Light-emitting element and method for manufacturing light-emitting element

Abstract

This invention provides a method for manufacturing a light-emitting element that suppresses the degradation of electrical performance caused by heat treatment. The light-emitting element is composed of a group III nitride semiconductor and is formed by sequentially stacking an n-layer (11), a light-emitting layer (12), and a p-layer (13), wherein the n-layer (11) has an Al content of 60% or more and a Si concentration of 5 × 10⁻⁶. 18 / cm 3 ~5×10 19 / cm 3 In the p-layer (13), the Al composition ratio is less than 60% and the Mg concentration is 1×10⁻⁶. 19 / cm 3 The above describes the manufacturing method of the light-emitting element, which includes: a p-electrode formation step, forming a p-electrode (16) by attaching it to a p-layer (13); an n-electrode formation step, forming an n-electrode by attaching it to an n-layer (11), wherein the n-electrode has: a V-layer with a thickness of 5 nm to 15 nm and an Al-layer attached to the V-layer; and a heat treatment step, performing heat treatment at any temperature in the range of 500 °C to 650 °C.

Description

Technical Field

[0001] This invention relates to a light-emitting element made of group III nitride semiconductor and a method for manufacturing the same. Background Technology

[0002] In recent years, the use of ultraviolet LEDs for sterilization and disinfection has attracted attention, and research and development aimed at improving the efficiency of ultraviolet LEDs are actively underway.

[0003] In UV-C light-emitting devices composed of group III nitride semiconductors, the use of Ti / Al-based materials for the n-contact electrode in contact with the n-type group III nitride semiconductor has become mainstream. Here, " / " indicates stacking, and A / B indicates a structure in which layers A and B are stacked sequentially. This also applies to the following description of the materials.

[0004] Ti / Al materials are alloyed at temperatures of 800–1000 °C to allow Ti to diffuse into group III nitride semiconductors, thereby reducing contact resistance.

[0005] Besides Ti / Al materials, V / Al materials are known. Patent document 1 describes V / Al formed on n-GaN, which can reduce contact resistance by alloying at 500-600°C.

[0006] Non-patent literature 1 provides an example of forming V / Al on GaN / AlGaN and investigates the mechanism of reduced contact resistance in V / Al. The study suggests that in V / Al, N in AlGaN combines with Al in V / Al to form AlN. x Nitrogen vacancies are generated in AlGaN, resulting in an n-type structure and thus reducing contact resistance. V is believed to control the reaction rate between N in AlGaN and Al in V / Al.

[0007] Existing technical documents

[0008] Patent documents

[0009] Patent Document 1: Japanese Patent Application Publication No. 10-112555

[0010] Non-patent literature

[0011] Non-Patent Literature 1: Noriyuki Yafune, "Formation of Low-Resistance Ohmic Contacts in Nitride Semiconductor Heterojunctions and Their Application in Field-Effect Transistors", Fukui University Dissertation, March 2016 Summary of the Invention

[0012] For Ti / Al, there is a problem that the alloying temperature required for Ti diffusion is as high as 800–1000 °C. At high alloying temperatures, the contact resistance of the p-electrode composed of p-GaN and ITO increases, leading to a higher forward voltage Vf. Furthermore, there is a narrow optimal range between alloying temperature and Ti film thickness.

[0013] Therefore, the object of the present invention is to provide a method for manufacturing a light-emitting element that suppresses the deterioration of electrical performance caused by heat treatment.

[0014] One aspect of the present invention is a method for manufacturing a light-emitting element.

[0015] The light-emitting element is composed of a group III nitride semiconductor, with an n-layer, a light-emitting layer, and a p-layer stacked sequentially. In the n-layer, the Al content is more than 60%, and the Si concentration is 5 × 10⁻⁶. 18 / cm 3 ~5×10 19 / cm 3 In the aforementioned p-layer, the Al composition is less than 60%, and the Mg concentration is 1×10⁻⁶. 19 / cm 3 The above describes the manufacturing method of the light-emitting element.

[0016] The p-electrode formation process involves attaching the p-layer to form a p-electrode; and

[0017] In the n-electrode formation process, an n-electrode is formed on the aforementioned n-layer. The n-electrode comprises: a V-layer with a thickness of 5 nm to 15 nm, composed of V or a metal primarily composed of V; and an Al-layer composed of Al or a metal primarily composed of Al, bonded to the V-layer; and

[0018] The heat treatment process is carried out at any temperature within the range of 500℃ to 650℃.

[0019] Another embodiment of the present invention is a light-emitting element, which is formed by sequentially stacking an n-layer, a light-emitting layer, and a p-layer made of group III nitride semiconductors, wherein the n-layer has an Al composition ratio of 60% or more and a Si concentration of 5 × 10⁻⁶. 18 / cm 3 ~5×10 19 / cm 3 In the aforementioned p-layer, the Al composition is less than 60%, and the Mg concentration is 1×10⁻⁶. 19 / cm 3 above,

[0020] The light-emitting element has:

[0021] The p-electrode is attached to the p-layer and set thereon;

[0022] An n-electrode is disposed on the n-layer, the n-electrode having: a composition of AlN x Or Al composition with more than n layers of Al y Ga 1－y N x The first layer consists of a first layer with a thickness of 1 nm to 3 nm, and a second layer attached to the first layer consists of a V-containing metal mainly composed of Al with a thickness of 50 nm to 500 nm.

