Light emitting diode epitaxial wafer and preparation method

Abstract

This invention provides a light-emitting diode epitaxial wafer and its fabrication method. The light-emitting diode epitaxial wafer includes a substrate, and a buffer layer, an undoped GaN layer, an N-type GaN layer, a multiple quantum well layer, an electron blocking layer, and a P-type GaN layer sequentially deposited on the substrate. The buffer layer includes a nitrided graphene buffer layer, an h-BN buffer layer, and a B-type GaN layer sequentially deposited on the substrate. x Al 1‑x N buffer layer, AlN buffer layer, wherein, the B x Al 1‑x The boron content in the N-buffer layer gradually decreases along the growth direction of the epitaxial layer. This invention achieves this by sequentially arranging a graphene nitride buffer layer, an h-BN buffer layer, and a boron buffer layer between the substrate and the epitaxial structure. x Al 1‑x N-buffer layers and AlN-buffer layers reduce lattice mismatch between structures, lower defect density, and improve the overall quality of LED epitaxial wafers.

Description

Technical Field

[0001] This invention relates to the field of optoelectronic technology, specifically to a light-emitting diode epitaxial wafer and its fabrication method. Background Technology

[0002] Light-emitting diodes (LEDs) are a commonly used semiconductor light-emitting device that emits light mainly by releasing energy through the recombination of electrons and holes. Against the backdrop of global energy shortages, the prospects of white LEDs in the lighting market have attracted worldwide attention. As a new type of solid-state light source, LED light sources are an effective alternative to traditional light sources such as incandescent lamps and fluorescent lamps.

[0003] GaN-based light-emitting diodes (LEDs) are attracting increasing attention due to their numerous advantages, including energy efficiency, environmental friendliness, small size, long lifespan, short response time, and adjustable color. GaN-based LEDs are primarily fabricated by depositing epitaxial structures on a substrate. Therefore, the quality of the epitaxial wafer and the lattice quality between the substrate and the epitaxial structure significantly affect the luminous efficiency of the LED. Sapphire substrates are commonly used for GaN-based LEDs. However, sapphire substrates have significant lattice defects. During the growth of the GaN-based epitaxial layer, lattice mismatch on the substrate makes it difficult for GaN adsorbed atoms to diffuse onto the surface, easily leading to lattice mismatch and making it difficult to form a smooth two-dimensional GaN film, resulting in low luminous efficiency of the epitaxial wafer.

[0004] Currently, to improve the lattice mismatch between the substrate and the GaN-based epitaxial layer, a common method is to grow an AlN buffer layer on the substrate, and then grow the GaN-based epitaxial layer on the buffer layer. However, growing the AlN buffer layer at high temperatures results in a significant difference in thermal expansion coefficients between the buffer layer and the substrate, causing thermal mismatch and preventing the release of thermal stress, which can easily lead to subsequent epitaxial cracking. Alternatively, growing the buffer layer at low temperatures is problematic because the AlN buffer layer at low temperatures is often polycrystalline or amorphous, resulting in poor crystal quality. Poor-quality crystals are prone to lattice mismatch with the GaN-based epitaxial layer, forming dislocation-extended multi-quantum-well active layers in LEDs. This leads to a decrease in the radiative recombination efficiency of electrons and holes in the multi-quantum-well layer, thereby reducing the LED's luminous efficiency. Summary of the Invention

[0005] Based on this, the purpose of the present invention is to provide a light-emitting diode epitaxial wafer and its preparation method, so as to solve the problem that thermal mismatch and lattice mismatch exist between the substrate and the epitaxial structure in the prior art, resulting in high defect density and low LED luminous efficiency.

[0006] This invention provides a light-emitting diode epitaxial wafer, comprising the following steps: a substrate, and a buffer layer, an undoped GaN layer, an N-type GaN layer, a multiple quantum well layer, an electron blocking layer, and a P-type GaN layer sequentially deposited on the substrate, wherein the buffer layer comprises a nitrided graphene buffer layer, an h-BN buffer layer, and a B-type GaN layer sequentially deposited on the substrate. x Al 1-x N buffer layer, AlN buffer layer, wherein, the B x Al 1-x The B content in the N buffer layer gradually decreases along the growth direction of the epitaxial layer.

