surface includes a light-absorbing material that is not easy to reflect light, and the left and right end portions 2553 and 2573 include reflective materials. The rightmost outer surface 2574 of the optical sensing module 207B is the outer surface of the third barrier structure 257, so the rightmost outer surface 2574 only includes reflective materials. The leftmost outer surface 2554 of the optical sensing module 207B is the outer surface of the first barrier structure 255, so the leftmost outer surface 2554 only includes reflective materials.

FIG. 3L shows a partial cross-sectional view of an optical sensing module in an embodiment of the present invention. Similar to the optical sensing module 207A in FIG. 3J. As shown in FIG. 3L, the optical sensing module 208A includes at least one flip-chip light emitting element 211 and at least one flip-chip light receiving element 231. The light emitting element 211 includes a first electrode 2111 and a second electrode 2112 located at the bottom of the light emitting element 211. The light receiving element 231 includes a first electrode 2311 and a second electrode 2312 located at the bottom of the light receiving element 231. The light emitting element 211 and the light receiving element 231 are separated by a second barrier wall 222. The light emitting element 211 is located in the space 225 between the first barrier wall 221 and the second barrier wall 222, and the light receiving element 231 is located in the space 226 between the second barrier wall 222 and the third barrier wall 223. The first barrier wall 221 is a reflective material. The second barrier wall 222 includes a first portion 2223 and a second portion 2224 adjacent to each other. The outer surface of the first portion 2223 is the second inner surface 2222 of the second barrier wall 222, facing the light emitting element 211. The outer surface of the second portion 2224 is the first inner surface 2221 of the second barrier wall 222, facing the light receiving element 231. The first portion 2223 is a reflective material, and the second portion 2224 is a light absorbing material that is not easy to reflect light. Therefore, the reflection coefficients of the two opposite outer surfaces of the second barrier wall 222 are different. The second outer surface 2232 of the third barrier wall 223 may face another light receiving element or light emitting element (not shown) in the optical sensing module. If the second outer surface 2232 faces another light receiving element, as shown in FIG. 3L, the third barrier wall 223 is a light absorbing material that is not easy to reflect light. If the second outer surface 2232 faces another light emitting element, the second outer surface 2232 may selectively be adjacent to another barrier wall containing a reflective material (not shown). The surfaces 2211, 2212, 2222, 2221, 2231, 2232 of the first barrier wall 221, the second barrier wall 222, and the third barrier wall 223 are parallel to each other in the up-down direction and arranged in a straight line.

The spaces 225 and 226 may be filled with transparent packaging materials to protect and fix the light emitting element 211 and the light receiving element 231. The lower surfaces of the first electrode 2111 and the second electrode 2112 of the light emitting element 211 and the first electrode 2311 and the second electrode 2312 of the light receiving element 231 are exposed to the lower surface of the optical sensing module 208A. Transparent packaging materials include silicone, epoxy, polyimide (PI), benzocyclobutene (BCB), perfluorocyclobutane (PFCB), SU8, acrylic resin, polymethyl methacrylate (PMMA), polyethylene terephthalate (PET), polycarbonate (PC), polyetherimide, fluorocarbon polymer, alumina (Al ₂ O ₃ ), SINR, and spin-on glass (SOG).

FIG. 3M shows a partial cross-sectional view of an optical sensing module in an embodiment of the present invention. Similar to the optical sensing module 208A in FIG. 3L. As shown in FIG. 3M, the optical sensing module 208B includes at least one flip-chip light emitting element 211 and at least one flip-chip light receiving element 231. The light emitting element 211 includes a first electrode 2111 and a second electrode 2112, such as positive and negative electrodes, located at the bottom of the light emitting element 211. The light receiving element 231 includes a first electrode 2311 and a second electrode 2312, such as positive and negative electrodes, located at the bottom of the light receiving element 231. The light emitting element 211 and the light receiving element 231 are separated by a second barrier wall 222. The light emitting element 211 is located in the space 255 between the first barrier wall 221 and the second barrier wall 222, and the light receiving element 231 is located in the space 226 between the second barrier wall 222 and the third barrier wall 223. The first barrier wall 221 can reflect light from the light emitting element 211 and is a reflective material/structure. The second barrier wall 222 includes a first portion 2223 and a second portion 2224 adjacent to each other. The outer surface of the first portion 2223 is the second inner surface 2222 of the second barrier wall 222, facing the light emitting element 211. The outer surface of the second portion 2224 is the first inner surface 2221 of the second barrier wall 222, facing the light receiving element 231. The first portion 2223 is a reflective material, and the second portion 2224 is a light absorbing material that is not easy to reflect light. Therefore, the reflection coefficients of the two opposite outer surfaces of the second baffle 222 are different. The second outer surface 2232 of the third baffle 223 can face another light receiving element or light emitting element in the optical sensing module (not shown). If the second outer surface 2232 faces another light receiving element, as shown in Figure 3L, the third baffle 223 is a light absorbing material that is not easy to reflect light. If the second outer surface 2232 faces another light emitting element, the second outer surface 2232 can be selectively adjacent to another baffle containing a reflective material (not shown). The inner surface 2212 of the first baffle 221 facing the light emitting element 211 has an inclination angle not equal to 90 degrees with respect to the bottom surface 2081 of the optical sensing module 208B. The second inner surface 2222 of the second baffle 222 facing the light emitting element 211 has an inclination angle not equal to 90 degrees with respect to the bottom surface 2081 of the optical sensing module 208B. The first inner surface 2221 of the second baffle 222 facing the light receiving element 231 has an inclination angle not equal to 90 degrees with respect to the bottom surface 2081 of the optical sensing module 208B. The inner surface 2231 of the third baffle 223 facing the light receiving element 231 has an inclination angle not equal to 90 degrees with respect to the bottom surface 2081 of the optical sensing module 208B. Therefore, in a cross-sectional view, the second baffle 222 has a shape that is narrow at the top and wide at the bottom, and the space 225 has a shape that is wide at the top and narrow at the bottom, and the space 226 also has a shape that is wide at the top and narrow at the bottom.

The spaces 225 and 226 may be filled with transparent packaging materials to protect and fix the light emitting element 211 and the light receiving element 231. The lower surfaces of the first electrode 2111 and the second electrode 2112 of the light emitting element 211 and the first electrode 2311 and the second electrode 2312 of the light receiving element 231 are exposed to the lower surface of the optical sensing module 208B.

Figure 4A is a schematic diagram of a non-invasive reflective optical sensing module placed on the human body, such as the wrist. The optical sensing module 401 includes at least one light emitting element 411 and at least one light receiving element 431 placed in a carrier 420. The light emitting element 411 emits light toward the skin, and the light passes through subcutaneous tissue, muscles, body cells, arteries 402, veins, etc. When the light passes through the skin and irradiates body cells and blood, absorption, penetration, scattering, and reflection occur. The light receiving element then absorbs the light scattered/reflected back from the body cells and blood, and based on the changes in the reflected and scattered light, some physiological signal information can be obtained, such as heart rate, blood sugar, blood pressure, blood oxygen concentration, etc. Taking heart rate as an example, the blood flow in artery 402 changes regularly as the heart contracts and relaxes. Therefore, the optical properties of light scattered and reflected in artery 402 due to changes in blood volume are different from the optical properties of other body cells. In other words, during the heartbeat, the light returned from the skin received by the light receiving element 431 is modulated by the volume change of blood in artery 402. This signal is a photoplethysmogram (PPG), which is used to obtain physiological information of heart rate. This diagram only uses the wrist as an example. The optical sensing module of the present invention can also be applied to other skin surfaces of the human body to monitor physiological signals, such as fingers, earlobes, chest, and forehead.

Figure 4B shows a schematic diagram of a circuit module of an optical sensing system according to an embodiment of the present invention. The optical sensing system includes an optical sensing module 400 having a plurality of light emitting elements 411, 412, and a light receiving element 431. The current control circuit 460 is coupled to the light emitting elements 411, 412 for driving the light emitting elements 411, 412. The amplifier 441 is coupled to the light receiving element 431 for receiving and amplifying the electrical signal generated by the light receiving element 431 after receiving light. The filter 442 is coupled to the output end of the amplifier 441 for eliminating noise. The ADC circuit 443 is coupled to the output end of the filter 442 for converting the analog electrical signal into a digital electrical signal, and the value of this digital electrical signal represents the magnitude of the light intensity. The signal processing module 450 is coupled to the current control circuit 460 and the ADC circuit 443. The signal processing module 450 includes a processor 452 and a storage device 451. The signal processing module 450 receives the electrical signal from the ADC circuit 443, and the processor 452 stores, calculates, and analyzes the electrical signal. The processor 452 also outputs a signal to the current control circuit 460 for appropriately adjusting the light intensity of the light emitting elements 411 and 412. The optical sensing system can transmit the sensing results to a remote display device, such as a watch or a mobile phone, through wireless transmission, such as NFC, WiFi, Bluetooth, or other appropriate communication protocols.

Figure 5A is a schematic diagram of a photoplethysmogram (PPG). The PPG signal is related to changes in blood volume in blood vessels. When the heart contracts and relaxes, the blood volume flowing through the arteries is different, causing the light that penetrates the skin and enters the blood vessels to produce different reflected/scattered light intensities. Therefore, the light intensity sensed by the light receiving element will produce corresponding waveforms as the heart contracts and relaxes. When the heart beats periodically, physiological information related to the heart or blood vessels, such as heart rate, can be obtained through this photoplethysmogram. Referring to Figure 5A, the vertical axis represents the normalized light intensity sensed by the light receiving element. In one cycle of the PPG signal, the first wave peak 501 represents the time when the heart is completely relaxed, the first wave valley 502 represents the time boundary between the heart's contraction and relaxation, the second wave peak 503 represents the blood reflux phenomenon generated when the heart changes from relaxation to contraction, and the second wave valley 504 represents the time when the heart is completely contracted. The slope changes and time delay distances between the first wave peak 501, the first wave trough 502, the second wave peak 503, and the second wave trough 504 can reflect physiological phenomena related to the heart and blood vessels, such as blood oxygen concentration ( _SpO2 ), pulse rate, respiratory rate, stiffness index, reflection index, pulse transit time (PTT), and pulse wave velocity (PWV)... etc. By calculating the time difference of the first wave peak 501 in different and adjacent cycles, the heartbeat cycle and thus the heart rate information can be obtained. The value of the PPG signal is the sum of a DC value that is not easily changed with time and an AC value that changes with time. The AC value is the amount of light intensity change caused by changes in blood volume in the arteries as the heart contracts and relaxes. The DC value is the intensity of scattered/reflected light that is not affected by changes in skin color, subcutaneous tissue, cells, veins, bones, muscles, etc. as the heart contracts and relaxes.

