JP6694650B2 - Semiconductor light emitting element - Google Patents

Description

  The present invention relates to a semiconductor light emitting device.

  The light emitting diode of Patent Document 1 has an ohmic contact layer, a second metal layer, a first metal layer, an insulating layer, a p-type contact layer, a p-type clad layer, and an MQW (Multiple Quantum Well) on one surface of a support substrate. The active layer, the n-type cladding layer, and the n-type contact layer have a semiconductor layer laminated in this order and have an ODR structure. That is, the contact portion is embedded in a partial region of the insulating layer between the p-type contact layer and the first metal layer, and thereby the first metal layer and the p-type contact layer are electrically connected. There is. A p-side electrode is provided on the back surface of the support substrate, and a ring-shaped n-side electrode is provided on the n-type contact layer.

JP, 2007-221029, A

  In the invention of Patent Document 1, although the light extraction efficiency is improved by the ODR structure, there still remains a factor that reduces the light extraction efficiency. For example, since the contact portion of the ODR structure is made of AuZn and the p-type contact layer to be connected to it is made of AlGaInP-based semiconductor, the junction portion thereof becomes the eutectic portion. Since the eutectic portion has a property of absorbing light, the reflectance of light in the metal layer is reduced, and as a result, the light extraction efficiency is reduced.

  An object of the present invention is to provide a semiconductor light emitting device capable of improving the light extraction efficiency as compared with the conventional one.

A semiconductor light emitting device according to an embodiment of the present invention includes a substrate, a metal layer on the substrate, a light emitting layer, and a first light emitting layer disposed on the substrate side with respect to the light emitting layer. A semiconductor layer including a conductive type layer and a second conductive type layer disposed on the opposite side of the substrate with respect to the light emitting layer; and a translucent conductive layer between the metal layer and the semiconductor layer, Light transmission including at least a first portion having a refractive index n ₁ and a second portion arranged on the metal layer side with respect to the first portion and having a refractive index n ₂ lower than the refractive index n _1. And a conductive layer.

  With this structure, the refractive index of the translucent conductive layer gradually decreases in the order of the first portion and the second portion from the semiconductor layer toward the metal layer, so that the refractive index of the portion near the semiconductor layer is reduced. Can be close to the refractive index of the semiconductor layer. This can reduce the difference in the refractive index at the interface between the semiconductor layer and the light-transmitting conductive layer, so that the light generated in the light-emitting layer and traveling toward the metal layer is prevented from being reflected before being incident on the light-transmitting conductive layer. be able to. Therefore, the light transmittance of the translucent conductive layer is improved, and the reflectance of the metal layer can be improved. Moreover, since the second portion having a relatively low refractive index is disposed on the metal layer side, when the light reflected by the metal layer passes through the translucent conductive layer, the light is incident from the second portion to the first portion. , From a medium with a small refractive index to a medium with a large refractive index. Therefore, it is possible to suppress the reflection and return to the metal layer side again at the boundary between the first portion and the second portion. As a result, the light extraction efficiency of the semiconductor light emitting device can be improved.

In the semiconductor light emitting device according to one embodiment of the present invention, the first portion is a first light-transmitting conductive layer having the refractive index n ₁ , and the second portion is a second light transmitting conductive layer having the refractive index n ₂ . It may be a transparent conductive layer.
In the semiconductor light emitting device according to one embodiment of the present invention, the first light-transmissive conductive layer and the second light-transmissive conductive layer are made of ITO (indium tin oxide), ZnO (zinc oxide) and IZO (indium zinc oxide). It may consist of a combination.

In the semiconductor light emitting device according to one embodiment of the present invention, the first conductivity type layer includes a contact layer connected to the translucent conductive layer and having a refractive index n ₀ higher than the refractive index n _1. Good.
In this case, the refractive index has a relationship of n ₀ > n ₁ > n ₂ from the first conductive type contact layer to the second part through the first part of the translucent conductive layer, and the first part is , And functions as a refractive index relaxation portion that compensates for the refractive index difference between the contact layer and the second portion.

A semiconductor light emitting device according to another embodiment of the present invention is a substrate, a metal layer on the substrate, a metal layer formed on the metal layer, a light emitting layer, and the light emitting layer disposed on the substrate side. the first conductivity type layer, and a semiconductor layer comprising a second conductivity type layer disposed on the opposite side of the substrate to the light-emitting layer, the refractive index n _a between the metal layer and the semiconductor layer And a light-transmitting conductive layer having an insulating layer between the light-transmitting conductive layer and the semiconductor layer, the insulating layer having a refractive index n _b higher than the refractive index n _a. The layer includes a contact portion penetrating the insulating layer and connected to the first conductivity type layer.

  According to this configuration, the insulating layer functions as a refractive index relaxation portion that compensates for the refractive index difference between the semiconductor layer and the translucent conductive layer, so that the refractive index of the portion close to the semiconductor layer becomes the refractive index of the semiconductor layer. You can get closer. Thereby, it is possible to suppress the light generated in the light emitting layer and traveling toward the metal layer from being reflected before being incident on the translucent conductive layer. In addition, since the contact between the contact portion of the translucent conductive layer and the first conductivity type layer is not a eutectic junction, it is possible to prevent light from being absorbed at the junction. Therefore, the light transmittance of the translucent conductive layer is improved, and the reflectance of the metal layer can be improved.

  Moreover, since the translucent conductive layer having a relatively low refractive index is disposed on the metal layer side, when the light reflected by the metal layer passes through the translucent conductive layer and the insulating layer, it is insulated from the translucent conductive layer. It is also possible to suppress the reflection and return to the metal layer side again at the interface with the layer. Further, since the translucent conductive layer is selectively connected to the semiconductor layer by utilizing the contact portion, it is possible to flow current evenly in the plane of the semiconductor layer by adjusting the arrangement form of the contact portion. it can. As a result, the light extraction efficiency of the semiconductor light emitting device can be improved.

In the semiconductor light emitting device according to another embodiment of the present invention, the first conductivity type layer includes a contact layer connected to the contact portion and having a refractive index n ₀ higher than a refractive index n _{b of the} insulating layer. You can leave.
In this case, the first conductivity type contact layer toward ToruHikarishirube conductive layer through the insulating layer, the refractive index has become a relation of _{n 0> n b> n a} , the insulating layer, the contact layer and the translucent It functions as a refractive index relaxation portion that compensates for the refractive index difference with the conductive layer.