[0023] According to the above-described manner of the present invention, the deterioration of electrical properties caused by heat treatment can be suppressed. Attached Figure Description

[0024] [ Figure 1 [Illustration 1] is a diagram showing the structure of the light-emitting element in the embodiment.

[0025] [ Figure 2 [ ] is a diagram showing the structure of the n-electrode 17.

[0026] [ Figure 3 [ ] is a diagram showing the manufacturing process of the light-emitting element in the embodiment.

[0027] [ Figure 4 [Illustration] is a schematic diagram showing the changes in the layer composition of the n-electrode before and after heat treatment.

[0028] [ Figure 5 [1] is a graph showing the relationship between the contact resistivity of the n-electrode 17 and the heat treatment temperature.

[0029] [ Figure 6 [] is a graph representing the If-Vf characteristics.

[0030] [ Figure 7 [] is a graph representing the If-Po characteristic.

[0031] [ Figure 8 [] is a diagram representing a TEM image and its element mapping.

[0032] [ Figure 9 [] is a diagram representing a TEM image and its element mapping.

[0033] [ Figure 10 [] is a diagram representing a TEM image and its element mapping.

[0034] [ Figure 11 [] is a diagram representing a TEM image and its element mapping.

[0035] [ Figure 12 [ ] is a graph showing the relationship between the film formation rate of layer V and the contact resistivity of n.

[0036] [ Figure 13 [] is a graph showing the relationship between the film formation rate of layer V and Rq.

[0037] [ Figure 14 [ ] is a graph representing the AFM image of the V layer surface.

[0038] [Symbol Explanation]

[0039] 10: Substrate

[0040] 11: n layers

[0041] 12: Emissive layer

[0042] 13: p layer

[0043] 14: Electron blocking layer

[0044] 16: p electrode

[0045] 17: n electrode Detailed Implementation

[0046] One method for manufacturing a light-emitting element is that the light-emitting element is composed of a group III nitride semiconductor, and is formed by sequentially stacking an n-layer, a light-emitting layer, and a p-layer. In the n-layer, the Al composition ratio is more than 60%, and the Si concentration is 5 × 10⁻⁶. 18 / cm 3 ~5×10 19 / cm 3 In the p-layer, the Al composition is less than 60% and the Mg concentration is 1×10⁻⁶. 19 / cm 3 That's all. Furthermore, the method for manufacturing this light-emitting element includes:

[0047] The p-electrode formation process involves attaching the p-layer to form a p-electrode.

[0048] In the n-electrode formation process, an n-electrode is formed on the aforementioned n-layer. The n-electrode comprises: a V-layer with a thickness of 5 nm to 15 nm, composed of V or a metal primarily composed of V; and an Al-layer, composed of Al or a metal primarily composed of Al, attached to the V-layer.

[0049] The heat treatment process is carried out at any temperature within the range of 500℃ to 650℃.

[0050] During the heat treatment process, the V layer diffuses into the Al layer and disappears. The structure of the n electrode can then be changed to: an AlN electrode attached to the n layer. x Or Al composition with more than n layers of Al y Ga 1－y N x The first layer consists of Al, and the second layer, which is attached to the first layer, consists of V-containing metals, mainly Al.

[0051] The p-electrode can also be a transparent conductive material, and the heat treatment process can be carried out in an oxygen-containing atmosphere. Therefore, it is possible to simultaneously alloy the p-electrode and the n-electrode using transparent conductive materials. The heat treatment process can also be carried out in a mixed atmosphere of nitrogen and oxygen, where the oxygen concentration is 0.1 vol% to 1 vol%. The p-electrode formation process can also include a calcination step after the p-electrode is formed.

[0052] The deposition rate of the V layer in the n-electrode formation process can also be below 0.71 nm / s. This allows the contact resistance of the n-electrode to decrease steadily.

[0053] Another method for manufacturing light-emitting elements is a method for manufacturing light-emitting elements composed of group III nitride semiconductors, wherein an n-layer, a light-emitting layer, and a p-layer are stacked sequentially. This method has the following characteristics:

[0054] The n-electrode formation process involves attaching an n-layer to form an n-electrode, wherein the n-electrode comprises: a V-layer with a thickness of 5 nm to 15 nm, consisting of V or a metal primarily composed of V, and an Al-layer attached to the V-layer, consisting of Al or a metal primarily composed of Al. The heat treatment process involves performing heat treatment at any temperature within the range of 500°C to 650°C.

[0055] In the n-electrode formation process, the deposition rate of the V layer is set to below 0.71 nm / s. During the heat treatment process, the V layer diffuses into the Al layer and disappears, and the structure of the n-electrode becomes: an AlN-based electrode attached to the n-layer. x Or Al composition with more than n layers of Al y Ga 1－y N x The first layer consists of an Al-based V-containing metal, and the second layer is attached to the first layer.

