A sapphire gallium nitride heterogeneous material epitaxial structure and epitaxial growth method thereof

Abstract

The present invention provides a sapphire gallium nitride heterogeneous material epitaxial structure and an epitaxial growth method thereof, relating to the technical field of semiconductor devices. The epitaxial structure comprises: a sapphire substrate, an AlN buffer layer, a GaN channel layer and an AlGaN barrier layer; the sapphire substrate is the basis of the epitaxial structure; the sapphire substrate is provided with a nano pattern, which is specifically a pattern array composed of a plurality of pattern units in an array manner, and each pattern unit is provided with a nano ball; the AlN buffer layer is provided on the sapphire substrate; the GaN channel layer is provided on the AlN buffer layer for electron transmission; the AlGaN barrier layer is provided on the GaN channel layer for forming a two-dimensional electron gas together with the GaN channel layer; the present invention can guide the growth direction of the crystal and limit the propagation of dislocations through the nano pattern, thereby significantly reducing the dislocation density, reducing the defects caused by lattice mismatch, improving the GaN epitaxial quality, and improving the performance and reliability of the device.

Description

Technical Field

[0001] The present invention relates to the technical field of semiconductor devices, and in particular to a sapphire gallium nitride heterogeneous material epitaxial structure and an epitaxial growth method thereof. Background Art

[0002] Gallium nitride (GaN) semiconductor chips are a semiconductor material widely used in high-power, high-frequency, and high-temperature environments. Due to its wide bandgap and high thermal and electrical conductivity, GaN can operate stably at higher voltages and frequencies, making it particularly suitable for high-performance, long-life power electronics and radio frequency (RF) applications.

[0003] Epitaxial structures are crucial in gallium nitride (GaN) semiconductor chips, as they can reduce defects and dislocations caused by lattice mismatch between the substrate and the material. Currently, epitaxial structures mostly use silicon, sapphire, and other substrates.

[0004] Currently, whether Si or sapphire is used as the substrate, a planar substrate is often used. There is usually a large lattice mismatch between GaN and the substrate material. Due to the lattice mismatch, a large number of dislocations and other defects often accumulate on the planar substrate. These defects will directly affect the quality of the epitaxial material and reduce the performance and reliability of the device. Summary of the Invention

[0005] In order to solve the technical problem that traditional planar substrates often accumulate a large number of dislocations and other defects, which directly affect the quality of epitaxial materials and reduce the performance and reliability of devices, the present invention provides a sapphire gallium nitride heterogeneous material epitaxial structure and its epitaxial growth method.

[0006] The technical solutions provided by the embodiments of the present invention are as follows:

[0007] A first aspect of an embodiment of the present invention provides a sapphire gallium nitride heterogeneous material epitaxial structure, comprising: a sapphire substrate, an AlN buffer layer, a GaN channel layer, and an AlGaN barrier layer;

[0008] The sapphire substrate is the basis of the epitaxial structure;

[0009] The sapphire substrate has a nano pattern, which is specifically a pattern array composed of multiple pattern units in an array manner, and each pattern unit is provided with a nano ball;

[0010] An AlN buffer layer is provided on a sapphire substrate;

[0011] The GaN channel layer is provided on the AlN buffer layer for electron transport;

[0012] The AlGaN barrier layer is arranged on the GaN channel layer and is used to form a two-dimensional electron gas together with the GaN channel layer.

[0013] A second aspect of an embodiment of the present invention provides a sapphire gallium nitride heterogeneous material epitaxial growth method for preparing a sapphire gallium nitride heterogeneous material epitaxial structure as described in the first aspect, the method comprising:

[0014] S1: using self-assembled SiO2 nanospheres as a sacrificial etching mask;

[0015] S2: Transferring the nanosphere pattern to the sapphire surface by dry etching to prepare a sapphire substrate with a nanopattern;

[0016] S3: Forming an AlN buffer layer on a sapphire substrate by metal organic chemical vapor deposition technology;

[0017] S4: preparing a stepped channel mask on the AlN buffer layer;

[0018] S5: Growing a GaN channel layer in the stepped channel mask using metal organic chemical vapor deposition technology;

[0019] S6: An AlGaN barrier layer is deposited on the GaN channel layer through metal organic chemical vapor deposition technology, and a two-dimensional electron gas is formed by the AlGaN barrier layer and the GaN channel layer.

