Semi-polar surface gallium nitride epitaxial layer and preparation method thereof

Abstract

The invention discloses a semi-polar surface gallium nitride epitaxial layer and a preparation method thereof. The preparation method comprises the following steps: providing a semi-polar surface gallium nitride substrate; a semi-polar surface gallium nitride epitaxial layer is grown on the semi-polar surface gallium nitride substrate in a homoepitaxial mode; wherein the semipolar surface is a () surface. The homoepitaxial growth of the semi-polar surface gallium nitride epitaxial layer is carried out by taking the semi-polar surface gallium nitride substrate as a substrate, so that defect driving factors caused by lattice mismatch or thermal mismatch are weakened fundamentally, and the semi-polar surface gallium nitride epitaxial layer with high crystal quality can be obtained.

Description

Technical Field

[0001] This invention belongs to the field of semiconductor materials technology, specifically relating to a semi-polar gallium nitride epitaxial layer and its preparation method. Background Technology

[0002] Gallium nitride (GaN) possesses characteristics such as a wide bandgap, high breakdown electric field, high saturation drift velocity, and excellent chemical and thermal stability, and has been widely used in blue / green / violet light-emitting diodes, lasers, and high-frequency, high-power power electronic devices. Currently, commercial GaN-based optoelectronic devices and some power devices still use polar c-plane (0001) wurtzite-structured gallium nitride epitaxial layers grown on substrates such as sapphire or silicon carbide as the base material. However, c-plane wurtzite-structured gallium nitride epitaxial layers exhibit significant spontaneous polarization and piezoelectric polarization effects along the

[0001] direction. In heterojunction structures such as InGaN / GaN quantum wells, the aforementioned polarization effect introduces a strong built-in electric field, causing the quantum well band to tilt. This results in the spatial separation of electron and hole wave functions, known as the quantum-confined Stark effect (QCSE). This significantly reduces the radiative recombination efficiency of charge carriers, and is more pronounced in long-wavelength (such as green and red) emission bands. It is one of the important factors limiting the performance improvement of high-efficiency long-wavelength GaN-based light-emitting devices.

[0003] To overcome the quantum confinement Stark effect and improve device efficiency, the epitaxial growth of nonpolar (e.g., m-plane, a-plane) and semi-polar gallium nitride (GaN) epitaxial layers has gradually become a research focus in academia and industry. Compared to c-plane GaN epitaxial layers, nonpolar and semi-polar GaN epitaxial layers can significantly weaken the polarization field, thereby reducing the adverse effects of the quantum confinement Stark effect on the luminescence efficiency of GaN-based quantum well structures. Among them, the semi-polar (m-plane, a-plane) Gallium nitride (GaN) epitaxial layers are widely considered a potential ideal material for realizing high-efficiency, long-wavelength InGaN-based light-emitting devices due to their ability to significantly reduce polarization fields and their greater facilitator for In composition incorporation. Currently, existing technologies primarily employ a three-step epitaxial growth process on m-plane sapphire substrates to fabricate semi-polar (GaN) epitaxial layers. The gallium nitride epitaxial layer consists of a low-temperature grown AlN buffer layer, a high-temperature grown AlN buffer layer, and a heteroepitaxially grown semi-polar (GaN) layer. Gallium nitride epitaxial layers with a 3D surface. This multi-step buffering and epitaxial control strategy significantly improved the fabricated semi-polarity (SPS) of the epitaxial layer. This improves the crystal quality and optical properties of gallium nitride epitaxial layers with a three-step epitaxial growth process, effectively reducing the density of defects such as stacking faults and through dislocations on the basal plane. It also exhibits a significant anisotropic structure within the plane, with this anisotropy varying with the azimuth angle. This type of semi-polar (GaN) epitaxial layer is fabricated through a three-step epitaxial growth process. In gallium nitride epitaxial layers, the dislocations are predominantly mixed-type dislocations, and the orientation exhibits an approximately 58.4° rotation relative to the substrate, resulting in significant linear polarization of light emission. Therefore, this type of highly polarized half-polarity (SPS) Gallium nitride epitaxial layers can provide a potential material basis for group III nitride lighting and display-related light-emitting devices (such as display and backlight applications).

