Preparation method of gallium nitride-based laser

Abstract

The invention provides a preparation method of a gallium nitride-based laser, which can be applied to the technical field of gallium nitride semiconductor lasers. The method comprises the following steps: providing a gallium nitride substrate; sequentially growing a gallium nitride buffer layer, a lower limiting layer, a lower waveguide layer, an active region, an upper waveguide layer, an electron blocking layer, a novel upper limiting layer, a novel p-type gallium nitride layer and an ohmic contact layer on the gallium nitride substrate to obtain an epitaxial structure; the growth method of the novel upper limiting layer and the novel p-type gallium nitride layer is a step-by-step doping method; and the structures of the novel upper limiting layer and the novel p-type gallium nitride layer are superlattice structures. The doping efficiency and ionization efficiency of Mg impurities at a low growth temperature are improved through a step-by-step doping method and a superlattice polarization induced doping method, and large Mg doping concentration and high hole concentration can be realized at a relatively low growth temperature, so that preparation of low-temperature p-type AlGaN and GaN layers is realized, and the photoelectric property of the gallium nitride-based blue-green laser is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of gallium nitride semiconductor lasers, and in particular to a method for preparing a gallium nitride-based laser. Background Art

[0002] Gallium nitride-based lasers, as the best among semiconductor optoelectronic devices, are widely used in many cutting-edge fields such as laser display, laser communication and laser surgery. In particular, laser display technology is hailed as the pinnacle of display technology, and in this field, chip-level semiconductor red, green and blue primary color lasers play a pivotal role. At present, the development of red and blue semiconductor lasers is relatively mature, while green semiconductor lasers are still in the early stages of exploration. Gallium nitride-based blue-green semiconductor lasers, with their excellent performance, are regarded as a very potential solution in the field of blue-green lasers. They can not only achieve continuous adjustable wavelength, but also integrate three primary color lasers on a single chip to meet diverse needs.

[0003] In the development of green lasers, p-type preparation technology is a basic and thorny issue. Due to the high thermal stability requirements of blue-green quantum wells, high-temperature grown p-type aluminum gallium nitride (AlGaN) and gallium nitride (GaN) layers often damage the quantum wells, thus affecting the overall performance of the device. Therefore, blue-green lasers place stringent requirements on the growth conditions of p-type AlGaN and GaN layers: low-temperature growth, high doping efficiency, and high activation efficiency.

[0004] In the preparation of p-type AlGaN and GaN, magnesium (Mg) is often used as a p-type dopant. However, Mg easily forms a difficult-to-activate Mg-H complex in GaN, requiring extremely high ionization energy to activate the acceptor impurities. This results in the use of higher growth temperatures when growing p-type AlGaN and GaN by Metal-Organic Chemical Vapor Deposition (MOCVD), and high-temperature annealing after epitaxial growth to activate the acceptor impurities. This process is in sharp contrast to the low-temperature growth requirements of blue-green lasers. In addition, Mg atoms also have unfavorable factors such as memory effect, floating effect, and self-compensation effect during the doping process, which further increases the difficulty of achieving efficient doping of p-type AlGaN and GaN layers at lower growth temperatures. Summary of the invention

[0005] 1. Technical issues to be resolved

[0006] In order to solve at least one of the above-mentioned problems existing in the prior art, an embodiment of the present invention provides a method for preparing a gallium nitride-based laser, which improves the doping efficiency and ionization efficiency of Mg impurities at low growth temperature through a step-by-step doping method and a superlattice polarization induced doping method, and can achieve a large Mg doping concentration and a high hole concentration at a relatively low growth temperature of 800~950℃, thereby realizing the preparation of low-temperature p-type AlGaN and GaN layers.

[0007] (II) Technical solution

[0008] In view of the above problems, an embodiment of the present invention provides a method for preparing a gallium nitride-based laser.

[0009] According to a first aspect of the present invention, a method for preparing a gallium nitride-based laser is provided, comprising: providing a gallium nitride substrate; sequentially growing a gallium nitride buffer layer, a lower confinement layer, a lower waveguide layer, an active region, an upper waveguide layer, an electron blocking layer, a novel upper confinement layer, a novel p-type gallium nitride layer, and an ohmic contact layer on the gallium nitride substrate to obtain an epitaxial structure; and preparing electrodes, wherein the growth method of the novel upper confinement layer is a step-by-step doping method; the growth method of the novel p-type gallium nitride layer is a step-by-step doping method; the structure of the novel upper confinement layer is a superlattice structure; and the structure of the novel p-type gallium nitride layer is a superlattice structure.