[0020] The beneficial effects brought about by the technical solution provided by the embodiment of the present invention include at least:

[0021] In the present invention, the sapphire substrate has a nano-pattern, which can guide the growth direction of the crystal and limit the propagation of dislocations, significantly reduce the dislocation density, reduce the defects caused by lattice mismatch, improve the quality of GaN epitaxy, and improve the performance and reliability of the device. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0023] Figure 1 A schematic structural diagram of a sapphire gallium nitride heterogeneous material epitaxial structure provided in an embodiment of the present invention.

[0024] Figure 2 A schematic flow chart of a sapphire gallium nitride heterogeneous material epitaxial growth method provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0025] The technical solution of the present invention is described below in conjunction with the accompanying drawings.

[0026] Reference Manual Figure 1 , showing a structural schematic diagram of a sapphire gallium nitride heterogeneous material epitaxial structure provided by an embodiment of the present invention.

[0027] An embodiment of the present invention provides a sapphire gallium nitride heterogeneous material epitaxial structure, comprising: a sapphire substrate 1, an AlN buffer layer 2, a GaN channel layer 3, and an AlGaN barrier layer 4.

[0028] The sapphire substrate 1 is the basis of the epitaxial structure, providing a supporting platform and ensuring the epitaxial growth of gallium nitride (GaN) material.

[0029] The sapphire substrate 1 has a nano pattern thereon. Specifically, the nano pattern is a pattern array composed of a plurality of pattern units in an array manner. Nano balls are arranged on each pattern unit.

[0030] It should be noted that nanopatterning can guide the directional growth of crystals, reducing dislocations and defects caused by lattice mismatch, thereby improving the crystal quality of the GaN layer. The introduction of nanospheres can form localized growth areas during the growth process, promoting better fusion of GaN materials in these areas and reducing the accumulation of cracks and stress.

[0031] An AlN buffer layer 2 is deposited on the sapphire substrate 1. The AlN buffer layer 2 mitigates the lattice mismatch between the sapphire substrate and the GaN channel layer. This layer provides a smoother interface for GaN epitaxial growth, reduces stress, and prevents cracks or dislocations caused by thermal expansion differences during GaN growth.

[0032] The GaN channel layer 3, disposed on the AlN buffer layer 2, is used for electron transport. The GaN channel layer 3 is the core layer of the entire heterostructure. GaN has excellent electron mobility and a high electron saturation velocity, making it important for applications in high-frequency, high-power electronic and optoelectronic devices.

[0033] The AlGaN barrier layer 4 is disposed on the GaN channel layer 3 and is used to form a two-dimensional electron gas together with the GaN channel layer 3. The high energy bandwidth characteristics of AlGaN enable it to effectively form a high-density two-dimensional electron gas above the GaN layer, enhancing the conductivity and operating efficiency of the device.

[0034] The beneficial effects brought about by the technical solution provided by the embodiment of the present invention include at least:

[0035] In the present invention, the sapphire substrate has a nano-pattern, which can guide the growth direction of the crystal and limit the propagation of dislocations, significantly reduce the dislocation density, reduce the defects caused by lattice mismatch, improve the quality of GaN epitaxy, and improve the performance and reliability of the device.

[0036] Optionally, the pattern parameters of the nano-pattern include: pattern unit shape, pattern unit width, the number of nano-balls arranged on each pattern unit, and the radius of the nano-balls.

[0037] Optionally, the pattern unit shape may be a triangle, a square or a regular hexagon.

[0038] In a possible implementation, the pattern parameters of the nanopattern are optimized and determined using a Seagull optimization algorithm.

[0039] The Seagull Optimization Algorithm (SOA) is a heuristic optimization algorithm that mimics the foraging behavior of seagulls. This algorithm simulates the cooperative and competitive behavior exhibited by seagulls during foraging, leveraging their path selection, group collaboration, and distribution strategies when searching for food to find the optimal solution. By simulating the movement and interactions of seagulls within the search space, the SOA continuously adjusts its search strategy to quickly find the global optimal solution or a near-optimal solution. Due to its strong global search capabilities and high convergence speed, the SOA has broad application prospects in solving complex optimization problems.

[0040] Among them, those skilled in the art can set the size of the weight coefficient λ1 of device performance and the weight coefficient λ2 of interface quality according to actual conditions, and the present invention does not limit this.

[0041] In actual application, the weight coefficient λ1 of device performance can be set to 0.7 and the weight coefficient λ2 of interface quality can be set to 0.3.