[0007] The beneficial effects of this invention are: This invention provides a light-emitting diode epitaxial wafer, comprising a substrate and a nitrided graphene buffer layer, an h-BN buffer layer, and a B-type graphene buffer layer sequentially deposited on the substrate. x Al 1-x An N-type buffer layer and an AlN-type buffer layer are deposited, followed by the sequential deposition of an undoped GaN layer, an N-type GaN layer, a multiple quantum well layer, an electron blocking layer, and a P-type GaN layer to obtain the target light-emitting diode. A nitrided graphene buffer layer is deposited on the substrate to utilize the weak van der Waals forces to release the stress between the substrate and the nitrided graphene, reducing dislocation density. Furthermore, the h-BN buffer layer has a hexagonal crystal structure, similar to that of graphene, which can further reduce lattice mismatch. Additionally, B... x Al 1-x The N-type buffer layer can reduce the lattice mismatch between the h-BN buffer layer and the AlN buffer layer. The AlN buffer layer can provide nucleation sites for subsequent epitaxial growth, which is beneficial to the film formation and crystal quality improvement of the epitaxial structure. By sequentially arranging a graphene nitride buffer layer, an h-BN buffer layer, and a B-type buffer layer between the substrate and the epitaxial structure... x Al 1-x N-type buffer layer and AlN-type buffer layer reduce thermal mismatch and lattice mismatch between structures, reduce defect density, and improve the luminous efficiency of LED epitaxial wafers.

[0008] Preferably, the thickness of the nitrided graphene buffer layer is 1 nm to 20 nm, the thickness of the h-BN buffer layer is 1 nm to 20 nm, and the thickness of the B... x Al 1-x The thickness of the N buffer layer is 1 nm to 50 nm, and the thickness of the AlN buffer layer is 1 nm to 100 nm.

[0009] Preferably, the B x Al 1-x The value of x in the N-buffer layer ranges from 0 to 1.

[0010] Preferably, the multi-quantum-well layer comprises alternating stacked InGaN quantum-well layers and AlGaN quantum-barrier layers.

[0011] In another aspect, the present invention provides a method for preparing the above-mentioned light-emitting diode epitaxial wafer, characterized by comprising the following steps:

[0012] Provide a substrate;

[0013] A nitrided graphene buffer layer, an h-BN buffer layer, and a B-type buffer layer are sequentially deposited on the substrate. x Al 1-x N-buffer layer, AlN-buffer layer;

[0014] An undoped GaN layer, an N-type GaN layer, a multiple quantum well layer, an electron blocking layer, and a P-type GaN layer are sequentially deposited on the AlN buffer layer.

[0015] Wherein, the B x Al 1-x The B content in the N buffer layer gradually decreases along the growth direction of the epitaxial layer.

[0016] Preferably, the nitrided graphene buffer layer is deposited in PECVD with a deposition power of 2KW to 5KW, a deposition temperature of 300℃ to 800℃, and a sputtering pressure of 1 torr to 50 torr;

[0017] After the nitrided graphene buffer layer is deposited, its surface is subjected to N2 plasma treatment at a temperature of 300℃ to 800℃.

[0018] Preferably, the carbon source sputtered in the PECVD is CH4.

[0019] Preferably, the h-BN buffer layer, the B x Al 1-x The AlN buffer layer is deposited in MOCVD at a temperature of 700℃ to 900℃ and a growth pressure of 50 torr to 300 torr.

[0020] Preferably, the h-BN buffer layer, the B x Al 1-x The growth atmosphere during the deposition of the N buffer layer and the AlN buffer layer is a mixture of N2 / NH3 with a ratio of 1:1 to 1:10.

[0021] Preferably, the h-BN buffer layer, the B x Al 1-x The N buffer layer and the AlN buffer layer use NH3 as the N source during the deposition process. x Al 1-x The AlN buffer layer and the AlN buffer layer use trimethylaluminum as the aluminum source during the deposition process.

[0022] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the epitaxial wafer structure of the light-emitting diode provided by the present invention;

[0024] Figure 2 This is a flowchart of the method for fabricating an epitaxial wafer of a light-emitting diode provided by the present invention;

[0025] Explanation of key component symbols:

[0026] Nitrogen-based graphene buffer layer 21 h-BN buffer layer 22 <![CDATA[B x Al 1-x N buffer layer 23]]> 23 AlN buffer layer 24 Undoped GaN layer 30 N-type GaN layer 40 Multiple quantum well layers 50 Electron blocking layer 60 P-type GaN layer 70

[0027] The following detailed description, in conjunction with the accompanying drawings, will further illustrate the present invention. Detailed Implementation

[0028] To facilitate understanding of the present invention, a more complete description will be given below with reference to the accompanying drawings. Several embodiments of the invention are illustrated in the drawings. However, the invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete.

