TWI846125B - Semiconductor light-emitting device having distributed bragg reflector - Google Patents

Abstract

A semiconductor light-emitting device includes a substrate, a light-emitting stack formed on the substrate, and a distributed Bragg reflector adjacent to the substrate or the light-emitting stack. The light-emitting stack emits a light having a peak wavelength of λ nm. The distributed Bragg reflector includes a plurality of dielectric- layered pairs and each dielectric-layered pair includes a first dielectric layer and a second dielectric layer wherein the first dielectric layer has a first optical thickness and a first refractive index and the second dielectric layer has a second optical thickness and a second refractive index. One of the first optical thickness and the second optical is less than 0.25kλ nm and the other of the first optical thickness and the second optical thickness is greater than 0.25kλ nm wherein k is a positive odd number.

Description

Semiconductor light emitting element with Bragg reflection structure

The present invention relates to a semiconductor light-emitting element, and more particularly to a semiconductor light-emitting element having a Bragg reflection structure.

A light-emitting diode (LED) is a solid-state semiconductor device that can emit light of a specific wavelength when a predetermined bias voltage is applied. The various indicators of a light-emitting diode, such as brightness, luminous efficiency, forward voltage, thermal resistance, and light shape, can be improved by adjusting the structure. The present disclosure proposes a novel light-emitting diode structure that can adjust the light shape of the light-emitting diode to be applicable to a wider range of uses.

A semiconductor light-emitting element comprises a substrate, a light-emitting stack located on the substrate, and a Bragg reflection structure adjacent to the substrate or the light-emitting stack; wherein the light-emitting stack emits a light with a peak wavelength of λ  nm; the Bragg reflection structure comprises a plurality of dielectric layer pairs, each dielectric layer pair comprises a first dielectric layer and a second dielectric layer respectively; the first dielectric layer has a first optical thickness and a first refractive index, and the second dielectric layer has a second optical thickness and a second refractive index; one of the first optical thickness and the second optical thickness is less than 0.25kλ  nm and the other of the first optical thickness and the second optical thickness is greater than 0.25kλ  nm, and k is a positive odd number.

The embodiments of the present disclosure are described in detail below and are illustrated in the drawings. The embodiments of the present disclosure can be understood together with the corresponding drawings, and the drawings are also considered as part of the description of the embodiments of the present disclosure. It should be understood that in order to clearly present the features of the embodiments of the present disclosure, the drawings are not drawn with the actual proportions of the components.

FIG. 1 shows a first embodiment of a semiconductor light-emitting device according to the present disclosure. The semiconductor light-emitting device 10 comprises a substrate 100, a Bragg reflection structure 101, a semiconductor light-emitting stack 102, a first electrode 103, and a second electrode 104. The semiconductor light-emitting stack 102 is located on the upper surface of the substrate 100 and sequentially comprises a first conductivity type semiconductor contact layer 102a, a first conductivity type semiconductor confinement layer 102b, an active structure 102c, a second conductivity type semiconductor confinement layer 102d, and a second conductivity type semiconductor contact layer 102e. The first conductive semiconductor confinement layer 102b and the second conductive semiconductor confinement layer 102d are used to confine carriers (electrons and holes) in the active structure 102c to prevent the carriers from overflowing the active structure 102c and reducing the light-emitting efficiency. The first conductive semiconductor confinement layer 102b and the second conductive semiconductor confinement layer 102d each have a band gap greater than the band gap of the active structure 102c. The first conductive semiconductor contact layer 102a has a doping concentration greater than the doping concentration of the first conductive semiconductor confinement layer 102b. The first electrode 103 is located on the first conductive semiconductor contact layer 102a and forms a good electrical contact, such as an ohmic contact, with the first conductive semiconductor contact layer 102a. The second conductive semiconductor contact layer 102e has a doping concentration greater than the doping concentration of the second conductive semiconductor confinement layer 102d. The second electrode 104 is located on the second conductive semiconductor contact layer 102e and forms a good electrical contact, such as an ohmic contact, with the second conductive semiconductor contact layer 102e. The active structure 102c includes, for example, a multiple quantum well (MQW) structure, and emits visible light or invisible light having a peak wavelength of λ nm when driven. The first conductivity type is, for example, an n-type and the second conductivity type is, for example, a p-type.

The Bragg reflection structure 101 is located on the lower surface of the substrate 100 to reflect the light emitted by the active structure 102c. The Bragg reflection structure 101 includes a plurality of dielectric layer pairs, wherein each dielectric layer pair includes a first dielectric layer 101a and a second dielectric layer 101b, the first dielectric layer 101a has a first geometric thickness GT1, a first optical thickness OT1, and a first refractive index n1, the second dielectric layer 101b has a second geometric thickness GT2, a second optical thickness OT2, and a second refractive index n2, one of the first optical thickness OT1 and the second optical thickness OT2 is less than 0.25kλ nm and the other of the first optical thickness OT1 and the second optical thickness OT2 is greater than 0.25kλ nm, and k is a positive odd number, such as 1, 3, 5 or 7. In this embodiment, the first refractive index n1 is greater than the second refractive index n2, for example, the first refractive index n1 is between 1.7 and 3, and the second refractive index n2 is between 1.2 and 1.7; the substrate 100 includes sapphire, for example, the first dielectric layer 101a includes titanium oxide ( _TiOx ), niobium oxide ( _NbOx ) or tantalum oxide ( _TaOx ), and the second dielectric layer 101b includes silicon oxide ( _SiOx ), aluminum oxide ( _AlOx ) or magnesium fluoride ( _MgFx ). In another embodiment, the first refractive index n1 is smaller than the second refractive index n2, for example, the first refractive index n1 is greater than or equal to 1.2 and less than 1.7, and the second refractive index n2 is greater than or equal to 1.7 and less than or equal to 3; the substrate 100 comprises sapphire, for example, the first dielectric layer 101a comprises silicon oxide (SiO _x ), aluminum oxide (AlO _x ) or magnesium fluoride (MgF _x ), for example, and the second dielectric layer 101b comprises titanium oxide (TiO _x ), niobium oxide (NbO _x ) or tantalum oxide (TaO _x ), for example. In one embodiment, the number of the plurality of dielectric layer pairs is greater than 3 pairs, for example, 4 to 20 pairs. The refractive index of the substrate 100 is, for example, between the first refractive index n1 and the second refractive index n2. The optical thickness described in the present disclosure is defined as the product of the geometric thickness of the dielectric layer and its refractive index. For example, the first optical thickness OT1 of the first dielectric layer 101a is the product of its geometric thickness GT1 and its first refractive index n1. The substrate 100 of this embodiment is located between the Bragg reflection structure 101 and the semiconductor light emitting stack 102. Therefore, the light emitted downward from the semiconductor light emitting stack 102 penetrates the substrate 100 and is reflected back to the substrate 100 by the Bragg reflection structure 101 and is extracted from the surface of the semiconductor light emitting stack 102 and the side surface of the substrate 100. The Bragg reflection structure 101 has a reflectivity of at least 70% for the light emitted by the active structure 102c.