[0042] In this paper, the fitness function combines factors related to device performance, such as carrier mobility, electron density of the two-dimensional electron gas, and breakdown voltage, while also considering interface quality factors such as GaN interface roughness and lattice mismatch. By adjusting the weight coefficients of these parameters, the optimization algorithm can effectively improve the device's electrical performance and structural quality, reduce defects, and ensure optimal performance under different operating conditions. This allows for more precise design of nanopatterns, maximizes device efficiency, and promotes the development of high-performance GaN-based devices.

[0043] Optionally, the pattern parameters of the nanopattern are optimized and determined by using a Seagull optimization algorithm, specifically including:

[0044] Initialize the seagull individuals. Each seagull individual represents a feasible set of model parameters. Each seagull individual consists of multiple dimensional components, and each component represents a model parameter.

[0045] In the global search phase, avoid collisions and move towards the optimal individual:

[0046] ;

[0047] ;

[0048] ;

[0049] in, represents the position of the i-th seagull individual after the global search phase at the t-th iteration, represents the position of the i-th seagull after anti-collision processing at the t-th iteration, A represents the control factor, represents the position of the i-th seagull individual at the t-th iteration, represents the displacement of the i-th seagull individual towards the optimal individual at the t-th iteration, B represents the search balance factor, represents the optimal individual position at the tth iteration.

[0050] In the present invention, by introducing a collision avoidance mechanism during the global search phase and moving individual seagulls toward the optimal individual, the efficiency and accuracy of the search process can be effectively improved. Specifically, by adjusting the control factor A and the search balance factor B, the exploration and development behaviors of individual seagulls can be balanced, collisions between individuals during the search process can be avoided, and unnecessary repeated calculations can be reduced, thereby accelerating the search process. At the same time, by guiding individuals to move toward the optimal solution, the algorithm can be accelerated to converge to the global optimal solution or a solution close to the optimal solution. This method enhances the global search capability and local optimization capabilities of the seagull optimization algorithm, improving its effectiveness in solving complex optimization problems.

[0051] A = [ 1 − lg ( 9 t T ) ] × f c ;

[0052] Among them, t represents the current number of iterations, T represents the maximum number of iterations, and f c Indicates a linearly decreasing frequency.

[0053] In this invention, the value of the control factor is gradually reduced as the number of iterations increases. As the algorithm progresses, the exploration phase gradually shifts to a more refined local search, helping the optimization algorithm converge to the optimal solution or a near-optimal solution more quickly. A larger control factor in the early stages facilitates a broad search space, while a smaller control factor in the later stages promotes more precise local optimization, avoiding premature convergence while maintaining a balance between global and local search capabilities. This dynamic adjustment strategy improves the algorithm's search efficiency and accuracy.

[0054] ;

[0055] Here, r1 represents a random number between 0 and 1.

[0056] In this invention, since the search balance factor is proportional to the square of the control factor, a larger control factor in the initial iterations results in a larger search balance factor, thereby increasing the breadth of the exploration space and encouraging the algorithm to conduct a more extensive search. As iterations proceed, a reduction in the control factor gradually reduces the search balance factor, prompting the algorithm to conduct a more focused local search, thereby improving search accuracy and accelerating convergence. This dynamic adjustment maintains the algorithm's stability and efficiency, helping to enhance its ability to find optimal or near-optimal solutions.

[0057] In the local search phase, a random number r2 is generated. Based on the random number r2, the spiral search strategy and the encirclement strategy are selected in parallel, and the displacement is performed in a spiral motion:

[0058] ;

[0059] ;

[0060] ;

[0061] ;

[0062] ;

[0063] in, represents the position of the i-th seagull after spiral motion at the t-th iteration, x represents the spiral flight coefficient in the x-direction, y represents the spiral flight coefficient in the y-direction, z represents the spiral flight coefficient in the z-direction, r represents the radius of the spiral flight trajectory, θ represents a random number between 0 and 2π, u and v represent spiral constants, and e represents a natural constant.

[0064] Optionally, the helical constant u can be 2, and the helical constant v can be 3.

[0065] In the present invention, by introducing the parallel selection of spiral search strategy and encirclement strategy in the local search stage, the flexibility and accuracy of the search can be effectively improved. When , individual seagulls move in spiral motion, making the search more diverse and able to explore a wider area in the search space. When , a surrounding strategy is adopted to more closely converge individuals toward the optimal solution. This dynamic selection mechanism enhances local search accuracy while maintaining global search capabilities. The introduction of spiral flight trajectories further increases the diversity of the search process. By adjusting factors such as natural constants and spiral constants, the search process can be progressively optimized, avoiding the dilemma of being trapped in a local optimal solution. Overall, this strategy enables the Seagull Optimization Algorithm to demonstrate greater flexibility, accuracy, and convergence efficiency in complex optimization problems.