[0029] It should be noted that when a component is said to be "fixed to" another component, it can be directly on the other component or there may be an intervening component. When a component is said to be "connected to" another component, it can be directly connected to the other component or there may be an intervening component. The terms "vertical," "horizontal," "left," "right," and similar expressions used in this document are for illustrative purposes only.

[0030] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0031] This invention provides a light-emitting diode epitaxial wafer and its fabrication method, wherein a nitrided graphene buffer layer, an h-BN buffer layer, and a B-type epitaxial layer are sequentially arranged between the substrate and other epitaxial structures. x Al 1-x N-buffer layer, AlN-buffer layer, through nitrided graphene buffer layer, h-BN-buffer layer, B x Al 1-xThe N-buffer layer and AlN-buffer layer reduce thermal and lattice mismatch between the substrate and the epitaxial structure, thereby reducing defect density and improving the luminous efficiency of the LED epitaxial wafer.

[0032] For details, please refer to Figure 1 The light-emitting diode epitaxial wafer provided in this embodiment of the invention includes: a substrate 10, and a buffer layer 20, an undoped GaN layer 30, an N-type GaN layer 40, a multiple quantum well layer 50, an electron blocking layer 60, and a P-type GaN layer 70 sequentially deposited on the substrate. The buffer layer 20 includes a nitrided graphene buffer layer 21, an h-BN buffer layer 22, and a B-type GaN layer 70 sequentially deposited on the substrate 10. x Al 1-x N buffer layer 23, AlN buffer layer 24, wherein B x Al 1-x The B content in the N buffer layer gradually decreases along the growth direction of the epitaxial layer.

[0033] GaN-based light-emitting diodes can be made from one of the following substrates: silicon, sapphire, SiO2-sapphire composite, silicon carbide, gallium nitride, or zinc oxide. Sapphire substrates are the most commonly used substrate material due to their mature fabrication process, low cost, readily available material, high cost-effectiveness, ease of cleaning and processing, and excellent stability at high temperatures. Therefore, this embodiment uses a sapphire substrate. However, sapphire substrates have very large lattice defects. According to theoretical calculations, the critical thickness for mismatch dislocations is much smaller than the thickness of an atomic layer. Therefore, it is impossible to form a complete atomic layer in the initial growth. Dislocations caused by lattice mismatch between the substrate and the epitaxial layer will further extend into the multi-quantum well layer, leading to a decrease in the radiative recombination efficiency of electrons and holes in the multi-quantum well layer and a decrease in LED luminous efficiency. Therefore, it is necessary to introduce a suitable buffer layer to control crystal defects, improve the quality of subsequent crystal growth, and alleviate the stress caused by lattice and thermal mismatch between the substrate and the epitaxial layer.

[0034] Specifically, in this embodiment, a buffer layer 20 is introduced between the substrate 10 and the undoped GaN layer 30. The buffer layer 20 includes a nitrided graphene buffer layer 21, an h-BN buffer layer 22, and a B-type graphene buffer layer 23 sequentially deposited on the substrate 10. x Al 1-xN-buffer layer 23, AlN-buffer layer 24; Graphene is the most commonly used two-dimensional material for van der Waals epitaxial growth. The weak van der Waals interactions in graphene can effectively release stress and reduce dislocation density, thus making it easy to obtain high-quality epitaxial films by depositing epitaxial layers on graphene. The graphene buffer layer can reduce the interfacial interaction between the substrate 10 and the subsequent epitaxial layer by two orders of magnitude. The graphene buffer layer allows for large lattice mismatches between the epitaxial layer and the substrate. The relatively complete graphene lattice can cover crystal defects, and the migration barrier of group III metal atoms on graphene is very low. The h-BN buffer layer is a hexagonal boron nitride buffer layer with a hexagonal crystal structure, similar to the hexagonal structure of graphene, which can further reduce lattice mismatch and improve the crystal quality of the subsequent epitaxial layer; B x Al 1-x The N-buffer layer 23 is deposited between the h-BN buffer layer 22 and the AlN buffer layer 24, which can effectively reduce the lattice mismatch between the h-BN buffer layer 22 and the AlN buffer layer 24 and improve the crystal quality of the AlN buffer layer 24. The AlN buffer layer 24 can improve the forming nucleation sites for the subsequent growth of undoped GaN layers. It is beneficial to the film formation and crystal quality improvement of GaN-based epitaxial materials and alleviates the stress caused by lattice mismatch and thermal mismatch between the substrate and the GaN-based epitaxial layer.