FIG. 2 shows a first example of the Bragg reflection structure 101 disclosed in the aforementioned embodiment. As shown in FIG. 2 , the Bragg reflection structure 101 includes 12 pairs of dielectric layer pairs, and includes the 1st, 2nd, 3rd, 4th…23rd and 24th layers in a stacking order, wherein the 1st, 3rd, 5th, 7th…23rd layers are first dielectric layers 101a, and the 2nd, 4th, 6th, 8th…24th layers are second dielectric layers 101b. The adjacent first dielectric layers 101a and second dielectric layers 101b form a dielectric layer pair, wherein the first refractive index n1 of the first dielectric layer 101a is greater than the second refractive index n2 of the second dielectric layer 101b; in a dielectric layer pair, the first dielectric layer 101a is closer to the substrate 100 than the second dielectric layer 101b. In this embodiment, the first optical thickness OT1 of the first dielectric layer 101a is less than 0.25kλ nm, for example, 0.2kλ nm; taking k=1 as an example, (the first optical thickness OT1/λ) is 0.2, as shown in FIG. 2. In this embodiment, the second optical thickness OT2 of the second dielectric layer 101b is greater than 0.25kλ nm, for example, 0.3kλ nm; taking k=1 as an example, (the second optical thickness OT2/λ) is 0.3, as shown in FIG. 2. In one embodiment, the first optical thickness is greater than 0.15kλ and less than 0.25kλ nm and the second optical thickness is greater than 0.25kλ and less than 0.35kλ nm. The dielectric layer pairs meeting the above optical thickness relationship are repeated continuously for more than 3 pairs. In one embodiment, the sum of the first optical thickness OP1 and the second optical thickness OP2 of each dielectric layer pair of the Bragg reflection structure 101 is (0.5±0.05) kλ nm. In one embodiment, in the Bragg reflection structure 101, the first layer is closest to the substrate 100 and the 24th layer is farthest from the substrate 100. In one embodiment, the first layer is in direct contact with the substrate 100. In another embodiment, a window layer (not shown) is selectively provided between the first layer and the substrate 100, and the window layer is transparent to the light emitted by the active structure to increase the light extraction of the semiconductor light-emitting element 10. The thickness of the window layer is greater than that of the first dielectric layer 101 a and the second dielectric layer 101 b , for example, approximately between 300 nm and 1000 nm. The material of the window layer is different from the material of the first layer of the Bragg reflection structure 101 and the material of the substrate 100 .

FIG. 3 is a schematic diagram of an optical path, showing the optical path diagram of light with a peak wavelength of λ nm passing through a dielectric layer pair of the Bragg reflection structure as in the first example and a dielectric layer pair of the Bragg reflection structure of a comparative example. Specifically, please refer to FIGS. 1 to 3 simultaneously. The active structure 102c of the semiconductor light emitting element 10 can emit light with a peak wavelength of λ nm, and a portion of the light is directed toward the substrate 100 and is reflected by the Bragg reflection structure 101 and extracted from the surface of the semiconductor light emitting stack 102 and the side surface of the substrate 100. For the convenience of explanation, FIG. 3 only illustrates a dielectric layer pair of the Bragg reflection structure 101 for illustration and uses the comparative example to illustrate the effect of the present embodiment. The difference between the Bragg reflection structures of the present embodiment and the comparative example is only in the optical thickness, which is described in detail as follows. As shown in FIG. 3 , in a dielectric layer pair, the first optical thickness OT1′ and the second optical thickness OT2′ of the comparative example are both 0.25λ nm (taking k=1 as an example); in contrast, the first optical thickness OT1 of the present embodiment is less than 0.25λ nm (taking k=1 as an example) and the second optical thickness OT2 is greater than 0.25λ nm (taking k=1 as an example), wherein the sum of the first optical thickness OT1′ and the second optical thickness OT2′ of the comparative example is equal to the sum of the first optical thickness OT1 and the second optical thickness OT2 of the present embodiment. The optical paths of the light emitted by the active structure 102c reflected by the dielectric layer pairs of the comparative example and the present embodiment are shown as paths L1 and L2, respectively. After the light enters the first dielectric layer (OT1, OT1'), it is refracted at the interface between the first dielectric layer and the second dielectric layer (OT2, OT2') and enters the second dielectric layer; then, it is reflected at the interface between the second dielectric layer and the first dielectric layer below it (not shown), that is, it is reflected at the interface between the second dielectric layer and the first dielectric layer opposite to another dielectric layer below it. As shown in FIG. 3, the horizontal displacement S2 of the optical path L2 is greater than the horizontal displacement S1 of the optical path L1, indicating that the Bragg reflection structure 101 of the present embodiment has a better light field divergence effect than the comparative example. Therefore, the use of the Bragg reflection structure 101 of the first embodiment of the present disclosure can make the semiconductor light-emitting element 10 have a wider light-emitting angle.

