CN105006506A - Light emitting device - Google Patents

Abstract

The present invention discloses a light-emitting device, which comprises: a light-emitting stack, comprising a first surface and a second surface opposite to the first surface, the light-emitting stack emits a light having a wavelength between 365 nanometers and 550 nanometers; and a first electrode formed on the first surface and comprising a first metal layer and a second metal layer repeatedly overlapping, wherein the first electrode has a reflectivity relative to light greater than 95%, and the thermal stability of the first metal layer is higher than that of the second metal layer, and the reflectivity of the second metal layer to light is higher than that of the first metal layer.

Description

light emitting device

technical field

The invention relates to a light emitting device, in particular to a light emitting device with a reflective layer.

Background technique

The light-emitting principle of a light-emitting diode (LED) is that electrons move between n-type semiconductors and p-type semiconductors to release energy. Because the light emitting principle of light emitting diodes is different from that of incandescent lamps that heat filaments, light emitting diodes are also called cold light sources. Furthermore, the better environmental tolerance, longer service life, lighter weight and portability, and lower power consumption of light-emitting diodes make it considered as another choice of light source in the lighting market. LEDs are used in various fields such as traffic signs, backlight modules, street lamps, and medical equipment, and have gradually replaced traditional light sources.

The light-emitting stack of the light-emitting diode is epitaxially grown on a conductive substrate or an insulating substrate. LEDs with conductive substrates can form an electrode on top of the light emitting stack, and are generally called vertical LEDs. A light emitting diode with an insulating substrate needs to expose two semiconductor layers with different polarities through an etching process, and form electrodes on the two semiconductor layers respectively, which is generally called a horizontal light emitting diode. The advantages of vertical light-emitting diodes are small electrode shading area, good heat dissipation effect, and no additional etching epitaxy process. However, the conductive substrate currently used to grow epitaxy has the problem of easily absorbing light, which affects the luminous efficiency of light-emitting diodes. The advantage of horizontal light-emitting diodes is that the insulating substrate is usually a transparent substrate, and light can be emitted from all directions of the light-emitting diode. However, there are disadvantages such as poor heat dissipation, large electrode shading area, and epitaxial etching process loss of light-emitting area.

The above light emitting diodes can be further connected to other components to form a light emitting device. The light-emitting diode can be connected to the sub-carrier through the side with the substrate, or formed between the sub-carrier and the light-emitting diode with solder or adhesive material, so as to form a light-emitting device. In addition, the sub-carrier may further include a circuit, which is electrically connected to the electrodes of the LEDs through a conductive structure such as a metal wire.

Contents of the invention

In order to solve the above problems, the present invention discloses a light-emitting device, comprising: a light-emitting stack comprising a first surface and a second surface opposite to the first surface, the light-emitting stack emits a light having a light wavelength between 365 nm and 550 nm wavelength; and a first electrode is formed on the first surface and includes a first metal layer and a second metal layer overlapping repeatedly, wherein the first electrode has a relative light reflectance greater than 95% and the first metal layer The thermal stability of the second metal layer is higher than that of the second metal layer, and the reflectivity of the second metal layer for light is higher than that of the first metal layer.

The present invention also discloses a light-emitting device, comprising: a light-emitting laminate comprising a first surface and a second surface opposite to the first surface, the light-emitting laminate emits a light having a wavelength between 365 nanometers and 550 nanometers, and The first surface includes a first portion having a first electrical property and a second portion having a second electrical property; a first electrode including a first electrode pad and a reflective laminate including a first metal layer and a first metal layer The two metal layers overlap repeatedly and are electrically connected to the first part of the first surface. The reflective laminate has a relative light reflectivity greater than 95%, wherein the thermal stability of the first metal layer is higher than that of the second metal layer, and the second metal layer has a higher thermal stability. The reflectivity of the two metal layers for light is higher than that of the first metal layer; a second electrode including a second electrode pad and an ohmic contact layer is formed on the second part of the first surface; and a carrier includes a first conductor The pad is electrically connected to the first electrode and a second conductive pad is electrically connected to the second electrode pad.

Description of drawings

1A to 1E are schematic diagrams of a manufacturing method of a light-emitting device according to a first embodiment of the present invention;

FIG. 1F is a schematic diagram of a reflective stack in the first embodiment of the present invention;

FIG. 2 is a schematic diagram of a light emitting device according to a second embodiment of the present invention.

