JP2018117089A - Light-emitting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a light-emitting device capable of having an excellent contact for both of a p-side and an n-side, and realizing a p-electrode and an n-electrode with a high reflectance ratio.SOLUTION: A p-electrode 16 and an n-electrode 17 have a structure formed by laminating an Ni layer 100 formed by Ni, an AL alloy layer 101 formed by an Al alloy, a Ti layer 102 formed by Ti, a first Au layer 103 formed by Au, a second Au layer 104 similarly formed by Au, and an Al layer 105 formed by Al from an insulation film 15 side in this order. The Ni layer 100 is equal to 3 to 8Å, the Al alloy layer 101 is equal to 100nm. The Ni layer 100 is provided in an island shape so as to be isolated into a plural number. Thus, the Al alloy layer 101 of the Ni layer 100 is provided so as to embed a region between islands of the Ni layer 100. Also, both of the Ni layer 100 and the Al alloy layer 101 are contacted onto a transparent electrode 14 and an n layer 11.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a light emitting device made of a group III nitride semiconductor, and particularly has a feature in an electrode material.

  In a face-up type light-emitting element made of a group III nitride semiconductor, it is necessary to suppress the light extraction efficiency from being reduced due to light being absorbed by the p electrode and the n electrode. One of the methods is to use a material having a high reflectance as a material for the p electrode and the n electrode. For example, Ti / Rh capable of contacting both the transparent electrode and the n layer is used as the p electrode and the n electrode. Since the p electrode and the n electrode are made of the same material, the p electrode and the n electrode can be formed at the same time, and the manufacturing process can be simplified. Here, the symbol “/” means a laminate, and A / B means a laminate structure in which A is deposited and then B is deposited. Hereinafter, “/” is used in the same meaning in the description of the material.

  Patent Document 1 describes that the barrier metal covering the p-electrode and the n-electrode are made of the same material, and Ti / Rh / Ti / Au / Al is exemplified as the material.

Japanese Patent Laid-Open No. 2006-62970

  The inventors examined whether good contact could be made on both the transparent electrode and the n layer using Al or an Al alloy which is a material having a higher reflectance than Rh and is inexpensive. As a result, it was found that when Al was formed on the transparent electrode, an oxide film was formed at the interface between the transparent electrode and Al, resulting in high resistance, and good contact with the transparent electrode could not be obtained.

  Accordingly, an object of the present invention is to realize a p-electrode and an n-electrode that can make good contact with both the p-side and the n-side and have high reflectivity.

  The present invention includes a semiconductor layer made of a group III nitride semiconductor and laminated in the order of an n layer, a light emitting layer, and a p layer, a transparent electrode provided on the p layer, and a p electrode provided in contact with the transparent electrode And the n electrode made of the same material as the p electrode, the p electrode and the n electrode are positioned on the transparent electrode with respect to the p electrode, and the n electrode Is formed in contact with the first layer made of Al or an Al alloy and separated into a plurality of islands in the first layer, the p electrode is in contact with the transparent electrode, and the n electrode is And a second layer made of an Al alloy containing Ni, Co, Cu, or at least one element of Ni, Co, and Cu in contact with the n layer.

  The average film thickness of the second layer is desirably 3 to 8 mm. Within this range, the p electrode and the n electrode can make better contact with both the transparent electrode and the n layer.

  For the first layer, Al or any Al alloy can be used. The Al alloy is, for example, an Al—Ni alloy, an Al—Nd alloy, or an Al—Ta alloy. If Al or Al-Ni alloy is used, contact can be made better and the driving voltage can be reduced. If Al-Nd alloy or Al-Ta alloy is used, the p-electrode is obtained due to its high reflectance. In addition, the absorption of light by the n-electrode can be further reduced, and the light output can be improved.

  The thickness of the first layer is desirably 100 nm or more. The reflectance of the first layer can be sufficiently increased, light absorption by the p electrode and the n electrode can be further reduced, and the light output can be improved.

  According to the present invention, good contact can be made with both the transparent electrode on the p-layer side and the n-layer, and a p-electrode and an n-electrode with high reflectivity can be realized with a low-cost material. As a result, the output of the light emitting element can be improved at a low cost.

