JP2007311375A - MANUFACTURING METHOD OF p-TYPE GROUP III-V COMPOUND SEMICONDUCTOR AND MANUFACTURING METHOD OF LIGHT-EMITTING ELEMENT - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method of a p-type group III-V compound semiconductor containing Al which can allow to exhibit high p-type conductivity in a method using a catalytic layer on a semiconductor layer, can be manufactured at a low cost and can also realize good ohmic contact with an electrode. <P>SOLUTION: The manufacturing method of the p-type group III-V compound semiconductor includes a first step of forming a p-type group III-V compound semiconductor layer doped with p-type impurities; a second step of forming the catalytic layer on the p-type group III-V compound semiconductor layer; and a third step of applying thermal processing to the p-type group III-V compound semiconductor layer in a state where the catalytic layer is attached. In this method, the p-type group III-V compound semiconductor layer contains Al and the catalytic layer contains at least one kind of Ni, Ag and Cu. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for producing a p-type group III-V compound semiconductor and a method for producing a group III-V compound semiconductor light emitting device.

In gallium nitride-based compound semiconductors, it has been difficult to form a semiconductor exhibiting p-type conductivity for a long time. The reason is that in semiconductor crystal growth, hydrogen is incorporated into the semiconductor crystal and combined with the doped p-type impurity, and does not exhibit p-type conductivity.
On the other hand, a method of irradiating Mg doped gallium nitride with a low-velocity electron beam (see Patent Document 1) and a method of heat-treating Mg-doped gallium nitride in an atmosphere containing no hydrogen (see Patent Document 2) ) And the like, it has been found that a p-type impurity in a semiconductor passivated by hydrogen can be dehydrogenated and activated, thereby obtaining a semiconductor exhibiting p-type conductivity.

However, the above-described method using electron beam irradiation makes it difficult to uniformly treat the entire surface of the wafer, and even if it is possible, it takes time to perform the treatment and the apparatus becomes large. There are problems such as being expensive. Therefore, for the formation of a p-type gallium nitride compound semiconductor, a method using heat treatment that can uniformly treat a sample of a large area is considered industrially suitable. In the method by heat treatment disclosed in No. 2, heat treatment needs to be performed at a high temperature of about 700 to 900 ° C. in order to ensure a high carrier concentration. When heat treatment is performed at such a high temperature, the crystal forming the light emitting layer is likely to be deteriorated. For example, In _x Ga _1-x N (0 <x ≦ 1), which is a ternary mixed crystal gallium nitride compound semiconductor containing In. ) Causes spinodal decomposition and the crystal is liable to deteriorate, and there is a problem that a visible light emitting element having sufficient light emission intensity cannot be obtained.

  Therefore, as a method of lowering the temperature of the heat treatment, in the method of forming an electrode of a p-type gallium nitride compound semiconductor disclosed in Patent Document 3, after forming Pt on the acceptor impurity addition layer, at least 400 ° C. in an atmosphere containing oxygen. In the technique of heat-treating at a temperature of 5 and the method of manufacturing a p-type gallium nitride-based compound semiconductor disclosed in Patent Document 4, Co is vapor-deposited on the surface of the gallium nitride-based compound semiconductor to which an acceptor impurity is added and the heat treatment is performed in an oxygen atmosphere. A technique for performing a heat treatment by removing the oxidized Co film after the heat treatment, or by performing a heat treatment in an atmosphere gas containing no oxygen disclosed in Patent Document 5 and Patent Document 6 at a low temperature. Although methods for obtaining p-type conductivity have been disclosed, all have problems (see the prior art in Patent Document 7).

As a method for solving these problems, Patent Document 7 discloses a technique of forming a layer called a “catalyst layer” on a p-type gallium nitride compound semiconductor layer and performing a heat treatment.
JP-A-2-257679 JP-A-5-183189 JP 11-186605 A Japanese Patent Laid-Open No. 11-145518 Japanese Patent Laid-Open No. 11-177134 Japanese Patent Laid-Open No. 11-354458 JP 2002-26389 A

  The invention of the above-mentioned Patent Document 7 is based on the applicant of the present application, and is characterized in that, in forming a p-type semiconductor layer, a catalyst layer made of metal or the like is formed on the semiconductor layer and then heat-treated. However, subsequent studies have revealed that when the semiconductor layer of a p-type gallium nitride compound or the like contains Al as a composition, the difference in effective carrier concentration depends on the type of catalyst layer. In particular, this tendency was strong when 0.5% by mass or more, preferably 5% by mass or more of Al was contained.