[0056] Furthermore, the process can include a p-electrode formation step, in which a p-electrode made of a transparent conductive material is formed on the p-layer, and the heat treatment step can be performed in an oxygen-containing atmosphere. Calcination can also be performed after the p-electrode is formed.

[0057] The heat treatment process can also be carried out at any time within the range of 1 to 10 minutes.

[0058] A light-emitting element is a light-emitting element composed of an n-layer, a light-emitting layer, and a p-layer, which are made of group III nitride semiconductors, stacked sequentially. In the n-layer, the Al content is more than 60%, and the Si concentration is 5 × 10⁻⁶. 18 / cm 3 ~5×10 19 / cm 3 In the p-layer, the Al composition is less than 60% and the Mg concentration is 1×10⁻⁶. 19 / cm 3The above describes the light-emitting element, which includes: a p-electrode disposed on the p-layer; and an n-electrode disposed on the n-layer, comprising: an AlN-based electrode. x Or Al composition with more than n layers of Al y Ga 1－y N x The first layer consists of a first layer with a thickness of 1 nm to 3 nm, and a second layer attached to the first layer consists of a V-containing metal mainly composed of Al with a thickness of 50 nm to 500 nm.

[0059] The concentration of V in the second layer can also be 5 mol% to 10 mol%. A third layer composed of at least one of Ti, TiN, Ni, Pt, and Au can also be present on the second layer. The thickness of the third layer can also be 20 nm to 1000 nm. The p-electrode can also be ITO or IZO.

[0060] (Implementation Method)

[0061] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

[0062] Figure 1 This diagram illustrates the structure of the light-emitting element according to an embodiment. The emission wavelength is, for example, 200–280 nm. Figure 1 As shown, the light-emitting element of Embodiment 1 has a substrate 10, an n-layer 11, a light-emitting layer 12, a p-layer 13, an electron blocking layer 14, a p-electrode 16, and an n-electrode 17.

[0063] (Structure of substrate 10)

[0064] Substrate 10 is a sapphire substrate with the c-side as the main surface. In addition to sapphire, any material can be used as long as it has high transmittance relative to the emission wavelength and can enable the growth of group III nitride semiconductors.

[0065] (11-layer structure)

[0066] The n-layer 11 is located on the substrate 10 via a buffer layer (not shown). The n-layer 11 is composed of n-AlGaN with an Al composition ratio of 60% or more. Here, the Al composition ratio of the group III nitride semiconductor is the molar ratio (%) of Al to group III metal. That is, the group III nitride semiconductor is made of the general formula Al x Ga y In z When N(0≦x≦1, 0≦y≦1, 0≦z≦1, x+y+z=1) is used, the Al composition ratio is x×100 (%). The n-type impurity is Si, and the Si concentration is 5×10⁻⁶. 18 ~5×10 19 / cm 3The n-layer 11 can also be composed of multiple layers. In this case, it is sufficient that the Al composition ratio of the uppermost layer of the n-layer 11 (the contact layer with the n-electrode 17) is 60% or more.

[0067] The Al composition of the n-layer 11 is more preferably 65-90%, and even more preferably 70-85%. The Si concentration of the n-layer 11 is more preferably 8 × 10⁻⁶. 18 ~3×10 19 / cm 3 Further preferred is 1×10 19 ~2×10 19 / cm 3 .

[0068] (Structure of light-emitting layer 12)

[0069] The emitting layer 12 is located on the n-layer 11. The emitting layer 12 is an MQW structure with alternating well and barrier layers. The repetition count is, for example, 2 to 5. The well layer is made of AlGaN, and its Al composition ratio is set according to the desired emission wavelength. The barrier layer is AlGaN with a higher Al composition ratio than the well layer. Alternatively, it can be AlGaInN with a higher bandgap energy than the well layer. Alternatively, the emitting layer 12 can also be an SQW structure.

[0070] (Structure of electron blocking layer 14)

[0071] An electron blocking layer 14 is located on the light-emitting layer 12. The electron blocking layer 14 is composed of p-AlGaN with a higher Al content than the barrier layer in the light-emitting layer 12. By setting the electron blocking layer 14, the diffusion of electrons injected from the n electrode 17 through the light-emitting layer 12 toward the p layer 13 is suppressed.

[0072] (Structure of p layer 13)

[0073] p-layer 13 is located on electron blocking layer 14. p-layer 13 is composed of p-AlGaN / p-GaN. The p-type impurity is Mg. The concentration of Mg is 1 × 10⁻⁶. 19 / cm 3 The above applies. The p-layer 13 can also be a single layer, as long as it is AlGaN with an Al composition ratio of less than 60% in the contact layer with the p-electrode 16.

[0074] A groove 22 reaching the depth of layer n 11 is formed in a portion of the surface of layer p 13. Layer n 11 is exposed at the bottom of the groove 22.

[0075] (Structure of p-electrode 16)

[0076] p-electrode 16 is located on p-layer 13. p-electrode 16 is made of ITO. In addition to ITO, transparent conductive materials such as IZO can also be used. Furthermore, materials other than transparent conductive materials such as Ni / Al, Ni / Au, Rh, Ru, Pt, and Pd can also be used.