3 is a cross-sectional view illustrating a structure of a light-emitting element of Example 1. The top view which looked at the light emitting element of Example 1 from upper direction. The figure which showed the laminated structure of the p electrode 16 and the n electrode 17. FIG. Sectional drawing shown about the structure of the light emitting element of a modification. FIG. 6 shows a manufacturing process of the light-emitting element of Example 1. The graph which showed the relationship between the thickness of Ni layer 100, and p side contact property. The graph which showed the relationship between the thickness of Ni layer, and n side contact property. The graph which showed the relationship between the thickness of the Ni layer 100, and the forward voltage VF. 3 is a graph showing the relationship between the thickness of the Ni layer 100 and the total radiant flux. The graph which compared the total radiant flux of Example 1 and Comparative Example 1. FIG.

  Hereinafter, specific examples of the present invention will be described with reference to the drawings. However, the present invention is not limited to the examples.

  FIG. 1 is a diagram showing the configuration of the light emitting device of Example 1. FIG. FIG. 2 is a plan view of the light emitting device of Example 1 as viewed from above. 1 is a cross-sectional view taken along line A-A ′ in FIG. 2. As shown in FIG. 2, the light-emitting element of Example 1 is a rectangular face-up element in plan view.

  As shown in FIG. 1, the light emitting device of Example 1 includes a substrate 10, a semiconductor layer made of a group III nitride semiconductor stacked in this order on the substrate 10, an n layer 11, a light emitting layer 12, and a p layer 13, p A current blocking layer 18 provided in a predetermined region on the layer 13, a transparent electrode 14 provided on the p layer 13 and the current blocking layer 18, and an insulating film 15 covering the transparent electrode 14 and the exposed n layer 11; The p electrode 16 and the n electrode 17 are provided on the insulating film 15 so as to be separated from each other, and the protective film 19 covers the upper surface of the element. Hereinafter, each configuration will be described in detail.

(Configuration of substrate 10)
The substrate 10 is a growth substrate for forming a group III nitride semiconductor on its main surface. The surface of the substrate 10 on the side of the n layer 11 is subjected to uneven processing (not shown), so that the light extraction efficiency is improved. The material of the substrate 10 may be other than sapphire, and Si, GaN, SiC, ZnO or the like may be used.

(Configuration of semiconductor layer)
The configuration of the n layer 11, the light emitting layer 12, and the p layer 13 may be any configuration conventionally employed as the configuration of the light emitting element. For example, the n layer 11 includes an n-contact layer made of n-GaN, an electrostatic withstand voltage layer in which undoped GaN and n-GaN are sequentially stacked, and an n superlattice layer in which n-GaN and InGaN are alternately and repeatedly stacked. It is a laminated structure. The light emitting layer 12 has an MQW structure in which a structure in which a well layer made of InGaN, a cap layer made of GaN or AlGaN, and a barrier layer made of AlGaN are sequentially laminated is taken as one unit, and this is repeated several times. The p layer 13 has a structure in which a p-clad layer in which p-AlGaN and p-InGaN are alternately and repeatedly stacked, and a p-contact layer made of p-GaN are sequentially stacked.

  A groove 20 having a depth reaching the n layer 11 is provided in a predetermined region on the surface of the p layer 13. The groove 20 exposes the surface of the n layer 11 in order to provide the n electrode 17. The pattern of the groove 20 is slightly wider than the pattern of the n-electrode 17.

(Configuration of transparent electrode 14)
The transparent electrode 14 is continuously formed on the p layer 13 and the current blocking layer 18. The material of the transparent electrode 14 is IZO (zinc-doped indium oxide). In addition, conductive oxides such as ITO (tin-doped indium oxide) and ICO (cerium-doped indium oxide) can be used.

(Configuration of insulating film 15)
The insulating film 15 is provided so as to cover the entire upper surface of the element. That is, it is formed so as to cover from the surface of the n layer 11 exposed on the bottom surface of the groove to the surface of the transparent electrode 14. The material of the insulating film 15 is SiO ₂ . Of course, the material of the insulating film 15 is not limited to SiO ₂ , but oxide films such as TiO ₂ , Nb ₂ O ₅ , Al ₂ O ₃ , ZrO ₂ , and HfO ₂ , nitride films such as SiN and TiN, and acids such as SiON. A nitride film, a fluoride film such as MgF _2, or the like can be used. Moreover, it can be set as the lamination | stacking of those materials.