In the semiconductor light emitting device according to another embodiment of the present invention, the translucent conductive layer may have a refractive index that gradually decreases from the semiconductor layer toward the metal layer.
According to this structure, the refractive index of the portion close to the insulating layer can be made close to the refractive index of the insulating layer, so that the difference in refractive index at the interface between the insulating layer and the light-transmitting conductive layer can be reduced. Thereby, reflection at the interface can be suppressed, so that the light transmittance of the translucent conductive layer can be further improved.

In the semiconductor light emitting device according to another embodiment of the present invention, the insulating layer may include a SiN film, and in that case, the SiN film is gradually formed from the semiconductor layer toward the metal layer. It may have a smaller refractive index.
In the semiconductor light emitting device according to another embodiment of the present invention, the translucent conductive layer may include ITO (indium tin oxide).

In a semiconductor light emitting device according to another embodiment of the present invention, the insulating layer comprises a single layer film of SiN film having a refractive index of 1.9 to 2.2 and a thickness of 3000Å to 3500Å, The conductive layer may be a single layer film of ITO having a thickness of 550Å to 650Å.
Such a combination can improve the reflectance of light in the wavelength band of 500 nm to 900 nm, for example.

In the semiconductor light emitting device according to another embodiment of the present invention, the contact part may include a plurality of contact parts discretely arranged in a plane of the substrate.
Further, the semiconductor light emitting device according to one embodiment and another embodiment of the present invention may have the following configurations.
For example, the contact layer may include p-type GaP, and the p-type GaP may include carbon as an impurity.

In addition, the metal layer may include Au, and the substrate may include a silicon substrate.
Further, the semiconductor light emitting element may include a front surface electrode on the semiconductor layer, or may include a back surface electrode on the back surface of the substrate.
Further, the surface of the semiconductor layer may be formed in a fine uneven shape.

FIG. 1 is a plan view showing a semiconductor light emitting device according to an embodiment of the present invention. FIG. 2 is a sectional view taken along the line II-II in FIG. FIG. 3A is a diagram showing a manufacturing process of the semiconductor light emitting device of FIGS. 1 and 2. FIG. 3B is a diagram showing a step subsequent to FIG. 3A. FIG. 3C is a diagram showing a step subsequent to FIG. 3B. FIG. 3D is a diagram showing a step subsequent to FIG. 3C. FIG. 3E is a diagram showing a step subsequent to FIG. 3D. FIG. 3F is a diagram showing a step subsequent to FIG. 3E. FIG. 3G is a diagram showing a step subsequent to FIG. 3F. FIG. 3H is a diagram showing a step subsequent to FIG. 3G. 3I is a diagram showing a step subsequent to FIG. 3H. FIG. 4 is a plan view showing a semiconductor light emitting device according to another embodiment of the present invention. FIG. 5 is a sectional view taken along the line VV of FIG. FIG. 6A is a diagram showing a manufacturing process of the semiconductor light emitting device of FIGS. 4 and 5. FIG. 6B is a diagram showing a step subsequent to FIG. 6A. FIG. 6C is a diagram showing a step subsequent to FIG. 6B. FIG. 6D is a diagram showing a step subsequent to FIG. 6C. FIG. 6E is a diagram showing a step subsequent to FIG. 6D. FIG. 6F is a diagram showing a step subsequent to FIG. 6E. FIG. 6G is a diagram showing a step subsequent to FIG. 6F. 6H is a diagram showing a step subsequent to FIG. 6G. FIG. 6I is a diagram showing a step subsequent to FIG. 6H. FIG. FIG. 6J is a diagram showing a step subsequent to FIG. 6I. FIG. 7 is a diagram showing a modification of the semiconductor light emitting device of FIGS. 1 and 2. FIG. 8 is a diagram showing a modification of the insulating layer shown in FIG. FIG. 9 is a graph for explaining the effect of the present invention. FIG. 10 is a graph for explaining the effect of the present invention. FIG. 11 is a graph for explaining the effect of the present invention. FIG. 12 is a graph for explaining the effect of the present invention. FIG. 13 is a graph for explaining the effect of the present invention. FIG. 14 is a graph for explaining the effect of the present invention. FIG. 15 is a graph for explaining the effect of the present invention. FIG. 16 is a graph for explaining the effect of the present invention. FIG. 17 is a diagram showing a structure of a semiconductor light emitting device according to a comparative example. FIG. 18 is a diagram showing a structure of a semiconductor light emitting device according to a reference example. FIG. 19 is a diagram showing the luminance of Examples, Comparative Examples and Reference Examples.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 is a plan view showing a semiconductor light emitting device 1 according to an embodiment of the present invention. FIG. 2 is a sectional view taken along the line II-II in FIG.
This semiconductor light emitting device 1 includes a substrate 2, a metal layer 3 on the substrate 2, a light-transmissive conductive layer 4 on the metal layer 3, and an AlInGaP-based system as an example of the semiconductor layer of the present invention on the light-transmissive conductive layer 4. The semiconductor laminated structure 5, the p-side electrode 6 (back surface electrode) formed so as to contact the back surface of the substrate 2 (the surface opposite to the AlInGaP-based semiconductor laminated structure 5), and the surface of the AlInGaP-based semiconductor laminated structure 5 are formed. And an n-side electrode 7 (front surface electrode) formed so as to be in contact with each other.

  The substrate 2 is composed of a silicon substrate in this embodiment. Of course, the substrate 2 may be formed of a semiconductor substrate such as GaAs (gallium arsenide) or GaP (gallium phosphide). In this embodiment, the substrate 2 is formed in a substantially square shape in plan view as shown in FIG. 1, but the planar shape of the substrate 2 is not particularly limited, and may be rectangular in plan view, for example. Further, the thickness of the substrate 2 may be, for example, about 150 μm.

  In this embodiment, the metal layer 3 is made of Au or an alloy containing Au. The metal layer 3 may be a single layer of each of the Au layer and the Au alloy layer, or may be a layer in which a plurality of these layers and other metal layers are laminated. When the metal layer 3 has a plurality of laminated structures, it is preferable that at least the contact surface with the translucent conductive layer 4 is formed of an Au layer or an Au alloy layer (for example, AuBeNi). As an example, a laminated structure shown by (transparent conductive layer 4 side) Au / Mo / Au / Ti (substrate 2 side) can be given. Further, in the metal layer 3, even if a clear boundary is not formed between the plurality of metal materials forming the metal layer 3 and the plurality of metal materials are sequentially distributed from the substrate 2 side, for example. Good. On the other hand, in this embodiment, the metal layer 3 has a first metal layer 26 (described later) and a second metal layer 27 (described later) formed by bonding the growth substrate 24 (described later) and the substrate 2 as described below. It is formed by joining. Therefore, there may be a boundary in the thickness direction of the Au layer forming the metal layer 3 due to the bonding surface generated during the bonding step.