[0010] In some exemplary embodiments, a novel upper confinement layer is grown by a step-by-step doping method, including: nitriding the epitaxial surface of a first epitaxial structure obtained after growing an electron blocking layer by nitrogen; growing an undoped gallium nitride layer of a first preset thickness on the electron blocking layer using trimethylgallium as a gallium source; stopping the growth of the undoped gallium nitride layer and maintaining the flow of ammonia to nitride the surface of the undoped gallium nitride layer; maintaining the flow of ammonia and performing p-type doping on the undoped gallium nitride layer after nitridation using bismuth magnesium as a magnesium source until a first preset doping concentration is reached to obtain a p-type doped gallium nitride layer; and growing an undoped aluminum gallium nitride layer on the p-type doped nitride layer using trimethylaluminum as an aluminum source and trimethylgallium as a gallium source, wherein the growth temperature of the novel upper confinement layer grown by the step-by-step doping method is 800°C-950°C.

[0011] In some exemplary embodiments, the superlattice structure of the novel upper confinement layer includes 60 periods of p-type doped gallium nitride layers and undoped aluminum gallium nitride layers, and growing the novel upper confinement layer using a step-doping method includes repeatedly executing the method of claim 2 60 times.

[0012] In some exemplary embodiments, a novel p-type gallium nitride layer is grown by a step-doping method, comprising: nitriding the epitaxial surface of a second epitaxial structure obtained after growing a novel upper confinement layer by nitrogen; growing an undoped gallium nitride layer of a second preset thickness on the novel upper confinement layer using trimethyl gallium as a gallium source; stopping the growth of the undoped gallium nitride layer and maintaining the flow of ammonia to nitridate the surface of the undoped gallium nitride layer; maintaining the flow of ammonia and using bismuth magnesium as a magnesium source to p-dope the undoped gallium nitride layer after nitridation until a second preset doping concentration is reached to obtain a p-type doped gallium nitride layer; and growing an undoped gallium nitride layer on the p-type doped nitride layer using trimethyl gallium as a gallium source, wherein the growth temperature of the novel p-type gallium nitride layer grown by the step-doping method is 800°C-950°C.

[0013] In some exemplary embodiments, the superlattice structure of the novel p-type gallium nitride layer includes 6 periods of p-type doped gallium nitride layers and undoped gallium nitride layers, and growing the novel p-type gallium nitride layer by a step-doping method includes repeatedly performing the method of claim 4 6 times.

[0014] In some exemplary embodiments, preparing the electrode includes: forming an n-type electrode on a side of the substrate away from the gallium nitride buffer layer; and forming a p-type electrode on a side of the ohmic contact layer away from the substrate.

[0015] In some exemplary embodiments, at least one of the following features is included: the material of the gallium nitride buffer layer includes gallium nitride; the material of the lower confinement layer includes aluminum gallium nitride; the material of the lower waveguide layer includes indium gallium nitride; the material of the upper waveguide layer includes indium gallium nitride; the material of the electron blocking layer includes aluminum gallium nitride; and the material of the ohmic contact layer includes gallium nitride.

[0016] In some exemplary embodiments, at least one of the following features is included: the doping type of the gallium nitride substrate is unintentional doping; the doping type of the gallium nitride buffer layer is n-type doping, and the doping concentration is 1×10 18 cm -3 -5×10 18 cm -3 ; The doping type of the lower confinement layer is n-type doping, and the doping concentration is 1×10 18 cm -3 -5×10 18 cm -3 ; The doping type of the lower waveguide layer is n-type doping, and the doping concentration is 8×10 16 cm -3 -2×10 17 cm -3 ; The doping type of the upper waveguide layer is p-type doping, and the doping concentration is 3×10 19 cm -3 -7×10 19 cm-3 The electron blocking layer is doped with p-type doping and the doping concentration is 3×10 19 cm -3 -7×10 19 cm -3 ; The doping type of the ohmic contact layer is p-type doping, and the doping concentration is 8×10 19 cm -3 -2×10 20 cm -3 .