[0004] However, heteroepitaxial growth has a semi-polarity ( In the case of gallium nitride epitaxial layers, the defect density is difficult to further reduce. Furthermore, due to the complexity of defect types (including penetrating dislocations and basal stacking faults), although the three-step epitaxial growth method described above effectively reduced the defect density, it remains at a relatively high level. In addition, the fabricated semi-polar ( The surface morphology stability of gallium nitride epitaxial layers is still limited by the process window, and morphology problems such as ripples, stripes or steps are prone to occur. These morphologies are often coupled with semi-polar growth dynamics, merging process and anisotropic defect distribution, which will affect subsequent heterostructure stacking and device processing window, leading to problems such as uneven quantum well barrier and unstable two-dimensional electron gas / hole transport, thus affecting device performance.

[0005] Therefore, in order to address the above-mentioned technical problems, it is necessary to provide a semi-polar gallium nitride epitaxial layer and its preparation method. Summary of the Invention

[0006] The purpose of this invention is to provide a semi-polar gallium nitride epitaxial layer and its preparation method, which can obtain high-quality semi-polar (GaN) epitaxial layer through homoepitaxial growth. Gallium nitride epitaxial layer.

[0007] To achieve the above objectives, an embodiment of the present invention provides the following technical solution:

[0008] A method for fabricating a semi-polar gallium nitride epitaxial layer, the method comprising the following steps:

[0009] Provides gallium nitride substrates with semi-polar surfaces;

[0010] A semi-polar gallium nitride epitaxial layer is homoepitaxially grown on the semi-polar gallium nitride substrate;

[0011] Wherein, the semi-polar surface is ( )noodle.

[0012] In one embodiment, a semi-polar gallium nitride epitaxial layer is homoepitaxially grown on the semi-polar gallium nitride substrate using molecular beam epitaxy or metal-organic chemical vapor deposition.

[0013] In one embodiment, a semi-polar gallium nitride epitaxial layer is homoepitaxially grown on the semi-polar gallium nitride substrate using molecular beam epitaxy, comprising:

[0014] A gallium nitride substrate with a semi-polar surface is subjected to a 1×10 -10 ~1×10 -11 Under a vacuum of mbar, the temperature is increased to 350℃~800℃ at a heating rate of 0.1℃ / s ~ 10℃ / s;

[0015] Gallium source beam and nitrogen plasma source beam are obtained by gallium source and nitrogen source respectively, and a semi-polar gallium nitride epitaxial layer is homogeneously grown on a semi-polar gallium nitride substrate.

[0016] The obtained semi-polar gallium nitride epitaxial layer was cooled to room temperature at a cooling rate of 1℃ / min ~ 30℃ / min.

[0017] In one embodiment, a gallium source beam is obtained by heating the gallium source to a temperature of 500°C to 800°C, and the flow rate of the gallium source beam is 0.01 Å / s to 1 Å / s.

[0018] In one embodiment, the nitrogen source is nitrogen gas, and a nitrogen plasma source beam is obtained by radio frequency cracking of nitrogen gas. The flow rate of nitrogen gas is 0.5 sccm to 5 sccm, and the power of radio frequency cracking of nitrogen gas is 100W to 350W.

[0019] In one embodiment, the method further includes, prior to the step of homoepitaxially growing a semi-polar gallium nitride epitaxial layer on the semi-polar gallium nitride substrate:

[0020] The semi-polar gallium nitride substrate is pretreated by an annealing process to remove water molecules and impurities from its surface. The vacuum level in the annealing process is 1×10⁻⁶. -8 ~1×10 -9 mbar, the annealing process is carried out at a temperature of 150℃~250℃.

[0021] In one embodiment, prior to the step of homoepitaxially growing a semi-polar gallium nitride epitaxial layer on the semi-polar gallium nitride substrate, the method further includes:

[0022] The semi-polar gallium nitride substrate was planarized using a plasma annealing process with a vacuum level of 1×10⁻⁶. -10 ~1×10 -11 mbar, the temperature in the plasma annealing process is 300℃~800℃.