[0077] (Structure of n-electrode 17)

[0078] The n-electrode 17 is located on the n-layer 11 exposed on the bottom surface of the groove 22. Figure 2 The image shown is an enlarged view of the n-electrode 17 structure. Figure 2 As shown, the n electrode 17 has a structure of a first layer 17A in contact with the n layer 11, a second layer 17B attached to the first layer 17A, and a third layer 17C attached to the second layer 17B.

[0079] Layer 1, 17A, is composed of AlN. x The structure has a thickness of 1–3 nm. x is, for example, 0.4–0.7. Furthermore, x can decrease as it moves away from the n-layer 11 in the thickness direction. In this case, the average value of x in the thickness direction is 0.4–0.7. Additionally, there is also a case where Ga diffuses from the n-layer 11 side, in which case the first layer 17A has a higher Al composition ratio than the n-layer 11. y Ga1- y Nx (0.4 ≦ x ≦ 0.7). If the Al composition ratio of layer n 11 is a, then a < y ≦ 1. y is, for example, 0.7 or more. Furthermore, in this case, x can decrease as it moves away from layer n 11 in the thickness direction, and y can increase as it moves away from layer n 11 in the thickness direction.

[0080] The second layer, 17B, is composed primarily of Al, with some V and Ti, and has a thickness of 50–500 nm. The Al, V, and Ti ratio in the second layer, 17B, is, for example, 50–85 mol% Al, 5–20 mol% V, and 10–30 mol% Ti. The third layer, 17C, is composed of Ti and has a thickness of 20–100 nm. This n-electrode 17 structure is obtained by alloying V / Al / Ti at 500–650 °C. This will be discussed in detail later.

[0081] The above-described structure reduces the contact resistance between the n-electrode 17 and the n-layer 11. For example, the contact resistivity between the n-electrode 17 and the n-layer 11 is 4 × 10⁻⁶. －4 Ω·cm 2 The following is the reason, initially believed to be due to AlN. x The first layer 17A serves as a good contact layer for the n-layer 11. Secondly, it is believed that nitrogen vacancies are generated on the surface of the n-layer 11, making it n-type and reducing contact resistance.

[0082] It should be noted that the third layer, 17C, is provided as a covering layer to suppress Al evaporation in the n-electrode 17 during alloying. Besides Ti, TiN, Ni, Pt, Au, etc., can also be used.

[0083] (Manufacturing method)

[0084] Next, the manufacturing method of the light-emitting element according to the embodiment will be described with reference to the accompanying drawings.

[0085] First, a sapphire substrate 10 is prepared. Next, using MOCVD, an n-layer 11, a light-emitting layer 12, an electron-blocking layer 14, and a p-layer 13 are sequentially stacked on the substrate 10 via a buffer layer (see reference). Figure 3 (a)

[0086] Next, dry etching is performed on the designated area of ​​p layer 13 up to n layer 11 to form trench 22 (refer to...). Figure 3 (b)

[0087] Next, a p electrode 16 made of ITO is formed by sputtering and vapor deposition in a specified area on the p layer 13 (see reference). Figure 3 (c) Next, the ITO is subjected to a heat treatment of calcination and crystallization. This heat treatment is carried out under a nitrogen atmosphere at 500–600°C for 1–10 minutes. It should be noted that the calcination heat treatment can be omitted.

[0088] Next, on the exposed n-layer 11 at the bottom of the tank 22, an n-electrode 17 composed of V / Al / Ti is formed by sputtering and vapor deposition (see reference). Figure 3 (d) The thickness of the V layer is 5–15 nm, the thickness of the Al layer is 50–500 nm, and the thickness of the Ti layer is 20–100 nm. The V layer is V or a metal with V as the main component. The Al layer is Al or a metal with A as the main component. The Ti layer is Ti or a metal with Ti as the main component.

[0089] Next, a heat treatment is performed at a temperature of 500–650°C for 1–10 minutes in an oxygen-containing atmosphere. The oxygen-containing atmosphere is, for example, a mixture of an inert gas such as nitrogen and oxygen, with an oxygen concentration of, for example, 0.1–1% by volume. The heat treatment is preferably performed under reduced pressure, for example, 1 × 10⁻⁶. 2 ~1×10 4 Pa. Furthermore, a heat treatment temperature of 550–650°C is more preferable.

[0090] This heat treatment can achieve both the alloy of p electrode 16 and the alloy of n electrode 17, while simultaneously reducing the contact resistance between p electrode 16 and p layer 13, as well as the contact resistance between n electrode 17 and n layer 11.

[0091] Ti / Al, typically used as the material for n-electrode 17, has a high alloying temperature of 800–1000 °C. Therefore, the formation, calcination, and alloying of p-electrode 16 must be performed after the formation and alloying of n-electrode 17. In addition, if p-electrode 16 is calcined after the formation of n-electrode 17, there is a problem that fly-off material from p-electrode 16 will adhere to the surface of n-electrode 17.