[0017] In some exemplary embodiments, at least one of the following features is included: the sum of the thicknesses of the gallium nitride substrate and the gallium nitride buffer layer is 150 μm ± 10 μm; the thickness of the lower confinement layer is 1 μm ± 0.1 μm; the thickness of the lower waveguide layer is 200 nm ± 20 nm; the thickness of the upper waveguide layer is 100 nm ± 10 nm; the thickness of the electron blocking layer is 20 nm ± 2 nm; and the thickness of the ohmic contact layer is 10 nm ± 1 nm.

[0018] In some exemplary embodiments, the active region includes an indium gallium nitride multi-quantum well layer, wherein the indium gallium nitride multi-quantum well layer includes three quantum barriers and two quantum wells, wherein the material of the quantum barriers includes indium gallium nitride, the doping type is n-type doping, and the doping concentration is 8×10 16 cm -3 -2×10 17 cm -3 The thickness of the quantum barrier in contact with the lower waveguide layer is 5nm±1nm, and the thickness of the other two quantum barriers is 10nm±1nm; the material of the quantum well includes indium gallium nitride, the doping type is n-type doping, and the doping concentration is 3×10 16 cm -3 -7×10 16 cm -3 , the thickness of the single-layer quantum well is 2.5nm±0.5nm; and the content of indium in the quantum well is higher than the content of indium in the quantum barrier.

[0019] (III) Beneficial effects

[0020] It can be seen from the above technical solutions that the method for preparing a gallium nitride-based laser provided by the embodiment of the present invention has at least the following beneficial effects:

[0021] The step-by-step doping method and the superlattice polarization induced doping method improve the doping efficiency and ionization efficiency of Mg impurities at low growth temperatures, and can achieve a large Mg doping concentration and a high hole concentration at a relatively low growth temperature of 800-950°C, thereby realizing the preparation of low-temperature p-type AlGaN and GaN layers, which can improve the photoelectric performance of GaN-based blue-green lasers that are sensitive to growth temperature, and effectively improve the output characteristics of GaN-based blue-green lasers. At the same time, the new step-by-step multi-stage doping method does not require the introduction of new equipment or additional process methods, does not increase additional manufacturing costs, and is conducive to large-scale mass production. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The above contents and other objects, features and advantages of the present invention will become more apparent through the following description of the embodiments of the present invention with reference to the accompanying drawings, in which:

[0023] Figure 1 A schematic diagram of a process for preparing a gallium nitride-based laser according to an embodiment of the present invention is shown;

[0024] Figure 2 A schematic diagram of the structure of a gallium nitride-based laser according to an embodiment of the present invention is shown;

[0025] Figure 3 The schematic diagram shows a process flow diagram of growing a novel upper confinement layer by adopting a step-by-step doping method according to an embodiment of the present invention;

[0026] Figure 4 A schematic diagram of supplying exogenous substances during the process of growing a novel upper confinement layer by a step-by-step doping method according to an embodiment of the present invention is shown;

[0027] Figure 5 A schematic diagram of a process of growing a novel p-type gallium nitride layer by a step-by-step doping method according to an embodiment of the present invention is shown; and

[0028] Figure 6 The schematic diagram shows the supply of exogenous substances in the process of growing a novel p-type gallium nitride layer by a step-by-step doping method according to an embodiment of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] 1-n-type electrode; 2-gallium nitride substrate; 3-gallium nitride buffer layer; 4-lower confinement layer; 5-lower waveguide layer; 6-active region; 61-quantum barrier; 62-quantum well; 7-upper waveguide layer; 8-electron blocking layer; 9-new upper confinement layer; 10-new p-type gallium nitride layer; 11-ohmic contact layer; 12-p-type electrode. DETAILED DESCRIPTION

[0030] In order to make the purpose, technical scheme and advantages of the present invention more clearly understood, the present invention is further described in detail below in combination with specific embodiments and with reference to the accompanying drawings. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0031] Figure 1 The flowchart of a method for preparing a gallium nitride-based laser according to an embodiment of the present invention is schematically shown.

[0032] like Figure 1 As shown, a method for preparing a gallium nitride-based laser according to an embodiment of the present invention includes steps S110 to S130.

[0033] In step S110 , a gallium nitride substrate 2 is provided.