(Configuration of p-electrode 16)
The p-electrode 16 includes a p-pad portion 160 that is electrically connected to the outside of the device, and a p-wiring portion 161 that extends from the p-pad portion 160.

  The p pad portion 160 is circular and is located on the insulating film 15. As shown in FIG. 2, the p-pad portion 160 is located on one short side.

  From the p pad portion 160, one linear p wiring portion 161 extends parallel to the long side. The line width of the p wiring portion 161 is 3.5 μm. The p wiring portion 161 is located near the center in the short side direction. In the insulating film 15, a hole 21 is provided in a region overlapping the p wiring part 161 in plan view, and the entire pattern of the p wiring part 161 is in contact with the transparent electrode 14 exposed on the bottom surface of the hole 21. Yes. That is, the p electrode 16 is in line contact with the transparent electrode 14.

  Further, the p wiring portion 161 is connected not at the center portion of the p pad portion 160 but at the end portion. Thereby, the p wiring part 161 can be secured longer and the contact area with the transparent electrode 14 can be increased, so that the forward voltage VF can be further reduced.

  As described above, of the p-electrode 16, the p-pad portion 160 is disposed on the insulating film 15 so as not to contact the transparent electrode 14, and the p-wiring portion 161 extending in a wiring shape is brought into contact with the transparent electrode 14. By doing so, the current is efficiently diffused in the plane so that the light emission intensity distribution becomes uniform. The p wiring portion 161 is in line contact with the transparent electrode 14 to increase the contact area with the transparent electrode 14, thereby reducing the forward voltage VF.

(Configuration of n-electrode 17)
The n electrode 17 has an n pad portion 170 electrically connected to the outside of the element, and an n wiring portion 171 extending from the n pad portion 170.

  The n pad portion 170 has a shape in which an oval is halved in the lateral direction, and is located on the insulating film 15. As shown in FIG. 2, the n pad portion 170 is located near the center of the short side opposite to the p pad portion 160 side.

  The n wiring portion 171 extends from the n pad portion 170 along the short side, bends at a rectangular corner of the light emitting element, and in the long side direction toward the short side on the p pad portion 160 side in the vicinity of the long side. A linear shape extending in the direction extending to the vicinity of the p-pad portion 160. The n wiring portion 171 is located on the insulating film 15. The p wiring part 161 and the n wiring part 171 are parallel, and the interval is ½ of the length of the short side. By this n wiring portion 171, the current is uniformly diffused in the plane.

  In the insulating film 15, a plurality of holes 21 penetrating the insulating film 15 are provided at equal intervals in a region below the n wiring portion 171. The n layer 11 is exposed on the bottom surface of the hole 21. The n wiring portion 171 is provided so as to fill the hole 21, and the n wiring portion 171 is in contact with and electrically connected to the n layer 11 through the hole 21. That is, the n electrode 17 is in point contact with the n layer 11.

(Material of p-electrode 16 and n-electrode 17)
The p electrode 16 and the n electrode 17 are made of Ni / Al alloy / Ti / Au / Au / Al. That is, the Ni layer 100 made of Ni, the Al alloy layer 101 made of Al alloy, the Ti layer 102 made of Ti, the first Au layer 103 made of Au, the second Au layer 104 made of Au, and the Al layer 105 made of Al are insulated. In this structure, the layers are laminated in order from the film 15 side. The thickness of each layer is 3 to 8 mm, 100 nm, 70 nm, 10 nm, 1500 nm, and 10 nm in the order of lamination.

  FIG. 3 shows a laminated structure of the p electrode 16 and the n electrode 17. FIG. 3A is a diagram showing a stacked structure of the p wiring portion 161 in a region where the p wiring portion 161 and the transparent electrode 14 are in contact with each other through the hole 21. FIG. 3B is a diagram showing a stacked structure of the n wiring portion 171 in a region where the n wiring portion 171 and the n layer 11 are in contact with each other through the hole 21.