[0092] Therefore, in this embodiment, by using V / Al / Ti as the n-electrode 17, the alloying temperature is lowered, and by simultaneously alloying the n-electrode 17 and the p-electrode 16, the number of heat treatments is reduced. The lower heat treatment temperature and fewer heat treatments result in suppression of deterioration in the electrical performance of the light-emitting element. Furthermore, since the n-electrode 17 is formed after the p-electrode 16 is calcined, no fly ash from the p-electrode 16 adheres to the surface of the n-electrode 17.

[0093] Through this heat treatment, the structure of the n-electrode 17 becomes as follows. In the V / Al / Ti structure of the n-electrode 17, V diffuses into Al but not into the n-layer 11 and Ti. This diffusion causes the V layer to disappear. Furthermore, the Al in the V / Al / Ti reacts with the N in the n-layer 11 to form AlN at the interface between the n-layer 11 and the Al layer. x V is considered to act as a catalyst to promote the reaction between Al and N. After this heat treatment, the structure of the n electrode 17 becomes a three-layer structure: the first layer 17A, which is in contact with the n layer 11 and is composed of AlN. x The structure consists of a second layer 17B, attached to the first layer 17A, composed of a V-containing metal, primarily Al, and a third layer 17C, attached to the second layer 17B, composed of Ti.

[0094] Because the n-electrode 17 has this structure, the contact resistance between the n-electrode 17 and the n-layer 11 is reduced. The reason is as described above. That is, it is initially thought to be due to the AlN... x The first layer 17A, which is constructed, serves as a good contact layer for the nth layer 11, and is secondly considered to be due to AlN x The formation of nitrogen holes in the n-layer 11 further promotes the n-type formation of the n-layer 11.

[0095] If the thickness of the V layer is within the range of 5–15 nm, the contact resistance between the n electrode 17 and the n layer 11 can be reduced. However, when the thickness is less than 5 nm or greater than 15 nm, the contact resistance cannot be sufficiently reduced. When the V layer is less than 5 nm, the high contact resistance is considered to be due to the V layer being too thin to fully exert its role in promoting the reaction between Al and N, resulting in AlN... x Insufficient formation. Furthermore, the high contact resistance when the V layer thickness exceeds 15 nm is attributed to the fact that when the V layer is thick, incomplete diffusion occurs, leaving residues that hinder AlN from forming at the interface of the n-layer 11.x The formation of.

[0096] Similarly, to ensure no V layer residue, it is preferable to set the V layer deposition rate to below 0.71 nm / s. (Refer to...) Figure 4 The reasons for this should be explained. Figure 4 This is a schematic diagram showing the changes in the layer structure of n-electrode 17 before and after heat treatment. Figure 4 (a) shows the case where the deposition rate of layer V is greater than 0.71 nm / s. Figure 4 (b) is the case where the film formation rate of layer V is less than or equal to 0.71 nm / s.

[0097] When the deposition rate of the V layer exceeds 0.71 nm / s, V clusters may form, resulting in numerous protrusions on the surface of the V layer. Figure 4 (a) Reference). If the protrusions are high, they may not diffuse after heat treatment and remain, resulting in high contact resistance. Therefore, if the deposition rate of the V layer is set to less than or equal to 0.71 nm / s, the V layer can be deposited flatly. Figure 4 (b) Reference). If the V layer is thin and uniform, uniform AlN without V layer residue can be obtained after heat treatment. x This allows for a stable reduction in the contact resistance of the n-electrode 17. The deposition rate of the V-layer is more preferably 0.38 nm / s or less. There is no particular limitation on the lower limit of the deposition rate of the V-layer, as long as it is greater than 0. However, if the deposition rate is too slow, formation will take time, so a rate of 0.1 nm / s or more is preferred.

[0098] Furthermore, the Rq (root mean square height) of the V-layer surface where the V-layer is formed is preferably 0.83 or less. When Rq is 0.83 or less, the V-layer is sufficiently flat, which can reduce the contact resistance as described above. The Rq of the V-layer surface is more preferably 0.4 or less.

[0099] Furthermore, compared to using Ti / Al as the material for the n-electrode 17, this heat treatment can reduce the contact resistance between the p-electrode 16 and the p-layer 13. This is believed to be because when the heat treatment temperature is reduced to 500–650°C, the formation of nitrogen holes in the p-layer 13 is suppressed. By reducing the contact resistance of the p-electrode 16, the forward voltage Vf of the light-emitting element in this embodiment can be reduced.

[0100] Furthermore, in the light-emitting element of the embodiment, an increase in light output Po can be achieved. This is believed to be due to the reduction in heat treatment temperature, which suppresses the diffusion of Mg from the p-layer 13 to the light-emitting layer 12. The diffusion length of Mg is, for example, 10 nm or less.

[0101] In the light-emitting element described above, it is possible to reduce the forward voltage Vf and increase the light output Po. Furthermore, it is possible to prevent the adhesion of fly ash from the p electrode 16 to the surface of the n electrode 17.