[0023] In one embodiment, the plasma annealing process uses nitrogen plasma, which is generated by radio frequency cracking of nitrogen gas.

[0024] In one embodiment, the flow rate of the nitrogen gas is 0.5 sccm to 5 sccm, and the power of the radio frequency pyrolysis nitrogen gas is 100W to 350W.

[0025] Another embodiment of the present invention provides the following technical solution:

[0026] A semi-polar gallium nitride epitaxial layer is prepared according to the above-described preparation method.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] This invention uses a semi-polar gallium nitride substrate as the substrate for homoepitaxial growth of a semi-polar gallium nitride epitaxial layer, which fundamentally weakens the defect-driving factors caused by lattice mismatch or thermal mismatch, and is conducive to obtaining a semi-polar gallium nitride epitaxial layer with higher crystal quality.

[0029] This invention uses plasma annealing to treat the surface of a semi-polar gallium nitride substrate, providing a clean and flat surface for the growth of a semi-polar gallium nitride epitaxial layer, which is beneficial for obtaining a high-quality semi-polar gallium nitride epitaxial layer. Attached Figure Description

[0030] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0031] Figure 1 This is a schematic flowchart of the method for preparing a semi-polar gallium nitride epitaxial layer in Embodiment 1 of the present invention;

[0032] Figure 2 This is an RHEED image of the gallium nitride epitaxial layer with a semi-polar surface in Embodiment 1 of the present invention;

[0033] Figure 3 This is an STM image of the gallium nitride epitaxial layer with a semi-polar surface in Embodiment 1 of the present invention;

[0034] Figure 4 This is a magnified STM image of a semi-polar gallium nitride epitaxial layer in Embodiment 1 of the present invention. Detailed Implementation

[0035] To enable those skilled in the art to better understand the technical solutions in the present disclosure, the following will clearly and completely describe the technical solutions in the embodiments of the present disclosure in conjunction with the accompanying drawings in the embodiments of the present disclosure. Obviously, the described embodiments are only a part of the embodiments of the present disclosure, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the present disclosure without creative efforts shall fall within the scope of protection of the present disclosure.

[0036] The present invention discloses a method for preparing a semi-polar gallium nitride epitaxial layer, including:

[0037] Providing a semi-polar gallium nitride substrate;

[0038] Homoepitaxially growing a semi-polar gallium nitride epitaxial layer on the semi-polar gallium nitride substrate;

[0039] wherein the semi-polar plane is the ( ) plane.

[0040] The present invention also discloses a semi-polar gallium nitride epitaxial layer, which is prepared according to the above preparation method.

[0041] The following further illustrates the present invention with specific examples.

[0042] Example 1:

[0043] As shown in Figure 1 , the method for preparing the semi-polar gallium nitride epitaxial layer in this embodiment includes the following steps:

[0044] S1. Providing a semi-polar gallium nitride substrate.

[0045] wherein the semi-polar plane is the ( ) plane, that is, the semi-polar gallium nitride substrate is a semi-polar ( ) plane gallium nitride substrate.

[0046] S2. Homoepitaxially growing a semi-polar gallium nitride epitaxial layer on the semi-polar gallium nitride substrate.

[0047] wherein the semi-polar gallium nitride epitaxial layer is a semi-polar ( ) plane gallium nitride epitaxial layer.

[0048] Furthermore, before performing this step, it also includes pre-treating the semi-polar gallium nitride substrate through an annealing process to remove water molecules and impurities on the surface of the semi-polar gallium nitride substrate. The vacuum degree in the pre-treatment is 1×10 -8 ~1×10<00 (mbar, and the temperature in the pre-treatment is 150°C to 250°C.