Symbol Description

100 light fixtures

101 growth substrate

102 first semiconductor layer

104 luminous layer

106 second semiconductor layer

108 Luminous Laminations

108a first surface

108b second surface

110 current blocking layer

112 first electrode

112a first metal layer

112b second metal layer

114 barrier layer

114a first barrier layer

114b second barrier layer

116 Conductive bonding layer

118 conductive substrate

L light

120 second electrode

200 light fixtures

202 transparent substrate

203 insulating layer

204 first semiconductor layer

206 luminous layer

208 Second semiconductor layer

210 Luminous Laminations

210a first surface

210b Part I

210c Part II

210d second surface

214a first metal layer

214b second metal layer

216 barrier layer

218 carrier

220 Second conducting pad

222 The first conductive pad

224 Second electrode pad

226 first electrode pad

228 The first conductive channel

230 second conductive channel

231 ohm contacts

L ₁ light

Detailed ways

Please refer to FIG. 1A to FIG. 1E , which show a method of manufacturing a light emitting device according to a first embodiment of the present invention.

As shown in FIG. 1A , a buffer layer 103 and a light emitting stack 108 are epitaxially grown sequentially on a growth substrate 101 . The growth substrate 101 can be a transparent substrate such as sapphire, or a conductive substrate such as silicon carbide. The buffer layer 103 may include an unintentionally doped aluminum nitride, aluminum gallium nitride or gallium nitride, and the light emitting stack 108 may include gallium nitride, and the buffer layer 103 may reduce the growth substrate 101 and the light emitting stack 108 because defects due to mismatch. The light emitting stack 108 may include a first semiconductor layer 102 , a light emitting layer 104 and a second semiconductor layer 106 . The first semiconductor layer 102 and the second semiconductor layer 106 can be, for example, a cladding layer or a confinement layer, which can provide electrons and holes respectively, so that the electrons and holes can combine in the light-emitting layer 104 to emit light. . The materials of the first semiconductor layer 102, the light-emitting layer 104, and the second semiconductor layer 106 may include III-V group semiconductor materials, such as Al _x In _y Ga _(1-xy) N, wherein 0≦x, y≦1; (x +y)≦1. According to the material of the light-emitting layer 104, the light-emitting body can emit green light with a wavelength between 530 nm and 570 nm, blue light with a wavelength between 450 nm and 490 nm, or ultraviolet light with a wavelength between 365 nm and 405 nm. . The first semiconductor layer 102 can be an n-type semiconductor layer, and the second semiconductor layer 106 can be a p-type semiconductor layer.

As shown in FIG. 1B , a patterned current blocking layer 110 is formed on a first surface 108 a of the light emitting stack 108 , that is, on the second semiconductor layer 106 . The current blocking layer 110 can be an insulating oxide such as silicon oxide or titanium oxide; it can also be silicon nitride.

As shown in FIG. 1C, a first electrode 112 is formed on the first surface 108a of the light emitting stack 108 and covers the current blocking layer 110, and then a first electrode 112 can be covered on the uncovered surface of the first surface 108a and the first electrode 112. The barrier layer 114 may include a first barrier layer 114a and a second barrier layer 114b. The entire current blocking layer 110 is covered by the first electrode 112 , and the first electrode 112 shrinks into the blocking layer 114 on the first surface 108 a. The first electrode 112 can be a reflective stack, which includes a first metal layer 112a and a second metal layer 112b that overlap repeatedly, wherein the thermal stability of the first metal layer 112a is higher than that of the second metal layer 112b, and the second metal layer 112b The reflectivity of the second metal layer 112b is higher than that of the first metal layer 112a. For example, the first metal layer 112a can be aluminum, and the second metal layer 112b can be silver. The metal layer 112b can overlap 2-12 times. In this embodiment, the first electrode 112 has a first metal layer 112a directly contacting the first surface 108a. The material of the barrier layer 114 may include alloys or laminates of titanium, tungsten, platinum, and nickel. The thickness of the first metal layer 112a can be between 1～10A, the thickness of the second metal layer 112b can be between 100～700A, especially, the thickness of the first metal layer 112a can be about 3A, and the first electrode 112 The total thickness may be approximately between 1400A to 1500A or above 1500A. In order to make the first electrode 112 in ohmic contact with the second semiconductor layer 106 of the light emitting stack 108, after the formation of the first electrode 112, it can be carried out at a temperature of 500 degrees (°C) for 40 minutes. 112b and a high-temperature annealing of the second semiconductor layer 106. For example, when the first metal layer 112b is silver and the second semiconductor layer 106 is p-type GaN, a high-temperature annealing of silver and p-type GaN is performed, and the first metal layer 112a can be The second metal layer 112b is stabilized during the high temperature annealing process. In addition to pure aluminum, the first metal layer 112 a may also include alloys or laminates of aluminum, titanium, tungsten, platinum, and nickel, so as to improve the stability of the first electrode 112 .