  The role of each layer in the laminated structure of the p electrode 16 and the n electrode 17 is as follows. The Ni layer 100 is a layer provided for making good contact with the transparent electrode 14. The Al alloy layer 101 reflects the light emitted from the light-emitting layer 12 and toward the p-electrode 16 and the n-electrode 17 in order to make a good contact with the n-layer 11. And a layer provided to reduce light absorption by the n-electrode 17. The Ti layer 101 is a layer that blocks diffusion of metal between the Al alloy layer 101 and the first Au layer 103. The first Au layer 103 is a layer for preventing surface oxidation. The second Au layer 104 is a layer for transporting current. The Al layer 105 is a layer for improving adhesion with the protective film 19.

  As shown in FIG. 3, the Ni layer 100 is provided in a plurality of islands. Therefore, the Al alloy layer 101 on the Ni layer 100 is provided so as to fill a region between the islands of the Ni layer 100.

  Therefore, in the region of the hole 21 where the p electrode 16 and the transparent electrode 14 are in contact, both the Ni layer 100 and the Al alloy layer 101 are in contact with the transparent electrode 14 as shown in FIG. Ni has high oxidation resistance and does not form an oxide between the transparent electrode 14 and the Ni layer 100, and the transparent electrode 14 and the Ni layer 100 are in direct contact with each other. Therefore, a local conduction region is formed between the transparent electrode 14 and the Ni layer 100, and the p electrode 16 can make good contact with the transparent electrode 14.

  In the region of the hole 21 where the n electrode 17 and the n layer 11 are in contact, both the Ni layer 100 and the Al alloy layer 101 are in contact with the n layer 11 as shown in FIG. The Al alloy layer 101 can satisfactorily make contact with the n layer 11, and a conduction region is formed between the n layer 11 and the Al alloy layer 101. Therefore, the n electrode 17 can make good contact with the n layer 11.

  Thus, although the p electrode 16 and the n electrode 17 are made of the same material, good contact can be made with respect to both the transparent electrode 14 and the n layer 11.

  The thickness of the Ni layer 100 is 3 to 8 mm. Here, the thickness is an average film thickness, and is a thickness when converted into one film having a uniform thickness. If the Ni layer 100 is formed to be separated into a plurality of islands, the thickness of the Ni layer 100 is not limited to the above range, but is preferably 3 to 8 mm as in the first embodiment. If the thickness of the Ni layer 100 is 3 mm or more, the p-electrode 16 can make good contact with the transparent electrode 14. Further, if the thickness of the Ni layer 100 is 8 mm or less, the n-electrode 17 can make good contact with the n-layer 11. A more desirable thickness of the Ni layer 100 is 6 to 8 mm.

  Instead of the Ni layer 100, a layer made of Co or Cu may be used, or an alloy containing at least one element of Ni, Co, and Cu as a main component may be used.

  The Al alloy layer 101 is made of an Al—Ni alloy. In addition to the Al—Ni alloy, any Al alloy such as an Al—Nd alloy or an Al—Ta alloy can be used. Moreover, you may use Al instead of an alloy. In particular, Al or an Al—Nd alloy is preferably used because of the low contact resistance to the n layer 11. The n electrode 17 can make better contact with the n layer 11. Moreover, since the Al—Nd alloy has a high reflectance, an improvement in light output can be expected by reducing light absorption of the p electrode 16 and the n electrode 17. Since the Ni layer 100 is very thin and is formed in an island shape, the light traveling toward the p electrode 16 and the n electrode 17 is hardly affected by the Ni layer 100, and the reflectance of the p electrode 16 and the n electrode 17 is not affected. Is substantially equal to the reflectance of the Al alloy layer 101.

  The thickness of the Al alloy layer 101 is not limited to 100 nm, but is preferably 75 nm or more. This is because by setting the thickness to 75 nm or more, the reflectance can be sufficiently increased, and light absorption by the p-electrode 16 and the n-electrode 17 can be sufficiently suppressed. There is no particular upper limit on the thickness, but it is desirable that the thickness be 300 nm or less in consideration of saturation for improving the reflectance. More desirably, it is 75 to 200 nm.