  Since the contact layer of p-type gallium nitride compound semiconductor containing Al can improve the transmittance of light emission, it is considered advantageous in the efficiency of taking out the light emitted in the light emitting layer to the outside. However, it has been found that when Al is mixed in as a composition, the band gap is increased and the contact resistance is increased.

  The present invention has been proposed in view of the above, and is a p-type III-V compound semiconductor containing Al, which exhibits high p-type conductivity in a method used for a catalyst layer on the semiconductor layer. It is an object of the present invention to provide a method for producing a p-type group III-V compound semiconductor that can be produced at low cost and can achieve good ohmic contact with an electrode.

As a result of research to achieve the above object, when a p-type III-V compound semiconductor containing Al is produced, a specific metal is used as the catalyst layer when a catalyst layer is formed on the semiconductor layer and heat-treated. And found that there is a remarkable effect in increasing the conductivity. The present invention is based on this research result and comprises the following inventions.
(1) a first step of producing a p-type III-V compound semiconductor layer to which a p-type impurity is added, a second step of producing a catalyst layer on the p-type III-V compound semiconductor layer, And a third step of heat-treating the p-type III-V compound semiconductor layer with the catalyst layer attached thereto. In the method for producing a p-type III-V compound semiconductor, the p-type III-V compound semiconductor A method for producing a p-type group III-V compound semiconductor, wherein the layer contains Al and the catalyst layer contains at least one of Ni, Ag, and Cu.
(2) The method for producing a p-type III-V compound semiconductor according to (1), wherein the p-type III-V compound semiconductor is a gallium nitride compound semiconductor.

(3) The p-type III-V group according to (1) or (2) above, wherein the amount of Al contained in the p-type III-V compound semiconductor is 0.5 atomic% or more. A method for manufacturing a compound semiconductor.
(4) The method for producing a p-type group III-V compound semiconductor according to any one of the above (1) to (3), wherein the amount of Al contained in the p-type group III-V compound semiconductor is 5 to 50 atomic% .
(5) The method for producing a p-type group III-V compound semiconductor according to any one of (1) to (4), wherein the catalyst layer contains one or more of Cu and Ag.
(6) The method for producing a p-type III-V compound semiconductor according to any one of (1) to (5), wherein the heat treatment temperature in the third step is 200 ° C. or higher.
(7) The manufacturing method of the p-type III-V compound semiconductor in any one of said (1)-(6) including the 4th process of peeling a catalyst layer after the said 3rd process.

(8) The method for producing a p-type group III-V compound semiconductor according to any one of (1) to (7), wherein the thickness of the catalyst layer is in the range of 1 nm to 100 nm.
(9) The p-type group III-V compound semiconductor according to any one of (1) to (8), wherein the catalyst layer contains Ni, Ag or Cu in a range of 50 to 100 atomic%. Manufacturing method.
(10) The p-type III-V group compound semiconductor layer has a thickness in the range of 1 nm to 5 μm, and the p-type III-V group compound semiconductor according to any one of (1) to (9) is manufactured. Method.
(11) In the method for producing a light-emitting element including an n-type layer composed of a III-V group compound semiconductor layer, a light-emitting layer, and a p-type layer, the p-type layer is a group III-V compound semiconductor layer containing Al, A method for manufacturing a light-emitting element, comprising forming a catalyst layer containing at least one of Ni, Ag, or Cu on the p-type layer, and then performing heat treatment.
(12) The method for manufacturing a light-emitting element according to (11), wherein the p-type III-V compound semiconductor is a gallium nitride compound semiconductor.

(13) The method for manufacturing a light-emitting element according to (11) or 12, wherein the amount of Al contained in the p-type III-V compound semiconductor is 0.5 atomic% or more.
(14) The method for manufacturing a light-emitting element according to any one of (11) to (13), wherein the amount of Al contained in the p-type III-V compound semiconductor is 5 to 50 atomic%.
(15) The method for manufacturing a light-emitting element according to any one of (11) to (14), wherein the catalyst layer includes one or more of Cu and Ag.
(16) The method for manufacturing a light-emitting element according to any one of (11) to (15), wherein the heat treatment temperature is 200 ° C. or higher.