[0035] Furthermore, the lattice constant of the h-BN layer is in The lattice constant of the AlN layer is around [value missing]. To reduce the lattice mismatch between the h-BN buffer layer 22 and the AlN buffer layer 24, a B-type buffer is used between the h-BN buffer layer 22 and the AlN buffer layer 24. x Al 1-x N buffer layer 23 performs the transition, further, B x Al 1-x The content of B in the N buffer layer 23 gradually decreases along the growth direction of the epitaxial layer, wherein B x Al 1-x In buffer layer 23 N, the value of x ranges from 0 to 1; B x Al 1-x The increase or decrease of B content in N buffer layer 23 is inversely proportional to the increase or decrease of Al content, that is, B... x Al 1-x The content of B in the N buffer layer 23 gradually decreases along the growth direction of the epitaxial layer, so B x Al 1-x In the N buffer layer 23, the Al content gradually increases along the growth direction of the epitaxial layer. In B... x Al 1-x The higher the B content in buffer layer 23, the better the B content. x Al 1-x The more similar the elemental contents of the N buffer layer 23 and the h-BN buffer layer 22, the better the B...x Al 1-x The less lattice mismatch there is between the N-buffer layer 23 and the h-BN-buffer layer 22, the better. Similarly, in B... x Al 1-x The higher the Al content in buffer layer 23, the better the B content. x Al 1-x The more similar the elemental contents of the N buffer layer 23 and the AlN buffer layer 24, the better the B... x Al 1-x The less lattice mismatch there is between the N buffer layer 23 and the AlN buffer layer 24, the better. Therefore, the B... x Al 1-x The N buffer layer 23 is arranged in an elemental variation structure, with a high B content and low Al content near the h-BN buffer layer 22, gradually transitioning to a high Al content and low B content near the AlN buffer layer 24. This elemental variation is achieved by setting a gradually changing B content between the h-BN buffer layer 22 and the AlN buffer layer 24. x Al 1-x The N buffer layer 23 effectively reduces the lattice mismatch between the h-BN buffer layer 22 and the AlN buffer layer 24, further improving the crystal quality of the epitaxial AlN buffer layer 24.

[0036] Preferably, the thickness of the nitrided graphene buffer layer is 1 nm to 20 nm, the thickness of the h-BN buffer layer is 1 nm to 20 nm, and the thickness of B... x Al 1-x The thickness of the N buffer layer 23 is 1 nm to 50 nm, and the thickness of the AlN buffer layer is 1 nm to 100 nm. A suitable buffer layer thickness can both release stress between the substrate and the epitaxial layer and improve the crystal quality of the GaN epitaxial layer. Preferably, the thickness of the nitrided graphene buffer layer is 5 nm, the h-BN buffer layer is 10 nm, and the B... x Al 1-x The N buffer layer is 15nm, and the AlN buffer layer is 20nm.

[0037] In addition, in this embodiment, the multiple quantum well layer 50 includes an InGaN quantum well layer 51 and an AlGaN quantum barrier layer 52 that are alternately stacked on the GaN layer 40. Specifically, the number of stacking periods is 6 to 12, wherein the thickness of the InGaN quantum well layer is 2 to 5 nm, the growth pressure is 50 to 300 torr, the thickness of the AlGaN quantum barrier layer is 5 nm to 15 nm, the growth pressure is 50 to 300 torr, and the Al composition is 0.01 to 0.1. Specifically, in MOCVD, an undoped GaN layer 30, an N-type GaN layer 40, a multiple quantum well layer 50, an electron blocking layer 60, and a P-type GaN layer 70 can be deposited. In this embodiment, high-purity N2 is used as the carrier gas, high-purity NH3 as the N source, trimethylgallium (TMGa) and triethylgallium (TEGa) as gallium sources, trimethylaluminum (TMAl) as the aluminum source, silane (SiH4) as the N-type dopant, and magnesium dicthene (CP2Mg) as the P-type dopant for epitaxial growth.

[0038] Please see Figure 2 This is a method for preparing an epitaxial wafer of a light-emitting diode according to an embodiment of the present invention. Specifically, the method for preparing an epitaxial wafer of a light-emitting diode provided by the present invention includes steps S10-S70.