FIG. 4 shows a second example of the Bragg reflection structure disclosed in the first embodiment. As shown in FIG. 4 , the Bragg reflection structure 101 includes 12 pairs of dielectric layer pairs, and includes the 1st, 2nd, 3rd, 4th…23rd and 24th layers in a stacking order, wherein the 1st, 3rd, 5th, 7th…23rd layers are first dielectric layers 101a, and the 2nd, 4th, 6th, 8th…24th layers are second dielectric layers 101b. The adjacent first dielectric layers 101a and second dielectric layers 101b constitute a dielectric layer pair, wherein the first refractive index n1 of the first dielectric layer 101a is greater than the second refractive index n2 of the second dielectric layer 101b; in a dielectric layer pair, the first dielectric layer 101a is closer to the substrate 100 than the second dielectric layer 101b. In this embodiment, the first optical thickness OT1 of the first dielectric layer 101a is greater than 0.25kλ nm, for example, 0.3kλ nm; taking k=1 as an example, (the first optical thickness OT1/λ) is 0.3, as shown in FIG. 4. In this embodiment, the second optical thickness OT2 of the second dielectric layer 101b is less than 0.25kλ nm, for example, 0.2kλ nm; taking k=1 as an example, (the second optical thickness OT2/λ) is 0.2, as shown in FIG. 4. In one embodiment, the first optical thickness is greater than 0.25kλ and less than 0.35kλ nm and the second optical thickness is greater than 0.15kλ and less than 0.25kλ nm. The dielectric layer pairs meeting the above optical thickness relationship are repeated continuously for more than 3 pairs. In one embodiment, the sum of the first optical thickness OP1 and the second optical thickness OP2 of each dielectric layer pair of the Bragg reflection structure 101 is (0.5±0.05) kλ nm. In one embodiment, in the Bragg reflection structure 101, the first layer is closest to the substrate 100 and the 24th layer is farthest from the substrate 100. In one embodiment, the first layer is in direct contact with the substrate 100.

FIG. 5 is a schematic diagram of an optical path, showing the optical path diagram of light with a peak wavelength of λ nm passing through a dielectric layer pair of the Bragg reflection structure as in the second example and a dielectric layer pair of the Bragg reflection structure in the above-mentioned comparative example. Specifically, please refer to FIGS. 1, 4-5 at the same time. The active structure 102c of the semiconductor light-emitting element 10 can emit light toward the substrate 100, and the light is reflected by the Bragg reflection structure 101 and extracted from the surface of the semiconductor light-emitting stack 102 and the side surface of the substrate 100. For the convenience of explanation, FIG. 5 only illustrates a dielectric layer pair of the Bragg reflection structure 101 for illustration and uses the comparative example to illustrate the effect of the present embodiment. The difference between the Bragg reflection structures of the present embodiment and the comparative example is only in the optical thickness, which is described in detail as follows. As shown in FIG. 5 , in a dielectric layer pair, the first optical thickness OT1′ and the second optical thickness OT2′ of the comparative example are both 0.25λ nm (taking k=1 as an example); in contrast, the first optical thickness OT1 of the present embodiment is greater than 0.25λ nm and the second optical thickness OT2 is less than 0.25λ nm (taking k=1 as an example), wherein the sum of the first optical thickness OT1′ and the second optical thickness OT2′ of the comparative example is equal to the sum of the first optical thickness OT1 and the second optical thickness OT2 of the present embodiment. The optical paths of the light emitted by the active structure 102c reflected by the dielectric layer pairs of the comparative example and the present embodiment are shown as paths L1 and L3, respectively. After the light enters the first dielectric layer (OT1, OT1'), it is refracted at the interface between the first dielectric layer and the second dielectric layer (OT2, OT2') and enters the second dielectric layer; then, it is reflected at the interface between the second dielectric layer and the first dielectric layer below it (not shown), that is, it is reflected at the interface between the second dielectric layer and the first dielectric layer opposite to another dielectric layer below it. As shown in FIG. 5, the horizontal displacement S3 of the path L3 is smaller than the horizontal displacement S1 of the path L1, indicating that the Bragg reflection structure 101 of this embodiment has a better light field convergence effect than the comparative example. Therefore, the use of the Bragg reflection structure 101 of this example can make the semiconductor light-emitting element 10 have a more concentrated light-emitting angle.

FIG6 shows a second embodiment of a semiconductor light emitting device according to the present disclosure. The semiconductor light emitting device 20 comprises a substrate 100, a Bragg reflection structure 101, a semiconductor light emitting stack 102, a first electrode 103, and a second electrode 104. The semiconductor light emitting stack 102 is located on the upper surface of the substrate and sequentially comprises a first conductive type semiconductor contact layer 102a, a first conductive type semiconductor confinement layer 102b, an active structure 102c, a second conductive type semiconductor confinement layer 102d, and a second conductive type semiconductor contact layer 102e. The first conductive type semiconductor confinement layer 102b and the second conductive type semiconductor confinement layer 102d are used to confine carriers (electrons and holes) in the active structure 102c to prevent the carriers from overflowing out of the active layer 103b and reducing the light-emitting efficiency. The first conductive type semiconductor confinement layer 102b and the second conductive type semiconductor confinement layer 102d each have a band gap greater than the band gap of the active structure 102c. The Bragg reflection structure 101 is located on the second conductive type semiconductor contact layer 102e, wherein the Bragg reflection structure 101 includes an opening to expose a portion of the second conductive type semiconductor contact layer 102e. The first conductive semiconductor contact layer 102a has a doping concentration greater than that of the first conductive semiconductor confinement layer 102b, and the first electrode 103 is located on the first conductive semiconductor contact layer 102a and forms a good electrical contact, such as an ohmic contact, with the first conductive semiconductor contact layer 102a. The second conductive semiconductor contact layer 102e has a doping concentration greater than the doping concentration of the second conductive semiconductor confinement layer 102d, and the second electrode 104 is located on the second conductive semiconductor contact layer 102e and forms a good electrical contact, such as an ohmic contact, with the second conductive semiconductor contact layer 102e through the opening. The active structure 102c, for example, includes a multiple quantum well (MQW) structure, and emits visible light or invisible light with a peak wavelength of λ nm when driven. The first conductive type is, for example, an n-type and the second conductive type is, for example, a p-type.