Referring to FIG. 1D, a conductive substrate 118 is bonded to the light-emitting stack 108 through a conductive bonding layer 116. The conductive bonding layer 116 is interposed between the conductive substrate 118 and the barrier layer 114, and may include metals such as gold, indium, nickel or its alloy. At this time, the light emitting stack 108 includes the first semiconductor layer 102 , the light emitting layer 104 , and the second semiconductor layer 106 interposed between the growth substrate 101 and the conductive substrate 118 . A laser (not shown) can be used to decompose the buffer layer 103 to remove the growth substrate 101, and the remaining buffer layer 103 can be removed by dry etching and wet etching.

Please refer to FIG. 1E , after the manufacturing process of removing the buffer layer 103 in FIG. 1D , the light emitting stack 108 may expose a second surface 108 b. The second surface 108b serves as a main light-emitting surface and is also a surface of the first semiconductor layer 102 . The second surface 108b can be a roughened surface to increase the light-emitting efficiency. A second electrode 120 can be formed on the second surface 108 b corresponding to the position of the current blocking layer 110 . When a driving current is injected into the light-emitting stack 108 through the second electrode 120 and the conductive substrate 118, the light-emitting layer 104 will emit light L due to the combination of electrons and holes, and the light L can be reflected by the first electrode 112 and pass through the second surface. 108b shoots out. In this embodiment, when the wavelength of the light L is between 365 nanometers and 550 nanometers, the first electrode 112 may have a reflectivity greater than 95%, and may even have a reflectivity as high as 98% to 100%. In this embodiment, the first electrode 112 formed by the first metal layer 112a with high thermal stability and the second metal layer 112b with high reflectivity can improve the high-temperature annealing of the high-reflectivity metal (such as silver) and the semiconductor layer in the prior art. After the reflectivity is significantly reduced, and such a phenomenon is because high-reflectivity metals such as silver are unstable after high-temperature annealing, and when the light-emitting stack of the prior art receives a high current greater than 350mA, the high-reflectivity metal will More unstable and further reduce the reflectivity. In this embodiment, the first metal layer 112a has a high reflectivity close to that of the second metal layer 112b and has good ohmic contact with the second semiconductor layer 106, and the first metal layer 112a has a higher reflectivity than the second metal layer 112b. Therefore, the first metal layer 112a can keep the second metal layer 112b stable during the high-temperature annealing with the second semiconductor layer 106 so as not to cause a large decrease in reflectivity after the high-temperature annealing. In addition, in an actual test, even if a current slightly higher than 350mA is input to the light-emitting stack 108, the reflectivity of the first electrode 112 does not decrease significantly.

Please refer to FIG. 2 , which shows a light emitting device according to a second embodiment of the present invention. The light emitting device 200 includes: a light emitting stack 210 including a first surface 210a and a second surface 210d opposite to the first surface 210a, the light emitting stack 210 emits _a light L1 having the same wavelength as the light L in the first embodiment, And the first surface 210a includes a first portion 210b having a first electrical property and a second portion 210c having a second electrical property; a first electrode 217 comprising a first electrode pad 226 and a first metal layer 214a and a second metal layer 214b are repeatedly and alternately formed to be electrically conductive to the first portion 210b of the first surface 210a, and have _a relative reflectivity of light L1 greater _than 95%, so that light L1 is transmitted from the second surface 210d Emitted from the light emitting stack; a second electrode 250 including a second electrode pad 224 and an ohmic contact layer 231 formed on the second portion 210c of the first surface 210a; and a carrier 218 including a first conductive pad 222 It is electrically connected to the first electrode 217 and a second conductive pad 220 is electrically connected to the second electrode pad 224 . The light emitting stack 210 may comprise a first semiconductor layer 204 with a second portion 210c and a second surface 210d on both sides of the first surface 210a, a light emitting layer 206, and a second semiconductor layer 208 having a first portion of the first surface 210a. 210b. The second portion 210c of the first surface 210a is formed by removing part of the second semiconductor layer 208 and the light emitting layer 206 . An insulating layer 203 is formed on the first surface 210 a of the light emitting stack 210 , and grooves are formed by an etching process, and metal can be filled to form conductive channels in a subsequent process. The first electrode 217 may further include a barrier layer 216 covering the first metal layer 214a and the second metal layer 214b to form a reflective laminate, and a first conductive channel 228 penetrating the insulating layer 203, and the two ends are respectively connected to the barrier. Layer 216 and first electrode pad 226 . Materials of the first metal layer 214a and the second metal layer 214b may be the same as those of the first embodiment. The first metal layer 214a can be in direct contact with the second semiconductor layer 208, and in this embodiment, the first metal layer 214a and the second metal layer 214b can be overlapped repeatedly 2-12 times, which can further improve the light L ₁ The reflectivity is above 95%, even between 98% and 100%. In other embodiments, a metal oxide layer (not shown) may be formed between the first electrode 217 and the second semiconductor layer 208 to facilitate current distribution. The second electrode 250 may further have a second conductive channel 230 , two ends of which are respectively connected to the ohmic contact layer 231 and the second electrode pad 224 . A transparent substrate 202 can be formed on the second surface 210d of the light emitting stack 210. The transparent substrate 202 can be a growth substrate for the epitaxial growth of the light emitting stack 210, such as a sapphire substrate, but in other embodiments, the transparent substrate 202 can also be are removed, and the second surface 210d can be formed as a roughened surface through an etching process as in the first embodiment. The first electrode pad 226 , the second electrode pad 224 , the first conductive channel 228 and the second conductive channel 230 may include a stack of metals such as nickel, gold and/or titanium. The ohmic contact layer 231 of the first electrode 250 may include a stack of metals such as chromium, platinum and/or gold. Areas of the first electrode pad 226 and the second electrode pad 224 may be larger than the cross-sectional areas of the first conductive channel 228 and the second conductive channel 230 respectively and extend on the surface of the insulating layer 203 to facilitate receiving high current from the carrier 218 .