[0039] Step S10: Provide a substrate;

[0040] The substrate can be selected from one of the following: silicon substrate, sapphire substrate, SiO2-sapphire composite substrate, silicon carbide substrate, gallium nitride substrate, and zinc oxide substrate. Preferably, a sapphire substrate is selected. Sapphire is currently the most commonly used substrate material. Sapphire substrates have mature manufacturing processes, low prices, are easy to clean and process, and have good stability at high temperatures. Therefore, a sapphire substrate is used in this embodiment.

[0041] Step S20: Sequentially deposit a nitrided graphene buffer layer, an h-BN buffer layer, and a B-type graphene buffer layer on the substrate. x Al 1-x N-buffer layer, AlN-buffer layer.

[0042] Specifically, in this embodiment, the thickness of the nitrided graphene buffer layer is 1 nm to 20 nm. The nitrided graphene buffer layer can be deposited by PECVD (Plasma Enhanced Chemical Vapor Deposition). PECVD has a fast deposition rate, good film quality, fewer pinholes, and is not prone to cracking. The deposition power of the nitrided graphene buffer layer is 2 kW to 5 kW, the deposition temperature is 300 °C to 800 °C, and the sputtering pressure is 1 torr to 50 torr. After deposition, its surface is treated with N2 plasma at a temperature of 300 to 800 °C. Preferably, the nitrided graphene buffer layer is deposited in PECVD with a deposition power of 3.5 kW, a deposition temperature of 600 °C, and a sputtering pressure of 20 torr, followed by N2 plasma treatment at a temperature of 400 °C. Furthermore, in the PECVD deposition, high-purity CH4 is used as the carbon source for sputtering.

[0043] Furthermore, in this embodiment, an h-BN buffer layer is deposited on the nitrided graphene buffer layer, wherein the N atoms of the nitrided graphene buffer layer are bonded to the B atoms of the h-BN buffer layer. This significantly increases the number of adsorbed B atoms in the nitrided graphene buffer layer, thereby increasing the number of nucleation sites for h-BN and improving the deposition efficiency and quality of h-BN. (h-BN buffer layer, B) x Al 1-x The N-buffer layer and AlN-buffer layer are deposited by MOCVD (Metal-organic Chemical Vapor Deposition). MOCVD is a novel vapor phase epitaxial growth technology developed on the basis of vapor phase epitaxy (VPE). It can use one of the following gases as a carrier gas: high-purity H2, high-purity N2, or a mixture of high-purity H2 and high-purity N2, and high-purity NH3 as the N source. MOCVD has a wide range of applications, easy control of epitaxial layer growth, and good uniformity over large areas.

[0044] Optionally, in this embodiment, the h-BN buffer layer is 1nm to 20nm, and B... x Al 1-x The N-type buffer layer is 1nm–50nm, and the AlN-type buffer layer is 1nm–100nm; h-BN buffer layers and B-type buffer layers are deposited via MOCVD. x Al 1-x The deposition temperature for N-buffer layers and AlN-buffer layers is 700℃~900℃, and the growth pressure is 50 torr~300 torr. B x Al 1-x In the N buffer layer, the B component ranges from 0 to 1, gradually decreasing along the growth direction of the epitaxial layer; B x Al 1-xThe gradual decrease in B composition in the N-buffer layer 23 can reduce the lattice mismatch between the h-BN buffer layer 22 and the AlN buffer layer, and improve the crystal quality of the AlN buffer layer. (h-BN buffer layer, B...) x Al 1-x The growth atmosphere for the N-buffer layer and the AlN-buffer layer is a mixture of N2 / NH3 with a composition ratio of 1:1 to 1:10. Appropriate deposition temperature and growth pressure in MOCVD can improve atomic mobility, ensuring that the deposited grains can connect into a surface within a relatively small thickness, transforming into two-dimensional epitaxial growth, forming a smooth nucleation surface, reducing the contact angle of nucleation growth, and improving the crystal quality of the buffer layer.