[0034] In step S120, a gallium nitride buffer layer 3, a lower confinement layer 4, a lower waveguide layer 5, an active region 6, an upper waveguide layer 7, an electron blocking layer 8, a novel upper confinement layer 9, a novel p-type gallium nitride layer 10, and an ohmic contact layer 11 are sequentially grown on a gallium nitride substrate 2 to obtain an epitaxial structure. The growth method of the novel upper confinement layer 9 is a step-by-step doping method; the growth method of the novel p-type gallium nitride layer 10 is a step-by-step doping method; the structure of the novel upper confinement layer 9 is a superlattice structure; and the structure of the novel p-type gallium nitride layer 10 is a superlattice structure.

[0035] Figure 3 The schematic diagram shows a process flow of growing a novel upper confinement layer 9 by adopting a step-by-step doping method according to an embodiment of the present invention; Figure 4 The schematic diagram of supplying exogenous substances during the process of growing the novel upper confinement layer 9 by adopting the step-by-step doping method according to an embodiment of the present invention is schematically shown.

[0036] like Figure 3 and Figure 4 As shown, the method for growing the novel upper confinement layer 9 by adopting the step-by-step doping method according to an embodiment of the present invention includes steps S210 to S250.

[0037] In step S210 , the epitaxial surface of the first epitaxial structure obtained after the electron blocking layer 8 is grown is nitrided by nitrogen.

[0038] In step S220, trimethylgallium is used as a gallium source to grow a non-doped gallium nitride layer with a first preset thickness on the electron blocking layer 8. Preferably, the first preset thickness is 6 nm±0.6 nm.

[0039] In step S230 , the growth of the non-doped gallium nitride layer is stopped, and the flow of ammonia gas is maintained to nitride the surface of the non-doped gallium nitride layer.

[0040] In step S240, the ammonia gas is kept flowing, and the non-doped gallium nitride layer after nitridation is p-doped with cyclopentadienyl magnesium as a magnesium source until a first preset doping concentration is reached to obtain a p-type doped gallium nitride layer. Preferably, the first preset doping concentration is 1×10 19 cm -3 -3×10 19 cm -3 .

[0041] In step S250, trimethylaluminum is used as an aluminum source and trimethylgallium is used as a gallium source to grow an undoped aluminum gallium nitride layer on the p-type doped nitride layer. Preferably, the thickness of the undoped aluminum gallium nitride layer is 4 nm.

[0042] The temperatures in the above steps S210-S250 are all 800°C-950°C.

[0043] Preferably, the superlattice structure of the novel upper confinement layer 9 includes 60 periods of p-type doped gallium nitride layers and undoped aluminum gallium nitride layers, and growing the novel upper confinement layer 9 by the step-doping method includes repeatedly executing the method of claim 2 60 times.

[0044] Figure 5 The schematic diagram shows a process flow of growing a novel p-type gallium nitride layer 10 by adopting a step-by-step doping method according to an embodiment of the present invention; Figure 6 The schematic diagram of supplying exogenous substances during the process of growing the novel p-type gallium nitride layer 10 by the step-by-step doping method according to an embodiment of the present invention is schematically shown.

[0045] like Figure 5 and Figure 6 As shown, the method for growing a novel p-type gallium nitride layer 10 by adopting a step-by-step doping method according to an embodiment of the present invention includes steps S310 to S350.

[0046] In step S310 , the epitaxial surface of the second epitaxial structure obtained after growing the novel upper confinement layer 9 is nitrided by nitrogen.

[0047] In step S320, trimethylgallium is used as a gallium source to grow a non-doped gallium nitride layer of a second preset thickness on the novel upper confinement layer 9. Preferably, the second preset thickness is 5 nm±1 nm.

[0048] In step S330 , the growth of the non-doped gallium nitride layer is stopped, and the flow of ammonia gas is maintained to nitride the surface of the non-doped gallium nitride layer.

[0049] In step S340, the ammonia gas is kept flowing, and the non-doped gallium nitride layer after nitridation is p-doped with cyclopentadienyl magnesium as the magnesium source until the second preset doping concentration is reached to obtain a p-type doped gallium nitride layer. Preferably, the second preset doping concentration is 1×10 19 cm -3 -3×10 19 cm -3 .