In another embodiment, the Bragg reflection structure 101 covers not only the second conductive type semiconductor contact layer 102e, but also the surface of the semiconductor light emitting stack 102, the surface of the first conductive type semiconductor contact layer 102a, the first electrode 103, and part of the surface of the second electrode 104. The Bragg reflection structure 101 includes an opening exposing another part of the surface of the first electrode 103, and another opening exposing another part of the surface of the second electrode 104. The semiconductor light emitting element 20 further includes first and second electrode pads (not shown), which are electrically contacted with the first electrode 103 and the second electrode 104 through the two openings, respectively. The first electrode pad and the second electrode pad are respectively larger in area than the first electrode 103 and the second electrode 104. The first and second electrode pads include a single layer or a multi-layer stacked structure such as Sn/Au, Sn/AuSn, SnAg/AuSn, SnAg/Sn/AuSn, etc., made of metal materials such as Sn, Au, or alloys thereof, for forming electrical connections with the carrier during the packaging process.

The Bragg reflection structure 101 includes a plurality of dielectric layer pairs, wherein each dielectric layer pair includes a first dielectric layer 101a and a second dielectric layer 101b, respectively. The first dielectric layer 101a has a first geometric thickness GT1, a first optical thickness OT1, and a first refractive index n1, and the second dielectric layer 101b has a second geometric thickness GT2, a second optical thickness OT2, and a second refractive index n2. One of the first optical thickness OT1 and the second optical thickness OT2 is less than 0.25kλ nm and the other of the first optical thickness and the second optical thickness is greater than 0.25kλ nm, and k is a positive odd number, such as 1, 3, 5 or 7. In this embodiment, the first refractive index n1 is greater than the second refractive index n2. For example, the first refractive index n1 is greater than or equal to 1.7 and less than or equal to 3, and the second refractive index n2 is greater than or equal to 1.2 and less than 1.7. The first dielectric layer 101a includes, for example, titanium oxide ( _TiOx ), niobium oxide ( _NbOx ), or tantalum oxide ( _TaOx ), and the second dielectric layer 101b includes, for example, silicon oxide ( _SiOx ), aluminum oxide ( _AlOx ), or magnesium fluoride ( _MgFx ). In another embodiment, the first refractive index n1 is smaller than the second refractive index n2, for example, the first refractive index n1 is greater than or equal to 1.2 and less than 1.7, and the second refractive index n2 is greater than or equal to 1.7 and less than or equal to 3; the first dielectric layer 101a includes, for example, silicon oxide ( _SiOx ), aluminum oxide ( _AlOx ) or magnesium fluoride ( _MgFx ), and the second dielectric layer 101b includes, for example, titanium oxide ( _TiOx ), niobium oxide ( _NbOx ) or tantalum oxide ( _TaOx ). In each embodiment, the dielectric layer pairs that meet the size relationship of the optical thickness of the embodiment are continuously repeated for more than 3 pairs, for example, 4 to 20 pairs. The semiconductor light emitting stack 102 of this embodiment is located between the Bragg reflection structure 101 and the substrate 100. Therefore, the light emitted by the active structure 102c is reflected back to the semiconductor light emitting stack 102 by the Bragg reflection structure 101, and penetrates the substrate 100 and is extracted from the side surface of the semiconductor light emitting stack 102, the lower surface 100u of the substrate 100, and the side surface of the substrate 100. The Bragg reflection structure 101 has a reflectivity of 70% for the light emitted by the active structure 102c.

In one embodiment, the semiconductor light-emitting element 20 may selectively include a bottom layer (not shown) between the Bragg reflection structure 101 and the semiconductor light-emitting stack 102. That is, the bottom layer is first formed on the semiconductor light-emitting stack 102, and then the Bragg reflection structure 101 is formed on the bottom layer. The bottom layer includes a dielectric material, and its thickness is greater than the thickness of the first dielectric layer 101a and the second dielectric layer 101b. The bottom layer can provide the function of protecting the semiconductor light-emitting element 20 or protecting the semiconductor light-emitting stack 102, such as preventing external moisture from entering the semiconductor light-emitting element 20.

In another embodiment, the semiconductor light emitting element 20 may selectively include an upper layer (not shown) so that the Bragg reflection structure 101 is between the upper layer and the semiconductor light emitting stack 102. In other words, the Bragg reflection structure 101 is first formed on the semiconductor light emitting stack 102, and then the upper layer is formed. The upper layer includes a dielectric material, and its thickness is greater than the thickness of the first dielectric layer 101a and the second dielectric layer 101b. The upper layer can increase the strength of the entire Bragg reflection structure 101. For example, when the Bragg reflection structure 101 is subjected to an external force, the upper layer prevents the Bragg reflection structure 101 from being broken or damaged by the external force.