The PPG signal in Figure 5A can be used to obtain the perfusion index (PI) based on the DC and AC values. The PI value is defined as AC/DC=PI (%). The higher the photoelectric conversion efficiency of the light receiving element, the larger the PI value will be, and the first wave peak 501, the first wave valley 502, the second wave peak 503, and the second wave valley 504 will be easier to measure, so it is easier to obtain more physiological signals. If the PI value is not large enough, the PPG signal may only be able to resolve the first wave peak 501 with the strongest signal, and fewer physiological signals can be identified, for example, only the heart rate can be identified.

Figure 5B shows the PI values of the light receiving elements of two control groups (control group 1 and control group 2) and two light receiving elements according to the embodiments of the present invention (embodiment 1 and embodiment 2) measured using the same optical sensing system. The materials of control group 1 and control group 2 are both semiconductor materials containing IV group, such as: Silicon base materials. The size of control group 1 is 110milÎ110mil, the light receiving area is ^7.56mm2 , and PI=0.86%. The size of control group 2 is 80milÎ80mil, the light receiving area is ^4mm2 , and PI=0.64%. The materials of embodiment 1 and embodiment 2 are both semiconductor materials containing III-V group, such as: InGaP, InGaAs. The size of embodiment 1 is 80milÎ80mil, the light receiving area is ^4mm2 , and PI=0.86%. The size of Example 2 is 100mil×100mil, the light receiving area is 6.25mm ² , and PI=1.56%. Since Examples 1 and 2 are semiconductor materials of the III-V group, the photoelectric conversion efficiency (external quantum efficiency) is higher than that of the control group 1 and the control group 2. Therefore, at similar sizes, the PI values of Examples 1 and 2 are higher than those of the control group 1 and the control group 2. Here, a ratio N=PI (%)/light receiving area (mm ² ) can be defined for the light receiving element. N=0.11 for the control group 1, N=0.16 for the control group 2, N=0.21 for Example 1, and N=0.24 for Example 2. Therefore, it can be known that the optical sensing system using the embodiment of the present invention can obtain N greater than 0.2.

The perfusion index is related to the race and the part of the body being measured. The perfusion index measured above refers to the signal measured when the optical sensing module emits and receives green light, for example, green light with a wavelength between 500 and 580 nm, and is placed on the wrist of a yellow person. In the optical sensing module, the distance from the receiving surface of the light receiving element to the wrist skin is approximately 1 to 2 mm.

FIG. 6A is a partial cross-sectional schematic diagram of an optical sensing module in an embodiment of the present invention. The optical sensing module 601 is similar to the optical sensing module 203 in FIG. 3D, and includes a carrier 620, a light emitting element 611, and a light receiving element 631. The carrier 620 includes a first baffle 621, a second baffle 622, and a third baffle 623. The light emitting element 611 is located in a space 625 between the first baffle 621 and the second baffle 622, and the light receiving element 631 is located in a space 626 between the second baffle 622 and the third baffle 623. The carrier 620 includes a first supporting surface 641 for supporting the light emitting element 611, and a second supporting surface 642 for supporting the light receiving element 631. The inner surface 627 of the first baffle 621 facing the light emitting element 611 is not perpendicular to the first supporting surface 641, and has a blunt angle of inclination relative to the first supporting surface 641. The inner surface 628 of the second baffle 622 facing the light emitting element 611 is not perpendicular to the first supporting surface 641, and has a blunt angle of inclination relative to the first supporting surface 641. Therefore, the space 625 for accommodating the light emitting element 611 has a shape that is wide at the top and narrow at the bottom in a cross-sectional view. In other words, the width of the space 625 gradually widens as it moves away from the first supporting surface 641. The inner surface 629 of the second baffle 622 facing the light receiving element 631 is not perpendicular to the second bearing surface 642, and has an inclination angle relative to the second bearing surface 642. The inner surface 630 of the third baffle 623 facing the light receiving element 631 is not perpendicular to the second bearing surface 642, and has an inclination angle relative to the second bearing surface 642. Therefore, the space 226 for accommodating the light receiving element 631 has a shape that is wide at the top and narrow at the bottom in a cross-sectional view. In detail, the width of the space 626 gradually widens as it moves away from the second bearing surface 642. There is a distance H1 between the light emitting surface 612 of the light emitting element 611 and the uppermost surface of the carrier 620, and there is a distance H2 between the receiving surface 632 of the light receiving element 631 and the uppermost surface of the carrier 620, H1＜H2. Therefore, compared with the light receiving element 631, the light emitting element 611 can be closer to the surface of the skin to be tested, thereby increasing the intensity of light incident on the skin. The distance between the first supporting surface 641 and the lowermost surface of the carrier 620 is greater than the distance between the second supporting surface 642 and the lowermost surface of the carrier 620. In one embodiment, the light emitting element 611 has a height T, H2＞H1+T. In another embodiment, the baffles 621, 622, 623 may also be perpendicular to the first bearing surface 641 or the second bearing surface 642. In another embodiment, a reflective layer or a light absorbing layer is formed on the inner surfaces 627, 628, 629, 630 as shown in FIGS. 3B to 3D. In another embodiment, the baffles 621, 622, 623 may be as shown in FIGS. 3F to 3M, and the material of the baffles may include a reflective material or a light absorbing material that is not easily reflected.

Since the light emitting angle of the light emitting element is less than 150 degrees, for example, the general light emitting angle of the light emitting diode is 120 degrees, when the light emitting surface of the light emitting element is higher than the receiving surface of the light receiving element, the intensity of the light emitted by the light emitting element interfering with the light receiving element will be very small or even close to zero. Therefore, in the optical sensing module, a baffle is not required to isolate the light emitting element from the light receiving element, as shown in FIG6B. FIG6B is a partial cross-sectional schematic diagram of an optical sensing module in an embodiment of the present invention. The optical sensing module 602 includes a carrier 620, a light emitting element 611, and a light receiving element 631. The carrier 602 includes a first baffle 621, a third baffle 623, and a first supporting surface 641. The first bearing surface 641 is used to bear the light emitting element 611 and the light receiving element 631. The light emitting element 611 and the light receiving element 631 are located in the space 625 between the first baffle 621 and the third baffle 622. The inner surface 627 of the first baffle 621 facing the light emitting element 611/the light receiving element 631 is not perpendicular to the first bearing surface 641, and has an inclination angle relative to the first bearing surface 641. The inner surface 630 of the third baffle 623 facing the light emitting element 611/the light receiving element 631 is not perpendicular to the first bearing surface 641, and has an inclination angle relative to the first bearing surface 641. Therefore, the space 625 for accommodating the light emitting element 611/the light receiving element 631 has a shape that is wide at the top and narrow at the bottom in a cross-sectional view. In detail, the width of the space 625 gradually widens in the direction away from the first supporting surface 641. There is a distance H1 between the light emitting surface 612 of the light emitting element 611 and the uppermost surface of the supporting body 620, and there is a distance H2 between the receiving surface 632 of the light receiving element 631 and the uppermost surface of the supporting body 620, H1＜H2. There is a connecting device 644 for adjusting the height of the light emitting surface between the light emitting element 611 and the first supporting surface 641 of the supporting body 620, and the connecting device 644 has a width greater than that of the light emitting element 611. In one embodiment, the light emitting element 611 has a height T, H2＞H1+T. In another embodiment, the baffles 621 and 623 may also be perpendicular to the first bearing surface 641. Alternatively, a reflective layer or a light absorbing layer may be formed on the inner surfaces 627 and 630 as shown in FIGS. 3B to 3D. The connector 644 may be an electrically insulating material, including plastics, such as polypropylene (PP), polycarbonate (PC), polybutylene terephthalate (PBT), acrylonitrile-butadiene-styrene copolymer (ABS), a mixture of ABS and PC, or a ceramic material, such as alumina (Al ₂ O ₃ ). Ceramic materials may be manufactured by thick film processes, low temperature co-firing processes (LTCC) and thin film processes. The connector 644 may help the heat generated by the light emitting element 611 to be removed by conduction.

FIG. 6C is a partial cross-sectional schematic diagram of an optical sensing module in another embodiment of the present invention. The optical sensing module 603 is similar to the optical sensing module 601 in FIG. 6A, and includes a carrier 620, a light emitting element 611, and a light receiving element 631. There is a distance H1 between the light emitting surface 612 of the light emitting element 611 and the uppermost surface of the carrier 620, and there is a distance H2 between the receiving surface 632 of the light receiving element 631 and the uppermost surface of the carrier 620, and H1>H2. Therefore, compared with the light emitting element 611, the light receiving element 631 can be closer to the surface of the skin to be tested, thereby increasing the intensity of the received light and reducing the interference of the external ambient light.

Figure 6D is a partial cross-sectional schematic diagram of an optical sensing module in another embodiment of the present invention. As shown in Figure 6D, the optical sensing module 604 includes at least one flip-chip light emitting element 611 and at least one flip-chip light receiving element 631. The light emitting element 611 includes a first electrode and a second electrode (not shown) located at the bottom of the light emitting element 611. The light receiving element 631 includes a first electrode 6311 and a second electrode 6312 located at the bottom of the light receiving element 231. There is a connecting device 644 below the light emitting element 611, and the connecting device 644 has a width larger than the light emitting element 611. The connecting device 644 has two conductive through holes 6441 and 6442 that form an electrical connection with the first electrode and the second electrode of the light emitting element 611. There is a distance H1 between the light emitting surface 612 of the light emitting element 611 and the uppermost surface of the carrier 620, and there is a distance H2 between the receiving surface 632 of the light receiving element 631 and the uppermost surface of the carrier 620, H1＜H2. In one embodiment, the light emitting element 611 has a height T, H2＞H1+T. The light emitting element 611, the connecting device 644, and the light receiving element 631 are located in the space 625 between the first baffle 621 and the third baffle 623. The space 625 can be filled with a transparent packaging material to protect and fix the light emitting element 611, the light receiving element 631, and the connecting device 644. The inner surface 627 of the first baffle 621 facing the light emitting element 611/light receiving element 631 is not perpendicular to the bottom surface 624 of the optical sensing module 604, and the inner surface 630 of the third baffle 623 facing the light emitting element 611/light receiving element 631 is not perpendicular to the bottom surface 624 of the optical sensing module 604. Therefore, the space 625 for accommodating the light emitting element 611/light receiving element 631 has a shape that is wide at the top and narrow at the bottom in a cross-sectional view. In other words, the width of the space 625 gradually widens as it moves away from the bottom surface 624 of the optical sensing module 604. The conductive vias 6441, 6442, and the lower surfaces of the first electrode 6311 and the second electrode 6312 of the light receiving element 631 are exposed to the lowermost surface 624 of the optical sensing module 604. The material of the baffle may include a reflective material or a light absorbing material that is not easy to reflect light. The materials of the connecting device 644 and the transparent packaging material may refer to the description in the previous paragraph.