[0050] In step S350, trimethylgallium is used as a gallium source to grow an undoped gallium nitride layer on the p-type doped nitride layer. Preferably, the thickness of the gallium nitride layer is 5 nm ± 1 nm.

[0051] The temperatures of the above steps S310-S350 are all 800°C-950°C.

[0052] Preferably, the superlattice structure of the novel p-type gallium nitride layer 10 includes 6 periods of p-type doped gallium nitride layers and undoped gallium nitride layers, and growing the novel p-type gallium nitride layer 10 by the step-doping method includes repeatedly performing the method of claim 4 6 times.

[0053] In step S130 , electrodes are prepared.

[0054] In some exemplary embodiments, preparing the electrode includes: forming an n-type electrode 1 on a side of the substrate away from the gallium nitride buffer layer 3; and forming a p-type electrode 12 on a side of the ohmic contact layer 11 away from the substrate.

[0055] The step-by-step doping method and the superlattice polarization induced doping method improve the doping efficiency and ionization efficiency of Mg impurities at low growth temperatures, and can achieve a large Mg doping concentration and a high hole concentration at a relatively low growth temperature of 800-950°C, thereby realizing the preparation of low-temperature p-type AlGaN and GaN layers, which can improve the photoelectric performance of GaN-based blue-green lasers that are sensitive to growth temperature, and effectively improve the output characteristics of GaN-based blue-green lasers. At the same time, the new step-by-step multi-stage doping method does not require the introduction of new equipment or additional process methods, does not increase additional manufacturing costs, and is conducive to large-scale mass production.

[0056] The structures prepared by the above method are as follows Figure 2 , combined with Figure 2 And an embodiment of the present invention describes the characteristics of each layer, such as material and thickness.

[0057] For example, the material of the n-type electrode 1 includes a composite structure (Ti / Al / Ti / Au) composed of titanium (Ti), aluminum (Al), titanium, and gold (Au), and the thickness of each layer is 50 nm±5nm, 100nm±10nm, 50 nm±5nm, and 100nm±10nm. The doping type of the gallium nitride substrate 2 is unintentional doping. A gallium nitride buffer layer 3 is grown on the substrate using a two-step method. The gallium nitride buffer layer 3 is also n-type doped, and the doping concentration is 1×10 18 cm -3 -5×10 18 cm -3 The sum of the thickness of the gallium nitride substrate 2 and the gallium nitride buffer layer 3 is 150 μm ± 10 μm. A lower confinement layer 4 is grown on the gallium nitride buffer layer 3. The material of the lower confinement layer 4 is aluminum gallium nitride (Al x Ga 1-x N), where the Al component x is 8%, the doping type of the lower confinement layer 4 is n-type, and the doping concentration is 1×10 18 cm -3 -5×10 18 cm -3 The thickness is 1 μm ± 0.1 μm. The lower waveguide layer 5 is grown on the lower confinement layer 4. The material of the lower waveguide layer 5 is indium gallium nitride (InGaN). x Ga 1-x N), where the In component x is 8%, the thickness is 200nm±20nm, and the doping type of the lower waveguide layer 5 is n-type doping with a doping concentration of 8×10 16 cm -3 -2×10 17 cm -3 The active region 6 is located above the lower waveguide layer 5. The active region 6 includes an InGaN multi-quantum well 62 layer. The InGaN multi-quantum well 62 layer includes three quantum barriers 61 and two quantum wells 62. The material of the quantum barrier 61 includes InGaN (InGaN). x Ga 1-x N), where the In component x is 12%, the doping type is n-type doping, and the doping concentration is 8×10 16 cm -3 -2×10 17 cm -3 The thickness of the quantum barrier 61 in contact with the lower waveguide layer 5 is 5nm±1nm, and the thickness of the other two quantum barriers 61 is 10nm±1nm; the material of the quantum well 62 includes indium gallium nitride (ln x Ga 1-x N), where the In component x is 12%, the doping type is n-type doping, and the doping concentration is 3×10 16 cm -3 -7×10 16 cm-3 The thickness of the single-layer quantum well 62 is 2.5 nm ± 0.5 nm. The upper waveguide layer 7 is located above the active region 6. The material of the upper waveguide layer 7 includes (In x Ga 1-x N), where the In component x is 4%, the thickness is 100nm±10nm, the doping type is n-type doping, and the doping concentration is 8×10 16 cm -3 -2×10 17 cm -3 The upper waveguide layer 7 is provided with an electron blocking layer 8, and the material of the electron blocking layer 8 includes aluminum gallium nitride (Al x Ga 1-x N), where the Al component x is 15%, the thickness is 20nm±2nm, the doping type is p-type doping, and the doping concentration is 3×10 19 cm -3 -7×10 19 cm -3 The electron blocking layer 8 is provided with a novel upper confinement layer 9, which adopts a step-by-step doping method and a superlattice structure. The superlattice structure has 60 periods, and one period is divided into a p-type doped gallium nitride (GaN) layer with a thickness of 6nm±0.6nm and a doping concentration of 1×10 19 cm -3 -3×10 19 cm -3 , unintentionally doped with Al x Ga 1-x N layer, wherein the Al component x is 8%, the thickness is 4nm±0.4nm, and the total thickness of the superlattice is 600nm±60nm. On the new upper confinement layer 9 is a new p-type gallium nitride layer 10, which adopts a step-by-step doping method and a superlattice structure. The superlattice structure has a total of 6 periods, and one period is divided into an unintentionally doped GaN layer with a thickness of 5nm±1nm, a p-type doped GaN layer with a thickness of 5nm±1nm, and a doping concentration of 1×10 19 cm -3 -3×10 19 cm -3 The total thickness of the superlattice is 60nm±6nm. The new p-type gallium nitride layer 10 is provided with an ohmic contact layer 11. The material of the ohmic contact layer 11 includes GaN, the thickness is 10nm±1nm, the doping type is p-type doping, and the doping concentration is 8×10 19 cm -3 -2×10 20 cm -3On the ohmic contact layer 11 is a p-type electrode 12, and the constituent materials of the p-type electrode 12 are palladium (Pd), platinum (Pt), and gold (Au) (Pd / Pt / Au), and the thickness of each layer is 50nm±5nm, 50nm±5nm, and 600nm±60nm, respectively.