The metal layer 3 is formed so as to cover the entire surface of the substrate 2. The (total) thickness of the metal layer 3 may be, for example, about 0.5 μm.
The translucent conductive layer 4 is arranged at least on the first portion having a refractive index n ₁ and on the metal layer 3 side with respect to the first portion, and has a refractive index n ₂ lower than the refractive index n ₁ . Including two parts. In this embodiment, a first transparent conductive layer 41 (refractive index n ₁ ) as an example of the first portion, and a second transparent conductive layer 42 (refractive index n ₂ ) as an example of the second portion are provided. It has a two-layer structure. If the transparent conductive layer 4 has a structure in which the refractive index gradually decreases from the AlInGaP-based semiconductor laminated structure 5 toward the metal layer 3, for example, between the second transparent conductive layer 42 and the metal layer 3. In addition, a third translucent conductive layer (refractive index n ₃ <refractive index n ₂ ), a fourth translucent conductive layer (refractive index n ₄ <refractive index n ₃ ) ... The refractive index n _n <refractive index n _n-1 ) may be included.

  The first transparent conductive layer 41 and the second transparent conductive layer 42 may be made of, for example, a combination of ITO (indium tin oxide), ZnO (zinc oxide) and IZO (indium zinc oxide). The refractive indices of these materials are, for example, ITO = 1.7 to 2.3, ZnO = 2.0 and IZO = 1.9 to 2.4. As a combination, for example, the first transparent conductive layer 41 may be ZnO and the second transparent conductive layer 42 may be ITO. As a result, the interface between the metal layer 3 and the light-transmissive conductive layer 4 can be an Au / ITO interface, so that sufficient adhesion between the metal layer 3 and the light-transmissive conductive layer 4 can be ensured.

The translucent conductive layer 4 is formed so as to cover the entire surface of the metal layer 3. The (total) thickness of the transparent conductive layer 4 may be, for example, about 600Å.
The AlInGaP-based semiconductor laminated structure 5 includes a light emitting layer 8, a p-type semiconductor layer 9, and an n-type semiconductor layer 10. The p-type semiconductor layer 9 is arranged on the substrate 2 side with respect to the light emitting layer 8, and the n-type semiconductor layer 10 is arranged on the n side electrode 7 side with respect to the light emitting layer 8. Thus, the light emitting layer 8 is sandwiched by the p-type semiconductor layer 9 and the n-type semiconductor layer 10 to form a double heterojunction. Electrons are injected from the n-type semiconductor layer 10 and holes are injected into the light-emitting layer 8 from the p-type semiconductor layer 9. Light is generated by recombining these in the light emitting layer 8.

  The p-type semiconductor layer 9 includes a p-type GaP contact layer 11 (for example, 0.3 μm thick), a p-type GaP window layer 12 (for example, 1.0 μm thick), and a p-type AlInP clad layer 13 (for example 0 .8 μm thick). On the other hand, the n-type semiconductor layer 10 has an n-type AlInP cladding layer 14 (for example, 0.8 μm thick), an n-type AlInGaP window layer 15 (for example, 1.8 μm thick), and an n-type GaAs contact on the light emitting layer 8 in this order. It is formed by stacking layers 16 (for example, 0.3 μm thick).

The p-type GaP contact layer 11 and the n-type GaAs contact layer 16 are low resistance layers for making ohmic contact with the p-side electrode 6 and the n-side electrode 7, respectively. The p-type GaP contact layer 11 is made into a p-type semiconductor by doping GaP with a high concentration of, for example, C (carbon) as a p-type dopant (doping concentration is 2.0 × 10 ¹⁹ cm ⁻³ ). ing. If GaP contains C (carbon) as a dopant, a good ohmic contact can be obtained with ITO used as the material of the translucent conductive layer 4. The n-type GaAs contact layer 16 is made into an n-type semiconductor layer by doping GaAs with a high concentration of Si as an n-type dopant (the doping concentration is, for example, 1.0 × 10 ¹⁸ cm ⁻³ ). ing.

The p-type GaP window layer 12 is made into a p-type semiconductor by doping GaP with Mg as a p-type dopant (the doping concentration is, for example, 2.0 × 10 ¹⁸ cm ⁻³ ). On the other hand, the n-type AlInGaP window layer 15 is made into an n-type semiconductor layer by doping AlInGaP with, for example, Si as an n-type dopant (doping concentration is 1.0 × 10 ¹⁸ cm ⁻³ ).

The p-type AlInP cladding layer 13 is made into a p-type semiconductor by doping AlInP with, for example, Mg as a p-type dopant (doping concentration is 5.0 × 10 ¹⁷ cm ⁻³ ). On the other hand, the n-type AlInP cladding layer 14 is made into an n-type semiconductor layer by doping AlInP with Si as an n-type dopant (doping concentration is, for example, 5.0 × 10 ¹⁷ cm ⁻³ ).

The light emitting layer 8 has an MQW (multiple-quantum well) structure (multiple quantum well structure) containing, for example, InGaP, and light is generated by recombination of electrons and holes, and the generated light is emitted. It is a layer for amplification.
In this embodiment, the light-emitting layer 8 is a multiple quantum well structure in which a quantum well layer (for example, 5 nm thick) made of an InGaP layer and a barrier layer (for example, 4 nm thick) made of an AlInGaP layer are alternately and repeatedly laminated for a plurality of cycles. (MQW: Multiple-Quantum Well) structure. In this case, the InGaP quantum well layer has a relatively small bandgap when the In composition ratio is 5% or more, and the AlInGaP barrier layer has a relatively large bandgap. For example, the quantum well layers (InGaP) and the barrier layers (AlInGaP) are alternately and repeatedly laminated for 10 to 40 cycles, whereby the light emitting layer 8 having the multiple quantum well structure is formed. The emission wavelength corresponds to the bandgap of the quantum well layer, and the bandgap can be adjusted by adjusting the In composition ratio. As the In composition ratio increases, the band gap decreases and the emission wavelength increases. In this embodiment, the emission wavelength is set to 610 nm to 680 nm (for example, 625 nm) by adjusting the In composition in the quantum well layer (InGaP layer).