(17) The method for manufacturing a light-emitting element according to any one of (11) to (16), including a step of peeling the catalyst layer after the heat treatment.
(18) The method for producing a light-emitting element according to any one of (11) to (17), wherein the thickness of the catalyst layer is in the range of 1 nm to 100 nm.
(19) The method for manufacturing a light-emitting element according to any one of (11) to (18), wherein the catalyst layer contains Ni, Ag, or Cu in a range of 50 to 100 atomic%.
(20) The method for manufacturing a light-emitting element according to any one of (11) to (19), wherein the thickness of the p-type III-V compound semiconductor layer is in the range of 1 nm to 5 μm.

  Compared to the case where a catalyst layer made of a metal containing Ni, Ag or Cu is formed on a p-type group III-V compound semiconductor layer containing Al and heat-treated, so that another metal is used as the catalyst layer. There is a remarkable effect. That is, the carrier concentration can be remarkably increased, so that the conductivity can be increased and the p-type function can be fully exhibited.

Hereinafter, the present invention will be described in detail with reference to the drawings.
In the present invention, Group III-V compound semiconductors are based on GaN containing Al, and include those in which part or all of Ga is substituted with B and In. Moreover, the thing which substituted a part or all of N by P and As is also included. Expressed by the formula _{Al x B y In z Ga 1} -xyz N 1-ij P i As j (0 <x ≦ 1,0 ≦ y <1,0 ≦ z <1,0 ≦ j ≦ 1,0 ≦ i ≦ 1, 0 <x + y + z ≦ 1, 0 ≦ i + j ≦ 1). Among these general formulas, the method of the present invention is particularly effective and desirable in the case of a gallium nitride (GaN) -based compound semiconductor containing Al. I expressed this with general formula _{Al x B y In z Ga 1} -xyz N (0 <x <1,0 ≦ y <1,0 ≦ z <1,0 <x + y + z <1,) is. Of these, GaAlN and GaAlInN are more preferable.

Hereinafter, the present invention will be described taking a gallium nitride compound semiconductor as an example of a III-V compound semiconductor.
FIG. 1 is a diagram for explaining the concept of the procedure of a method for producing a p-type gallium nitride compound semiconductor according to the present invention. Referring to FIG. 1, in the method for producing a p-type gallium nitride compound semiconductor according to the present invention, first, as shown in FIG. 1A, a buffer layer is formed on a substrate 1 made of sapphire and other p-types made of various compositions and layer structures. A catalyst layer 7 is formed on the layer 2 that is not a layer and the p-type layer 3 doped with Mg to form a laminate (sample) 10, and the sample 10 is subjected to heat treatment. By this heat treatment, hydrogen bonded to Mg of the p-type layer 3 moves and bonds to the material forming the catalyst layer 7 as shown in FIG. Then, the sample 11 is impregnated with hydrochloric acid to remove the catalyst layer 7 to form a sample 12 as shown in FIG. In the p-type layer 3 of the sample 12, Mg that has been passivated by being bonded to hydrogen in the stage of the sample 10 is activated to increase the carrier concentration. Therefore, the p-type layer 3 has a sufficient p-type function. It will be possible to demonstrate.

It is necessary to perform annealing after forming the catalyst layer. As the temperature, a temperature of 200 ° C. or higher is necessary. Also, this temperature should be as low as possible. When the light emitting layer is made of InGaN, composition separation is likely to occur by heat treatment, and thus the light emission intensity may be lowered by heat treatment at a high temperature.
The present invention is characterized in that it includes one or more of Ni, Ag, and Cu as the catalyst layer. When these metals were used, the treatment temperature was successfully reduced by about 100 ° C. compared to the case where other metals such as Pd and Co described in Document 7 were used. This effect makes it possible to obtain a sufficient carrier concentration at a treatment temperature of 200 ° C. or higher. More preferably, the temperature is 400 ° C. or higher, and more preferably 500 ° C. or higher.
On the other hand, when the processing temperature is set to 900 ° C. or higher, the above InGaN crystal is decomposed. Conventionally, when AlGaN is used for the p-layer, a high temperature of 900 ° C. or higher has been required, but sufficient activation can be obtained by the treatment at a temperature of 900 ° C. or lower by the technique of the present invention. It is also possible to set the temperature to 700 ° C. or lower, which is more desirable from the viewpoint of preventing decomposition of InGaN.