(Configuration of the reflective film 22)
In the insulating film 15, a reflective film 22 made of Al is provided under the p pad portion 160, the n pad portion 170, and the n wiring portion 171. Since the reflective film 22 is in the insulating film 15, it is electrically insulated and migration is prevented. This reflection film 22 is provided to suppress light absorption by the p-electrode 16 and the n-electrode 17 by reflecting light traveling toward the p-electrode 16 and the n-electrode 17, thereby improving luminous efficiency. .

  In addition to Al, the reflective film 22 can be made of a highly reflective material such as Ag, Al alloy, or Ag alloy. The reflective film 22 may be a single layer or a multilayer. In the case of a multilayer, Al alloy / Ti, Ag alloy / Al, Ag alloy / Ti, Al / Ag / Al, Ag alloy / Ni, or the like can be used. In order to improve the adhesion between the reflective film 22 and the insulating film 15, a thin film such as Ti, Cr, or Al may be provided between the reflective film 22 and the insulating film 15.

  In addition, as shown in FIG. 4, the reflective film 22 does not need to be provided. Although the light output is reduced by not providing the reflective film 22, the manufacturing process becomes simpler and the cost can be reduced.

(Configuration of current blocking layer 18)
The current blocking layer 18 is provided between the p layer 13 and the transparent electrode 14 and in a region below the hole 21 (that is, below a region where the p wiring portion 161 and the transparent electrode 14 are in contact). Current blocking layer 18 is made of SiO _2. By providing the current blocking layer 18 in this way, the region under the hole 21 in the light emitting layer 12 is prevented from emitting light. Further, the light traveling toward the p wiring portion 161 is reduced by reflection at the interface between the current blocking layer 18 and the p layer 13. As a result, light absorption by the p wiring portion 161 is reduced to improve light output.

The material of the current blocking layer 18 is not limited to SiO ₂ , but oxide films such as TiO ₂ , Nb ₂ O ₅ , Al ₂ O ₃ , ZrO ₂ , and HfO ₂ , nitride films such as SiN and TiN, and oxynitrides such as SiON A film or a fluoride film such as MgF ₂ can be used. Moreover, it can be set as the lamination | stacking of those materials. A DBR structure may be used in order to increase the reflectance.

(Configuration of protective film 19)
A protective film 19 made of SiO ₂ is formed on the entire top surface excluding the p pad portion 160 and the n pad portion 170. The material of the protective film 19 is not limited to SiO ₂ , but oxide films such as TiO ₂ , Nb ₂ O ₅ , Al ₂ O ₃ , ZrO ₂ , and HfO ₂ , nitride films such as SiN and TiN, and oxynitride films such as SiON Fluoride films such as MgF ₂ can be used. Moreover, it can be set as the lamination | stacking of those materials.

  As described above, in the light-emitting element of Example 1, the p electrode 16 and the n electrode 17 are the stacked layers of the Ni layer 100 and the Al alloy layer 101, and the Ni layer 100 is formed in a plurality of island shapes on the transparent electrode 14 or the n layer 11. Since they are formed separately, good contact can be made with respect to both the transparent electrode 14 and the n layer 11, and the p electrode 16 and the n electrode 17 can be made of the same material.

  Moreover, since the p electrode 16 and the n electrode 17 have the Al alloy layer 101 on the Ni layer 100, the reflectance is high. Therefore, light emitted from the light emitting layer 12 and traveling toward the p electrode 16 and the n electrode 17 can be effectively reflected by the Al alloy layer 101, and light absorption by the p electrode 16 and the n electrode 17 is reduced. As a result, the light output of the light emitting device of Example 1 is improved.

(Method for Manufacturing Light-Emitting Element of Example 1)
Next, the manufacturing method of the light emitting element of Example 1 will be described with reference to FIG.