FIG. 6E is a partial cross-sectional schematic diagram of an optical sensing module in another embodiment of the present invention. The optical sensing module 605 includes at least one flip-chip light emitting element 611 and at least one flip-chip light receiving element 631. The light emitting element 611 includes a first electrode 6111 and a second electrode 6112 located at the lower portion of the light receiving element 611. The first electrode 6111 and the second electrode 6112 are surrounded by a supporting structure 613, which not only surrounds the first electrode 6111 and the second electrode 6112, but also covers the lower surface of the light emitting element 611. The outer surface of the supporting structure 613 is flush with the outer surface of the light emitting element 611. The bottom surface of the support structure 613 is flush with the bottom surfaces of the first electrode 6111 and the second electrode 6112. The support structure 613 can be a reflective material, a light-absorbing material that does not easily reflect light, or a transparent packaging material. The light receiving element 631 includes a first electrode 6311 and a second electrode 6312 located at the bottom of the light receiving element 231. There is a distance H1 between the light-emitting surface 612 of the light-emitting element 611 and the top surface of the carrier 620, and there is a distance H2 between the receiving surface 632 of the light-receiving element 631 and the top surface of the carrier 620, H1＜H2. In one embodiment, the light-emitting element 611 has a height T, H2＞H1+T. The light emitting element 611 and the light receiving element 631 are located in a space 625 between the first baffle 621 and the third baffle 623. The space 625 can be filled with a transparent packaging material to protect and fix the light emitting element 611 and the light receiving element 631. The inner surface 627 of the first baffle 621 facing the light emitting element 611/light receiving element 631 is not perpendicular to the bottom surface 624 of the optical sensing module 605, and the inner surface 630 of the third baffle 623 facing the light emitting element 611/light receiving element 631 is not perpendicular to the bottom surface 624 of the optical sensing module 605. Therefore, the space 625 for accommodating the light emitting element 611/light receiving element 631 has a shape that is wide at the top and narrow at the bottom in a cross-sectional view. In detail, the width of the space 625 gradually widens in the direction away from the bottom surface 624 of the optical sensing module 605. The lower surfaces of the first electrode 6111 and the second electrode 6112 of the light emitting element 611, and the first electrode 6311 and the second electrode 6312 of the light receiving element 631 are exposed to the bottom surface 624 of the optical sensing module 605. The material of the baffle may include a reflective material or a light absorbing material that is not easily reflected. The material of the transparent encapsulation material may refer to the description in the previous paragraph.

In another embodiment, the optical sensing module has a plurality of light emitting elements of different wavelength bands and a plurality of light receiving elements of corresponding different receiving wavelength bands. By emitting light of different wavelength bands to the organism to be detected, such as human skin, and by detecting the reflected light of different wavelength bands, a variety of different physiological signals can be obtained, such as blood oxygen, blood pressure, heart rate, blood sugar, etc. FIG. 7A is a top view of an optical sensing module according to another embodiment of the present invention. The optical sensing module 701 includes a carrier 720, a first light receiving element 731, a second light receiving element 732, a third light receiving element 733, a first light emitting element 711, a second light emitting element 712, and a third light emitting element 713. The carrier 720 includes a housing 721 and a baffle 722, which are used to separate a first space 724 and a second space 725, wherein the second space 725 is larger than the first space 724. The first space 724 has a plurality of light emitting elements of different wavelength bands, and the second space 725 has a plurality of light receiving elements of different wavelength bands. The first light emitting element 711, the second light emitting element 712, and the third light emitting element 713 are located in the first space 724. The first light receiving element 731, the second light receiving element 732, and the third light receiving element 733 are located in the second space 725. The first light emitting element 711, the second light emitting element 712, and the third light emitting element 713 have different dominant wavelengths/peak wavelengths, for example, green light between 500 and 580 nm, red light between 610 and 700 nm, or infrared light greater than 700 nm. The first light receiving element 731, the second light receiving element 732, and the third light receiving element 733 are located in the second space 725, and the receiving wavelength bands correspond to the ranges of the dominant wavelengths/peak wavelengths of the first light emitting element 711, the second light emitting element 712, and the third light emitting element 713, respectively. The areas of the light receiving elements 731, 732, and 733 are larger than the light emitting elements 711, 712, and 713.

In another embodiment, in an optical sensing module having multi-band light emitting elements and light receiving elements, the number of light receiving elements is less than the number of light emitting elements. In detail, one light receiving element can receive light from light emitting elements of different emission bands. As shown in FIG. 7B , the optical sensing module 702 includes a carrier 720, a first light emitting element 711, a second light emitting element 712, a third light emitting element 713, and a first light receiving element 731. The carrier 720 includes a housing 721 and a baffle 722 to separate a first space 724 and a second space 725, wherein the second space 725 is larger than the first space 724. The first space 724 has a plurality of light emitting elements of different bands, and the second space 725 has a first light receiving element 731 whose number is less than the number of light emitting elements in the first space 724. The dominant wavelengths/peak wavelengths of the first light emitting element 711, the second light emitting element 712, and the third light emitting element 713 are different, for example, green light between 500 and 580 nm, red light between 610 and 700 nm, or infrared light greater than 700 nm. The receiving wavelength band of the first light receiving element 731 covers the dominant wavelengths/peak wavelengths of the first light emitting element 711, the second light emitting element 712, and the third light emitting element 713. The area of the first light receiving element 731 is larger than that of the light emitting elements 711, 712, and 713.

Please refer to FIG. 8, which is a cross-sectional view of a light receiving element 8 (e.g., a photodiode) of an embodiment of the present disclosure. FIG. 9 is an upper view of FIG. 8 and does not show the protective layer 86. FIG. 10 is a simplified three-dimensional schematic diagram of FIG. 8. The light receiving element 8 comprises a III-V semiconductor compound and an active region (or depletion region) to convert light energy into electrical energy or photocurrent. In detail, the light receiving element 8 of the present embodiment comprises a first semiconductor stack 81 and a substrate 82. The substrate 82 can be used to support the first semiconductor stack 81 and other layers or structures thereon. The first semiconductor stack 81 is located on the substrate 82 and comprises a first type semiconductor structure 811, a second type semiconductor structure 812 and a The active region 813 is located between the first type semiconductor structure 811 and the second type semiconductor structure 812. In this article, the first type and the second type refer to different conductivity types. If holes are the majority carriers, it is called p-type, and if electrons are the majority carriers, it is called n-type. For example, the conductivity type of the first type semiconductor structure 811 is p-type, and the conductivity type of the second type semiconductor structure 812 is n-type, and vice versa.

The active region 813 is a region of the light receiving element 8 for absorbing light, and the wavelength range of the light to be absorbed is determined by the material (or band gap) of the active region 813. In other words, the active region 813 can absorb light with energy greater than its band gap. The band gap of the active region 813 can be designed to be between 0.72ev and 1.77ev (the corresponding wavelength is infrared light between 700nm and 1700nm), between 1.77ev and 2.03ev (the corresponding wavelength is red light between 610nm and 700nm), between 2.1ev and 2.175ev (the corresponding wavelength is yellow light between 570nm and 590nm), between 2.137ev and 2.48ev (the corresponding wavelength is infrared light between 500nm and 580nm). nm), between 2.53ev and 3.1ev (its corresponding wavelength is blue light or deep blue light between 400 nm and 490 nm), or between 3.1ev and 4.96ev (its corresponding wavelength is ultraviolet light between 250 nm and 400 nm). The active region 813 of this embodiment is a semiconductor layer including a dopant and the doping concentration is less than that of the first type semiconductor structure 811 or/and the second type semiconductor structure 812. Specifically, the doping concentration of the dopant in the active region 813 is lower than 5Î10 ¹⁶ cm ^-3 , for example, the doping concentration may be 1Î10 ¹⁵ cm ^-3 to 5Î10 ¹⁶ cm ^-3 The dopant of the active region 813 of the present embodiment and the dopant of the first type semiconductor structure 811 make the active region 813 and the first type semiconductor structure 811 have the same conductivity type, or the dopant of the active region 813 and the dopant of the first type semiconductor structure 811 are made of the same material. In another embodiment, the active region 813 is a semiconductor layer that is not intentionally doped with a dopant. The active region 813 of the light receiving element 8 of the present embodiment can be used to absorb wavelengths between 500 nm and 580 nm. In this embodiment, the active region 813 is a single-layer structure located between the first type semiconductor structure 811 and the second type semiconductor structure 812. In another embodiment, the first type semiconductor structure 811 and the second type semiconductor structure 812 are in direct contact, and the active region 813 is an interface between the first type semiconductor structure 811 and the second type semiconductor structure 812.

The light receiving element 8 of this embodiment further includes a first electrode pad 83 and a second electrode pad 84 electrically connected to the first semiconductor stack 81 to conduct the photocurrent generated by the first semiconductor stack 81 absorbing light. The first electrode pad 83 and the second electrode pad 84 are respectively located on opposite sides of the first semiconductor stack 81, so that the light receiving element 8 forms a vertical type. In detail, the first semiconductor stack 81 has a first surface S1 connected to the substrate 82, a second surface S2 opposite to the first surface S1 and away from the substrate 82, and a side surface S3 connecting the first surface S1 and the second surface S2, and the first electrode pad 83 is located on the substrate 82, and the second electrode pad 84 is located on the second surface S2.