[0049] Specifically, in this embodiment, the semi-polarity (SPI) is controlled in the front chamber of the molecular beam epitaxy device. The gallium nitride substrate is pretreated. First, a semi-polar ( The gallium nitride substrate is introduced from the atmosphere into the front chamber of the molecular beam epitaxy equipment, and the front chamber is evacuated to a vacuum level of 1×10⁻⁶ using mechanical and molecular pumps. -8 ~1×10 - 9 After reaching the mbar level, for half-polarity ( The gallium nitride substrate was subjected to low-temperature annealing and degassing treatment at 200℃ for 2-48 hours to remove semi-polar ( Water molecules and other impurities adsorbed on the surface of the gallium nitride substrate.

[0050] Preferably, after pretreatment of the semi-polar gallium nitride substrate, the process further includes planarization of the semi-polar gallium nitride substrate by plasma annealing, wherein the vacuum degree in the plasma annealing process is 1×10⁻⁶. -10 ~1×10 - 11 mbar, the temperature in the plasma annealing process is 300℃~800℃.

[0051] Specifically, in this embodiment, the semi-polar ( The gallium nitride substrate is planarized.

[0052] More specifically, in the plasma annealing process of this embodiment, the plasma is nitrogen plasma, which is generated by radio frequency cracking of nitrogen gas. First, the pretreated semi-polar ( The gallium nitride substrate is transferred from the front-end chamber of the molecular beam epitaxy (MBE) equipment to the growth chamber, and the vacuum level of the growth chamber is increased to 1×10⁻⁶. -10 ~1×10 - 11 mbar; then nitrogen gas is introduced into the growth chamber at a flow rate of 0.5 sccm to 5 sccm, and nitrogen gas is decomposed to generate nitrogen plasma at a radio frequency power of 100W to 350W; then the temperature is set to 300℃ to 800℃ for semi-polar ( The gallium nitride substrate was subjected to high-temperature plasma annealing for 5 to 60 minutes to further remove semi-polarity ( Impurities on the surface of a gallium nitride substrate are removed and its lattice is rearranged to obtain a flat surface.

[0053] semi-polar ( Gallium nitride substrates can be damaged and contain impurities such as carbon and metal ions during fabrication and processing (e.g., cutting, grinding, polishing, cleaning, and handling / storage). Furthermore, the semi-polar nature of gallium nitride substrates can introduce these impurities. When a gallium nitride substrate is exposed to air, it will adsorb oxygen atoms on the surface and undergo re-oxidation to form a gallium oxide layer. (Semi-polar) Subsurface damage or residual stress propagation on the gallium nitride substrate, as well as defects such as surface impurities and oxide layers, can affect the subsequent epitaxial growth of semipolar ( During the process of regenerating gallium nitride epitaxial layers, the growth quality is affected by the semi-polar () regeneration. Plasma annealing can effectively remove the semi-polar () regeneration. The impurities and oxide layer on the surface of the gallium nitride substrate can be removed, and the lattice can be rearranged to eliminate subsurface damage and residual stress, effectively improving the surface flatness and benefiting subsequent semi-polarization (SPD). Growth of gallium nitride epitaxial layers on the surface.

[0054] Furthermore, in this embodiment, the molecular beam epitaxy device is vacuum interconnected with the ultra-high vacuum scanning tunneling microscope (STM) to achieve semi-polarity ( Planarization treatment or semi-polar (GaN) substrate After the growth of the gallium nitride epitaxial layer, it can be easily transferred to the chamber of an ultra-high vacuum scanning tunneling microscope for characterization to obtain the surface morphology. The vacuum level of the chamber in the ultra-high vacuum scanning tunneling microscope is 1×10⁻⁶. -10 ~1×10 -11 mbar. The planarized semi-polar ( The surface of the gallium nitride substrate was characterized to confirm whether a clean and flat surface was obtained.

[0055] Furthermore, a semi-polar gallium nitride epitaxial layer is homoepitaxially grown on a semi-polar gallium nitride substrate using molecular beam epitaxy or metal-organic chemical vapor deposition.

[0056] Preferably, in this embodiment, a semi-polar gallium nitride epitaxial layer is homoepitaxially grown on a semi-polar gallium nitride substrate using molecular beam epitaxy.