  As shown in FIGS. 1 and 2, the AlInGaP-based semiconductor laminated structure 5 has a mesa portion 17 formed by removing a part thereof. More specifically, part of the n-type semiconductor layer 10, the light emitting layer 8 and the p-type semiconductor layer 9 is removed by etching from the surface of the AlInGaP-based semiconductor laminated structure 5 over the entire circumference of the AlInGaP-based semiconductor laminated structure 5. A mesa portion 17 having a substantially rectangular cross section is formed. The shape of the mesa portion 17 is not limited to the substantially square shape in cross section, and may be, for example, a trapezoid. As a result, the p-type GaP window layer 12 of the p-type semiconductor layer 9 and the layer closer to the substrate 2 than the p-type GaP window layer 12 form a lead-out portion 18 that is pulled out laterally from the mesa portion 17. As shown in FIG. 1, the mesa portion 17 is surrounded by the drawer portion 18 in a plan view.

  In this embodiment, a fine concavo-convex shape 19 is formed on the surface of the mesa portion 17. The fine irregularities 19 can diffuse the light extracted from the AlInGaP-based semiconductor laminated structure 5. In this embodiment, as described later, the n-type GaAs contact layer 16 is selectively removed according to the shape of the n-side electrode 7 to expose the n-type AlInGaP window layer 15, and the exposed surface has a fine pattern. The uneven shape 19 is formed. In FIG. 1, the fine concavo-convex shape 19 is omitted for clarity.

In this embodiment, the p-side electrode 6 as the back surface electrode is made of Au or an alloy containing Au. Specifically, a laminated structure represented by (substrate 2 side) Ti / Au / Mo / Au may be used. The p-side electrode 6 is formed so as to cover the entire back surface of the substrate 2.
In this embodiment, the n-side electrode 7 as the surface electrode is made of Au or an alloy containing Au. Specifically, (AlInGaP based semiconductor laminated structure 5 side) may be a laminated structure represented by Au / Ge / Ni / Au.

  Further, the n-side electrode 7 integrally includes a pad electrode portion 20 and a branch electrode portion 21 that selectively extends in a branch shape from the pad electrode portion 20 so as to partition a certain region around the pad electrode portion 20. Included. In this embodiment, the pad electrode portion 20 is arranged substantially in the center of the mesa portion 17 in a plan view, and the surrounding regions 22A and 22B are provided between the pad electrode portion 20 and each of the four corners of the mesa portion 17. , 22C, 22D are formed so as to partition the branch-shaped electrode portion 21. Each of the surrounding regions 22A to 22D intersects the branch-shaped electrode portion 21A extending in a cross shape from the pad electrode portion 20 toward each peripheral edge of the mesa portion 17 and the cross-shaped branch electrode portion 21 to form the mesa portion 17. It is surrounded by a branch electrode portion 21B extending along each peripheral edge and a pad electrode portion 20. On the other hand, the area outside the branch-shaped electrode portion 21B except the surrounding areas 22A to 22D is the outer peripheral area 23 of the mesa portion 17.

Further, in this embodiment, since the n-type GaAs contact layer 16 has the same shape as the n-side electrode 7, the n-type AlInGaP window layer 15 is exposed in the surrounding regions 22A to 22D and the outer peripheral region 23. ..
3A to 3I are views showing a manufacturing process of the semiconductor light emitting device 1 of FIGS. 1 and 2 in the order of processes.

  To manufacture the semiconductor light emitting device 1, for example, as shown in FIG. 3A, the AlInGaP based semiconductor laminated structure 5 is formed on the growth substrate 24 made of GaAs or the like by epitaxial growth. As the growth method, a known growth method such as a molecular beam epitaxial growth method or a metal organic chemical vapor deposition method can be applied. At this stage, the AlInGaP-based semiconductor laminated structure 5 has the n-type AlInGaP etching stop layer 25, the n-type GaAs contact layer 16, the n-type AlInGaP window layer 15, the n-type AlInP cladding layer 14, and the light emission in order from the growth substrate 24 side. It includes a layer 8, a p-type AlInP cladding layer 13, a p-type GaP window layer 12 and a p-type GaP contact layer 11. After forming the AlInGaP-based semiconductor laminated structure 5, the translucent conductive layer 4 is formed by, for example, an evaporation method.

Next, as shown in FIG. 3B, a first metal layer 26 (for example, 1.7 μm thick) is formed on the translucent conductive layer 4 by, for example, a vapor deposition method. The first metal layer 26 is made of Au or an alloy containing Au, and at least the outermost surface is made of an Au layer.
The next step is a step of bonding the growth substrate 24 and the substrate 2 together. In the bonding step, the first metal layer 26 on the growth substrate 24 and the second metal layer 27 on the substrate 2 are bonded. The second metal layer 27 is made of Au or an alloy containing Au, and at least the outermost surface is made of an Au layer. The second metal layer 27 is formed on the surface of the substrate 2 (the surface opposite to the surface on which the p-side electrode 6 is formed) by, for example, an evaporation method before the bonding.

  More specifically, as shown in FIG. 3C, the growth substrate 24 and the substrate 2 are overlapped with the first and second metal layers 26, 27 facing each other, and the first and second metal layers 26, 27 are stacked. Join 27. The joining of the first and second metal layers 26, 27 may be performed by thermocompression bonding, for example. The conditions for thermocompression bonding may be, for example, a temperature of 250 ° C. to 700 ° C., preferably about 300 ° C. to 400 ° C., and a pressure of 10 MPa to 20 MPa. By this joining, as shown in FIG. 3D, the first and second metal layers 26 and 27 are combined to form the metal layer 3.

  Next, as shown in FIG. 3D, the growth substrate 24 is removed by, for example, wet etching. Since the n-type AlInGaP etching stop layer 25 is formed on the outermost surface of the AlInGaP-based semiconductor laminated structure 5, the n-type GaAs contact layer 16 that contributes to the characteristics of the semiconductor light emitting device 1 during the wet etching. The n-type AlInGaP window layer 15 and the like need not be affected. Then, the n-type AlInGaP etching stop layer 25 is also removed.

  The next step is a step of forming the n-side electrode 7. In this embodiment, the n-side electrode 7 is formed by the lift-off method. More specifically, as shown in FIG. 3E, first, a resist 28 having openings having the same pattern as the electrode pattern of the n-side electrode 7 is formed on the n-type GaAs contact layer 16. Next, the electrode material film 29 is laminated on the AlInGaP-based semiconductor laminated structure 5 by, for example, a vapor deposition method.