In this embodiment, the light receiving element 8 is a vertical type, so the substrate 82 is a conductive material, and includes a metal material, a semiconductor material or a transparent conductive material. The metal material can be but not limited to copper (Cu), aluminum (Al), chromium (Cr), tin (Sn), gold (Au), nickel (Ni), titanium (Ti), platinum (Pt), lead (Pb), zinc (Zn), cadmium (Cd), antimony (Sb), cobalt (Co) or alloys thereof; the semiconductor material can be but not limited to Group IV semiconductors or Group III-V semiconductors, such as silicon (Si), germanium (Ge), Silicon carbide (SiC), gallium nitride (GaN), gallium phosphide (GaP), gallium arsenide (GaAs), gallium arsenide phosphide (AsGaP) or indium phosphide (InP), etc.; the transparent conductive material can be but not limited to oxide, diamond-like carbon film (DLC) or graphene, and the oxide is, for example, indium tin oxide (ITO), indium oxide (InO), tin oxide (SnO), cadmium tin oxide (CTO), antimony tin oxide (ATO), aluminum zinc oxide (AZO), zinc tin oxide (ZTO), gallium zinc oxide (GZO), indium tungsten oxide (IWO), zinc oxide (ZnO) or indium zinc oxide (IZO). In another embodiment, when the light receiving element 8 is of a non-vertical type, the substrate 8 may further include an insulating material, such as sapphire, glass, nitride or oxide (such as aluminum oxide (Al ₂ O ₃ ) or aluminum nitride (AlN), etc. In addition, the substrate 82 can be transparent or opaque. The first semiconductor stack 81 can be grown on the substrate 82 or another growth substrate by an epitaxial method such as metal organic chemical vapor deposition (MOCVD), molecular beam epitaxy (MBE) or hydride vapor phase epitaxy (HVPE). If the first semiconductor stack 81 is generated on the growth substrate, the first semiconductor stack 81 can be bonded to the substrate 82 through a bonding layer (not shown) by substrate transfer technology, and the growth substrate can be selectively removed. The substrate 82 can be selectively doped or not doped with an impurity. The conductivity type of the substrate 82 can be n-type or p-type. In the present embodiment, the material of the substrate 82 is p-type gallium arsenide.

Please refer to Figures 9 and 10. The second surface S2 is the main light-absorbing surface of the light-receiving element 8. To prevent the second electrode pad 84 from shielding too much of the second surface S2, thereby reducing the light-absorbing area and causing a decrease in the photoelectric conversion efficiency, the area of the second electrode pad 84 is not more than 15% of the second surface S2, preferably not more than 10% of the second surface S2, and more preferably not more than 5% of the second surface S2, as viewed from the top view of the light-receiving element 8. In addition, the area of the second electrode pad 84 is preferably greater than 0.08% of the second surface, so as to facilitate wire bonding later. In detail, in one embodiment, the area of the second electrode pad 84 is 0.08% to 5% of the second surface S2. In this embodiment, the area of the second electrode pad 84 is 0.3% to 0.5% of the area of the second surface S2. In one embodiment, the diameter or the longest side of the second electrode pad 84 is not less than 30 μm. In addition, the second electrode pad 84 in this embodiment is far away from the geometric center T1 of the second surface S2 and is adjacent to the edge T2 of the first semiconductor stack 81. The second surface S2 of this embodiment only has the second electrode pad 84, and no other conductive material (such as an extended electrode) is formed on the second surface S2. In other embodiments, in addition to the second electrode pad 84, an extended electrode is provided on the second surface S2 to connect the second electrode pad 84, and when viewed from above, the total area of the extended electrode and the second electrode pad 84 is no more than 15% of the area of the second surface S2 and greater than 0.08% of the area of the second surface S2.

As shown in FIG. 8 , in this embodiment, the light receiving element 8 further includes a protective layer 86 covering the first semiconductor stack 81. Specifically, the protective layer 86 covers the second surface S2 and the side surface S3 to completely cover the first semiconductor stack 81, thereby preventing external moisture or corrosive substances from entering the first semiconductor stack 81 and causing adverse effects on the electrical properties or stability of the first semiconductor stack 81. The protective layer 86 of this embodiment directly contacts the second surface S2 and the side surface S3 of the first semiconductor stack 81. Specifically, the protective layer 86 directly contacts a side wall S31 of the first semiconductor structure 811, a side wall S32 of the active layer 813, and a side wall S33 of the second semiconductor structure 812, so as to increase the protective effect on the first semiconductor stack 81. The protective layer 86 is composed of a single layer structure and has a reflectivity of less than 20% for a wavelength range of 400 nm to 1000 nm. The protective layer 86 can also be used to reduce the reflection effect of incident light on the first semiconductor stack 81, so as to serve as an anti-reflection layer. For example, the material of the protective layer 86 can be an oxide or a nitride, such as _silicon oxide (SiO2), aluminum oxide ( _Al2O3 ) or silicon nitride (SiN). The refractive index of the protective layer 86 is less than the refractive index of the first semiconductor stack 81 to reduce the probability of light reflection on the second surface S2 and the side surface S3. For example, the refractive index of the protective layer 86 is about 1.4 to 2.1. The protective layer 86 of this embodiment is 300Å to 1000Å of silicon nitride. In one embodiment, in order to achieve a better anti-reflection effect, the thickness of the protective layer 86 is an integer multiple of a quarter wavelength, which is the wavelength at which the active region 813 has the highest external quantum efficiency. In other embodiments, the light receiving element 8 may also choose to omit the protective layer 86, and reduce the entry of moisture or corrosive substances into the first semiconductor stack 81 by covering the light receiving element 8 with a packaging structure (not shown). In one embodiment, the protective layer 86 is a multi-layer structure, and the difference in refractive index between two adjacent layers is less than 0.7. For example, the protective layer 86 includes a first layer of silicon dioxide and a second layer of silicon nitride adjacent to the first layer.

The first semiconductor stack 81 of the light receiving element 8 of this embodiment further includes a buffer layer 814 and a first barrier layer 815 disposed between the first semiconductor structure 811 and the substrate 82. The buffer layer 814 is used to increase the epitaxial quality of the first semiconductor structure 811 and the layers thereon; the energy gap of the first barrier layer 815 is larger than that of the first semiconductor structure 811, and is used to prevent carriers from being recombined at the interface between the first semiconductor structure 811 and the first barrier layer 815, thereby increasing the photocurrent of the light receiving element 8. The buffer layer 814 and the first barrier layer 815 each have a dopant, so that they have the same conductivity type as the first type semiconductor structure 812, and the dopant concentration of the buffer layer 814 and the first barrier layer 815 is greater than the dopant concentration of the first type semiconductor structure 811, for example, greater than 1Î10 ¹⁷ cm ^-3 . In addition, the first semiconductor stack 81 of the light receiving element 8 of this embodiment further includes a second barrier layer 816 disposed on the second semiconductor structure 812. The energy gap of the second barrier layer 816 is larger than that of the second semiconductor structure 812, and is used to prevent carriers from being compounded at the interface between the second barrier layer 816 and the second semiconductor structure 812, thereby increasing the photocurrent of the light receiving element 8. The second barrier layer 816 of this embodiment has a dopant, so that it has the same conductivity type as the second semiconductor structure 812. The material of the buffer layer 814 of this embodiment is InGaP, the material of the first barrier layer 815 is AlGaInP, and the material of the second barrier layer 816 is AlInP.

The light receiving element 8 further includes a contact layer 85 between the first semiconductor stack 81 and the second electrode pad 84. The contact layer 85 is a conductive material and can be selected according to the material of the first semiconductor stack 81 so that the contact layer 85 forms a good electrical contact and a low contact resistance with the second type semiconductor structure 812, such as forming an ohmic contact. For example, the material of the contact layer 85 can be selected as a III-V group semiconductor, such as gallium arsenide (GaAs) or gallium phosphide (GaP). In this embodiment, the doping concentration of the contact layer 85 is greater than the doping concentration of the second type semiconductor structure 812. The contact layer 85 has substantially the same position distribution as the second electrode pad 84, thereby preventing the contact layer 85 from shielding the second surface S2 (i.e., the main light absorption surface), thereby increasing the photoelectric conversion efficiency of the light receiving element 8.

In this embodiment, the materials of the first type semiconductor structure 811, the second type semiconductor structure 812 and the active region 813 include III-V group compound semiconductors, such as AlGaInAs series, AlGaInP series, AlInGaN series, AlAsSb series, InGaAsP series, InGaAsN series, AlGaAsP series, etc., for example: AlGaInP, GaAs, InGaAs, AlGaAs, GaAsP, GaP, InGaP, AlInP, GaN, InGaN, AlGaN and other compounds. In the embodiments of the present disclosure, unless otherwise specified, the chemical formula includes "compounds that meet the chemical dosage" and "compounds that do not meet the chemical dosage", wherein "compounds that meet the chemical dosage" means, for example, that the total element dosage of the group III elements is the same as the total element dosage of the group V elements, whereas "compounds that do not meet the chemical dosage" means, for example, that the total element dosage of the group III elements is different from the total element dosage of the group V elements. For example, a chemical formula of the AlGaInAs series means that the group III elements aluminum (Al) and/or gallium (Ga) and/or indium (In) are included, and the group V element arsenic (As) is included, wherein the total element dosage of the group III elements (aluminum and/or gallium and/or indium) can be the same as or different from the total element dosage of the group V elements (arsenic). In addition, if the compounds represented by the chemical formulas above are compounds that conform to the chemical dosage, the AlGaInAs series represents (Al _y1 Ga _{（ 1-y1 ）} ） _1-x1 In _x1 As, where 0≦x1≦1, 0≦y1≦1; the AlGaInP series represents (Al _y2 Ga _{（ 1-y2 ）} ） _1-x2 In _x2 P, where 0≦x2≦1, 0≦y2≦1; the AlInGaN series represents (Al _y3 Ga _{（ 1-y3 ）} ） _1-x3 In _x3 N, where 0≦x3≦1, 0≦y3≦1; the AlAsSb series represents AlAs _x4 Sb _{（ 1-x4 ）} , where 0≦x4≦1; the InGaAsP series represents In _x5 Ga _1-x5 As _1-y4 P _y4 , where 0≦x5≦1, 0≦y4≦1; the InGaAsN series represents In _x6 Ga _1-x6 As _1-y5 N _y5 , where 0≦x6≦1, 0≦y5≦1; the AlGaAsP series represents Al _x7 Ga _1-x7 As _1-y6 P _y6 , where 0≦x7≦1, 0≦y6≦1; the InGaPSb series represents In _x8 Ga _1-x8 P _y7 Sb _{1- y7} , where 0≦x8≦1, 0≦y7≦1. In this embodiment, the materials of the first type semiconductor structure 811, the second type semiconductor structure 812 and the active region 813 include indium gallium phosphide (In _z Ga _{( 1-z )} P), where 0＜z＜1. In other embodiments, the material of the first type semiconductor structure 811 can be AlGaInAs:Zn series, AlGaInP:Zn series or InGaPSb:Zn series, the material of the second type semiconductor structure 812 can be AlGaInAs:Si series, AlGaInP:Si series or InGaPSb:Si series, and the material of the active region 813 can be i-AlGaInAs series, i-AlGaInP series or i-InGaPSb series.