[0045] Preferably, an h-BN buffer layer and B are deposited in MOCVD. x Al 1-x The N-buffer layer and AlN-buffer layer use high-purity N2 as the carrier gas and high-purity NH3 as the N source. The growth atmosphere during the deposition process is a mixture of N2 / NH3 with a composition ratio of 1:1 to 1:10; B-buffer layer is deposited. x Al 1-x N-buffer layers and AlN-buffer layers were deposited using trimethylaluminum as the aluminum source; h-BN-buffer layers and B-buffer layers were deposited in MOCVD. x Al 1-x During the deposition of the N-buffer layer and the AlN-buffer layer, the growth atmosphere is free of H2 to avoid side reactions between H2 and the Al source. Preferably, the h-BN-buffer layer and the AlN-buffer layer are deposited in MOCVD. x Al 1-x N-buffer layer, AlN-buffer layer, B x Al 1-x In the N buffer layer, the B component gradually decreases from 1 to 0.1 along the epitaxial direction. (h-BN buffer layer, B) x Al 1-x The growth atmosphere for the N-buffer layer and the AlN-buffer layer was a mixture of N2 / NH3 with a ratio of 1:3, and the deposition temperature was 820℃. The growth pressure was 100 torr.

[0046] Step S30: Deposit an undoped GaN layer on the buffer layer.

[0047] Preferably, an undoped GaN layer is deposited on the AlN buffer layer. The growth temperature of the undoped GaN layer is 1050℃~1200℃, the pressure is 100 torr~600 torr, and the thickness is 1µm~5µm. Specifically, in this embodiment, the growth temperature of the undoped GaN layer is 1100℃, the growth pressure is 150 torr, and the growth thickness is 2µm~3µm. The higher growth temperature and lower pressure of the undoped GaN layer result in better crystal quality of the prepared GaN. At the same time, as the GaN thickness increases, the compressive stress is released through stacking faults, reducing line defects, improving crystal quality, and reducing reverse leakage current. However, increasing the GaN layer thickness consumes a large amount of Ga source material, which greatly increases the epitaxial cost of LEDs. Therefore, currently, LED epitaxial wafers are usually grown with undoped GaN at 2~3µm, which not only saves production costs but also provides GaN material with high crystal quality.

[0048] Step S40: Deposit an N-type GaN layer on the undoped GaN layer.

[0049] Preferably, the N-type GaN layer is grown at a temperature of 1050℃ to 1200℃, a pressure of 100 torr to 600 torr, a thickness of 2µm to 3µm, and a Si doping concentration of 1*e. 19 atoms / cm 3 ~5*e 19 atoms / cm 3 Specifically, in this embodiment, the N-type GaN layer is grown at a temperature of 1120°C, a growth pressure of 100 torr, a thickness of 2µm to 3µm, and a Si doping concentration of 2.5*e. 19 atoms / cm 3 First, the N-type GaN layer provides sufficient electrons for LED light emission. Second, the resistivity of the N-type GaN layer is higher than that of the transparent electrode on P-GaN. Therefore, sufficient Si doping can effectively reduce the resistivity of the N-type GaN layer. Finally, sufficient thickness of the N-type GaN can effectively release stress and improve the luminous efficiency of the LED.

[0050] Step S50: Deposit a multi-quantum-well layer on the N-type GaN layer.

[0051] Preferably, the multiple quantum well layers are InGaN quantum well layers and AlGaN quantum barrier layers alternately stacked on an N-type GaN layer, with a stacking period of 6 to 12. The InGaN quantum well layer is grown at a temperature of 790°C to 810°C, with a thickness of 2 nm to 5 nm and a growth pressure of 50 torr to 300 torr. The AlGaN quantum barrier layer is grown at a temperature of 800°C to 900°C, with a thickness of 5 nm to 15 nm and a growth pressure of 50 torr to 300 torr. The Al composition is 0.01 to 0.1. Specifically, in this embodiment, the multiple quantum well layer consists of alternating stacked InGaN quantum well layers and AlGaN quantum barrier layers, with a stacking period of 10. The InGaN quantum well is grown at a temperature of 795°C, has a thickness of 3.5 nm, a growth pressure of 200 torr, and an In composition of 0.22. The AlGaN quantum barrier layer is grown at a temperature of 855°C, has a thickness of 9.8 nm, a growth pressure of 200 torr, and an Al composition of 0.05. The active region of the multiple quantum wells is the region where electrons and holes recombine. A reasonable structural design can significantly increase the overlap of electron and hole wave functions, thereby improving the luminous efficiency of the LED device.

[0052] Step S60: Deposit an electron blocking layer on the multi-quantum-well layer.