  Next, as shown in FIG. 3F, the electrode material film 29 on the resist 28 is removed together with the resist 28. As a result, the n-side electrode 7 made of the electrode material film 29 remaining on the n-type GaAs contact layer 16 is formed. Then, the n-type GaAs contact layer 16 exposed from the n-side electrode 7 is removed by etching. As a result, the n-type AlInGaP window layer 15 is exposed in a portion other than the n-side electrode 7.

Next, as shown in FIG. 3G, a fine concavo-convex shape 19 is formed on the surface of the n-type AlInGaP window layer 15 by, for example, frosting (wet etching) or the like. The frost process may be performed by dry etching.
Next, as shown in FIG. 3H, the mesa portion 17 and the lead portion 18 are formed by selectively removing the peripheral portion of the AlInGaP-based semiconductor laminated structure 5. The mesa portion 17 and the lead portion 18 may be formed by, for example, wet etching.

Next, as shown in FIG. 3I, the p-side electrode 6 is formed on the back surface of the substrate 2 by, for example, a vapor deposition method. The semiconductor light emitting device 1 is obtained through the above steps.
As described above, according to the semiconductor light emitting device 1, the refractive index of the light-transmissive conductive layer 4 is the first light-transmissive conductive layer 41 (refractive index n ₁ ) and the 2 Since the light-transmissive conductive layer 42 (refractive index n ₂ <n ₁ ) is gradually reduced in order, the refractive index of the portion close to the AlInGaP-based semiconductor laminated structure 5 is brought close to that of the AlInGaP-based semiconductor laminated structure 5. be able to.

More specifically, for example, in FIG. 2, when the transparent conductive layer 4 is formed of a single layer film of ITO (for example, refractive index n _ITO = 1.89), the transparent conductive layer 4 and the p-type GaP contact layer 11 are formed. (e.g. refractive index _n GaP = 3.4) refractive index difference between the _(n GaP _{-n ITO)} is 1.51. On the other hand, as in this embodiment, for example, IZO (for example, refractive index n _IZO = 2.4) is inserted between ITO and GaP as a refractive index relaxation layer that compensates for the refractive index difference between ITO and GaP. By doing so, the difference in refractive index at the interface between the layers can be reduced. For example, by inserting IZO, refractive index difference between the GaP / IZO interface the _(n GaP _{-n IZO)} can be 1.0, the refractive index difference of IZO / ITO interface the _(n IZO _{-n ITO)} 0.51 In any case, the difference in refractive index is smaller than that in the case where the GaP / ITO interface is formed. Accordingly, it is possible to suppress the light generated in the light emitting layer 8 and traveling toward the metal layer 3 from being reflected when entering the translucent conductive layer 4 from the AlInGaP-based semiconductor laminated structure 5. Therefore, the light transmittance of the translucent conductive layer 4 is improved, and the reflectance of the metal layer 3 can be improved.

  Moreover, since the second light-transmissive conductive layer 42 having a relatively low refractive index is disposed on the metal layer 3 side, when the light reflected by the metal layer 3 passes through the light-transmissive conductive layer 4, the second light-transmissive conductive layer 42 is transmitted. The incident light from the conductive layer 42 to the first translucent conductive layer 41 is from a medium having a small refractive index to a medium having a large refractive index. Therefore, it is possible to suppress the reflection and return to the metal layer 3 side again at the interface between the first light-transmissive conductive layer 41 and the second light-transmissive conductive layer 42. As a result, the light extraction efficiency of the semiconductor light emitting device 1 can be improved.

Note that, in the above, the example in which the refractive index difference is provided by using different materials for the translucent conductive layer 4 has been shown. However, since ITO, ZnO, and IZO can change the refractive index depending on the composition, film forming method, crystal structure, etc., the first and second translucent conductive layers 41 and 42 have the same refractive index. Materials can also be used. For example, _ITO having a refractive index n _ITO of 2.3 may be used as the first transparent conductive layer 41, and _ITO having a refractive index n _ITO of 1.89 may be used as the second transparent conductive layer 42.

FIG. 4 is a plan view showing a semiconductor light emitting device 30 according to another embodiment of the present invention. FIG. 5 is a sectional view taken along the line VV of FIG. 4 and 5, the same elements as those shown in FIGS. 1 and 2 are designated by the same reference numerals, and the description thereof will be omitted.
In the semiconductor light emitting device 30, the insulating layer 31 is arranged between the translucent conductive layer 4 and the AlInGaP based semiconductor laminated structure 5.

In this embodiment, the insulating layer 31 is made of an insulating material having a refractive index n _b higher than the refractive index n _a of the translucent conductive layer 4. Specifically, the insulating layer 31 may be made of a SiN film, and in this embodiment, the insulating layer 31 is made of a single layer film of SiN. The refractive index of SiN can be easily controlled, for example, by changing the gas flow rate when forming the SiN film. For example, when forming the SiN film by using _SiH 4, NH _3, and _{N 2,} it is possible to increase the refractive index by increasing the flow rate of the SiH ₄ gas is a source of Si, the flow rate of SiH ₄ gas If it is reduced, the refractive index can be lowered. As a result, the refractive index of SiN can be controlled within the range of, for example, 1.85 to 2.4. That is, the refractive index n _a of ToruHikarishirube conductive layer 4 between the insulating layer 31 and the metal layer 3 in consideration, it may be adjusted to the refractive index of the insulating layer 31.

  On the other hand, since the insulating layer 31 separates the translucent conductive layer 4 and the AlInGaP-based semiconductor laminated structure 5 from each other, the translucent conductive layer 4 is connected to the p-type GaP contact through the contact hole 33 penetrating the insulating layer 31. It has a contact portion 32 connected to the layer 11. As a result, the semiconductor light emitting device 30 has an ODR (Omni-Directional-Reflector) structure.

The contact portions 32 are discretely arranged in the plane of the substrate 2 as shown in FIG. For example, they may be arranged in a matrix in the mesa portion 17 having a quadrangular shape in plan view.
In this embodiment, one outer row 321 including a plurality of contact portions 32 is provided in each outer peripheral region 23 outside the pair of branch electrode portions 21B. In each of the outer rows 321, the contact portions 32 are arranged along the branch-shaped electrode portions 21B with the same distance from the branch-shaped electrode portions 21B.