The material of the first electrode pad 83 may be the same as or different from the material of the second electrode pad 84. In one embodiment, the materials of the first electrode pad 83 and the second electrode pad 84 include metal materials or transparent conductive materials. The metal materials may include but are not limited to aluminum (Al), chromium (Cr), copper (Cu), tin (Sn), gold (Au), nickel (Ni), titanium (Ti), platinum (Pt), lead (Pb), zinc (Zn), cadmium (Cd), antimony (Sb), cobalt (Co), or alloys thereof; the transparent conductive material may include but are not limited to indium tin oxide (ITO), indium oxide (InO), tin oxide (SnO), indium oxide (ITO), indium oxide (InO ... Cadmium tin (CTO), antimony tin oxide (ATO), aluminum zinc oxide (AZO), zinc tin oxide (ZTO), gallium zinc oxide (GZO), indium tungsten oxide (IWO), zinc oxide (ZnO), indium zinc oxide (IZO), aluminum gallium arsenide (AlGaAs), gallium nitride (GaN), gallium phosphide (GaP), gallium arsenide (GaAs), gallium arsenide phosphide (GaAsP), diamond-like carbon film (DLC), or graphene.

FIG. 11 is a graph showing the relationship between wavelength and reflectivity of the light receiving elements of the embodiment and the comparative example. The lines in groups A and B respectively represent the relationship between wavelength and reflectivity of the light receiving elements of the first and second embodiments of the present disclosure. The structures of the light receiving elements of the first and second embodiments are roughly the same (as shown in FIG. 8), and both use III-V group semiconductors as the material of the first semiconductor stack 81. The difference is that the material of the active region 813 of the first semiconductor stack 81 of the light receiving element of the first embodiment is In _0.51 Ga _0.49 P, and the material of the first semiconductor stack 81 of the light receiving element of the second embodiment is (Al _0.1 Ga _0.9 ) _0.5 In _0.5 P. The lines in groups C and D represent the relationship between wavelength and reflectivity of the light receiving elements of the first and second comparative examples, respectively. The light receiving elements of the comparative examples all use group IV semiconductor stacks as the material of the semiconductor stacks, such as silicon (Si).

Please refer to Figures 12A and 12B, which are cross-sectional schematic diagrams of the light receiving elements of the first and second comparative examples, respectively. Figures 12A and 12B are for illustration only, and the light receiving elements of the first and second comparative examples may include other components. The light receiving element of the first comparative example includes a silicon semiconductor layer L1, a first electrode pad L2, and a second electrode pad L3, which are respectively located on opposite sides of the silicon semiconductor layer L1. The structure of the light receiving element of the second comparative example is similar to that of the light receiving element of the first comparative example, except that the light receiving element of the second comparative example further includes a Bragg reflection layer L4 on the main light absorption surface S of the light receiving element. The Bragg reflection layer L4 includes a plurality of first layers and a plurality of second layers overlapped with each other. The refractive index of the material of the first layer is different from the refractive index of the material of the second layer, and the refractive index between the two exceeds 0.8 to achieve a better filtering effect. For example, the materials of the first layer and the second layer are silicon dioxide (SiO ₂ ) and titanium dioxide (TiO ₂ ) respectively. The wavelength and reflectivity spectrum of the light receiving element in Figure 11 is measured using the HITACHI brand U-4100 instrument.

Referring to the A and B groups of lines in FIG. 11, in the first and second embodiments, the light receiving element has a reflectivity of less than 20% for light in the range of 400nm to 800nm. Referring to the C and D groups of lines in FIG. 11, the light receiving element of the first and second comparative examples has a significantly higher reflectivity for light in the range of 400nm to 800nm, for example: the C group of lines has two peaks at 450nm with a reflectivity of 44% and 680nm with a reflectivity of 37%, and the D group of lines has a reflectivity of more than 80% for light in the range of 650nm to 1000nm. In addition, the reflectivity of the light receiving element of the first and second embodiments has almost no fluctuation in the receiving wavelength band of green light (wavelength range of 500nm to 580nm), while the light receiving element of the second comparative example (D group of lines) has a fluctuation wavelength of about 15 to 20nm in the above receiving wavelength band. This fluctuation difference is due to the light receiving element of the second comparative example having a Bragg reflection layer. The above-mentioned fluctuation wavelength is the wavelength difference between two adjacent peaks or the wavelength difference between two troughs within the wavelength range.

Figure 13 is a graph showing the relationship between the wavelength and external quantum efficiency (EQE) of the light receiving elements of the first and second embodiments (groups A and B of lines) and the first and second comparative examples (groups C and D of lines). Referring to group A of lines, the wavelength at which the light receiving element of the first embodiment has the maximum external quantum efficiency is 475 nm, and the external quantum efficiency is approximately 92%. Referring to group B of lines, the wavelength at which the light receiving element of the second embodiment has the maximum external quantum efficiency is 477 nm, and the external quantum efficiency is approximately 85%. Referring to group C of lines, the wavelength at which the light receiving element of the first comparative example has the maximum external quantum efficiency is 840 nm, and the external quantum efficiency is approximately 74%. Referring to group D of lines, the wavelength at which the light receiving element of the second comparative example has the maximum external quantum efficiency is 620 nm, and the external quantum efficiency is approximately 75%. .

Referring to the lines in group C, the light receiving element of the first comparative example includes a Group IV semiconductor stack and does not have a Bragg reflection layer (refer to the structure of Figure 12A). The external quantum efficiency at a wavelength of 500nm to 700nm is 53% to 70%, and the external quantum efficiency at a wavelength between 700nm and 1000nm is greater than 60%, at 70% to 74%. Referring to the D group of lines, the light receiving element of the second comparative example includes a group IV semiconductor stack and has a Bragg reflection layer L4 located on the main light absorption surface S, and the Bragg reflection layer L4 is designed to reflect light with a wavelength between 700 nm and 1000 nm, that is, the Bragg reflection layer L4 is used to filter light in a non-receiving band (for the relevant description of the non-receiving band, please refer to the subsequent paragraphs), so most of the incident light in the above range can be blocked from entering the light receiving element of the second comparative example to generate an electrical signal. Therefore, the external quantum efficiency of the light receiving element of the second comparative example at wavelengths between 500 nm and 680 nm is 52% to 75%, and the external quantum efficiency at wavelengths between 700 nm and 1000 nm is less than 40%. However, in the first and second embodiments, the light receiving element has an external quantum efficiency greater than 70%, preferably greater than 78%, and more preferably greater than 83% for light in the wavelength range of 500 nm to 580 nm. The light receiving element of the first embodiment has an external quantum efficiency greater than 90% in the above wavelength range (500 nm to 580 nm). In the absence of a Bragg reflection layer, the light receiving element of the first and second embodiments has an external quantum efficiency less than 10%, preferably less than 3% for light in the wavelength range of 700 nm to 1000 nm. Although the light receiving elements of the first and second embodiments and the first and second comparative examples have an external quantum efficiency greater than 40% when the receiving band is the green light band (the range of 500 nm to 580 nm), when the detection environment has infrared light with a wavelength of 700 nm to 800 nm, the light receiving elements of the first and second embodiments and the second comparative example are less susceptible to the impact and improve the accuracy of the sensing results. The light receiving elements of the first and second embodiments and the first and second comparative examples have a higher signal ratio, and the definition of the signal ratio will be explained later. In addition, compared with the second comparative example, the light receiving elements of the first and second embodiments can omit the complicated process of preparing the Bragg reflection layer to simplify the manufacturing process of the light receiving element and reduce the cost. In other words, the conversion efficiency of the light receiving element of the first and second embodiments in the receiving band is higher than that of the first and second comparative examples. When the signal to be sensed is in the receiving band and is relatively weak, the light receiving element of the first and second embodiments will still generate a corresponding photocurrent. In addition, because the external quantum efficiency of the non-receiving band is very low, the light receiving element is not disturbed by the ambient light such as red light, infrared light, etc. with a band greater than 700nm. Therefore, the output current signal of the light receiving element of the first and second embodiments will have an excellent signal-to-noise ratio, thereby making the sensing result more accurate. The wavelength and external quantum efficiency spectrum of Figure 13 was measured using the SR300 instrument of the OPTOSOLAR brand.

The signal ratio of the light receiving element can be obtained by dividing the integral area of the external quantum efficiency of a wavelength range selected in a receiving band by the integral area of the external quantum efficiency of a wavelength range selected in a non-receiving band. For example, the wavelength range selected in the receiving band is 500 nm to 550 nm in the green band, and the wavelength range selected in the non-receiving band is 600 nm to 700 nm, which is greater than the wavelength of the receiving band, and is calculated by the following formula 1, where λ is the wavelength (nm) and EQE is the external quantum efficiency (%).

Formula 1:

Referring to FIG. 13, when the receiving band is the green light band, the first and second embodiments, and the second comparative example (lines in groups A, B, and D) also have low external quantum efficiencies in the non-receiving band. According to the definition of the signal ratio, the signal ratios of the first and second embodiments are greater than the signal ratio of the second comparative example, and the signal ratios of the first and second embodiments are greater than 1.4, preferably greater than 1.6, while the signal ratio of the light receiving element of the second comparative example does not exceed 1.2. Specifically, the signal ratio of the first embodiment is 1.63, the signal ratio of the second embodiment is 4.8, and the signal ratio of the second comparative example is 1.15.

Referring to Figure 13, when the receiving band is the green light band, the external quantum efficiency of the light receiving element of the first comparative example (line group C) without a Bragg reflection layer on the upper surface is less than the external quantum efficiency of the non-receiving band. The light receiving element of the second comparative example (line group D) has a Bragg reflection layer on the upper surface, so only a small amount of light in the non-receiving band enters the light receiving element for absorption and conversion into electrical signals, making the external quantum efficiency of the receiving band also much greater than the external quantum efficiency of the non-receiving band, and the difference is ≧40% and ≦75%. In contrast, the light receiving element of the embodiment of the present invention does not have a Bragg reflection layer and its external quantum efficiency in the non-receiving band is relatively low. Therefore, when light in both the receiving band and the non-receiving band enters the light receiving element, the difference between the external quantum efficiency of the receiving band and the external quantum efficiency of the non-receiving band can be ≧75%, preferably ≧80%, and even more preferably ≧85%.