[0058] The embodiments of the present invention are described above. However, these embodiments are only for the purpose of illustration, and are not intended to limit the scope of the present invention. Although each embodiment is described above, it does not mean that the measures in each embodiment cannot be used in combination advantageously. Without departing from the scope of the present invention, those skilled in the art may make various substitutions and modifications, which should all fall within the scope of the present invention.

Claims

1. A method for preparing a gallium nitride-based laser, characterized in that: The method comprises: Providing gallium nitride substrates; Growing a gallium nitride buffer layer, a lower confinement layer, a lower waveguide layer, an active region, an upper waveguide layer, an electron blocking layer, a novel upper confinement layer, a novel p-type gallium nitride layer, and an ohmic contact layer on the gallium nitride substrate in sequence to obtain an epitaxial structure; and Preparation of electrodes, Wherein, the growth method of the novel upper confinement layer is a step-by-step doping method; The growth method of the novel p-type gallium nitride layer is a step-by-step doping method; The structure of the novel upper confinement layer is a superlattice structure; and The structure of the novel p-type gallium nitride layer is a superlattice structure.

2. The method according to claim 1, characterized in that The step-by-step doping method is used to grow the novel upper confinement layer, comprising: nitriding the epitaxial surface of the first epitaxial structure obtained after growing the electron blocking layer by nitrogen; Using trimethylgallium as a gallium source, growing a non-doped gallium nitride layer of a first preset thickness on the electron blocking layer; Stopping the growth of the non-doped gallium nitride layer and maintaining the flow of ammonia gas to nitride the surface of the non-doped gallium nitride layer; Keeping the ammonia gas flowing, the non-doped gallium nitride layer after nitridation is p-doped using bismuthocene magnesium as a magnesium source until a first preset doping concentration is reached to obtain a p-type doped gallium nitride layer; and Using trimethylaluminum as an aluminum source and trimethylgallium as a gallium source, an undoped aluminum gallium nitride layer is grown on the p-type doped nitride layer. Wherein, the growth temperature of the novel upper confinement layer grown by the step-by-step doping method is 800° C.-950° C.

3. The method according to claim 2, characterized in that The superlattice structure of the novel upper confinement layer includes 60 periods of the p-type doped gallium nitride layer and the undoped aluminum gallium nitride layer, and the step-doping method for growing the novel upper confinement layer includes repeating the method of claim 2 60 times.