Although the present invention has been disclosed above, it is not intended to limit the scope, implementation sequence, or used materials and manufacturing methods of the present invention. Various modifications and changes made to the present invention do not depart from the spirit and scope of the present invention.

Claims (10)

1. A lighting device comprising: a light emitting stack comprising a first surface and a second surface opposite the first surface, the light emitting stack emitting a light having a wavelength between 365 nanometers and 550 nanometers; and The first electrode is formed on the first surface and includes a first metal layer and a second metal layer overlapping repeatedly, wherein the first electrode has a reflectivity of more than 95% relative to the above-mentioned light, and the first metal layer has a reflectivity greater than 95%. The thermal stability is higher than that of the second metal layer, and the reflectivity of the second metal layer is higher than that of the first metal layer. 2. The light emitting device as claimed in claim 1, wherein the first metal layer directly contacts the first surface. 3. The light-emitting device according to claim 1, further comprising: a barrier layer covering the first electrode on the first surface; a conductive substrate; a conductive bonding layer formed between the conductive substrate and the barrier layer; Two electrodes, having a pattern, formed on the second surface; and a current blocking layer, formed on the first surface corresponding to the position of the second electrode, wherein the light emitting stack includes a first semiconductor layer, has the second surface, The second semiconductor layer has the first surface, the light-emitting layer is located between the first semiconductor layer and the second semiconductor layer, and the first electrode is formed on a part of the first surface, and the light is emitted from the second surface in the light-emitting stack. 4. A lighting device comprising: A light-emitting stack comprising a first surface and a second surface opposite to the first surface, the light-emitting stack emits a light having a wavelength between 365 nm and 550 nm, and the first surface comprises a first portion having a first electrical and the second part has a second electrical nature; The first electrode includes the first electrode pad and the reflective stack includes the first metal layer and the second metal layer overlapped repeatedly and is electrically connected to the first part of the first surface. The reflective stack has a light relative to the light The reflectivity is greater than 95%, wherein the thermal stability of the first metal layer is higher than that of the second metal layer, and the reflectivity of the second metal layer for the light is higher than that of the first metal layer; a second electrode, including a second electrode pad and an ohmic contact layer, is formed on the second portion of the first surface; and The carrier includes a first conducting pad electrically connected to the first electrode and a second conducting pad electrically connected to the second electrode pad. 5. The light-emitting device according to claim 1 or 4, wherein the first metal layer and the second metal layer overlap repeatedly 2-12 times. 6. The light-emitting device according to claim 1 or 4, wherein the first metal layer comprises aluminum, the second metal layer is silver, or the first metal layer comprises an alloy of aluminum, titanium, tungsten, platinum, nickel or laminated. 7. The light emitting device according to claim 1 or 4, wherein the first metal layer has a thickness between 1˜10A, and the second metal layer has a thickness between 100A to 700A. 8. The light emitting device as claimed in claim 7, wherein the thickness of the first metal layer is about 3A. 9. The light-emitting device according to claim 4, further comprising an insulating layer covering the first surface, the first electrode pad and the second electrode pad are formed between a surface of the insulating layer and the carrier, wherein the The first electrode further includes: a barrier layer covering between the first portion of the first surface and the insulating layer; and a first conductive channel penetrating through the insulating layer to connect the first electrode pad and the barrier layer, the The second electrode further includes a second conductive channel penetrating through the insulating layer to connect the second electrode pad and the ohmic contact layer, wherein the light emitting stack includes: a first semiconductor layer having the second portion of the first surface and the second surface; a second semiconductor layer having the first portion of the first surface; and a light-emitting layer formed between the first semiconductor layer and the second semiconductor layer, and the light is emitted from the second surface in the light-emitting stack. 10. The light-emitting device as claimed in claim 1 or 4, wherein the reflectance of the stack formed by the first metal layer and the second metal layer with respect to the light is between 98% and 100%.