First, a substrate 10 made of sapphire having a concavo-convex surface is prepared and heat-treated in a hydrogen atmosphere to remove impurities adhering to the surface. Next, the n layer 11, the light emitting layer 12, and the p layer 13 are sequentially stacked on the substrate 10 using the MOCVD method. Source gases include TMG (trimethylgallium) as a Ga source, TMA (trimethylaluminum) as an Al source, TMI (trimethylindium) as an In source, ammonia as an N source, biscyclopentadienylmagnesium as a p-type dopant gas, n Silane is used as the type dopant gas. Hydrogen and nitrogen are used for the carrier gas.

Next, the current blocking layer 18 is formed on the p layer 13. The current blocking layer 18 is formed by photolithography and wet etching after forming a SiO ₂ film by vapor deposition or CVD. The pattern may be formed by photolithography, sputtering or vapor deposition, or lift-off. The current blocking layer 18 is formed only on the p layer 13 and the region including the hole 21 to be formed later.

  Next, the transparent electrode 14 is formed in a predetermined region on the p layer 13 and the current blocking layer 18. The transparent electrode 14 is formed with a pattern by photolithography and wet etching after forming an IZO film by sputtering.

  Next, a predetermined region on the surface of the p layer 13 is dry-etched to form the groove 20, and the n layer 11 is exposed on the bottom surface of the groove 20 (see FIG. 5A).

  Next, the insulating film 15 in which the reflective film 22 is embedded is formed so as to cover the entire upper surface. In detail, it forms as follows. First, a first insulating film is formed on the entire upper surface by a CVD method. Then, it is reflected by vapor deposition, photolithography, and etching on a predetermined region on the first insulating film (a region overlapping the p pad unit 160, the p wiring unit 161, the n pad unit 170, and the n wiring unit 171 to be formed later). A film 22 is formed. The reflective film 22 may be formed by lift-off. Next, a second insulating film is formed on the first insulating film and the reflective film 22 by a CVD method, and the first insulating film and the second insulating film are integrated into the insulating film 15. As described above, the insulating film 15 in which the reflective film 22 is embedded in the predetermined region is formed.

  In the case where the reflective film 22 is not provided as in the light emitting element of the modified example shown in FIG. 4, the manufacturing process can be further simplified and the manufacturing cost can be simplified because the insulating film 15 can be simply formed. Can be reduced.

  Next, a predetermined region of the insulating film 15 (a region where the p wiring portion 161 and the transparent electrode 14 or the n wiring portion 171 and the n layer 11 are in contact with each other) is dry-etched to form a hole 21 penetrating the insulating film 15. The transparent electrode 14 and the n layer 11 are exposed on the bottom surface of the hole 21 (see FIG. 5B).

  Next, a p pad portion 160 of the p electrode 16, a p wiring portion 161, an n pad portion 170 of the n electrode 17, and an n wiring portion 171 are formed in a predetermined region on the insulating film 15. The wiring part 161 is in contact with the transparent electrode 14 and the n wiring part 171 is formed in contact with the n layer 11 (see FIG. 5C). Patterning is performed by a lift-off method. This will be described in more detail as follows.

  First, a resist layer is formed on the insulating film 15 and the n layer 11 by photolithography. In the resist layer, regions where p pad portion 160 and p wiring portion 161 of p electrode 16 and n pad portion 170 and n wiring portion 171 of n electrode 17 will be formed later have an open pattern.

  Next, Ni layers 100 made of Ni are formed on the resist layer and on the insulating film 15 and the n layer 11 exposed in the openings by EB (electron beam) vapor deposition. Here, the thickness of 3 to 8 mm is an average thickness. When the average thickness is within this range, the Ni layer 100 is formed by being separated into a plurality of islands.

  Next, an Al alloy layer 101 made of Al—Ni is deposited to 100 nm, a Ti layer 102 made of Ti to 70 nm, and a first Au layer 103 made of Au to 10 nm in this order by sputtering. Here, the Al alloy layer 101 is formed so as to fill the region between the islands of the Ni layer 100. Therefore, in the region of the hole 21, both the Ni layer 100 and the Al alloy layer 101 are in contact with the transparent electrode 14 or the n layer 11.

  Next, the second Au layer 104 made of Au is 1500 nm and the Al layer 105 made of Al is laminated in order of 10 nm by RH (resistance heating) vapor deposition.