4. The method according to claim 1, characterized in that: The novel p-type gallium nitride layer is grown by the step-by-step doping method, comprising: nitriding the epitaxial surface of the second epitaxial structure obtained after growing the novel upper confinement layer by nitrogen; Using trimethylgallium as a gallium source, growing a non-doped gallium nitride layer of a second preset thickness on the novel upper confinement layer; Stopping the growth of the non-doped gallium nitride layer and maintaining the flow of ammonia gas to nitride the surface of the non-doped gallium nitride layer; Keeping the ammonia gas flowing, using bismuthocene magnesium as a magnesium source, p-doping the non-doped gallium nitride layer after nitridation until a second preset doping concentration is reached to obtain a p-type doped gallium nitride layer; and Using trimethylgallium as gallium source, an undoped gallium nitride layer is grown on the p-type doped nitride layer. Wherein, the growth temperature of the novel p-type gallium nitride layer grown by the step-by-step doping method is 800° C.-950° C.

5. The method according to claim 4, characterized in that The superlattice structure of the novel p-type gallium nitride layer includes 6 periods of p-type doped gallium nitride layers and undoped gallium nitride layers, and the step-by-step doping method to grow the novel p-type gallium nitride layer includes repeating the method of claim 4 6 times.

6. The method according to claim 1, characterized in that The electrode preparation comprises: forming an n-type electrode on a side of the substrate away from the gallium nitride buffer layer; and A p-type electrode is formed on a side of the ohmic contact layer away from the substrate.

7. The method according to claim 1, characterized in that Includes at least one of the following features: The material of the gallium nitride buffer layer includes gallium nitride; The material of the lower confinement layer includes aluminum gallium nitride; The material of the lower waveguide layer includes indium gallium nitride; The material of the upper waveguide layer includes indium gallium nitride; The material of the electron blocking layer includes aluminum gallium nitride; The material of the ohmic contact layer includes gallium nitride.

8. The method according to claim 1, characterized in that: Includes at least one of the following features: The doping type of the GaN substrate is unintentional doping; The doping type of the gallium nitride buffer layer is n-type doping, and the doping concentration is 1×10 18 cm -3 -5×10 18 cm -3 ; The doping type of the lower confinement layer is n-type doping, and the doping concentration is 1×10 18 cm -3 -5×10 18 cm -3 ; The doping type of the lower waveguide layer is n-type doping, and the doping concentration is 8×10 16 cm -3 -2×10 17 cm -3 ; The doping type of the upper waveguide layer is p-type doping, and the doping concentration is 3×10 19 cm -3 -7×10 19 cm -3 ; The doping type of the electron blocking layer is p-type doping, and the doping concentration is 3×10 19 cm -3 -7×10 19 cm -3 ; The doping type of the ohmic contact layer is p-type doping, and the doping concentration is 8×10 19 cm -3 -2×10 20 cm -3 .

9. The method according to claim 1, characterized in that: Includes at least one of the following features: The sum of the thickness of the gallium nitride substrate and the gallium nitride buffer layer is 150 μm±10 μm; The thickness of the lower limiting layer is 1 μm ± 0.1 μm; The thickness of the lower waveguide layer is 200nm±20nm; The thickness of the upper waveguide layer is 100nm±10nm; The thickness of the electron blocking layer is 20nm±2nm; The thickness of the ohmic contact layer is 10nm±1nm.

10. The method according to claim 1, characterized in that The active region includes an InGaN multi-quantum well layer, wherein the InGaN multi-quantum well layer includes three quantum barriers and two quantum wells. The material of the quantum barrier includes indium gallium nitride, the doping type is n-type doping, and the doping concentration is 8×10 16 cm -3 -2×10 17 cm -3 , the thickness of the quantum barrier in contact with the lower waveguide layer is 5nm±1nm, and the thickness of the remaining two layers of quantum barriers is 10nm±1nm; The material of the quantum well includes indium gallium nitride, the doping type is n-type doping, and the doping concentration is 3×10 16 cm -3 -7×10 16 cm -3 , the thickness of the single-layer quantum well is 2.5nm±0.5nm; and The content of indium in the quantum well is higher than the content of indium in the quantum barrier.

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