Among these, Ag and Cu are superior to Ni in that they are easy to form a film, are easy to peel off, and are inexpensive.
If one or more of these metals are included, other metals such as other metals described in Document 7 may be included. In this case, it is desirable that at least one of Ni, Ag, and Cu is contained by 50 atomic% or more.
The time for performing the heat treatment needs to be appropriately selected according to the temperature. If it is too short, a sufficient activation effect cannot be obtained, and if it is too long, the InGaN contained in the light emitting layer is decomposed and the output of the device is lowered.

  Ni, Ag, and Cu used as a catalyst layer in the present invention are metals having a small work function, and cannot be used as p-type electrodes as they are. For this reason, it is desirable to include the process of peeling a catalyst layer as a 4th process. Peeling can be easily performed by a method such as impregnation with acid or alkali. If surface flatness is required, dry etching may be performed.

The film thickness of the catalyst layer is desirably 1 nm to 100 nm. If it is thinner than this, it becomes difficult to form a uniform film, and if it is thicker than this, there is no difference in the effect as a catalyst layer, and only the film forming process time and the peeling process time are unnecessarily prolonged.
Since the catalyst layer is a metal film, a generally known film forming method can be used without any problem. Specifically, vacuum deposition, sputtering, chemical vapor deposition (CVD), and the like. Among these, vacuum deposition is a method suitable for forming a catalyst layer with little damage to the p-type gallium nitride compound semiconductor.

  The composition of Al contained in the p-type gallium nitride compound semiconductor is preferably 0.5% by mass or more because the effect of the present invention becomes remarkable. More preferably, it is 5 mass% or more. If the composition is less than this, it can be sufficiently activated even if another material is used as the catalyst layer. The upper limit of the Al content is preferably about 50 atomic% and preferably contains Ga or the like.

  When annealing the catalyst layer, it is desirable that the gas phase contains as little hydrogen as possible. The term “hydrogen” as used herein includes a compound containing a hydrogen atom. The pressure may be arbitrary, but a low pressure of 70 Torr or less is desirable. Further, it is necessary to make an effort to remove as much oxygen as possible from the gas phase in the heat treatment atmosphere so as not to generate metal oxides on the surface of the catalyst layer. Even when 1% by mass of oxygen is contained in the gas phase, metal oxidation may occur.

It is better not to include an oxide layer at the interface between the catalyst layer and the p layer, and it is desirable to pre-treat the p-type layer surface. The pretreatment may be dry or wet, but the wet is simpler and the cost can be reduced. As the wet treatment, acid treatment or alkali treatment can be used. In addition to the well-known impregnation and boiling with hydrochloric acid, phosphoric acid, sulfuric acid, ammonia, NaOH, KOH, etc., RCA cleaning, Piraniha cleaning, and the like can be used.
The film thickness of the p-type gallium nitride compound semiconductor is desirably 1 nm to 5 μm. If the film thickness is less than this, it is difficult to function as a p-type layer, so that it is not necessary to employ the element structure. If the film thickness is more than this, it is difficult to extract hydrogen from the deep bottom.

Example 1
Next, an embodiment of the present invention will be described with reference to FIG.
FIG. 2 is an explanatory view of a method for producing a semiconductor light emitting device (semiconductor light emitting diode) including a p-type gallium nitride compound semiconductor produced by the method of the present invention.
In this embodiment, a MOCVD method is used to form a buffer layer 22 made of AlN, an n-type layer 231 made of undoped GaN, an n-type layer 232 made of Ge-doped AlGaN, an InGaN layer on a substrate 21 made of sapphire. A multi-quantum well (MQW) layer 24 composed of a GaN layer, an Mg-doped AlGaN layer 25, and a p-type layer 26 composed of Mg-doped AlGaN were sequentially laminated to produce a wafer having a multilayer structure for a semiconductor light emitting device.