[0057] Specifically, in this embodiment, a semi-polar ( ) process is performed in a molecular beam epitaxy apparatus equipped with a gallium source and a nitrogen source. Growth of gallium nitride epitaxial layers on the surface.

[0058] More specifically, this step includes:

[0059] 1. A gallium nitride substrate with a semi-polar surface is placed in a 1×10⁻⁶ m² area. -10 ~1×10 -11Under a vacuum of mbar, the temperature is increased to 350℃~800℃ at a heating rate of 0.1℃ / s ~ 10℃ / s.

[0060] Specifically, semi-polarity ( A gallium nitride substrate is placed on the growth stage of the growth chamber of a molecular beam epitaxy (MBE) apparatus, and the semi-polar (SPE) substrate is heated by an electron beam to grow the substrate. The temperature of the gallium nitride substrate is increased to 350℃~800℃.

[0061] 2. Gallium source beam and nitrogen plasma source beam are obtained by using gallium source and nitrogen source respectively, and a semi-polar gallium nitride epitaxial layer is homogeneously grown on a semi-polar gallium nitride substrate.

[0062] Specifically, in this embodiment, a gallium source beam is obtained by heating the gallium source to 500℃~800℃, and the flow rate of the gallium source beam is controlled to be 0.01Å / s~1Å / s. In this embodiment, nitrogen gas is used as the nitrogen source, and a nitrogen plasma source beam is obtained by radio frequency splitting of nitrogen gas. The flow rate of nitrogen gas is 0.5sccm~5sccm, and the power of radio frequency splitting of nitrogen gas is 100W~350W.

[0063] More specifically, in this embodiment, mechanical baffles are provided at the gallium source beam port and the nitrogen plasma source beam port to ensure that the beam is stable and semi-polar ( After the gallium nitride substrate reaches the preset temperature, the mechanical baffle is opened so that the gallium source beam and the nitrogen ion beam are aligned precisely with the half-polarity of the growth stage. Gallium nitride substrate with semi-polar ( The growth of gallium nitride epitaxial layers was carried out. During the growth process, the semi-polarity was controlled by adjusting the opening time of the mechanical baffle. The growth time for the gallium nitride epitaxial layer is 3 min to 120 min.

[0064] 3. Cool the obtained semi-polar gallium nitride epitaxial layer to room temperature at a cooling rate of 1℃ / min ~ 30℃ / min.

[0065] It is worth noting that in this embodiment, the half-polarity ( Surface treatment, characterization, and half-polarity of gallium nitride substrates. The growth and characterization of gallium nitride epitaxial layers must be performed in an ultra-high vacuum environment. The quality of the vacuum environment directly affects the ability to grow high-quality semi-polar (SNP) epitaxial layers. The gallium nitride epitaxial layer is crucial, mainly in the following aspects:

[0066] (1) Reduced contamination: In an ultra-high vacuum environment, impurities in the air, such as oxygen, water vapor, and dust, are significantly reduced, thus preventing these impurities from being present in a semi-polar environment. Defects formed on the surface or interface of gallium nitride epitaxial layers are beneficial for obtaining high-purity, high-performance semi-polar (SNP) epitaxial layers. Gallium nitride epitaxial layer;

[0067] (2) Keep the surface clean: semi-polar ( The surface of the gallium nitride substrate, after treatment, can remain clean in an ultra-high vacuum environment, avoiding contamination during subsequent semi-polarization (SPS) processes. The growth process of gallium nitride epitaxial layers can cause contamination problems.

[0068] (3) Precise control of the purity of gallium and nitrogen sources: The vacuum environment eliminates the interference of oxygen and other impurities in the air, allowing for the homoepitaxial growth of semi-polar materials under pure conditions. Gallium nitride epitaxial layer;

[0069] (4) Controlling growth rate and uniformity: In a vacuum, the gallium source beam flows from the gallium source beam port to the semi-polar ( The transport process of the gallium nitride substrate is not affected by air molecules, which ensures uniform material deposition and allows for better control of the deposition rate and uniformity of molecular beam epitaxy.