  On the other hand, in the surrounding regions 22A to 22D inside the pair of branch-shaped electrode portions 21B, the inner row 322 including the plurality of contact portions 32 is provided. The inner row 322 is provided in a plurality of rows parallel to the outer row 321, for example. In this embodiment, two rows are formed so as to straddle the surrounding area 22A and the surrounding area 22D, and two rows are formed so as to straddle the surrounding area 22B and the surrounding area 22C.

Further, as shown in FIG. 5, each contact portion 32 may have a tapered cross-sectional shape in which the tip is narrowed toward the AlInGaP-based semiconductor laminated structure 5.
In addition, the translucent conductive layer 4 is composed of a single layer film of ITO, ZnO or IZO in this embodiment. For example, as a preferable combination of the insulating layer 31 and the translucent conductive layer 4, the insulating layer 31 is formed of a single-layer SiN film having a refractive index n _b of 1.9 to 2.2 and a thickness of 3000Å to 3500Å. That is, the translucent conductive layer 4 is made of a single layer film of ITO having a thickness of 550Å to 650Å. With such a combination, the reflectance of light in the wavelength band of 500 nm to 900 nm can be improved, for example. Of course, the light-transmitting conductive layer 4 has at least the first portion having the refractive index n ₁ and the first portion having the refractive index n ₁ within the range having the lower refractive index than the insulating layer 31, as in the above-described embodiment. And a second portion disposed on the metal layer 3 side and having a refractive index n ₂ lower than the refractive index n ₁ . That is, the translucent conductive layer 4 may have a refractive index that gradually decreases from the AlInGaP-based semiconductor laminated structure 5 toward the metal layer 3.

6A to 6J are views showing the manufacturing process of the semiconductor light emitting device 30 of FIGS. 4 and 5 in the order of processes.
To manufacture the semiconductor light emitting device 30, for example, as shown in FIG. 6A, the AlInGaP based semiconductor laminated structure 5 is formed on the growth substrate 24 made of GaAs or the like by epitaxial growth. As the growth method, a known growth method such as a molecular beam epitaxial growth method or a metal organic chemical vapor deposition method can be applied. At this stage, the AlInGaP-based semiconductor laminated structure 5 has the n-type AlInGaP etching stop layer 25, the n-type GaAs contact layer 16, the n-type AlInGaP window layer 15, the n-type AlInP cladding layer 14, and the light emission in order from the growth substrate 24 side. It includes a layer 8, a p-type AlInP cladding layer 13, a p-type GaP window layer 12 and a p-type GaP contact layer 11. After forming the AlInGaP-based semiconductor laminated structure 5, the insulating layer 31 is formed by, for example, the CVD method. After that, the contact hole 33 is formed by selectively etching the insulating layer 31.

Next, as shown in FIG. 6B, the transparent conductive layer 4 is formed on the insulating layer 31 by, for example, a vapor deposition method. The transparent conductive layer 4 enters the contact hole 33 and is connected to the p-type GaP contact layer 11.
Next, as shown in FIG. 6C, the first metal layer 26 (for example, 1.7 μm thick) is formed on the translucent conductive layer 4 by, for example, an evaporation method. The first metal layer 26 is made of Au or an alloy containing Au, and at least the outermost surface is made of an Au layer.

  The next step is a step of bonding the growth substrate 24 and the substrate 2 together. In the bonding step, the first metal layer 26 on the growth substrate 24 and the second metal layer 27 on the substrate 2 are bonded. The second metal layer 27 is made of Au or an alloy containing Au, and at least the outermost surface is made of an Au layer. The second metal layer 27 is formed on the surface of the substrate 2 (the surface opposite to the surface on which the p-side electrode 6 is formed) by, for example, an evaporation method before the bonding.

  More specifically, as shown in FIG. 6D, the growth substrate 24 and the substrate 2 are overlapped with the first and second metal layers 26 and 27 facing each other, and the first and second metal layers 26 and 27 are overlapped with each other. Join 27. The joining of the first and second metal layers 26, 27 may be performed by thermocompression bonding, for example. The conditions for thermocompression bonding may be, for example, a temperature of 250 ° C. to 700 ° C., preferably about 300 ° C. to 400 ° C., and a pressure of 10 MPa to 20 MPa. By this bonding, as shown in FIG. 6E, the first and second metal layers 26 and 27 are combined to form the metal layer 3.

  Next, as shown in FIG. 6E, the growth substrate 24 is removed by, for example, wet etching. Since the n-type AlInGaP etching stop layer 25 is formed on the outermost surface of the AlInGaP-based semiconductor laminated structure 5, the n-type GaAs contact layer 16 that contributes to the characteristics of the semiconductor light emitting element 30 during the wet etching. The n-type AlInGaP window layer 15 and the like need not be affected. Then, the n-type AlInGaP etching stop layer 25 is also removed.

  The next step is a step of forming the n-side electrode 7. In this embodiment, the n-side electrode 7 is formed by the lift-off method. More specifically, as shown in FIG. 6F, first, a resist 28 having openings having the same pattern as the electrode pattern of the n-side electrode 7 is formed on the n-type GaAs contact layer 16. Next, the electrode material film 29 is laminated on the AlInGaP-based semiconductor laminated structure 5 by, for example, a vapor deposition method.

  Next, as shown in FIG. 6G, the electrode material film 29 on the resist 28 is removed together with the resist 28. As a result, the n-side electrode 7 made of the electrode material film 29 remaining on the n-type GaAs contact layer 16 is formed. Then, the n-type GaAs contact layer 16 exposed from the n-side electrode 7 is removed by etching. As a result, the n-type AlInGaP window layer 15 is exposed in a portion other than the n-side electrode 7.

Next, as shown in FIG. 6H, fine unevenness 19 is formed on the surface of the n-type AlInGaP window layer 15 by, for example, frosting (wet etching). The frost process may be performed by dry etching.
Next, as shown in FIG. 6I, the mesa portion 17 and the lead portion 18 are formed by selectively removing the peripheral portion of the AlInGaP-based semiconductor laminated structure 5. The mesa portion 17 and the lead portion 18 may be formed by, for example, wet etching.

Next, as shown in FIG. 6J, the p-side electrode 6 is formed on the back surface of the substrate 2 by, for example, the vapor deposition method. The semiconductor light emitting device 30 is obtained through the above steps.
As described above, according to the semiconductor light emitting device 30, since the insulating layer 31 functions as a refractive index relaxation portion that compensates for the refractive index difference between the AlInGaP based semiconductor laminated structure 5 and the translucent conductive layer 4, the AlInGaP based semiconductor laminated layer. The refractive index of the portion close to the structure 5 can be made close to that of the semiconductor layer.