[0102] It should be noted that in this embodiment, the heat treatment after the formation of the n-electrode 17 is performed in an oxygen-containing atmosphere because a transparent conductive oxide such as ITO or IZO is used as the p-electrode 16. Therefore, when a material other than a transparent conductive oxide such as Ni / Al is used as the p-electrode 16, heat treatment can also be performed in an oxygen-free inert gas atmosphere. The inert gas is nitrogen or the like.

[0103] In addition, in the embodiment, the alloying of the p electrode 16 and the n electrode 17 are carried out simultaneously, but they can also be carried out independently.

[0104] (Results of various experiments)

[0105] Next, the various experimental results related to the light-emitting element of the implementation method will be explained.

[0106] (Experiment 1)

[0107] The light-emitting element (hereinafter, the light-emitting element as an example) is manufactured using the manufacturing method described above. The structure of each layer is as follows.

[0108] In layer n11, the Al composition is 60%, the thickness is 1.0 μm, and the Si concentration is 2.7 × 10⁻⁶. 19 / cm 3 .

[0109] The light-emitting layer 12 is an MQW structure consisting of a barrier layer, a well layer, another barrier layer, another well layer, and finally a barrier layer stacked sequentially. The well layer has an Al content of 40% and a thickness of 2.5 nm, while the barrier layer has an Al content of 50%, a thickness of 11 nm, and a Si concentration of 4.5 × 10⁻⁶. 18 / cm 3 The final barrier layer has an Al composition of 50%, a thickness of 5.5 nm, and a Si concentration of 2.5 × 10⁻⁶. 18 / cm 3 .

[0110] The electron blocking layer 14 has an Al composition of 85%, a thickness of 25 nm, and a Mg concentration of 1.0 × 10⁻⁶. 20 / cm 3 .

[0111] p-layer 13 is a structure consisting of a p-AlGaN capping layer and a p-GaN contact layer stacked sequentially. The capping layer has an Al composition of 60%, a thickness of 50 nm, and a Mg concentration of 5.0 × 10⁻⁶. 19 / cm 3 The contact layer thickness is 18 nm and the Mg concentration is 1.0 × 10⁻⁶. 20 / cm 3 .

[0112] The thickness of the V layer of n electrode 17 is 10 nm or 20 nm, the Al layer is 150 nm, and the Ti layer is 50 nm.

[0113] In addition, for comparison, the light-emitting element (hereinafter, the light-emitting element as a comparative example) was fabricated in the same manner as in the example, except for the difference in the electrode formation order, heat treatment, and V layer thickness of the n electrode 17. In the comparative example, the n electrode 17 was formed before the p electrode 16 was formed and alloyed at 800°C in a nitrogen atmosphere, followed by the formation of the p electrode 16, calcination at 550°C in a nitrogen atmosphere, and then alloying at 570°C in an oxygen-containing atmosphere. The V layer of the n electrode 17 was set to 20 nm.

[0114] Figure 5 This is a schematic diagram showing the relationship between the contact resistivity of the n-electrode 17 in the light-emitting element of the embodiment and the heat treatment temperature. The V-layer thickness of the n-electrode 17 is set to either 10 nm or 20 nm, and the heat treatment atmosphere is set to either a nitrogen atmosphere or an oxygen-containing atmosphere. The vertical axis of the figure represents the relative value when the contact resistivity of Comparative Example 1 is set to 1.

[0115] like Figure 5 As shown, when the V layer is 20 nm, the contact resistivity at a heat treatment temperature of 800 °C is the same as that of the comparative example, but the contact resistivity at temperatures below 800 °C is higher than that of the comparative example.

[0116] On the other hand, when the V layer is 10 nm, the contact resistivity at a heat treatment temperature of 550–650 °C is the same as that of the comparative example. Furthermore, at a heat treatment temperature of 570 °C, the contact resistivity remains unchanged even when the heat treatment atmosphere is changed from a nitrogen atmosphere to an oxygen-containing atmosphere. This demonstrates that when a material other than a transparent conductive material is used as the p-electrode 16, heat treatment can be performed in an oxygen-free atmosphere.

[0117] The results show that, in order to achieve the same contact resistance of the n electrode 17 as the comparative example under the same alloying heat treatment conditions as the p electrode 16, the thickness of the V layer should be set to 5–15 nm, and the heat treatment temperature to 550–650 °C. It should be noted that, depending on the material of the p electrode 16, 500–650 °C may also be acceptable.

[0118] (Experiment 2)

[0119] When the V layer of the n electrode 17 in the embodiment is set to 10 nm and the heat treatment temperature is set to 570 °C, the light output Po and the forward voltage Vf are compared with those of the comparative example. Figure 6 This is a schematic diagram of the If-Vf characteristics of the light-emitting elements in the embodiments and comparative examples. Figure 7 This is a schematic diagram of the If-Po characteristic. Figure 6 The light output Po is a relative value when the light output Po of the comparative example's light-emitting element at 350mA is set to 1. Compared to the comparative example's light-emitting element, the light output Po of the embodiment's light-emitting element is increased by 21.6% (at 350mA). Furthermore, as... Figure 6 As shown, compared to the light-emitting element of the comparative example, the forward voltage Vf of the light-emitting element of the embodiment is reduced by 0.25V (at 350mA).