[0070] (5) Optimize semi-polarity ( Surface structure and crystal quality of gallium nitride epitaxial layer: The vacuum environment provides stable deposition conditions, enabling semi-polar ( Gallium nitride epitaxial layers can grow uniformly to form ideal crystal structures, which is crucial for forming high-quality semi-polar (SNP) epitaxial layers. Gallium nitride epitaxial layers are very important;

[0071] (6) Improved surface and interface properties: In a vacuum, semi-polar ( Gallium nitride epitaxial layers can be applied in a pollution-free semi-polar ( Uniform deposition on the surface of a gallium nitride substrate, ultimately achieving a semi-polar ( The gallium nitride epitaxial layer has a smooth and defect-free surface. Simultaneously, the vacuum environment reduces chemical reactions and contamination at the interface, improving its purity and stability.

[0072] (7) Atom-by-layer deposition: Under ultra-high vacuum conditions, molecular beam epitaxy can achieve true atom-by-layer deposition and abrupt atomic interfaces between layers. This precise control is crucial for preparing semi-polar materials with specific structures and functions. The surface-mount gallium nitride epitaxial layer is crucial.

[0073] With heteroepitaxial growth semi-polarity ( Compared to a gallium nitride epitaxial layer, this embodiment uses a semi-polar ( ), a gallium nitride substrate is used as a substrate for homoepitaxial growth of a semi-polar ( ), gallium nitride epitaxial layer, which can effectively avoid the defect sources introduced by lattice matching or thermal matching. <> <>

[0074] See <> Figure 2 As shown, the semi-polar (<> ), gallium nitride epitaxial layer obtained by the preparation method in this embodiment is characterized by reflection high energy electron diffraction (Reflection High Energy Electron Diffraction, RHEED). The characterization results show that the diffraction image is mainly characterized by clear and continuous stripes, the stripes are bright and arranged in an orderly manner, and no obvious strong speckle or annular diffraction characteristics caused by a three-dimensional island-like rough surface are seen. The RHEED stripes have good continuity and certain symmetric distribution characteristics, indicating that the semi-polar (<> ), gallium nitride epitaxial layer grown homoepitaxially in this embodiment maintains a good crystallographic orientation relationship with the semi-polar (<> ), gallium nitride substrate, and the obtained semi-polar (<> ), gallium nitride epitaxial layer has a high surface order and epitaxial quality. <> <>

[0075] See <> Figure 3 As shown, the STM image of the semi-polar (<> ), gallium nitride epitaxial layer within a 20nm×20nm scanning range shows that its surface is overall uniform, with small surface fluctuations, presenting relatively fine periodic bright spots and atomic-scale fluctuation characteristics. The surface quality has reached the level capable of atomic-scale characterization, indicating that in this embodiment, by surface treatment of the semi-polar (<> ), gallium nitride substrate, the surface order of the prepared semi-polar ( <> ), gallium nitride epitaxial layer can be effectively improved. <> <><>

[0076] See <> Figure 4 As shown, further narrowing the scanning range, the characterization results show that the atomic-scale bright spot distribution on the surface of the prepared semi-polar (<> ), gallium nitride epitaxial layer is clearer, and locally shows a relatively regular periodic arrangement, indicating that the surface of the prepared semi-polar (<> ), gallium nitride epitaxial layer has an obvious atomic-scale ordered structure, proving that the preparation method in this embodiment can achieve high-quality epitaxial growth of the semi-polar (<> ), gallium nitride epitaxial layer. <> <>

[0077] From the above technical solutions, the present invention has the following beneficial effects: <> <>

[0078] This invention uses a semi-polar gallium nitride substrate as the substrate for homoepitaxial growth of a semi-polar gallium nitride epitaxial layer, which fundamentally weakens the defect-driving factors caused by lattice mismatch or thermal mismatch, and is conducive to obtaining a semi-polar gallium nitride epitaxial layer with higher crystal quality.

[0079] This invention uses plasma annealing to treat the surface of a semi-polar gallium nitride substrate, providing a clean and flat surface for the growth of a semi-polar gallium nitride epitaxial layer, which is beneficial for obtaining a high-quality semi-polar gallium nitride epitaxial layer.