More specifically, for example, in FIG. 5, when the transparent conductive layer 4 is formed of a single layer film of ITO (for example, refractive index n _ITO = 1.89), the transparent conductive layer 4 and the p-type GaP contact layer 11 are formed. (e.g. refractive index _n GaP = 3.4) refractive index difference between the _(n GaP _{-n ITO)} is 1.51. On the other hand, as in this embodiment, as a refractive index relaxation layer for compensating for the refractive index difference between ITO and GaP, for example, SiN (for example, refractive index n _SiN = 2.0) is inserted between ITO and GaP. By doing so, the difference in refractive index at the interface between the layers can be reduced. For example, by inserting a SiN, refractive index difference between the GaP / SiN interface the _(n GaP _{-n SiN)} can be a 1.4, the refractive index difference between the SiN / ITO interface the _(n SiN _{-n ITO)} 0.11 In any case, the difference in refractive index is smaller than that in the case where the GaP / ITO interface is formed. Accordingly, it is possible to suppress the light generated in the light emitting layer 8 and traveling toward the metal layer 3 from being reflected when entering the translucent conductive layer 4 from the AlInGaP-based semiconductor laminated structure 5.

  Moreover, since the ODR structure is formed by the plurality of contact portions 32 that are discretely arranged in the surface of the substrate 2, the current can be confined in a wide range, and the in-plane direction of the substrate 2 is evenly distributed. Light can be generated. Further, since the junction between the contact portion 32 of the translucent conductive layer 4 and the p-type GaP contact layer 11 is not a eutectic junction, it is possible to suppress light absorption at the junction portion.

From the above, the light transmittance of the translucent conductive layer 4 is improved, and the reflectance of the metal layer 3 can be improved.
Moreover, since the translucent conductive layer 4 having a relatively low refractive index with respect to the insulating layer 31 is disposed on the metal layer 3 side, the light reflected by the metal layer 3 passes from the translucent conductive layer 4 to the insulating layer 31. When passing through, the light-transmissive conductive layer 4 enters the insulating layer 31 from a medium having a small refractive index to a medium having a large refractive index. Therefore, it is possible to suppress the reflection and return to the metal layer 3 side again at the interface between the translucent conductive layer 4 and the insulating layer 31. As a result, the light extraction efficiency of the semiconductor light emitting device 30 can be improved.

Although the embodiments of the present invention have been described above, the present invention can be implemented in other forms.
For example, in the embodiment of FIGS. 1 and 2, the translucent conductive layer 4 has a laminated structure over the entire surface of the substrate 2 (that is, the laminated interface extends over the entire surface of the substrate 2). However, for example, the laminated structure may not be formed in the peripheral portion of the semiconductor light emitting device 1 that does not relatively contribute to the extraction of light. In this case, as shown in FIG. 7, the second light-transmissive conductive layer 42 may be embedded in, for example, the central portion of the first light-transmissive conductive layer 41, and a lamination interface may be formed on the bottom surface thereof.

In addition, in the embodiments of FIGS. 4 and 5, a SiN film having a constant refractive index in the thickness direction is given as an example of the insulating layer 31, but for example, the insulating layer 31 may be formed of AlInGaP as shown in FIG. The refractive index may be gradually reduced from the system semiconductor laminated structure 5 toward the metal layer 3. With such a configuration, for example, the flow rate of the SiH ₄ gas may be gradually reduced during the film formation of SiN.

  In addition, various design changes can be made within the scope of the matters described in the claims.

Next, the present invention will be described based on examples, but the present invention is not limited to the following examples.
First, the effect obtained by gradually decreasing the refractive index from the AlInGaP-based semiconductor laminated structure 5 toward the metal layer 3 will be described in detail based on actual measurement data.
(1) Comparison of ITO only, SiN + ITO, and SiO ₂ + ITO With respect to the structure of [Experimental sample] shown in FIGS. 9 and 10, the reflectance from the Au layer was measured by vertically incident light.

According to FIGS. 9 and 10, comparing the reflectance of the structure between the p-GaP layer and the Au layer with respect to light having a wavelength of 625 nm, SiN + ITO (levels 3 to 6)> ITO only (level 1)> SiO ₂ + ITO (level 2). That is, the layer has a lower refractive index than the p-GaP and ITO as SiO ₂ is, when interposed between the p-GaP and ITO, it is difficult to obtain a high reflectivity. It is considered that this is because the light is trapped and the reflectance is lowered. On the other hand, it was found that when the refractive index was decreased stepwise in the order of p-GaP / SiN / ITO as in levels 3 to 6, the light transmittance of ITO was improved and the reflectance was increased.

Further, from the comparison of Levels 3 and 4 (ITO = 1000Å), Level 5 (ITO = 2700Å) and Level 6 (ITO = 4000Å), it was found that the thinner the ITO film thickness is, the higher the reflectance is. In this respect, the preferable range was further examined for the combination of the ITO film thickness, the SiN film thickness, and the SiN refractive index.
(2) Comparison of ITO film thickness (without SiN film)
The reflectance from the Au layer was measured by vertically incidenting light on the structure of [Experimental sample] shown in FIG. 11. Four patterns of samples were prepared, and the thickness d of ITO was 631Å, 713Å, 950Å, and 2774Å, respectively.

From FIG. 11, it was found that the thinner the ITO film, the larger the amplitude, and the thicker the ITO, the smaller the amplitude. Further, regarding light having a wavelength of 625 nm, the sample of ITO = 2774Å had the highest reflectance. From this result, the preferable range of the ITO film thickness for improving the reflectance differs between the inserted state of the SiN film shown in FIGS. 9 and 10 and the state without the SiN film shown in FIG. I understood it. That is, when the SiN film is inserted, it is more preferable to change the ITO film thickness accordingly.
(3) Comparison of SiN film thickness (ITO = 950Å)
The reflectance from the Au layer was measured by vertically injecting light into the structure of [Experimental sample] shown in FIG. Five patterns were prepared for the samples, and the thickness d of the SiN film was set to 1023Å, 2428Å, 2980Å, 3437Å and 3944Å. As a reference, the reflectance of the sample without the SiN film was also measured.