[0066] Perform mutation operations on each seagull individual:

[0067] .

[0068] in, represents the position of the ith seagull individual after mutation at the tth iteration, P r represents a random individual, and ω represents an adaptive scaling factor.

[0069] In the present invention, by introducing a mutation operation, each seagull individual is adjusted in position based on its current position in combination with the difference between the optimal individual and the random individual, thereby avoiding falling into a local optimal solution.

[0070] ω = ω max − ( ω max − ω min ) sin [ π 2 ( t T ) 2 ] ;

[0071] Among them, ω max represents the maximum scale factor, ω min Indicates the minimum scale factor.

[0072] Optionally, the maximum scaling factor ω max The minimum scaling factor ω can be 2 min 0.5 can be used.

[0073] In this method, the scaling factor gradually decreases from a maximum to a minimum as the number of iterations increases. This change enables the algorithm to conduct a broad search in the early stages, exploring more potential solutions. In the later stages, the scaling factor is gradually reduced, allowing the algorithm to conduct a refined search in a localized area, thereby improving convergence speed and reducing jumps. This adaptive adjustment strategy helps avoid premature convergence and enhances the algorithm's global search capabilities, while ensuring precise local searches when approaching the optimal solution.

[0074] Determine whether the fitness value of the position after mutation is greater than the fitness value of the position before mutation. If so, replace the position before mutation with the position after mutation. Otherwise, keep the position before mutation unchanged.

[0075] Update the fitness value of each seagull individual and the global optimal individual.

[0076] Determine whether the current number of iterations has reached the maximum number of iterations. If so, output the model parameter set representing the seagull with the highest fitness. Otherwise, return to continue iteration.

[0077] In the present invention, the pattern parameters of the nanopattern are optimized by the seagull optimization algorithm, which can achieve efficient balance and optimization between multi-dimensional performance indicators. By simulating the behavior of a group of seagulls, the algorithm can quickly search for the global optimal solution or the approximate optimal solution, thereby optimizing the design of the nanopattern and improving the performance of the device. In device design, this method can effectively improve key parameters such as carrier mobility, density of two-dimensional electron gas, and breakdown voltage, while reducing interface roughness and lattice mismatch, and optimizing overall device performance and structural quality. This optimization strategy helps to accurately control pattern parameters and promote the development of high-efficiency, low-defect, high-performance GaN-based devices.

[0078] Reference Manual Figure 2 , shows a schematic flow chart of a sapphire gallium nitride heterogeneous material epitaxial growth method provided by an embodiment of the present invention.

[0079] An embodiment of the present invention provides a sapphire gallium nitride heterogeneous material epitaxial growth method for preparing the above sapphire gallium nitride heterogeneous material epitaxial structure, the method comprising:

[0080] S1: Using self-assembled SiO2 nanospheres as a sacrificial etching mask.

[0081] S2: The nanosphere pattern is transferred to the sapphire surface by dry etching to prepare a sapphire substrate 1 with a nano-pattern.

[0082] S3: forming an AlN buffer layer 2 on the sapphire substrate 1 by metal organic chemical vapor deposition technology.

[0083] Metal-organic chemical vapor deposition (MOCVD) is a technology widely used in the preparation of semiconductor materials, optoelectronic devices, and other functional thin-film materials. This method involves introducing metal-organic precursors and gaseous reactants into a reaction chamber, where they undergo a chemical reaction at high temperatures to deposit the desired thin-film material.

[0084] S4: preparing a stepped channel mask on the AlN buffer layer 2 .

[0085] It should be noted that the stepped channel mask causes GaN to undergo multiple turns during its growth to the area above the mask layer, effectively filtering out dislocations during the turns, thereby growing high-quality GaN. The geometric shape of the stepped channel controls the growth direction and nucleation position of GaN, effectively promoting the uniform growth of GaN crystals and reducing the generation of defects. The design of the stepped channel can improve the quality of the GaN layer by improving the nucleation and growth rate of GaN, while optimizing the surface flatness of the layer and reducing the surface roughness.

[0086] In a possible implementation, S4 specifically includes sub-steps S401 to S407:

[0087] S401: forming a first Si 3 N 4 mask layer on the AlN buffer layer 2 by low pressure chemical vapor deposition technology.