[0120] (Experiment 3)

[0121] For the light-emitting elements of the embodiments and comparative examples, the concentration distribution of Mg and H from the p-layer 13 to the n-layer 11 was determined using SIMS analysis. Next, the diffusion lengths of Mg and H were evaluated. The diffusion length is an indicator of the amount of atomic diffusion from the p-layer 13 to the light-emitting layer 12, and refers to the length from the interface between the p-layer 13 and the light-emitting layer 12 to the depth direction on the side of the light-emitting layer 12 where the concentration reaches the measurement limit. The measurement limit is 1 × 10⁻⁶. 17 / cm 3 Compared to the comparative example, the diffusion length of Mg in the embodiment was 8.3 nm shorter, and the diffusion length of H was 12.8 nm shorter. This indicates that the diffusion of Mg and H was suppressed due to the reduced heat treatment temperature in the embodiment. The increased light output Po of the light-emitting element in the embodiment compared to the comparative example is attributed to the suppression of Mg and H diffusion due to the reduced heat treatment temperature.

[0122] (Experiment 4)

[0123] For the light-emitting elements of the embodiments and comparative examples, the contact resistance of the p-electrode 16 was calculated. The results showed that the contact resistance of the p-electrode 16 in the embodiments was 0.24V lower than that in the comparative example. This is essentially consistent with the 0.25V difference in the forward voltage Vf in Experiment 2. Based on this result, the decrease in the forward voltage Vf of the light-emitting element in the embodiments compared to the comparative example is attributed to the reduction in heat treatment temperature, which suppresses the formation of nitrogen holes in the p-layer 13, thereby reducing the contact resistance of the p-electrode 16. Furthermore, as... Figure 6 As shown, compared to the comparative example, the light-emitting element of the embodiment suppresses leakage current at low current, which is consistent with the behavior of suppressing the formation of nitrogen holes.

[0124] (Experiment 5)

[0125] Even if the capping layer of p layer 13 in the embodiment is replaced with a thickness of 50 nm and a Mg concentration of 5.0 × 10⁻⁶, 19 / cm 3p-GaN with a thickness of 400 nm and a Mg concentration of 2.0 × 10⁻⁶ 19 / cm 3 The p-GaN stacked structure, similar to the embodiment, improves the light output Po and reduces the forward voltage Vf compared to the comparative example. Therefore, it can be seen that the effect of the embodiment remains unchanged regardless of whether the contact layer with the p electrode 16 is AlGaN or GaN.

[0126] (Experiment 6)

[0127] For the light-emitting element in the embodiment, a cross-sectional TEM image of the interface between the n-layer 11 and the n-electrode 17 is captured, and the elemental mapping is obtained using EDS. Figure 8 (a) is a TEM image, and (b) is an elemental mapping. Figure 9 (a) and (b) are the magnified TEM image and element mapping diagram of the interface.

[0128] like Figure 9 As shown in (b), V does not exist at the interface between layer n11 and electrode n17. On the other hand, as... Figure 8 As shown in (b), 5–10 mol% V is present in the middle of the Al layer. Therefore, it can be concluded that the V layer in the V / Al / Ti of the n-electrode 17 disappears due to heat treatment causing V to diffuse into the Al layer. Furthermore, it can be seen that due to the presence of N and Al at the interface between the n-layer 11 and the n-electrode 17, an AlN-based composite layer is formed. x The layers are formed. This is believed to be due to the reaction between the N in the AlGaN constituting the n-layer 11 and the Al in the V / Al / Ti of the n-electrode 17.

[0129] Therefore, it can be seen that after heat treatment, the structure of the n electrode 17 changes from V / Al / Ti to AlN. x The structure consists of a first layer 17A, a second layer 17B composed of metals containing V and Ti with Al as the main component, and a third layer 17C composed of Ti.

[0130] V is believed to act as a catalyst promoting the reaction between Al and N. This is because the V layer disappears from the interface between the n-layer 11 and the n-electrode 17, forming an AlN-based reaction. x The resulting layer thus achieves good contact with layer n, 11. Furthermore, due to... Figure 8 As shown in (b), V did not diffuse to the n-layer 11 and the Ti-layer. Therefore, it can be considered that since V did not diffuse excessively and remained extensively in the Al layer, it effectively played a role in promoting the reaction between Al and N.

[0131] (Experiment 7)

[0132] The thickness of the V layer of the n electrode 17 in the light-emitting element of the embodiment was changed to 20 nm, and TEM images and element mappings were obtained in the same manner as in Experiment 6. Figure 10 (a) is a TEM image, and (b) is an elemental mapping. Figure 11 (a) and (b) are further magnified TEM images and element mapping diagrams of the interface. For example... Figure 10 (b) Figure 11 As shown in (b), a V layer remains at the interface between the n-layer 11 and the n-electrode 17. Therefore, the reason why the contact resistance cannot be sufficiently reduced when the V layer is thick is believed to be that the heat-treated V layer did not diffuse completely and remained, hindering the AlN... x The formation of.