From FIG. 12, it was found that the smaller the SiN film thickness, the larger the amplitude, and the thicker the SiN film, the smaller the amplitude. Further, it was found that the reflectance of light having a wavelength of 625 nm becomes high when the SiN film thickness is around 3000 Å to 3500 Å.
(4) Comparison of SiN refractive index (ITO = 950Å)
The reflectance from the Au layer was measured by vertically injecting light into the structure of [Experimental sample] shown in FIG. Three patterns were prepared for the samples, and the refractive index n and the thickness d of the SiN film were set to (n = 1.995, d = 2428Å), (n = 2.261, d = 2673Å) and (n = 2.396). , D = 2413Å).

From FIG. 13, it was found that the higher the SiN refractive index, the more the peaks of the reflectance waveform tend to shift to the long wavelength side. Further, it is found that the SiN refractive index needs to be in the range of 1.995 to 2.261 in order to match the peak with light having a wavelength of 625 nm.
(5) Relationship between SiN film quality and ITO film thickness The reflectance from the Au layer was measured by vertically incident light on the structure of [Experimental sample] shown in FIGS. 14 to 16. The sample has three patterns regarding the quality of the SiN film, and the refractive index n and the thickness d of the SiN film are (n = 1.995, d = 1023Å), (n = 2.008, d = 2980Å) and (n = 2). .02, d = 3437Å). Further, three kinds of samples having different ITO film thicknesses were prepared from each sample. The ITO film thickness d was d = 631Å, d = 713Å and d = 950Å, respectively.

In all the results of FIGS. 14 to 16, it was found that the thinner the ITO film thickness, the higher the reflectance. This indicates that in the case of the SiN / ITO laminated structure, the reflectance tends to be higher as the ITO film thickness is smaller regardless of the quality of the SiN film.
On the other hand, comparing the results of FIGS. 14 to 16, the combination of the SiN film quality n = 2.008, d = 2980Å and the ITO film thickness d = 631Å (FIG. 15) has the highest reflectance (about 79%). It was Therefore, when the SiN film and the ITO are combined, a relatively high reflectance can be obtained by adjusting the SiN film quality (refractive index and film thickness) and the ITO film thickness in the vicinity of these values.
(6) Luminance Evaluation The present inventor further investigated to what extent the luminance of the semiconductor light emitting device is improved by the structure of the embodiment (SiN / ITO) of FIGS. 4 and 5. The brightness of the structure of FIG. 17 (Comparative Example 1) and the structure of FIG. 18 (Reference Examples 1 and 2) was also measured for comparison with other structures.

The structure of FIG. 17 is the same as the structure of FIG. 2 except that the translucent conductive layer 4 is composed of a single layer film of ITO. On the other hand, in the structure of FIG. 18, the translucent conductive layer 4 is not provided, and the SiO ₂ film (Reference Example 1) or the SiN film (Reference Example 2) is provided between the p-type GaP contact layer 11 (Mg-doped) and the metal layer 3. The metal layer 3 is directly bonded to the p-type GaP contact layer 11 with the insulating layer 34 of FIG.

  The measurement result of the luminance of each sample is shown in FIG. As is clear from FIG. 19, the structure of Example 1 has significantly improved luminance as compared with Comparative Example 1 and Reference Examples 1 and 2.

DESCRIPTION OF SYMBOLS 1 Semiconductor light emitting element 2 Substrate 3 Metal layer 4 Light-transmitting conductive layer 5 AlInGaP-based semiconductor laminated structure 6 p-side electrode 7 n-side electrode 8 Light-emitting layer 9 p-type semiconductor layer 10 n-type semiconductor layer 11 p-type GaP contact layer 19 Fine Concavo-convex shape 30 Semiconductor light emitting element 31 Insulating layer 32 Contact portion 41 First light-transmitting conductive layer 42 Second light-transmitting conductive layer

Claims (14)

Board,
A metal layer on the substrate,
A light emitting layer formed on the metal layer, a first conductivity type layer disposed on the substrate side with respect to the light emitting layer, and a second conductivity type disposed on the opposite side of the substrate with respect to the light emitting layer. A semiconductor layer including a layer;
A translucent conductive layer having _a refractive index na between the metal layer and the semiconductor layer;
An insulating layer between the translucent conductive layer and the semiconductor layer, the insulating layer having a refractive index n _b higher than the refractive index n _a ;
The translucent conductive layer includes a contact portion penetrating the insulating layer and connected to the first conductive type layer,
The semiconductor light emitting device, wherein the translucent conductive layer has a refractive index that gradually decreases from the semiconductor layer toward the metal layer. Board,
A metal layer on the substrate,
A light emitting layer formed on the metal layer, a first conductivity type layer disposed on the substrate side with respect to the light emitting layer, and a second conductivity type disposed on the opposite side of the substrate with respect to the light emitting layer. A semiconductor layer including a layer;
A translucent conductive layer having _a refractive index na between the metal layer and the semiconductor layer;
An insulating layer between the translucent conductive layer and the semiconductor layer, the insulating layer having a refractive index n _b higher than the refractive index n _a ;
The translucent conductive layer includes a contact portion penetrating the insulating layer and connected to the first conductive type layer,
The semiconductor light emitting device, wherein the insulating layer includes a SiN film having a refractive index that gradually decreases from the semiconductor layer toward the metal layer. The semiconductor light emitting device according to claim 1, wherein the first conductivity type layer includes a contact layer connected to the contact portion and having a refractive index n ₀ higher than a refractive index n _{b of the} insulating layer.   The semiconductor light emitting device according to claim 1, wherein the insulating layer includes a SiN film.   The semiconductor light emitting device according to claim 4, wherein the SiN film has a refractive index that gradually decreases from the semiconductor layer toward the metal layer.   The semiconductor light emitting device according to claim 1, wherein the translucent conductive layer contains ITO (indium tin oxide).   7. The semiconductor light emitting device according to claim 1, wherein the contact portion includes a plurality of contact portions that are discretely arranged in a plane of the substrate.   The semiconductor light emitting device according to claim 3, wherein the contact layer contains p-type GaP.   The semiconductor light emitting device according to claim 8, wherein the p-type GaP contains carbon as an impurity.   The semiconductor light emitting device according to claim 1, wherein the metal layer contains Au.   The semiconductor light emitting device according to claim 1, wherein the substrate includes a silicon substrate.   The semiconductor light emitting device according to claim 1, comprising a surface electrode on the semiconductor layer.   The semiconductor light emitting device according to claim 1, further comprising a back surface electrode on the back surface of the substrate.   The semiconductor light emitting device according to claim 1, wherein a surface of the semiconductor layer is formed in a fine uneven shape.

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