[0080] It will be apparent to those skilled in the art that this disclosure is not limited to the details of the exemplary embodiments described above, and that this disclosure can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of this disclosure is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within this disclosure. No reference numerals in the claims should be construed as limiting the scope of the claims.

[0081] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A method for preparing a semi-polar gallium nitride epitaxial layer, characterized in that, The preparation method includes the following steps: Provides gallium nitride substrates with semi-polar surfaces; A semi-polar gallium nitride epitaxial layer is homoepitaxially grown on the semi-polar gallium nitride substrate; Wherein, the semi-polar surface is ( )noodle.

2. The method for preparing a semi-polar gallium nitride epitaxial layer according to claim 1, characterized in that, A semi-polar gallium nitride epitaxial layer is homoepitaxially grown on the semi-polar gallium nitride substrate using molecular beam epitaxy or metal-organic chemical vapor deposition.

3. The method for preparing a semi-polar gallium nitride epitaxial layer according to claim 1, characterized in that, A semi-polar gallium nitride epitaxial layer is homoepitaxially grown on the semi-polar gallium nitride substrate using molecular beam epitaxy, including: A gallium nitride substrate with a semi-polar surface is subjected to a 1×10 -10 ~1×10 -11 Under a vacuum of mbar, the temperature is increased to 350℃~800℃ at a heating rate of 0.1℃ / s ~ 10℃ / s; Gallium source beam and nitrogen plasma source beam are obtained by gallium source and nitrogen source respectively, and a semi-polar gallium nitride epitaxial layer is homogeneously grown on a semi-polar gallium nitride substrate. The obtained semi-polar gallium nitride epitaxial layer was cooled to room temperature at a cooling rate of 1℃ / min ~ 30℃ / min.

4. The method for preparing a semi-polar gallium nitride epitaxial layer according to claim 3, characterized in that, A gallium source beam is obtained by heating the gallium source to a temperature of 500℃~800℃, and the flow rate of the gallium source beam is 0.01Å / s~1Å / s.

5. The method for preparing a semi-polar gallium nitride epitaxial layer according to claim 3, characterized in that, The nitrogen source is nitrogen gas. A nitrogen plasma source beam is obtained by radio frequency cracking of nitrogen gas. The flow rate of nitrogen gas is 0.5 sccm to 5 sccm, and the power of radio frequency cracking of nitrogen gas is 100W to 350W.

6. The method for preparing a semi-polar gallium nitride epitaxial layer according to claim 1, characterized in that, The step prior to the homoepitaxial growth of a semi-polar gallium nitride epitaxial layer on the semi-polar gallium nitride substrate further includes: The semi-polar gallium nitride substrate is pretreated by an annealing process to remove water molecules and impurities from its surface. The vacuum level in the annealing process is 1×10⁻⁶. -8 ~1×10 -9 mbar, the annealing process is carried out at a temperature of 150℃~250℃.

7. The method for preparing a semi-polar gallium nitride epitaxial layer according to claim 1, characterized in that, The step prior to the homoepitaxial growth of a semi-polar gallium nitride epitaxial layer on the semi-polar gallium nitride substrate further includes: The semi-polar gallium nitride substrate was planarized using a plasma annealing process with a vacuum level of 1×10⁻⁶. -10 ~1×10 -11 mbar, the temperature in the plasma annealing process is 300℃~800℃.

8. The method for preparing a semi-polar gallium nitride epitaxial layer according to claim 7, characterized in that, In the plasma annealing process, the plasma is nitrogen plasma, which is generated by radio frequency cracking of nitrogen gas.

9. The method for preparing a semi-polar gallium nitride epitaxial layer according to claim 8, characterized in that, The flow rate of the nitrogen gas is 0.5 sccm to 5 sccm, and the power of the radio frequency pyrolysis nitrogen gas is 100W to 350W.

10. A semi-polar gallium nitride epitaxial layer, characterized in that, The semi-polar gallium nitride epitaxial layer is prepared by the preparation method according to any one of claims 1 to 9.

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