[0053] Optionally, the electron blocking layer is AlInGaN with a thickness of 10–40 nm, a growth temperature of 900℃–1000℃, and a pressure of 100 torr–300 torr, wherein the Al component concentration is 0.005–0.1 and the In component concentration is 0.01–0.2. Specifically, in this embodiment, the electron blocking layer is AlInGaN with a thickness of 15 nm, wherein the Al component concentration gradually changes from 0.01 to 0.05 along the growth direction of the epitaxial layer, the In component concentration is 0.01, the growth temperature is 965℃, and the growth pressure is 200 torr. This can effectively limit electron overflow and reduce the blocking of holes, thereby improving the hole-to-electron-well injection efficiency.

[0054] Step S70: Deposit a P-type GaN layer on the electron blocking layer.

[0055] Optionally, the p-type GaN layer is grown at a temperature of 900℃-1050℃, a thickness of 10nm-50nm, a growth pressure of 100torr-600torr, and a Mg doping concentration of 1*e. 19 atoms / cm 3 ~1*e 21 atoms / cm 3 Specifically, in this embodiment, the p-type GaN layer is grown at a temperature of 985°C, has a thickness of 15 nm, a growth pressure of 200 torr, and a Mg doping concentration of 2*e. 20 atoms / cm 3Excessive Mg doping concentration can damage crystal quality, while low doping concentration can affect hole concentration. Meanwhile, for LED structures containing V-shaped pits, the higher growth temperature of the P-type GaN layer is beneficial for merging the V-shaped pits, resulting in a smooth LED epitaxial wafer.

[0056] Example 1

[0057] In this embodiment, a light-emitting diode epitaxial wafer is provided. Sapphire substrate is used, as it possesses advantages such as good thermal and chemical stability, high mechanical strength, mature technology, and relatively low price. The thickness of the nitrided graphene buffer layer is 5 nm, the thickness of the h-BN buffer layer is 10 nm, and the thickness of the B... x Al 1-x The thickness of the N buffer layer is 15 nm, the thickness of the AlN buffer layer is 20 nm, and the thickness of the B... x Al 1-x In the N-buffer layer, the B component gradually decreases from 1 to 0.1 along the growth direction of the epitaxial layer. (h-BN buffer layer, B) x Al 1-x The growth atmosphere during the deposition of the N buffer layer and AlN buffer layer was a mixture of N2 / NH3 with a composition ratio of 1:3, and the test was conducted at a current of 120mA / 60mA.

[0058] Example 2

[0059] The difference between the LED epitaxial wafer in this embodiment and the LED epitaxial wafer in Embodiment 1 is that the thickness of the nitrided graphene buffer layer is 10 nm.

[0060] Example 3

[0061] The difference between the LED epitaxial wafer in this embodiment and the LED epitaxial wafer in Embodiment 1 is that the thickness of the h-BN buffer layer is 15nm.

[0062] Example 4

[0063] The difference between the LED epitaxial wafer in this embodiment and the LED epitaxial wafer in Embodiment 1 is that, B x Al 1-x The thickness of the N buffer layer is 25 nm.

[0064] Example 5

[0065] The difference between the LED epitaxial wafer in this embodiment and the LED epitaxial wafer in Embodiment 1 is that the thickness of the AlN buffer layer is 35nm.

[0066] Example 6

[0067] The difference between the LED epitaxial wafer in this embodiment and the LED epitaxial wafer in Embodiment 1 is that, B x Al 1-x In the N buffer layer, the B component gradually decreases from 1 to 0.2 along the growth direction of the epitaxial layer.

[0068] Example 7

[0069] The difference between the LED epitaxial wafer in this embodiment and the LED epitaxial wafer in Embodiment 1 is that, B x Al 1-x In the N buffer layer, the B component gradually decreases from 0.7 to 0.1 along the growth direction of the epitaxial layer.

[0070] Example 8

[0071] The difference between the LED epitaxial wafer in this embodiment and the LED epitaxial wafer in Embodiment 1 lies in the h-BN buffer layer and B... x Al 1-x The growth atmosphere during the deposition of the N buffer layer and AlN buffer layer is a mixture of N2 / NH3 with a composition ratio of 1:5.

[0072] Example 9

[0073] The difference between the LED epitaxial wafer in this embodiment and the LED epitaxial wafer in Embodiment 1 lies in the h-BN buffer layer and B... x Al 1-x The growth atmosphere during the deposition of the N buffer layer and AlN buffer layer is a mixture of N2 / NH3 with a composition ratio of 2:3.