In another embodiment, before forming the Bragg reflection structure 101, a dense layer (not shown) can be formed directly on the surface of the second conductive semiconductor contact layer 102e by atomic layer deposition (ALD) to protect the semiconductor light-emitting stack 102. The material of the dense layer includes silicon oxide, aluminum oxide, uranium oxide, tantalum oxide, zirconium oxide, yttrium oxide, tantalum oxide, tantalum oxide, silicon nitride, aluminum nitride or silicon oxynitride. In this embodiment, the interface between the dense layer and the semiconductor stack 12 includes metal elements and oxygen, wherein the metal elements include aluminum, uranium, tantalum, zirconium, yttrium, tantalum, or tantalum. The dense layer has a thickness between 50 Å and 2000 Å, preferably between 100 Å and 1500 Å. In one embodiment, the dense layer can be conformally formed on the semiconductor light emitting stack 102, and can provide a better protection effect to the semiconductor light emitting stack 102 by its film properties, such as preventing moisture from entering the semiconductor light emitting stack 102, and can improve the adhesion between the Bragg reflection structure 101 and the semiconductor light emitting stack 102.

In one embodiment, the semiconductor light emitting device 20 includes a Bragg reflection structure 101, wherein the refractive index of the first dielectric layer 101a is greater than the refractive index n2 of the second dielectric layer 101b, the first optical thickness OT1 of the first dielectric layer 101a is less than 0.25kλ nm, and the second optical thickness OT2 of the second dielectric layer 101b is greater than 0.25kλ nm. As with the semiconductor light emitting device 10 of the first embodiment, the semiconductor light emitting device 20 can have a wider light emitting angle. In another embodiment, the semiconductor light emitting element 20 includes a Bragg reflection structure 101, wherein the refractive index of the first dielectric layer 101a is greater than the refractive index n2 of the second dielectric layer 101b, the first optical thickness OT1 of the first dielectric layer 101a is greater than 0.25kλ nm, and the second optical thickness OT2 of the second dielectric layer 101b is less than 0.25kλ nm. As with the semiconductor light emitting element 10 of the first embodiment, the semiconductor light emitting element 20 can have a more concentrated light emitting angle.

FIG. 7 shows a third embodiment of a semiconductor light emitting device in accordance with the present disclosure. The semiconductor light emitting device 30 is similar to the semiconductor light emitting device 20, and its Bragg reflection structure 101 is the same as the Bragg reflection structure 101 of the semiconductor light emitting device 20, except that the semiconductor light emitting device 30 does not include the substrate 100. The light emitted by the active structure 102c of this embodiment is reflected by the Bragg reflection structure 101 back to the semiconductor light emitting stack 102, and is extracted from the side surface of the semiconductor light emitting stack 102 and the upper surface 102u of the semiconductor light emitting stack 102.

In one embodiment, the semiconductor light emitting device 30 includes a Bragg reflection structure 101, wherein the refractive index of the first dielectric layer 101a is greater than the refractive index n2 of the second dielectric layer 101b, the first optical thickness OT1 of the first dielectric layer 101a is less than 0.25kλ nm, and the second optical thickness OT2 of the second dielectric layer 101b is greater than 0.25kλ nm. Like the semiconductor light emitting device 10 of the first embodiment, the semiconductor light emitting device 30 can have a wider light emitting angle. In another embodiment, the semiconductor light emitting element 30 includes a Bragg reflection structure 101, wherein the refractive index of the first dielectric layer 101a is greater than the refractive index n2 of the second dielectric layer 101b, the first optical thickness OT1 of the first dielectric layer 101a is greater than 0.25kλ nm, and the second optical thickness OT2 of the second dielectric layer 101b is less than 0.25kλ nm. As with the semiconductor light emitting element 10 of the first embodiment, the semiconductor light emitting element 30 can have a more concentrated light emitting angle.

In each of the above-mentioned embodiments, the Bragg reflection structure 101 may further include a plurality of dielectric layer pairs (not shown). Specifically, in addition to the dielectric layer pair consisting of the first dielectric layer 101a and the second dielectric layer 101b, the Bragg reflection structure 101 further includes another dielectric layer pair consisting of a third dielectric layer and a fourth dielectric layer, wherein the third dielectric layer and the first dielectric layer 101a have different optical thicknesses, and/or the fourth dielectric layer and the second dielectric layer 101b have different optical thicknesses. In one embodiment, the third dielectric layer and the first dielectric layer 101a include different materials, and/or the fourth dielectric layer and the second dielectric layer 101b include different materials. In another embodiment, the third dielectric layer and the first dielectric layer have different geometric thicknesses, and/or the fourth dielectric layer and the second dielectric layer 101b have different geometric thicknesses. The third dielectric layer has a third geometric thickness GT3, a third optical thickness OT3, and a third refractive index n3, and the fourth dielectric layer has a fourth geometric thickness GT4, a fourth optical thickness OT4, and a fourth refractive index n4. One of the third optical thickness OT3 and the fourth optical thickness OT4 is less than 0.25kλ nm and the other of the third optical thickness OT3 and the fourth optical thickness OT4 is greater than 0.25kλ nm, and k is a positive odd number.

In one embodiment, the first refractive index n1 of the first dielectric layer 101a is greater than the second refractive index n2 of the second dielectric layer 101b, and the third refractive index n3 of the third dielectric layer is greater than the fourth refractive index n4 of the fourth dielectric layer. In a dielectric layer pair, the first dielectric layer 101a is closer to the substrate 100 than the second dielectric layer 101b. In a dielectric layer pair, the third dielectric layer is closer to the substrate 100 than the fourth dielectric layer. The first optical thickness OT1 of the first dielectric layer 101a and the third optical thickness OT3 of the third dielectric layer are both less than 0.25 kλ nm, and the second optical thickness OT2 of the second dielectric layer 101b and the fourth optical thickness OT4 of the fourth dielectric layer are both greater than 0.25 kλ nm. The dielectric layer pairs meeting the above optical thickness relationship are stacked continuously in a number of three or more pairs.