  On the wafer having this multilayer structure, a catalyst layer 27 made of Ag having a thickness of 10 nm is formed by a resistance heating method using a vapor deposition machine to produce a sample 200 (FIG. 2A), and then A heat treatment was performed for 10 minutes at 450 ° C. in a nitrogen carrier gas by a similar procedure using a heat treatment furnace. In this way, a sample 201 was manufactured (FIG. 2B). Thereafter, the catalyst layer 27 made of Ag was removed by impregnating with HCl, and a sample (wafer) 202 having the p-type layer 26 as the outermost surface was produced (FIG. 2C).

When the carrier concentration was measured for the p-type layer 26 on the outermost surface of the wafer 202 subjected to such heat treatment, the carrier concentration was about 6 × 10 ¹⁷ cm ⁻³ and exhibited p-type conductivity. It is considered that this is because the hydrogen bonded to Mg in the p-type layer 26 moves to the catalyst layer 27 by the heat treatment, and as a result of combining with Ag in the catalyst layer 27, the carrier concentration in the p-type layer 26 increases. .
With respect to the wafer 202 after the heat treatment, a translucent electrode made of ITO and a bonding pad were formed on the surface side of the p-type layer 26 by known photolithography to form a p-side electrode.
Further, dry etching was then performed on the wafer 202 to expose a portion of the n-type layer 231 where the n-side electrode was to be formed, and an n-side electrode was fabricated in the exposed portion.

For the wafer on which the p-side and n-side electrodes were formed in this way, the back surface of the substrate 21 was ground and polished to form a mirror-like surface. Thereafter, the wafer was cut into 350 μm square chips, placed on the lead frame so that the electrodes were on top, and connected to the lead frame with gold wires to form a semiconductor light emitting diode.
When a forward current was passed between the p-side and n-side electrodes of the light emitting diode produced as described above, the forward voltage at a current of 20 mA was 3.2V. Moreover, when light emission was observed through the p side translucent electrode, the light emission wavelength was 465 nm and the light emission output showed 15 mW.

(Examples 2-3)
Next, 50 nm of Cu (Example 2) and Ni (Example 3) are formed as catalyst layers on an epitaxial substrate having the same structure as that used in Example 1, and the vacuum is 3 × 10 ⁻³ Torr. Then, heat treatment was performed at 500 ° C. for 5 minutes.
From this substrate, a light emitting diode was produced in the same procedure as in Example 1. Table 1 shows the carrier concentration of the p-type layer. Table 1 shows forward voltages at a current of 20 mA when a forward current is passed between the p-side and n-side electrodes of the light emitting diode. Moreover, when light emission was observed through the p side translucent electrode, the light emission wavelength was 525 nm and the light emission output showed 8 mW.
(Comparative Examples 1-6)

For a wafer having a multilayer structure manufactured by the MOCVD method in the same manner as in the examples, various catalyst layers are formed on the surface by the same method, and heat treatment is performed in a nitrogen gas atmosphere for 10 minutes, whereby Mg in the AlGaN layer is formed. And the catalyst layer was removed to produce a p-type layer made of AlGaN. The carrier concentrations of the p-type layers of the examples and comparative examples are shown in Table 1 above.

A p-side electrode and an n-side electrode were prepared in the same manner as in the example for the heat-treated wafer. Further, a light emitting diode was formed from this wafer in the same manner as in the example.
When a forward current was passed between the p-side and n-side electrodes of the light-emitting diode fabricated as described above, the forward voltage at a current of 20 mA was as shown in Table 1. Further, when light emission was observed through the p-side translucent electrode, the light emission wavelength and light emission output were almost the same as those in the second embodiment.

Thus, although there was no difference in the light emission output of a light emitting diode in Example and Comparative Examples 1-6, a big difference arose in the carrier voltage of the p-type layer and the forward voltage at a current of 20 mA.
In the above embodiment, the heat treatment is performed in a nitrogen gas atmosphere, but may be performed in another inert gas, for example, a rare gas such as Ar. Further, the heat treatment may be performed in a vacuum such as 3 × 10 ⁻³ Torr, as long as the pressure does not allow the oxidation to proceed, and the pressure value is not particularly limited.
In the embodiment, the catalyst layer is configured as a single layer film made of one type of metal, but may be formed as a multilayer film made of one type of metal or an alloy or compound of two or more types of metals.

  According to the present invention, the p-type electrode has a high carrier concentration, a low resistance, a low driving voltage, a high light emission output, and can be used for various display lamps.