Referring to the A-group lines in FIG. 13 , the light receiving element of the first embodiment has a wavelength (WA0) of maximum external quantum efficiency in a receiving band (e.g., green light of 500-580 nm) and a wavelength ( _WA1 ) at which the external quantum efficiency drops to 2% in a _non -receiving band greater than the receiving band, _WA0 and _WA1 are separated by _WA ; _WA1 ≧ _WA0 ; 0 nm＜ _WA (= _WA1 - _WA0 ) ≦250 nm, preferably 0 nm＜ _WA ≦220 nm. For example, _WA0 is about 500 nm, _WA1 is about 680 nm, and _WA is about 180 nm. Referring to the B group of lines, the wavelength (W _B0 ) of the maximum external quantum efficiency of the light receiving element of the second embodiment in the receiving band (e.g., green light of 500-580 nm) is separated from the wavelength (W _B1 ) at which the external quantum efficiency drops to 2% in the non-receiving band by W _B ; W _B1 ≧W _B0 ; 0 nm＜W _B (=W _B1 –W _B0 ) ≦200 nm, preferably 0 nm＜W _B ≦180 nm. For example, W _B0 is about 500 nm, W _B1 is about 630 nm, and W _B is about 130 nm.

The main light absorbing surface of the light receiving element of the first embodiment and the second embodiment has an area _MA (mm ² ) ≤ 6.5, preferably _MA (mm ² ) ≤ 5, and more preferably _MA (mm ² ) ≤ 4, for example: 3 mm ² , 2.25 mm ² , 1 mm ² . Within the spectral range shown in FIG. 13 , the maximum external quantum efficiencies of the light receiving elements of the first embodiment and the second embodiment are EQE _A (%) and EQE _B (%), respectively. _EQEA (%) or _EQEB (%)/ _MA ( ^mm2 )≧13, preferably _EQEA (%) or _EQEB (%)/ _MA ( ^mm2 )≧18, more preferably _EQEA (%) or _EQEB (%)/ _MA ( ^mm2 )≧20, and _EQEA (%) or _EQEB (%)/ _MA ( ^mm2 )≦95. For example: EQE _A (%) or EQE _B (%) = 92 with _MA (mm ² ) = 6.25, EQE _A (%) or EQE _B (%) = 92 with _MA (mm ² ) = 4, EQE _A (%) or EQE _B (%) = 92 with _MA (mm ² ) = 3, EQE _A (%) or EQE _B (%) = 85 with _MA (mm ² ) = 6.25, EQE _A (%) or EQE _B (%) = 85 with _MA (mm ² ) = 4, EQE _A (%) or EQE _B (%) = 85 with _MA (mm ² ) = 3.

In FIG. 13 , in the receiving wavelength range of the green light wavelength range (ie, 500 nm to 580 nm), the maximum external quantum efficiencies of the light receiving elements of the first embodiment and the second embodiment are EQE _C (%) and EQE _D (%), respectively. EQE _C (%) or EQE _D (%) / _MA (mm ² ) ≧ 13, preferably EQE _C (%) or EQE _D (%) / _MA (mm ² ) ≧ 18, more preferably EQE _C (%) or EQE _D (%) / _MA (mm ² ) ≧ 20, and EQE _C (%) or EQE _D (%) / _MA (mm ² ) ≦ 95, for example: EQE _C (%) or EQE _D (%) = 90 and _MA (mm ² ) = 6.25, EQE _C (%) or EQE _D (%) = 90 and _MA (mm ² ) = 4, EQE _C (%) or EQE _D (%) = 90 and MA (mm 2 ) = 3, EQE _C (%) or EQE _D (%) = 90 and _MA (mm ² ) = 3. （%) ＝84和_MA （mm ² ）＝6.25、 _EQEC （%) or _EQED （%) ＝84和_MA （mm ² ）＝4、 or _EQEC （%) or EQED （%) ＝84和_MA （mm ² ）＝ ₃ 。

The main light absorption surface of the light receiving element of the first comparative example has an area _MB (mm ² ) of about 5 and a maximum external quantum efficiency EQE _E , and the main light absorption surface of the light receiving element of the second comparative example has an area M _C (mm ² ) of about 9 and a maximum external quantum efficiency EQE _F . In the spectral range shown in FIG. 13 , the maximum external quantum efficiency EQE _E (%) of the light receiving element of the first comparative example has a ratio of EQE _E (%)/ _MB (mm ² ) to the area _MB of about 14, and the maximum external quantum efficiency EQE _F (%) of the light receiving element of the second comparative example has a ratio of EQE _F (%)/ _MB (mm ² ) to the area M _C of about 8, which are both smaller than the ratios of the first and second embodiments. In the range of the receiving wavelength band being the green light wavelength band (i.e., 500 nm to 580 nm), the maximum external quantum efficiencies of the light receiving elements of the first comparative example and the second comparative example are EQE _G (%) and EQE _H (%), respectively. The maximum external quantum efficiency EQE _G (%) of the light receiving element of the first comparative example has a ratio to the area _MB , EQE _H (%)/ _MB (mm ² ) of approximately 11, and the maximum external quantum efficiency EQE _G (%) of the light receiving element of the second comparative example has a ratio to the area M _C , EQE _H (%)/ _MB (mm ² ) of approximately 7, both of which are smaller than the ratios of the first and second embodiments.

Referring to Figures 11 and 13, referring to the A and B groups of lines, the reflectivity of the light receiving elements of the first and second embodiments for light with a wavelength of 530 nm is less than 5%, for example, 2.47% and 2.36% respectively, and the reflectivity of the light receiving elements of the first and second comparative examples for light with a wavelength of 530 nm is greater than 9%, for example, 14.13% and 9.75% respectively. In addition, the external quantum efficiency of the light receiving elements of the first and second embodiments for light with a wavelength of 530 nm is greater than 80%, for example, 89.88% and 81.42% respectively. With reference to the C and D groups of lines, the external quantum efficiency of the light receiving elements of the first and second comparative examples for light with a wavelength of 530 nm is less than 65%, for example, 55.81% and 59.98% respectively.

Figures 14A and 14B are simplified three-dimensional schematic diagrams and top views of another embodiment of the light receiving element of the present disclosure. Similar to the light receiving element 8 of the above-mentioned embodiment, the light receiving element 8a of this embodiment includes a substrate 82 and a first semiconductor stack 81 thereon, but the difference is that the light receiving element 8a of this embodiment further includes a second semiconductor stack 81a located between the first semiconductor stack 81 and the substrate 82. The second semiconductor stack 81a and the first semiconductor stack 81 of this embodiment include a III-V group semiconductor compound as an active region for absorbing light. The structure of the second semiconductor stack 81a can be the same as that of the first semiconductor stack 81, for example, including a first type semiconductor structure, an active region and a second type semiconductor structure (not shown). Its structure can also be different from that of the first semiconductor stack 81, which is not limited here.

Furthermore, the light receiving element 8a includes first electrode pads 83, 83a and second electrode pads 84, 84a. The first electrode pad 83 and the second electrode pad 84 are located on a side of the first semiconductor stack 81 away from the substrate 82, and are electrically connected to the first semiconductor stack 81, thereby transmitting a first photocurrent generated by the first semiconductor stack 81 absorbing light of a first wavelength. The first electrode pad 83a and the second electrode pad 84a are located on a side of the second semiconductor stack 81a away from the substrate 82, and are electrically connected to the second semiconductor stack 81a, thereby transmitting a second photocurrent generated by the second semiconductor stack 81a absorbing light of a second wavelength. The first semiconductor stack 81 includes a recessed area C1 to expose the first type semiconductor structure 811, and the first electrode pad 83 and the second electrode pad 84 are respectively located on the second type semiconductor structure 812 and the recessed area C1. Similarly, the second semiconductor stack 81a includes a recessed area C2 to expose the first type semiconductor structure, and the first electrode pad 83a and the second electrode pad 84a are respectively located on the second type semiconductor structure and the recessed area C2.

As described above, the first wavelength may be equal to, less than, or greater than the second wavelength. In other words, the energy gap of the active region of the second semiconductor stack 81a is different from or the same as the energy gap of the active region 813 of the first semiconductor stack 81. Preferably, the energy gap of the active region 813 of the first semiconductor stack 81 is greater than the energy gap of the active region 813 of the second semiconductor stack 81a. The energy gap of the active region 813 of the first semiconductor stack 81 of the present embodiment is 2.138eV~2.58eV, so as to absorb light in the wavelength range of 480nm~580nm. The energy gap of the active region 813 of the second semiconductor stack 81a is 1.77eV~2.138eV, so as to absorb light in the wavelength range of 580nm~700nm. For example, the material of the active region 813 of the first semiconductor stack 81 is InGaP with an energy gap of 2.25eV, which can absorb green light of 550nm. The material of the active region of the second semiconductor stack 81a is InGaAs with an energy gap of 1.88eV, which can absorb red light of 660nm.

In another embodiment, the energy gap of the first semiconductor stack 81 is 1.65eV to 4.13eV to absorb light with a wavelength range of 300nm to 750nm, and the energy gap of the second semiconductor stack 81a is 1.21eV to 1.65eV to absorb light with a wavelength range of 750nm to 1025nm. The active region 813 of the first semiconductor stack 81 can be a material of the AlGaInP series, such as InGaP, and the active region of the second semiconductor stack 81a can be a material of the AlGaAs series or InGaAsP series, such as InGaAs.

The first comparative example is a light receiving element using silicon as a semiconductor stack, and silicon has an external quantum efficiency higher than 40% for incident light of 500nm to 1000nm. Although the light receiving element of the first comparative example can absorb 550nm and 660nm light at the same time and convert them into electrical signals like the light receiving element 8a of the present embodiment, the current signal generated by it cannot be distinguished due to the different absorbed wavelengths, that is, although the light of the above two wavelengths can be absorbed by the light receiving element of the first comparative example to generate photocurrent, it is impossible to know the exact wavelength of light in the detection environment and further information such as the intensity ratio of the two wavelengths in the detection environment through the light receiving element of the first comparative example. Compared with the first comparative example, the light receiving element 8a of this embodiment can simultaneously obtain photocurrents from incident light of different wavelengths and distinguish the wavelengths absorbed, thereby increasing the discrimination rate for detecting ambient light sources, which has advantages in application in biomedical sensing.