In another embodiment, the first refractive index n1 of the first dielectric layer 101a is greater than the second refractive index n2 of the second dielectric layer 101b, and the third refractive index n3 of the third dielectric layer is greater than the fourth refractive index n4 of the fourth dielectric layer. In a dielectric layer pair, the first dielectric layer 101a is closer to the substrate 100 than the second dielectric layer 101b. In a dielectric layer pair, the third dielectric layer is closer to the substrate 100 than the fourth dielectric layer. The first optical thickness OT1 of the first dielectric layer 101a and the third optical thickness OT3 of the third dielectric layer are both greater than 0.25kλ nm, and the second optical thickness OT2 of the second dielectric layer 101b and the fourth optical thickness OT4 of the fourth dielectric layer are both less than 0.25kλ nm. The dielectric layer pairs meeting the above optical thickness relationship are stacked continuously in a number of three or more pairs.

In each of the above-mentioned embodiments, the substrate 100 may be an epitaxial substrate for epitaxially growing the semiconductor light-emitting stack 102 by, for example, metal organic chemical vapor deposition (MOCVD). In one embodiment, there are a plurality of protrusions separated from each other between the semiconductor light-emitting stack 102 and the substrate 100 to change the path of light to increase the light extraction efficiency. In one embodiment, the protrusions are formed by directly patterning the surface of the substrate 100 to a depth, and thus have the same composition material as the substrate 100. In another embodiment, a light-transmitting material layer is first formed on the upper surface of the substrate 100, and then the light-transmitting material layer is patterned to form the protrusions, wherein the protrusions have different composition materials from the substrate 100. Alternatively, the substrate 100 may be a bonding carrier substrate, and a bonding layer (not shown) is further included between the substrate 100 and the semiconductor light emitting stack 102. The semiconductor light emitting stack 102 originally epitaxially grown on the epitaxial substrate can be bonded to the substrate 100 through the bonding layer using wafer bonding technology. The bonding layer is transparent to the light emitted by the semiconductor light-emitting stack 102, and its material may be an insulating material, such as polyimide (PI), benzocyclobutene (BCB), perfluorocyclobutane (PFCB), magnesium oxide (MgO), Su8, epoxy resin, acrylic resin, cycloolefin polymer (COC), polymethyl methacrylate (PMMA), polyethylene terephthalate (PET), polycarbonate (PC), polyetherimide, fluorocarbon polymer, glass, aluminum oxide (AlOx), silicon oxide (SiOx), titanium oxide (TiOx), silicon nitride (SiNx) or spin-on glass (SOG).

The first conductive type semiconductor contact layer 102a, the first conductive type semiconductor confinement layer 102b, the active structure 102c, the second conductive type semiconductor confinement layer 102d, and the second conductive type semiconductor contact layer 102e all include the same series of III-V compound semiconductor materials, such as AlInGaAs series, AlGaInP series, or AlInGaN series. Among them, the AlInGaAs series can be expressed as (Al _x1 In _(1-x1) ) 1- _x2 Ga _x2 As, the AlInGaP series can be expressed as (Al _y1 In _(1-y1) ) _1-y2 Ga _y2 P, and the AlInGaN series can be expressed as (Al _z1 In _(1-z1) ) _1-z2 Ga _z2 N, where 0≦x1, y1, z1, x2, y2, z2≦1, and the same can be applied to the other series of materials not listed. The light emitted by the semiconductor light-emitting element is determined by the material composition of the active structure 102c. For example, when the material of the active structure 102c includes the AlGaInP series, infrared light with a peak wavelength λ of 700 to 1700 nm, red light with a peak wavelength λ of 610 to 700 nm, or yellow light with a peak wavelength λ of 530 to 570 nm can be emitted. When the material of the active structure 102c includes InGaN series, blue light or deep blue light with a peak wavelength λ of 400 nm to 490 nm or green light with a peak wavelength λ of 490 nm to 550 nm can be emitted. When the material of the active structure 102c includes AlGaN series, ultraviolet light with a peak wavelength λ of 250 nm to 400 nm can be emitted.

The first electrode 103 and the second electrode 104 are used to electrically connect to an external power source or an external element, and may include a transparent conductive material and/or a metal material. The transparent conductive material includes a metal oxide, a diamond-like carbon film (DLC), graphene, or a combination of the above materials. The metal material includes but is not limited to copper (Cu), aluminum (Al), indium (In), tin (Sn), gold (Au), platinum (Pt), zinc (Zn), silver (Ag), titanium (Ti), nickel (Ni), lead (Pb), palladium (Pd), germanium (Ge), chromium (Cr), cobalt (Co), cadmium (Cd), manganese (Mn), antimony (Sb), bismuth (Bi), gallium (Ga), tungsten (W), beryllium (Be), or alloys of the above materials.

FIG. 8A is a side view showing an embodiment of a light emitting device package structure 7 in accordance with the present disclosure. FIG. 8B is a cross-sectional view along line A-A' in FIG. 8A.

The light-emitting device package structure 7 includes a semiconductor light-emitting device 10, a package body 16, an opening 160, a first lead terminal 50a and a second lead terminal 50b, a metal bonding wire 14, and a light-transmitting resin 23. The first lead terminal 50a and the second lead terminal 50b are separately packaged in the package body 16, and the opening 160 exposes one end of the first lead terminal 50a and one end of the second lead terminal 50b. The semiconductor light-emitting device 10 is located in the opening 160 and on the second lead terminal 50b, and is electrically connected to the first lead terminal 50a and the second lead terminal 50b respectively by the metal bonding wire 14 (bonding wire). The light-transmitting resin 23 is filled in the opening 160, and the light-transmitting resin 23 may contain a wavelength conversion material (not shown), such as a fluorescent powder and/or a scattering material (not shown). In addition, the other end of the first lead terminal 50a and the other end of the second lead terminal 50b protrude from the outside of the package 16 to be electrically connected to an external power source or an external electronic component. As shown in FIG. 8A, the first lead terminal 50a and the second lead terminal 50b are bent and extended from one side surface of the package 16 to the other side surface adjacent thereto.