  Next, the resist layer is removed, and the metal stack formed on the resist layer is also removed. As described above, the p pad portion 160 and p wiring portion 161 of the p electrode 16 made of Ni / Al alloy / Ti / Au / Au / Al and the n pad portion 170 and the n wiring portion 171 of the n electrode 17 are formed in predetermined regions. Form.

  Next, the protective film 19 is formed on the entire surface excluding the p pad portion 160 and the n pad portion 170 by CVD, photolithography, and dry etching. Thus, the light-emitting element of Example 1 is manufactured. As described above, in the light emitting device of Example 1, the p electrode 16 and the n electrode 17 are made of materials that can make good contact with both the transparent electrode 14 and the n layer 11. The manufacturing process is simplified by forming the electrodes 17 simultaneously.

(Various experimental examples)
Next, various data relating to the light emitting element of Example 1 will be described.

  FIG. 6 is a graph showing the Ni layer 100 thickness dependence of the p-side contact property of the p-electrode 16 and the n-electrode 17. The p-side contact property was evaluated by a voltage value pp at 20 mA by forming a test element group (TEG) pattern on the transparent electrode 14 and having the same stacked structure as the p electrode 16 and the n electrode 17. . For comparison, the dependency of the voltage value pp on the Ti layer thickness was also evaluated for an electrode (Comparative Example 1) in which the Ni layer 100 and the Al alloy layer 101 were replaced with a laminate of a Ti layer and an Rh layer.

  As shown in FIG. 6, regardless of the thickness of the Ni layer 100 and the Ti layer, the electrode of Example 1 using the Ni layer 100 has a pp value compared to the electrode of the comparative example using the Ti layer. It was found that Example 1 can make better contact with the transparent electrode 14 than the comparative example. Further, as shown in FIG. 6, in the electrode of Example 1, it was found that as the thickness of the Ni layer 100 increased, the pp value suddenly decreased and became a substantially constant pp value at 3 mm or more.

  FIG. 7 is a graph showing the Ni layer 100 thickness dependence of the n-side contact property of the p-electrode 16 and the n-electrode 17. The n-side contact property was evaluated by a voltage value nn at 20 mA by forming a test element group (TEG) pattern on the n layer 11 and having the same stacked structure as the p electrode 16 and the n electrode 17. . Similarly, the voltage value nn was also evaluated for Comparative Example 1.

  As shown in FIG. 7, in both Example 1 and Comparative Example 1, it was found that the nn value increased as the thicknesses of the Ni layer 100 and the Ti layer increased. In particular, up to a thickness of 10 mm, the nn value increase was almost the same in Example 1 and Comparative Example 1. However, when the thickness was larger than 10 mm, the increase in the nn value was greater in Example 1. . In addition, it was found that the increase in the nn value was a slight increase below 8%.

  FIG. 8 is a graph showing the relationship between the forward voltage VF at 20 mA and the thickness of the Ni layer 100 for the light-emitting element of Example 1. The relationship between the forward voltage VF and the thickness of the Ni layer 100 is similarly shown for the light emitting element of Comparative Example 1.

  As shown in FIG. 8, in the light emitting device of Example 1, the VF sharply decreases until the thickness of the Ni layer 100 is 3 mm, becomes almost constant VF when the thickness is 3 to 8 mm, and increases slightly beyond 8 mm. I found out that In the light emitting device of Comparative Example 1, the VF gradually decreased until the thickness of the Ti layer was 12 mm. However, when the thickness was larger than 12 mm, the VF was substantially constant. It was also found that the VF of the light emitting element of Example 1 was smaller than that of the light emitting element of Comparative Example 1 at any thickness.

  6 to 8, it was found that by setting the thickness of the Ni layer 100 to 3 to 8 mm, good contact can be made on both the p side and the n side, and VF can be reduced. It was also found that the p-side contact property contributes more to VF than the n-side contact property.