Figures 14C and 14D are respectively a three-dimensional schematic diagram and a top view of a light receiving element 8b of another embodiment. The light receiving element 8b of this embodiment is substantially the same as the light receiving element 8a, except that the arrangement of the first electrode pads 83, 83a and the second electrode pads 84, 84a, 84b and the shape of the first semiconductor stack 81 are different. Specifically, the first semiconductor stack 81 of this embodiment has a side wall W1 coplanar with the side wall W2 of the second semiconductor stack 81a, whereby, from the top view, the first electrode pads 83, 83a and the second electrode pads 84, 84a can be arranged in a straight line. Therefore, the first semiconductor stack 81 of the light receiving element 8b of this embodiment has a larger light absorption surface than the light receiving element 8a of Figures 14A and 14B to increase the photoelectric conversion efficiency.

Figures 14E and 14F are respectively a three-dimensional schematic diagram and a top view of a light receiving element 8c of another embodiment. The light receiving element 8c of this embodiment is substantially the same as the light receiving element 8b, except that the first electrode pad 83 and the second electrode pad 84 of this embodiment are disposed between the first electrode pad 83a and the second electrode pad 84a. As with the light receiving element 8b of Figures 14C and 14D, the first semiconductor stack 81 of the light receiving element 8c has a larger light absorption surface than the light receiving element 8a of Figure 14B, thereby increasing the photoelectric conversion efficiency.

Figures 15A and 15B are a three-dimensional schematic diagram and a top view of another embodiment of the light receiving element 8d of the present disclosure. Similar to the light receiving element 8a of the above embodiment, the light receiving element 8d of the present embodiment includes a substrate 82 and a second semiconductor stack 81a and a first semiconductor stack 81 sequentially disposed thereon, but the difference is that the light receiving element 8d of the present embodiment further includes a third semiconductor stack 81b disposed between the second semiconductor stack 81a and the substrate 82. The third semiconductor stack 81b, the second semiconductor stack 81a, and the first semiconductor stack 81 of this embodiment include III-V group semiconductor compounds as active regions for absorbing light. The structure of the third semiconductor stack 81b can be the same as that of the first semiconductor stack 81, for example, including a first type semiconductor structure, an active region, and a second type semiconductor structure (not shown), but this is not limited here.

The light receiving element 8d further includes a first electrode pad 83b and a second electrode pad 84b located on a side of the third semiconductor stack 81b away from the substrate 82, and electrically connected to the third semiconductor stack 81b, thereby transmitting a third photocurrent generated by the third semiconductor stack 81b absorbing the third wavelength of light. The third semiconductor stack 81b includes a recessed area C3 to expose the second type semiconductor structure, and the first electrode pad 83b and the second electrode pad 84b are located on the first type semiconductor structure and the recessed area C3, respectively.

As described above, the third wavelength is equal to, greater than, or less than the second wavelength and the first wavelength. In other words, the energy gap of the third semiconductor stack 81b is the same as or different from the energy gaps of the first semiconductor stack 81 and the second semiconductor stack 81a. Preferably, the energy gap of the third semiconductor stack 81b is smaller than that of the second semiconductor stack 81a, and the energy gap of the second semiconductor stack 81a is smaller than that of the first semiconductor stack 81. The energy gap of the first semiconductor stack 81 of the present embodiment is 2.138eV to 2.58eV, so as to absorb light with a wavelength range of 480nm to 580nm. The energy gap of the second semiconductor stack 81a is 1.77eV to 2.138eV, so as to absorb light with a wavelength range of 580nm to 700nm. The energy gap of the third semiconductor stack 81b is 0.73eV to 1.55eV, so as to absorb light with a wavelength range of 800nm to 1696nm. For example, the material of the active region 813 of the first semiconductor stack 81 is 2.25 The material of the active region of the second semiconductor stack 81a is InGaP with a band gap of 1.88 eV, which can absorb 550 nm green light. The material of the active region of the third semiconductor stack 81b is InGaAs with a band gap of 0.95 eV, which can absorb 1300 nm infrared light.

Since the light receiving element 8b in this embodiment has the first semiconductor stack 81, the second semiconductor stack 81a and the third semiconductor stack 81b with different energy gaps, it is able to absorb incident light of different wavelengths, thereby simultaneously detecting light of multiple wavelengths in the environment.

Figures 15C and 15D are respectively a simplified three-dimensional diagram and a top view of another embodiment of the light receiving element 8e. The light receiving element 8e of this embodiment is roughly the same as Figures 15A and 15B, and the difference lies in the arrangement of the first electrode pads 83, 83a, 83b, the second electrode pads 84, 84a, 84b and the shapes of the first semiconductor stack 81 and the second semiconductor stack 81a. In detail, the first semiconductor stack 81 has a side wall W1 that is coplanar with the side wall W2 of the second semiconductor stack 81a, and. The second semiconductor stack 81a has a side wall W2 coplanar with the side wall W3 of the third semiconductor stack 81b, whereby, from the top view, the first electrode pads 83, 83a, 83b and the second electrode pads 84, 84a, 84b can be arranged in a straight line. Therefore, the light receiving element 8e of this embodiment has a larger first semiconductor stack 81 and second semiconductor stack 81a than the light receiving element 8d of FIGS. 15A and 15B, thereby increasing the photoelectric conversion efficiency.

FIG. 16 is a cross-sectional view of a semiconductor element 9 of an embodiment of the present disclosure. The semiconductor element 9 may be a light receiving element. The semiconductor element 9 includes a first semiconductor stack 91 and a second semiconductor stack 92 located on the first semiconductor stack 91, and an intermediate structure 93 located between the first semiconductor stack 91 and the second semiconductor layer 92. The semiconductor element 9 in this embodiment further includes a substrate 94, and the first semiconductor stack 91, the intermediate structure 93 and the second semiconductor stack 92 are sequentially located on the substrate 94. The structures of the first semiconductor stack 91 and the second semiconductor layer 92 may be the same as or different from the first semiconductor stack 81 in the above-mentioned embodiment. In detail, the first semiconductor stack 91 includes a first type semiconductor structure 911, an active region 912, and a second type semiconductor structure 913 sequentially disposed on a substrate 94; the second semiconductor layer 92 includes a first type semiconductor structure 921 away from the first semiconductor layer 91, an active region 922, and a second type semiconductor structure 923 adjacent to the first semiconductor stack 91. The absorption energy gap of the active region 912 of the first semiconductor stack 91 can be selected to be the same as or different from the absorption energy gap of the active region 922 of the second semiconductor stack 92. In this embodiment, the absorption energy gap of the active region 912 of the first semiconductor stack 91 is smaller than the absorption energy gap of the active region 922 of the second semiconductor stack 92, thereby generating different current signals for light of different wavelength bands. The photocurrent generated by the first semiconductor stack 91 is conducted by a first electrode pad 914 and a second electrode pad 915, and the photocurrent generated by the second semiconductor stack 92 is conducted by a first electrode pad 924 and a second electrode pad 925. In addition, the first-type semiconductor structures 911 and 921 have the same conductivity type, for example, both are N-type, and the second-type semiconductor structures 913 and 923 have the same conductivity type, for example, both are P-type.

The intermediate structure 93 includes a high conductivity layer 931, a first shielding layer 932 and a second shielding layer 933. The first shielding layer 932 is located between the high conductivity layer 931 and the second type semiconductor structure 913 of the first semiconductor stack 91, and the second shielding layer 933 is located between the high conductivity layer 931 and the second type semiconductor structure 923 of the second semiconductor stack 92. The material of the high conductivity layer 931 may be metal, alloy or highly doped semiconductor layer. When the material of the high conductivity layer 931 is a highly doped semiconductor layer, the dopant doped in the high conductivity layer 931 may make the highly doped layer 931 have the same or different conductivity type as the first type semiconductor structure.

When one of the semiconductor stacks absorbs light, electron-hole pairs are generated therein, and the electron holes will correspondingly generate induced charges in the intermediate structure 93. If the induced charges accumulate in the intermediate structure 93, it will have an adverse effect on the semiconductor element 9. The high conductivity layer 931 of the intermediate structure 93 can prevent the induced charges from accumulating in the intermediate structure 93. In particular, when the first semiconductor stack 91 and the second semiconductor stack 92 are generated with pulsed light of different frequencies, the design of the high conductivity layer 931 is important to avoid current crosstalk between the two photocurrents. For example, if the high-conductivity layer 931 is not provided, when the first semiconductor stack 91 is irradiated with light of a first frequency, the second semiconductor stack 92 will generate induced charges, causing noise in the output electrical signal of the second semiconductor stack 92. In short, if the high-doped layer 931 is not provided, the first semiconductor stack 91 and the second semiconductor stack 92 will be interfered by each other's actions, resulting in changes in the frequency, amplitude, waveform, etc. of the electrical signal. In addition, the first shielding layer 932 and the second shielding layer 933 are used to electrically isolate the first semiconductor stack 91 and the second semiconductor stack 92, so as to achieve the effect of independently controlling the first semiconductor stack 91 and the second semiconductor stack 92. In this embodiment, the dopant concentration of the high conductive layer 931 is greater than that of the first type semiconductor structure 913, 923, and the dopant concentration of the high doped layer 931 is greater than 1x10 ¹⁷ cm ^-3 . In this embodiment, the resistance values of the first shielding layer 932 and the second shielding layer 933 are both greater than 1x10 ⁶ ohms. In addition, in order to allow light to irradiate the first semiconductor stack 91, the intermediate structure 93 preferably has a high transmittance for the receiving band of the first semiconductor stack 91, for example, a transmittance greater than 85%.

The first semiconductor stack 91, the intermediate structure 93 and the second semiconductor stack 92 of this embodiment can preferably be obtained by epitaxial continuous growth, and the process steps of bonding the first semiconductor stack 91 and the second semiconductor stack 92 can be omitted to achieve the effect of saving process costs. However, in other embodiments, the first semiconductor stack 91, the intermediate structure 93 and the second semiconductor stack 92 can also be bonded together through transfer and bonding processes. In another embodiment, the intermediate structure 93 may include a first first-type semiconductor layer, a second-type semiconductor layer, and a second first-type semiconductor layer stacked in sequence on the second-type semiconductor structure 913 of the first semiconductor stack 91 to form an NPN structure or a PNP structure, which can also achieve the above-mentioned purpose of preventing current crosstalk between the first semiconductor stack 91 and the second semiconductor stack 92. The intermediate structure 93 described in this embodiment can also be applied between the first semiconductor stack 81 and the second semiconductor stack 81a of the light receiving elements 8a-8e, and/or between the second semiconductor stack 81a and the third semiconductor stack 81b of the light receiving elements 8d-8e.

It should be understood that the above-mentioned embodiments of the present invention can be combined or replaced with each other under appropriate circumstances, and are not limited to the specific embodiments described. The embodiments listed in the present invention are only used to illustrate the present invention and are not used to limit the scope of the present invention. Any obvious modification or change made by anyone to the present invention does not deviate from the spirit and scope of the present invention.