[0088] Low-pressure chemical vapor deposition (LPCVD) is a thin film deposition technology that uses low-pressure conditions to deposit thin films. A gaseous precursor is introduced into a reaction chamber, where a chemical reaction occurs at high temperatures, forming a thin film that is then deposited onto a substrate.

[0089] S402: Using standard photolithography and reactive ion etching techniques, a portion of the material on the first Si3N4 mask layer is removed to etch out a first parallel strip window array.

[0090] S403: Depositing a SiO2 layer on the first Si3N4 mask layer by plasma enhanced chemical vapor deposition technology.

[0091] Among them, plasma enhanced chemical vapor deposition (PECVD) is a technology that uses low-temperature plasma to excite gaseous precursors, causing them to undergo chemical reactions and deposit into thin films.

[0092] S404: depositing a second Si3N4 mask layer on the SiO2 layer by low pressure chemical vapor deposition technology.

[0093] S405: Using standard photolithography and reactive ion etching technology, remove part of the material on the second Si3N4 mask layer to etch out a second parallel strip window array.

[0094] Optionally, the second parallel strip window array has the same size as the first parallel strip window array.

[0095] Optionally, the width of each strip window in the first parallel strip window array is 2 μm, and the distance between adjacent strip windows is 12 μm; the width of each strip window in the second parallel strip window array is 2 μm, and the distance between adjacent strip windows is 12 μm.

[0096] S406: When the second parallel strip window array and the first parallel strip window array are laterally phase-shifted, a stepped channel is formed.

[0097] S407: The SiO2 layer is partially removed by using a buffered oxide etchant until the bottom window exposes the AlN buffer layer 2, thereby obtaining a stepped channel mask.

[0098] S5: growing a GaN channel layer 3 in the stepped channel mask by metal organic chemical vapor deposition technology.

[0099] In a possible implementation, S5 specifically includes sub-steps S501 and S502:

[0100] S501: Using TMGa and NH3 as precursors and H2 as carrier gas, the substrate temperature is maintained at 530°C to grow GaN in the stepped channel mask.

[0101] S502: Raise the substrate temperature to 1060° C. and maintain it for 240 minutes to continue growing GaN on the existing nucleation points to form a GaN channel layer 3.

[0102] S6: depositing an AlGaN barrier layer 4 on the GaN channel layer 3 by metal organic chemical vapor deposition technology, and forming a two-dimensional electron gas by the AlGaN barrier layer 4 and the GaN channel layer 3.

[0103] In the present invention, SiO2 nanospheres are first used as a sacrificial layer etching mask to form high-precision nanopatterns on the sapphire surface, reducing dislocations and defects and improving material quality. Subsequently, depositing an AlN buffer layer helps alleviate the lattice mismatch between sapphire and GaN, improving the quality of the GaN channel layer. The preparation of a stepped channel mask further optimizes the growth environment of GaN and helps form a high-quality two-dimensional electron gas (2DEG). This multi-step, precise control can significantly improve device performance, including higher electron mobility and lower defect density, making it suitable for high-frequency, high-performance nitride-based electronic devices.

[0104] The above description is only a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with this technical field can easily think of changes or replacements within the technical scope disclosed by the present invention, which should be covered by the scope of protection of the present invention.