It is a figure for demonstrating the procedure of the manufacturing method of the p-type gallium nitride compound semiconductor of this invention. It is explanatory drawing about the manufacturing method of the semiconductor light-emitting device comprised including the p-type gallium nitride type compound semiconductor produced by the method of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Substrate 2 Buffer layer 3 P-type layer 7 Catalyst layer 10 Sample 11 Sample 12 Sample 21 Substrate 22 Buffer layer 24 Multiple quantum well (MQW) layer 25 Undoped GaN layer 26 P-type layer 27 Catalyst layer 200 Sample 201 Sample 202 Wafer 202 Wafer 231 n-type layer 232 n-type layer

Claims (20)

  a first step of producing a p-type III-V compound semiconductor layer to which a p-type impurity is added; a second step of producing a catalyst layer on the p-type III-V compound semiconductor layer; and the catalyst layer And a third step of heat-treating the p-type III-V compound semiconductor layer in a state of attaching a p-type III-V compound semiconductor layer, wherein the p-type III-V compound semiconductor layer is made of Al. And the catalyst layer contains at least one of Ni, Ag, or Cu. A method for producing a p-type group III-V compound semiconductor.   The method for producing a p-type group III-V compound semiconductor according to claim 1, wherein the p-type group III-V compound semiconductor is a gallium nitride compound semiconductor.   The method for producing a p-type group III-V compound semiconductor according to claim 1 or 2, wherein the amount of Al contained in the p-type group III-V compound semiconductor is 0.5 atomic% or more.   The method for producing a p-type group III-V compound semiconductor according to any one of claims 1 to 3, wherein the amount of Al contained in the p-type group III-V compound semiconductor is 5 to 50 atomic%.   The method for producing a p-type group III-V compound semiconductor according to any one of claims 1 to 4, wherein the catalyst layer contains one or more of Cu and Ag.   The method for producing a p-type group III-V compound semiconductor according to any one of claims 1 to 5, wherein a heat treatment temperature in the third step is 200 ° C or higher.   The method for producing a p-type group III-V compound semiconductor according to any one of claims 1 to 6, further comprising a fourth step of peeling the catalyst layer after the third step.   The method for producing a p-type group III-V compound semiconductor according to any one of claims 1 to 7, wherein the catalyst layer has a thickness in a range of 1 nm to 100 nm.   The method for producing a p-type group III-V compound semiconductor according to any one of claims 1 to 8, wherein the catalyst layer contains Ni, Ag or Cu in a range of 50 to 100 atomic%.   The method for producing a p-type III-V group compound semiconductor according to any one of claims 1 to 9, wherein a film thickness of the p-type III-V group compound semiconductor layer is in a range of 1 nm to 5 µm.   In a method for manufacturing a light emitting device including an n-type layer, a light emitting layer, and a p-type layer made of a III-V group compound semiconductor layer, the p-type layer is an III-V group compound semiconductor layer containing Al, and the p-type layer A method for manufacturing a light-emitting element, which includes forming a catalyst layer containing at least one of Ni, Ag, and Cu on a layer and then performing heat treatment.   The method for manufacturing a light-emitting element according to claim 11, wherein the p-type III-V compound semiconductor is a gallium nitride-based compound semiconductor.   13. The method for manufacturing a light-emitting element according to claim 11, wherein the amount of Al contained in the p-type III-V compound semiconductor is 0.5 atomic% or more.   The method for manufacturing a light-emitting element according to claim 11, wherein the amount of Al contained in the p-type III-V compound semiconductor is 5 to 50 atomic%.   The method for manufacturing a light-emitting element according to claim 11, wherein the catalyst layer contains one or more of Cu and Ag.   The method for manufacturing a light-emitting element according to claim 11, wherein the heat treatment temperature is 200 ° C. or higher.   The method for manufacturing a light-emitting element according to claim 11, further comprising a step of peeling the catalyst layer after the heat treatment.   The method for manufacturing a light-emitting element according to claim 11, wherein the catalyst layer has a thickness in a range of 1 nm to 100 nm.   19. The method for manufacturing a light-emitting element according to claim 11, wherein the catalyst layer contains Ni, Ag, or Cu in a range of 50 to 100 atomic%.    20. The method for manufacturing a light-emitting element according to claim 11, wherein the thickness of the p-type III-V compound semiconductor layer is in the range of 1 nm to 5 μm.

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