1: Wearable device 100, 101, 102, 103, 200, 201, 202, 203, 204: Optical sensing module 205, 206A, 206B, 207A, 207B, 208A, 208B: Optical sensing module 401, 400, 601, 602, 603, 604, 605, 701, 702: Optical sensing module 111, 711: First light emitting element 112, 712: Second light emitting element 113, 114, 115, 116, 211, 214, 411, 412, 611: Light emitting element 131, 231, 431, 631: Light receiving element 120, 220, 420, 620, 720: carrier 121, 721: housing 122, 123, 722: baffle 124, 724: first space 125, 725: second space 126: third space G: interval 224: carrier 221, 621: first baffle 222, 622: second baffle 223, 623: third baffle 225, 226, 227', 625, 626: space 212, 232: first side surface 213, 233: second side surface 241, 242: light absorbing layer 243, 244: reflective layer 227, 228, 229, 230, 627, 628, 629, 630: inner surface θ ₁ : first tilt angle θ ₂ : second tilt angle 2211, 2232: first outer surface 2212, 2221, 2222, 2231: inner surface 2223, 2233: first portion 2224, 2234: second portion 251: first outermost wall 252: second outermost wall 253: third outermost wall 254: fourth outermost wall 2511, 2512, 2552, 2553: left end portion 2521, 2522, 2572, 2573: right end portion 2531, 2541, 2524, 2514, 2563, 2564: middle portion 2513, 2554: leftmost outer surface 2523, 2574: rightmost outer surface 2532, 2533: upper end 2534: uppermost outer surface 2542, 2543: Lower end 2544: Lower outer surface 255: First barrier wall structure 256: Second barrier wall structure 257: Third barrier wall structure 2551, 2561, 2562, 2571: One side 2081, 624: Lower surface 2111, 2311, 6111, 6311: First electrode 2112, 2312, 6112, 6312: Second electrode 402 : artery 441: amplifier 442: filter 443: ADC circuit 450: signal processing module 451: storage device 452: processor 460: current control circuit 501: first wave crest 502: first wave valley 503: second wave crest 504: second wave valley 612: light emitting surface 613: support structure 632: receiving surface 641: first supporting surface 642: second supporting surface 644: connecting device H1, H2: distance T: height 6441, 6442: conductive through hole 713: third light emitting element 731: first light receiving element 732: second light receiving element 733: third light receiving element 8, 8a, 8b, 8c, 8d, 8e: light receiving element 81: first semiconductor stack 81a: second semiconductor stack 8 1b: third semiconductor stack 811: first type semiconductor structure 812: second type semiconductor structure 813: active region 814: buffer layer 815: first barrier layer 816: second barrier layer 82: substrate 83, 83a, 83b: first electrode pad 84, 84a, 84b: second electrode pad 85: contact layer 86: protective layer 9: semiconductor element 91: first semiconductor Body stack 911: first type semiconductor structure 912: active region 913: second type semiconductor structure 914: first electrode 915: second electrode 92: second semiconductor body stack 921: first type semiconductor structure 922: active region 923: second type semiconductor structure 924: first electrode 925: second electrode 93: intermediate structure 931: high conductivity layer 932: first Shielding layer 933: second shielding layer S: main light absorbing surface S1: first surface S2: second surface S3: side surfaces S31, S32, S33: side wall T1: geometric center T2: edge P1, P2: protrusions C1, C2, C3: recess L1: silicon semiconductor layer L2: first electrode pad L3: second electrode pad L4: Bragg reflection layer B, B1, B2: body

FIG. 1A is a top view of an optical sensing module according to an embodiment of the present invention. FIG. 1B is a top view of an optical sensing module according to another embodiment of the present invention. FIG. 1C is a top view of an optical sensing module according to another embodiment of the present invention. FIG. 2A is a schematic diagram of an optical sensing module according to an embodiment of the present invention placed in a watch. FIG. 2B is a schematic diagram of an optical sensing module according to another embodiment of the present invention placed in a watch. FIG. 3A is a partial cross-sectional view of an optical sensing module according to an embodiment of the present invention. FIG. 3B is a partial cross-sectional view of an optical sensing module according to another embodiment of the present invention. FIG. 3C is a partial cross-sectional view of an optical sensing module according to another embodiment of the present invention. Figure 3D is a partial cross-sectional view of an optical sensing module according to another embodiment of the present invention. Figure 3E is a partial cross-sectional view of an optical sensing module according to another embodiment of the present invention. Figure 3F is a partial cross-sectional view of an optical sensing module according to another embodiment of the present invention. Figure 3G is a partial cross-sectional view of an optical sensing module according to another embodiment of the present invention. Figure 3H is a top view of an optical sensing module according to another embodiment of the present invention. Figure 3I is a top view of an optical sensing module according to another embodiment of the present invention. Figure 3J is a partial cross-sectional view of an optical sensing module according to another embodiment of the present invention. Figure 3K is a top view of an optical sensing module according to another embodiment of the present invention. Figure 3L is a partial cross-sectional view of an optical sensing module according to another embodiment of the present invention. FIG. 3M is a partial cross-sectional view of an optical sensing module according to another embodiment of the present invention. FIG. 4A is a schematic diagram of using an optical sensing module according to an embodiment of the present invention to be placed on a wrist for measurement. FIG. 4B is a schematic diagram of a circuit module of an optical sensing system according to an embodiment of the present invention. FIG. 5A is a photoplethysmography (PPG). FIG. 5B is a comparison table of the light receiving element according to an embodiment of the present invention and the light receiving element of a control group in an optical sensing system. FIG. 6A is a partial cross-sectional view of an optical sensing module according to another embodiment of the present invention. FIG. 6B is a partial cross-sectional view of an optical sensing module according to another embodiment of the present invention. FIG. 6C is a partial cross-sectional view of an optical sensing module according to another embodiment of the present invention. FIG. 6D is a partial cross-sectional view of an optical sensing module according to another embodiment of the present invention. FIG. 6E is a partial cross-sectional view of an optical sensing module according to another embodiment of the present invention. FIG. 7A is a top view of an optical sensing module according to another embodiment of the present invention. FIG. 7B is a top view of an optical sensing module according to another embodiment of the present invention. FIG. 8 is a cross-sectional view of a light receiving element according to an embodiment of the present invention. FIG. 9 is a top view of a light receiving element according to an embodiment of the present invention. FIG. 10 is a simplified three-dimensional schematic diagram of a light receiving element according to an embodiment of the present invention. FIG. 11 is a graph showing the relationship between wavelength and reflectivity of the light receiving elements of the embodiment and the comparative example. FIG. 12A is a cross-sectional view of the light receiving element of the first comparative example. FIG. 12B is a cross-sectional view of the light receiving element of the second comparative example. FIG. 13 is a graph showing the relationship between the wavelength and the external quantum efficiency of the light receiving element of the embodiment and the comparative example. FIG. 14A is a simplified three-dimensional schematic diagram of a light receiving element according to an embodiment of the present invention. FIG. 14B is a top view of a light receiving element according to another embodiment of the present invention. FIG. 14C is a simplified three-dimensional schematic diagram of a light receiving element according to another embodiment of the present invention. FIG. 14D is a top view of a light receiving element according to another embodiment of the present invention. FIG. 14E is a simplified three-dimensional schematic diagram of a light receiving element according to another embodiment of the present invention. FIG. 14F is a top view of a light receiving element according to another embodiment of the present invention. FIG. 15A is a simplified three-dimensional schematic diagram of a light receiving element according to another embodiment of the present invention. Figure 15B is a top view of a light receiving element according to another embodiment of the present invention. Figure 15C is a simplified three-dimensional schematic diagram of a light receiving element according to another embodiment of the present invention. Figure 15D is a top view of a light receiving element according to another embodiment of the present invention. Figure 16 is a cross-sectional schematic diagram of a semiconductor element according to an embodiment of the present invention.

100: Optical sensing module

111: First light emitting element

112: Second light emitting element

131: Light receiving element

124: First Space

125: Second Space

126: The Third Space

122, 123: Blockade

G: Interval

Claims (9)

An optical sensing module comprises: a carrier having a bottom surface; a first baffle located on the carrier and having an top surface; a first light receiving element located on the carrier and having a receiving surface; and a first light emitting element located on the carrier and having a light emitting surface; wherein the optical sensing module has at least one of the following features: (a) the first light receiving element and the first light emitting element are located between the top surface and the bottom surface, the receiving surface and the top surface have a first distance, the light emitting surface has a plane exposed to an ambient medium, and the light emitting surface and the top surface have a plane space between them. The optical sensing module has a second distance, and the first distance is different from the second distance; and (b) the optical sensing module includes a plurality of first light emitting elements, which are linearly arranged on the carrier along a first direction and separated from the first light receiving element by the first baffle, and the optical sensing module further includes a plurality of second light emitting elements, a second light receiving element and a second baffle, the plurality of second light emitting elements are linearly arranged on the carrier along the first direction and separated from the first light receiving element by the second baffle, and the second light receiving element is located on the carrier and arranged with the first light receiving element along the first direction. For example, the optical sensing module of item 1 of the patent application scope, wherein if the optical sensing module has feature (a), the bottommost surface of the first light receiving element and the bottommost surface of the first light emitting element are not at the same level. For example, in the optical sensing module of item 1 of the patent application, the surface of the first baffle facing the first light emitting element includes a reflective layer. For example, in the optical sensing module of item 1 of the patent application, the surface of the first baffle facing the first light receiving element includes a light absorbing layer. For example, in the optical sensing module of item 1 of the patent application, if the optical sensing module has feature (b), the first light receiving element and the second light receiving element are both located between the first baffle and the second baffle. For example, in the optical sensing module of item 1 of the patent application, if the optical sensing module has feature (b), the first baffle extends along the first direction. For example, the optical sensing module of item 1 of the patent application scope, wherein if the optical sensing module has feature (b), the optical sensing module further comprises a third light emitting element located on the carrier, and the plurality of first light emitting elements and the third light emitting element are not arranged along the first direction. For example, the optical sensing module of item 1 of the patent application scope, wherein if the optical sensing module has feature (b), the number of the plurality of first light emitting elements is greater than the number of the first light receiving elements. For example, in the optical sensing module of item 1 of the patent application, if the optical sensing module has feature (b), the first baffle has a first tilt angle relative to the carrier, the second baffle has a second tilt angle relative to the carrier, and the first tilt angle is the same as the second tilt angle.