Claims

1. A sapphire gallium nitride heterogeneous material epitaxial structure, characterized in that: include: Sapphire substrate, AlN buffer layer, GaN channel layer and AlGaN barrier layer; The sapphire substrate is the basis of the epitaxial structure; The sapphire substrate has a nano pattern, wherein the nano pattern is specifically a pattern array composed of a plurality of pattern units in an array manner, and each of the pattern units is provided with a nano ball; The AlN buffer layer is provided on the sapphire substrate; The GaN channel layer is provided on the AlN buffer layer; The AlGaN barrier layer is disposed on the GaN channel layer; Optimizing and determining pattern parameters of the nanopattern using a Seagull optimization algorithm; The optimizing and determining the pattern parameters of the nanopattern by the Seagull optimization algorithm specifically includes: Initialize the seagull individuals. Each seagull individual represents a feasible model parameter set. Each seagull individual consists of multiple dimensional components, and each component represents a model parameter. In the global search phase, avoid collisions and move towards the optimal individual: ； ； ； in, represents the position of the i-th seagull individual after the global search phase at the t-th iteration, represents the position of the i-th seagull after anti-collision processing at the t-th iteration, A represents the control factor, represents the position of the i-th seagull individual at the t-th iteration, represents the displacement of the i-th seagull individual towards the optimal individual at the t-th iteration, B represents the search balance factor, represents the optimal individual position at the tth iteration; ； Among them, t represents the current number of iterations, T represents the maximum number of iterations, and f c Indicates linearly decreasing frequency; ; Among them, r1 represents a random number between 0 and 1; In the local search phase, a random number r2 is generated. Based on the random number r2, the spiral search strategy and the encirclement strategy are selected in parallel, and the displacement is performed in a spiral motion: ； ； ； ； ； in, represents the position of the i-th seagull after spiral motion at the t-th iteration, x represents the spiral flight coefficient in the x-direction, y represents the spiral flight coefficient in the y-direction, z represents the spiral flight coefficient in the z-direction, r represents the radius of the spiral flight trajectory, θ represents a random number between 0 and 2π, u and v represent spiral constants, and e represents a natural constant; Perform mutation operations on each seagull individual: ； in, represents the position of the ith seagull individual after mutation at the tth iteration, P r represents a random individual, ω represents an adaptive scaling factor; Determine whether the fitness value of the position after mutation is greater than the fitness value of the position before mutation; if so, replace the position before mutation with the position after mutation; otherwise, keep the position before mutation unchanged; Update the fitness value of each seagull individual and the global optimal individual; Determine whether the current number of iterations has reached the maximum number of iterations; if so, output the model parameter set representing the seagull individual with the highest current fitness; otherwise, return to continue iteration.

2. The sapphire gallium nitride heterogeneous material epitaxial structure according to claim 1, characterized in that: The pattern parameters of the nano-pattern include: pattern unit shape, pattern unit width, the number of nano-balls arranged on each pattern unit, and the radius of the nano-balls.

3. A method for epitaxial growth of sapphire gallium nitride heterogeneous material, characterized in that: For preparing the sapphire gallium nitride heterogeneous material epitaxial structure according to any one of claims 1 to 2, the method comprises: S1: using self-assembled SiO2 nanospheres as a sacrificial etching mask; S2: transferring the nanosphere pattern to the sapphire surface by dry etching to prepare the sapphire substrate having the nanopattern; S3: depositing the AlN buffer layer on the sapphire substrate by metal organic chemical vapor deposition technology; S4: preparing a stepped channel mask on the AlN buffer layer; S5: growing a GaN channel layer in the stepped channel mask by metal organic chemical vapor deposition technology; S6: depositing the AlGaN barrier layer on the GaN channel layer using a metal organic chemical vapor deposition technique, and forming a two-dimensional electron gas through the AlGaN barrier layer and the GaN channel layer; The S4 specifically includes: S401: depositing a first Si3N4 mask layer on the AlN buffer layer by low pressure chemical vapor deposition technology; S402: Using standard photolithography and reactive ion etching techniques, remove part of the material on the first Si3N4 mask layer to etch out a first parallel strip window array; S403: depositing a SiO2 layer on the first Si3N4 mask layer by plasma enhanced chemical vapor deposition technology; S404: depositing a second Si3N4 mask layer on the SiO2 layer by low pressure chemical vapor deposition technology; S405: Using standard photolithography and reactive ion etching techniques, a portion of the material on the second Si3N4 mask layer is removed to etch out a second parallel strip window array; S406: When the second parallel strip window array and the first parallel strip window array are laterally phase-shifted, a stepped channel is formed; S407: Partially remove the SiO2 layer using a buffered oxide etchant until the bottom window exposes the AlN buffer layer, thereby obtaining the stepped channel mask.

4. The sapphire gallium nitride heterogeneous material epitaxial growth method according to claim 3, characterized in that: The second parallel strip window array has the same size as the first parallel strip window array.

5. The sapphire gallium nitride heterogeneous material epitaxial growth method according to claim 4, characterized in that: The width of each strip window in the first parallel strip window array is 2 μm, and the distance between adjacent strip windows is 12 μm. The width of each strip window in the second parallel strip window array is 2 μm, and the distance between adjacent strip windows is 12 μm.

6. The sapphire gallium nitride heterogeneous material epitaxial growth method according to claim 5, characterized in that: The S5 specifically includes: S501: using TMGa and NH3 as precursors, H2 as carrier gas, maintaining the substrate temperature at 530°C, and growing GaN in the stepped channel mask; S502: Raise the substrate temperature to 1060°C and maintain it for 240 minutes to continue growing GaN on the existing nucleation points to form a GaN channel layer.

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