[0133] (Experiment 8)

[0134] During the fabrication of the light-emitting element in this embodiment, the film-forming rate of the V layer of the n-electrode 17 was varied, and the contact resistivity of n was measured. Table 1 shows the contact resistivity of the V layer at various film-forming rates. Furthermore, Figure 12 Film formation rate of layer V A schematic diagram showing the relationship between contact resistivity and n. Table 1 and... Figure 12 The n-contact resistivity in the figure is based on the film formation rate. The contact resistivity at that time is the standard value.

[0135] [Table 1]

[0136]

[0137] From Table 1, Figure 12 It can be seen that the film formation rate is At that time, the contact resistivity of n is basically constant at 1, and the film formation rate is... At that time, the n-contact resistivity became 1.22, a slight increase. However, the n-contact resistivity was still within a perfectly acceptable range. Additionally, when the film deposition rate became... At this point, the contact resistivity of n increases significantly to 2.21. Therefore, the optimal film formation rate for the V layer is [missing value]. The following is preferred.

[0138] (Experiment 9)

[0139] A 10 nm V layer was formed on a sapphire substrate, and the surface of the V layer was observed as the deposition rate of the V layer changed. Figure 13 Film formation rate of layer V The relationship between Rq and Rq (nm) is shown in the graph. Rq was calculated on a 2μm square sample. Additionally, Figure 14 The image shown is an AFM image of the V layer surface. Figure 14 (a) shows the film formation rate in layer V as... At that time, (b) is the film formation rate of layer V. At that time, (c) is the film formation rate of layer V. hour.

[0140] like Figure 13 , 14 It can be seen that the faster the V-layer forms, the rougher the V-layer surface becomes, and the greater the number and height of the protrusions. Furthermore, from... Figure 12 and Figure 13 , 14 The comparison shows that as the deposition rate of the V layer increases, the thickness deviation of the V layer becomes larger, and this deviation is an important factor contributing to the increase in the contact resistance of V / Al. Furthermore, from... Figure 12 and Figure 13 The comparison shows that Rq is preferably below 0.83.

[0141] [Industry availability]

[0142] The light-emitting element of this invention can be used for sterilization, disinfection, etc.

Claims

1. A method for manufacturing a light-emitting element, wherein the light-emitting element is composed of a group III nitride semiconductor and is formed by sequentially stacking an n-layer, a light-emitting layer, and a p-layer, wherein the n-layer has an Al content of 60% or more and a Si concentration of 5 × 10⁻⁶. 18 / cm 3 ~5×10 19 / cm 3 The p-layer has an Al content of less than 60% and a Mg concentration of 1×10⁻⁶. 19 / cm 3 above, The method for manufacturing the light-emitting element includes: The p-electrode formation process involves attaching the p-layer to form a p-electrode; and In the n-electrode formation process, an n-electrode is formed on the n-layer. The n-electrode comprises: a V-layer with a thickness of 5 nm to 15 nm, composed of V metal or a metal primarily composed of V; an Al-layer composed of Al metal or a metal primarily composed of Al, attached to the V-layer; and a Ti-layer composed of Ti or a Ti-based layer, attached to the Al-layer. The heat treatment process is carried out at any temperature within the range of 500℃ to 650℃. wherein In the heat treatment process, the V layer diffuses into the Al layer and disappears, and the structure of the n electrode becomes: attached to the n layer, consisting of AlN... x Or Al composition higher than the nth layer of Al y Ga 1－y N x The structure comprises a first layer, a second layer attached to the first layer consisting of a metal primarily composed of Al and containing V, and a third layer attached to the second layer consisting of Ti or primarily composed of Ti. Furthermore, in the n-electrode formation process, the film formation rate of the V layer is 0.71 nm / s or less.

2. The method for manufacturing a light-emitting element according to claim 1, wherein The p-electrode is made of a transparent conductive material, and the heat treatment process is carried out in an oxygen-containing atmosphere.

3. The method of manufacturing a light-emitting element according to claim 2, wherein The heat treatment process is carried out in a mixed gas atmosphere of nitrogen and oxygen, wherein the oxygen concentration in the mixed gas is 0.1% to 1% by volume.

4. The method for manufacturing a light-emitting element according to claim 1 or 2, wherein, The heat treatment process is performed for any time within the range of 1 to 10 minutes.

5. A light-emitting element manufactured by the method of claim 1, comprising an n-layer, a light-emitting layer, and a p-layer composed of group III nitride semiconductors, wherein the n-layer has an Al content of 60% or more and a Si concentration of 5 × 10⁻⁶. 18 / cm 3 ~5×10 19 / cm 3 The p-layer has an Al content of less than 60% and a Mg concentration of 1×10⁻⁶. 19 / cm 3 above, The light-emitting element has: The p electrode is disposed on the p layer; and An n-electrode, disposed on the n-layer, has the following characteristics: it is made of AlN x Or Al composition higher than the nth layer of Al y Ga 1－y N x The structure comprises a first layer with a thickness of 1 nm to 3 nm, a second layer disposed on the first layer, which is composed of a V-containing metal mainly composed of Al and has a thickness of 50 nm to 500 nm, and a third layer disposed on the second layer, which is composed of Ti or mainly composed of Ti.

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