[0074] Compare with Example 1

[0075] The difference between the LED epitaxial wafer in this embodiment and the LED epitaxial wafer in Embodiment 1 is that the buffer layer is only a 35nm thick AlN buffer layer.

[0076] Please refer to Table 1, which shows a comparison of some parameters and corresponding transmittance of the above embodiments and comparative examples.

[0077] Table 1

[0078]

[0079] As shown in Table 1, the photoelectric efficiency of the LED epitaxial wafer provided by the present invention is improved by 1-2% compared with the currently mass-produced chips.

[0080] It should be noted that the above implementation process is only for illustrating the feasibility of this application, but it does not mean that the LED epitaxial wafer of this application has only the above-mentioned implementation processes. On the contrary, as long as the LED epitaxial wafer of this application can be implemented, it can be included in the feasible implementation scheme of this application. In addition, the structural part of the LED epitaxial wafer in the embodiments of this invention corresponds to the method part of preparing the LED epitaxial wafer of this invention, and its specific implementation details are also the same, and will not be repeated here.

[0081] In the description of this specification, references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0082] The above embodiments merely illustrate several implementation methods of the present invention, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this patent should be determined by the appended claims.

Claims

1. A light-emitting diode epitaxial wafer, characterized in that, The substrate includes a buffer layer, an undoped GaN layer, an N-type GaN layer, a multiple quantum well layer, an electron blocking layer, and a P-type GaN layer sequentially deposited on the substrate. The buffer layer includes a nitrided graphene buffer layer, an h-BN buffer layer, and a B-type GaN layer sequentially deposited on the substrate. x Al 1-x N buffer layer, AlN buffer layer, wherein, the B x Al 1-x The B content in the N buffer layer gradually decreases along the growth direction of the epitaxial layer.

2. The light-emitting diode epitaxial wafer according to claim 1, characterized in that, The thickness of the nitrided graphene buffer layer is 1 nm to 20 nm, and the thickness of the h-BN buffer layer is 1 nm to 20 nm. x Al 1-x The thickness of the N buffer layer is 1 nm to 50 nm, and the thickness of the AlN buffer layer is 1 nm to 100 nm.

3. The light-emitting diode epitaxial wafer according to claim 1, characterized in that, The B x Al 1-x The value of x in the N-buffer layer ranges from 0 to 1.

4. The light-emitting diode epitaxial wafer according to claim 1, characterized in that, The multiple quantum well layer comprises alternating stacked InGaN quantum well layers and AlGaN quantum barrier layers.

5. A method for preparing a light-emitting diode epitaxial wafer according to any one of claims 1-4, characterized in that, Includes the following steps: Provide a substrate; A nitrided graphene buffer layer, an h-BN buffer layer, and a B-type buffer layer are sequentially deposited on the substrate. x Al 1-x N-buffer layer, AlN-buffer layer; An undoped GaN layer, an N-type GaN layer, a multiple quantum well layer, an electron blocking layer, and a P-type GaN layer are sequentially deposited on the AlN buffer layer. Wherein, the B x Al 1-x The B content in the N buffer layer gradually decreases along the growth direction of the epitaxial layer.

6. The preparation method according to claim 5, characterized in that: The nitrided graphene buffer layer was deposited in PECVD with a deposition power of 2KW~5KW, a deposition temperature of 300℃~800℃, and a sputtering pressure of 1 torr~50 torr. After the nitrided graphene buffer layer is deposited, its surface is subjected to N2 plasma treatment at a temperature of 300℃~800℃.

7. The preparation method according to claim 6, characterized in that: The carbon source sputtered in the PECVD is CH4.

8. The preparation method according to claim 5, characterized in that: The h-BN buffer layer, the B x Al 1-x The AlN buffer layer and the AlN buffer layer are deposited in MOCVD at a deposition temperature of 700℃~900℃ and a growth pressure of 50 torr~300 torr.

9. The preparation method according to claim 8, characterized in that: The h-BN buffer layer, the B x Al 1-x The growth atmosphere during the deposition of the N buffer layer and the AlN buffer layer is a mixture of N2 / NH3 with a composition ratio of 1:1 to 1:

10.

10. The preparation method according to claim 8, characterized in that: The h-BN buffer layer, the B x Al 1-x The N buffer layer and the AlN buffer layer use NH3 as the N source during the deposition process. x Al 1-x The AlN buffer layer and the AlN buffer layer use trimethylaluminum as the aluminum source during the deposition process.

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