The opening 160 of the light-emitting element package structure 7 has a longitudinal shape, and a semiconductor light-emitting element 10 is installed therein. In one embodiment, the semiconductor light-emitting element 10 is longitudinally long when viewed from above. The long side direction (X-axis direction) of the opening 160 is consistent with the long side direction of the semiconductor light-emitting element 10, and the side wall 160a of the opening 160 can be an inclined surface to reflect and guide the light R emitted by the semiconductor light-emitting element 10 toward the light emitting direction of the opening, thereby increasing the luminous efficiency of the overall light-emitting element package structure 7. The longitudinally long semiconductor light-emitting element 10 is matched with the longitudinally long package structure 7, and is suitable for the backlight module of a side-projection backlight display. In one embodiment, the distance D2 between the semiconductor light emitting element 10 and the top of the side wall 160a in the Y-axis direction is smaller than the distance D1 between the semiconductor light emitting element 10 and the top of the side wall 160a in the X-axis direction. As the side projection backlight display becomes thinner and lighter, the width of the light emitting element package structure 7 in the Y-axis direction becomes smaller and smaller. Similarly, the distance D2 between the semiconductor light emitting element 10 and the top of the side wall 160a in the Y-axis direction also becomes smaller and smaller. When the distance D2 between the semiconductor light emitting element 10 and the top of the side wall 160a in the Y-axis direction is smaller, the tilt angle of the side wall 160a is closer to vertical, so that the side light emitted by the semiconductor light emitting element 10 is reflected back and forth on the side wall 160a more times, thereby increasing the proportion absorbed by the side wall 160a, and reducing the brightness of the light emitting element package structure 7. According to an embodiment of the present disclosure, the semiconductor light emitting element 10 includes the second exemplary Bragg reflection structure 101, which has a more concentrated light emitting angle, that is, the proportion of light emitted from the front of the semiconductor light emitting element 10 is higher, and the proportion of light emitted from the side is lower. Therefore, the semiconductor light-emitting element 10 is arranged in the light-emitting element package structure 7. Since the ratio of light emitted from the side of the semiconductor light-emitting element 10 is relatively small, the possibility of the side light of the semiconductor light-emitting element 10 being absorbed by the side wall 160a can be further reduced, thereby improving the brightness of the light-emitting element package structure 7. The aspect ratio of the semiconductor light-emitting element 10 described in the present disclosure can be adjusted with the design change of the light-emitting element package structure. The light-emitting elements described in the present disclosure are all applicable to a rectangular package structure whose width in the Y-axis direction is smaller than that in the X-axis direction. In one embodiment, for example, the aspect ratio of the semiconductor light-emitting element can be 2 to 1 or more, which is applicable to the light-emitting element package structure 7.

FIG. 9 shows a schematic diagram of a display device. The display device includes a frame 40, a side projection backlight module 200 and a liquid crystal panel 90. The side projection backlight module 200 includes a reflective film 80, a light guide plate 70, a carrier 22, a plurality of light emitting element packaging structures 7 and an optical diffusion sheet 46. The plurality of light emitting element packaging structures 7 and a circuit structure (not shown) are disposed on the carrier 22, and the circuit structure is used to control the light emitting element packaging structure 7. The light emitting device package structure 7 is opposite to one side of the light guide plate 70. When the light emitting device package structure 7 emits light and its light rays R enter the light guide plate 70 from the side of the light guide plate 70, the light guide plate 70 changes the direction of the light rays R and directs the light toward the optical diffuser 46, so as to provide a uniform light source to the liquid crystal panel 90 located above the optical diffuser 46. In this embodiment, the light emitting device package structure 7 including the aforementioned semiconductor light emitting device 10 is applied to the backlight module 200, and the semiconductor light emitting device 10 includes the aforementioned second exemplary Bragg reflection structure 101, which has a more concentrated light emitting angle. As can be seen from FIG. 9 , when the intensity of the light R emitted by the light-emitting element package structure 7 in the Z-axis direction is stronger and/or the light-emitting angle in the Z-axis direction is more concentrated, the brightness of the side-projection backlight module 200 can be improved.

The side projection backlight module 200 disclosed in the present application is not limited to using the aforementioned light emitting element package structure 7 including the semiconductor light emitting element 10. In other embodiments, the side projection backlight module 200 may use a light emitting element package structure including the aforementioned semiconductor light emitting element 20 or 30, the semiconductor light emitting element 20 or 30 may be packaged in the light emitting element package structure in a flip chip form, and the semiconductor light emitting element 20 or 30 also includes the aforementioned second exemplary Bragg reflection structure 101. In this way, the same effect can be obtained.

FIG. 10 shows a schematic cross-sectional view of a display device. The display device includes a direct-type backlight module 300 and a liquid crystal panel 90'. The direct-type backlight module 300 includes a reflective film 60, an optical film 46' (for example, including a diffusion film, a prism film, etc.), and a plurality of light-emitting element packaging structures 8 disposed on the reflective film 60. In this embodiment, the light-emitting element packaging structure 8 includes the aforementioned semiconductor light-emitting element 10, and the semiconductor light-emitting element 10 includes the aforementioned first example Bragg reflection structure 101, which has a more divergent light-emitting angle. The light-emitting element packaging structure 8 emits light R', and the light R' is incident from the light incident surface of the optical film 46'. The optical film 46' disperses the light R' uniformly, providing a uniform backlight source for the liquid crystal panel 90' above it. As can be seen from FIG. 10 , when the light R′ emitted by the light emitting element package structure 8 has a wider light emitting angle, the light diffusion of the optical film 46′ can be made more efficient, thereby obtaining a more uniform backlight source. In other embodiments, the direct-type backlight module 300 disclosed in the present disclosure can use a light emitting element package structure including the aforementioned semiconductor light emitting element 20 or 30, and the semiconductor light emitting element 20 or 30 can be packaged in the light emitting element package structure in a flip-chip form, and the semiconductor light emitting element 20 or 30 includes the aforementioned first example Bragg reflection structure 101. In addition, the aforementioned light emitting element package structure can be directly replaced by the semiconductor light emitting element 10, 20 or 30 without the need for additional packaging, and in this way, the same effect can be obtained.