  FIG. 9 is a graph showing the dependence of the total radiant flux on the thickness of the Ni layer 100 when the light emitting device of Example 1 is driven at 20 mA. As shown in FIG. 9, the total radiant flux tends to increase as the thickness of the Ni layer 100 increases, and it has been found that when the thickness is 6 mm or more, the total radiant flux tends to be almost constant and saturated. . From FIGS. 6 to 8 and FIG. 9, it was found that the thickness of the Ni layer 100 is optimally 6 to 8 mm in order to improve the light output while maintaining VF.

  FIG. 10 is a graph comparing the total radiant flux when the light-emitting element of Example 1 and the light-emitting element of Comparative Example 1 are driven at 20 mA. The thickness of the Ni layer 100 in Example 1 and the thickness of the Ti layer in Comparative Example 1 were 6 mm and 8 mm. As shown in FIG. 10, the light output of the light emitting device of Example 1 was higher than that of the light emitting device of Comparative Example 1, and the light output was improved by 0.6 to 2.2%.

  In Example 2, the Ni layer 100 is changed to an Al alloy containing Ni (for example, an Al—Ni alloy). In an Al alloy containing Ni, a plurality of Ni grains are precipitated in the Al alloy by heat treatment. Therefore, similarly to the Ni layer 100 of the first embodiment, a structure is obtained in which Ni grains are separated into a plurality of islands on the transparent electrode 14 or the n layer 11. Further, the space between the Ni grains is filled with an Al alloy, and the Al alloy is also in contact with the transparent electrode 14 or the n layer 11. That is, the same structure as in Example 1 is realized by heat-treating an Al alloy containing Ni. As a result, the same effect as in the first embodiment can be obtained.

  In addition to Al alloys containing Ni, Al alloys containing Co and Cu can also be used. That is, an Al alloy containing at least one element of Ni, Co, and Cu may be used.

(Various modifications)
The light emitting element of Example 1 has a structure in which the p electrode is in line contact and the n electrode is in point contact, but is not limited thereto, and may be any of point contact, line contact, and surface contact.

  Further, although the light-emitting elements of Examples 1 and 2 are face-up type elements, the present invention can also be applied to flip-chip type elements.

  In Example 1, a Ni layer is formed by vapor deposition or sputtering to form a plurality of island-shaped shapes. In Example 2, Ni particles are precipitated in an Al alloy containing Ni. In the Al alloy, a shape in which Ni is separated into a plurality of islands is formed, but the present invention is not limited to these methods. Any formation is possible as long as an Al alloy is provided in contact with the transparent electrode or the n layer, and a Ni layer is formed by separating the Al alloy into a plurality of islands, and the Ni layer is in contact with the transparent electrode or the n layer. The method can be adopted.

  The light-emitting element of the present invention can be used as a light source for a lighting device or a display device.

10: Substrate 11: n layer 12: light emitting layer 13: p layer 14: transparent electrode 15: insulating film 16: p electrode 17: n electrode 18: current blocking layer 19: protective film 22: reflective film 100: Ni layer 101: Al alloy layer 102: Ti layer 103: 1st Au layer 104: 2nd Au layer 105: Al layer 160: p pad part 161: p wiring part 170: n pad part 171: n wiring part

Claims (5)

A semiconductor layer made of a group III nitride semiconductor and stacked in the order of an n layer, a light emitting layer, and a p layer, a transparent electrode provided on the p layer, a p electrode provided in contact with the transparent electrode, A light-emitting element provided in contact with the n-layer and having an n-electrode made of the same material as the p-electrode,
The p electrode and the n electrode are
The p-electrode is positioned on the transparent electrode, the n-electrode is positioned on the n-layer, and a first layer made of Al or an Al alloy;
The p-electrode is formed into a plurality of islands and is in contact with the transparent electrode, the n-electrode is in contact with the n-layer, Ni, Co, Cu, or Ni, Co, And a second layer made of an Al alloy containing at least one element of Cu.   The light emitting device according to claim 1, wherein an average film thickness of the second layer is 3 to 8 mm.   The light emitting device according to claim 2, wherein the second layer is made of Ni.   4. The light emitting device according to claim 1, wherein the first layer is made of Al, an Al—Ni alloy, an Al—Nd alloy, or an Al—Ta alloy. 5.   5. The light-emitting element according to claim 1, wherein the first layer has a thickness of 100 nm or more.

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