The above embodiments are merely illustrative of the principles and effects of the present application, and are not intended to limit the present application. Any modification and variation of the above embodiments made by a person with ordinary knowledge in the technical field to which the present application belongs without violating the technical principles and spirit of the present application still falls within the scope of the present application.

10, 20, 30: semiconductor light-emitting element 7, 8: light-emitting element package structure 16: package body 160: opening 160a: side wall 22: carrier 23: light-transmitting resin 50a, 50b: wire terminal 40: frame 46, 46': optical film 60, 80: reflective film 70: light guide plate 90, 90': liquid crystal panel 100: substrate 100u: lower surface of substrate 101: Bragg reflection structure 101a: first dielectric layer 101b: second dielectric layer 102: semiconductor light-emitting stack 102a: first conductivity type semiconductor contact layer 102b: first conductivity type semiconductor confinement layer 102c: active structure 102d: second conductive type semiconductor confinement layer 102e: second conductive type semiconductor contact layer 102u: upper surface of semiconductor light-emitting layer 103: first electrode 104: second electrode 200, 300: backlight module L1, L2, L3: optical path D1, D2: spacing R, R’: light

FIG. 1 is a cross-sectional schematic diagram showing a first embodiment of a semiconductor light-emitting device in accordance with the present disclosure.

FIG. 2 shows a first example of a Bragg reflection structure according to the first embodiment of the present disclosure.

FIG. 3 is an optical schematic diagram showing the optical path diagram of light passing through the Bragg reflection structure as shown in the first example.

FIG. 4 shows a second example of the Bragg reflection structure disclosed in the first embodiment of the present disclosure.

FIG. 5 is an optical schematic diagram showing the optical path diagram of light passing through the Bragg reflection structure as shown in the second example.

FIG6 is a cross-sectional schematic diagram showing a second embodiment of a semiconductor light-emitting device in accordance with the present disclosure.

FIG. 7 is a schematic cross-sectional view showing a third embodiment of a semiconductor light-emitting element in accordance with the present disclosure.

FIG. 8A is a side view showing an embodiment of a light emitting device package structure consistent with the present disclosure.

Figure 8B is a cross-sectional view along line segment A-A’ in Figure 8A.

FIG. 9 is a schematic diagram of a display device according to an embodiment of the present disclosure.

FIG. 10 is a schematic diagram of a display device according to another embodiment of the present disclosure.

10: Semiconductor light-emitting element

100: Substrate

101: Bragg reflection structure

101a: first dielectric layer

101b: Second dielectric layer

102: Semiconductor light-emitting stack

102a: first conductive semiconductor contact layer

102b: first conductivity type semiconductor confinement layer

102c: Active structure

102d: Second conductivity type semiconductor confinement layer

102e: Second conductive type semiconductor contact layer

103: First electrode

104: Second electrode

Claims (10)

A semiconductor light-emitting element comprises: a substrate; a light-emitting stack located on the substrate and emitting a light, wherein the light has a peak wavelength of λ nm; and a Bragg reflection structure adjacent to the substrate or the light-emitting stack, wherein the Bragg reflection structure comprises a plurality of dielectric layer pairs, each dielectric layer pair comprises a first dielectric layer and a second dielectric layer, wherein the first dielectric layer has a first optical thickness and a first refractive index, and the second dielectric layer has a second optical thickness and a second refractive index; wherein one of the first optical thickness and the second optical thickness is less than 0.25 kλ nm and the other of the first optical thickness and the second optical thickness is greater than 0.25 kλ nm. nm, k is a positive odd number; wherein the first refractive index is greater than the second refractive index, and the first optical thickness is greater than 0.25kλ and the second optical thickness is less than 0.25kλ. A semiconductor light-emitting element as described in claim 1, wherein the pairs of the plurality of dielectric layer pairs are repeated continuously for more than 3 pairs. The semiconductor light-emitting element as described in claim 1, wherein the substrate is between the Bragg reflection structure and the light-emitting stack. A semiconductor light-emitting element as described in claim 1, wherein the light-emitting stack is between the substrate and the Bragg reflection structure. The semiconductor light-emitting element as described in claim 4 further includes an electrode located on the light-emitting stack and electrically connected to the light-emitting stack. The semiconductor light-emitting element as described in claim 5 further comprises an electrode pad; wherein the Bragg reflection structure covers the light-emitting stack and a portion of the surface of the electrode; and the Bragg reflection structure comprises an opening exposing another portion of the surface of the electrode, and the electrode pad forms an electrical contact with the electrode through the opening. The semiconductor light-emitting element as described in claim 4 further comprises a bottom layer between the Bragg reflection structure and the light-emitting stack; or further comprises an upper layer, wherein the Bragg reflection structure is between the upper layer and the light-emitting stack. A semiconductor light-emitting element as described in claim 1, wherein the first optical thickness is less than 0.35kλ, and the second optical thickness is greater than 0.15kλ. The semiconductor light-emitting element as described in claim 1, wherein the sum of the first optical thickness and the second optical thickness of each dielectric layer pair is (0.5±0.05)kλ. A semiconductor light-emitting element as described in claim 1, wherein the first refractive index is greater than or equal to 1.7 and less than or equal to 3; and/or the second refractive index is greater than or equal to 1.2 and less than 1.6.

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