Method for preparing n-type gallium nitride self-supporting substrate and heavily doped gan substrate and application

Abstract

The application belongs to the technical field of gallium nitride substrate preparation, and particularly relates to a preparation method of n-type gallium nitride self-supporting substrate and a heavily doped GaN substrate and application. The preparation method of the n-type gallium nitride self-supporting substrate comprises the following steps: (1) sequentially epitaxially growing a buffer layer and a gallium nitride thick film on an original substrate; (2) peeling off the gallium nitride thick film to obtain a gallium nitride peeled sheet; (3) according to a germanium atom theoretical doping concentration of the gallium nitride peeled sheet, performing neutron irradiation treatment on the gallium nitride peeled sheet to obtain a germanium-doped gallium nitride peeled sheet; and (4) performing annealing treatment on the germanium-doped gallium nitride peeled sheet to obtain an n-type gallium nitride self-supporting substrate. The n-type gallium nitride self-supporting substrate obtained by the preparation method has a carrier concentration of 5x10 19 / cm 3 Without exogenous silicon or germanium dopants, the n-type gallium nitride self-supporting substrate obtained by the preparation method can be doped after the gallium nitride peeled sheet is formed, and the doping amount and doping concentration of the germanium element can be accurately controlled, which is suitable for large-scale production.

Description

Technical Field

[0001] This application belongs to the field of gallium nitride substrate preparation technology, specifically relating to a method for preparing an n-type gallium nitride self-supporting substrate and a heavily doped GaN gallium substrate and its applications. Background Technology

[0002] Gallium nitride (GaN), as a representative of third-generation semiconductor materials, possesses unique physical properties, including a high breakdown field strength (3.3 MV / cm) and a high electron saturation velocity (2.5 × 10⁻⁶). 7 Its high thermal conductivity (2.3 W / cm•K) and excellent chemical stability give it significant advantages in manufacturing next-generation high-efficiency power converters and high-performance RF amplifiers. It is widely used in important application scenarios such as blue-green lasers, 5G communications, phased array radar, new energy vehicles and smart grids, and is gradually becoming a core supporting material for the third-generation semiconductor industry.

[0003] Semiconductor substrates are the foundation for the epitaxial growth of functional layers, and their crystal quality, conductivity, and thermal conductivity directly affect the performance, reliability, and cost of devices. Gallium nitride homopolymer substrates are ideal materials for growing GaN epitaxial layers (GaN-on-GaN). However, due to the high melting point of gallium nitride crystals (2500℃) and the pressure required for uniform melting (up to 6 GPa), GaN cannot be directly grown using melt methods, resulting in high fabrication costs for gallium nitride homopolymer substrates. Therefore, gallium nitride homopolymer substrate fabrication technology, especially n-type heavily doped gallium nitride substrate fabrication technology, has become a hot research topic in industry and academia.

[0004] GaN free-standing substrates are obtained by growing a sufficiently thick GaN film on a heterogeneous substrate and then peeling it off. Hydride vapor phase epitaxy (HVPE) is currently the mainstream technology for growing gallium nitride free-standing substrates in the industry, favored for its advantages such as fast growth rate (up to hundreds of μm / h) and relatively low cost. GaN substrates achieve n-type doping by adding shallow donor impurity elements such as Si or Ge. However, since germanium dopant germanane (GeH4) is highly flammable and toxic, its compatibility with the HVPE process is poor. Therefore, silicon (Si) has become the most mature n-type dopant element for GaN free-standing substrates in the industry. In the HVPE process, Si dopant is introduced into the reaction chamber in the form of silane (SiH4) or chlorosilane (SiH2Cl2). Si atoms replace Ga sites, providing an additional electron to form a shallow donor level (ionization energy of about 30 meV), resulting in high activation efficiency and good process controllability.

[0005] Due to the anti-surfactant effect of silicon impurities, as the Si doping concentration increases during the HVPE process, a nitrogen-atom layer (SiGaN3) forms on the GaN surface, introducing a repulsive electric dipole moment that hinders GaN growth, leading to surface morphology deterioration and thus limiting further increases in Si concentration. Domestic and international research has found that the highest achievable effective carrier concentration using HVPE epitaxial growth technology combined with the dopant silane (SiH4) is limited to 3 × 10⁻⁶. 18 / cm 3 (The highest level achievable by leading domestic companies) This doping concentration level cannot meet the requirements for heavy doping levels (carrier concentration of 5×10⁻⁶) in next-generation high-power, low-loss vertical GaN devices. 18 / cm 3 The above requirements, along with the need for extremely low substrate resistance, have created a serious technical bottleneck.

[0006] Considering the current status of n-type gallium nitride self-supporting substrate fabrication technology and the existing technical bottlenecks preventing the fabrication of heavily doped gallium nitride substrates, there is an urgent need to develop new gallium nitride substrate doping processes and fabrication methods to overcome the limitations of high-concentration n-type doping and to prepare heavily doped gallium nitride self-supporting substrates. Summary of the Invention

[0007] This application provides a method for preparing an n-type gallium nitride self-supporting substrate and a heavily doped GaN substrate and its application, aiming to solve the problem that the doping concentration of the n-type gallium nitride self-supporting substrate prepared by the prior art cannot reach the level of heavy doping concentration.

[0008] The first aspect of this application provides a method for fabricating an n-type gallium nitride self-supporting substrate, comprising the following steps:

[0009] (1) A buffer layer and a thick gallium nitride film are epitaxially grown sequentially on the original substrate; (2) Peel off the gallium nitride thick film to obtain a gallium nitride stripper sheet; (3) Based on the theoretical doping concentration of germanium atoms in the gallium nitride stripper, neutron irradiation treatment was performed on it to obtain germanium-doped gallium nitride stripper; (4) Anneal the germanium-doped gallium nitride strip to obtain an n-type gallium nitride self-supporting substrate.

[0010] According to some embodiments of the method for preparing an n-type gallium nitride self-supporting substrate described in this application, in step (1), the original substrate includes a sapphire substrate, a silicon carbide substrate, a silicon substrate, or a gallium nitride substrate.

[0011] According to some embodiments of the method for fabricating an n-type gallium nitride self-supporting substrate described in this application, the diameter of the original substrate is 2 inches, 4 inches, 6 inches, 8 inches, or 12 inches.

[0012] According to some embodiments of the method for fabricating n-type gallium nitride self-supporting substrates described in this application, the epitaxial growth method includes metal-organic chemical vapor deposition (MOCVD) or hydride vapor phase epitaxy (HVPE).

[0013] According to some embodiments of the method for fabricating an n-type gallium nitride self-supporting substrate described in this application, the buffer layer includes one or more of aluminum nitride, gallium nitride, indium nitride, and zinc oxide.

[0014] According to some embodiments of the method for fabricating an n-type gallium nitride self-supporting substrate described in this application, the thickness of the gallium nitride thick film is 300-5000 μm.

[0015] According to some embodiments of the method for preparing an n-type gallium nitride self-supporting substrate described in this application, the gallium nitride thick film has a hexagonal wurtzite structure and a space group of P63mc.

[0016] According to some embodiments of the method for preparing an n-type gallium nitride self-supporting substrate described in this application, in step (2), the thick film stripping method includes laser stripping, spontaneous stripping, and chemical stripping.

[0017] According to some embodiments of the method for fabricating an n-type gallium nitride self-supporting substrate described in this application, the theoretical germanium atom doping concentration of the gallium nitride stripper is calculated based on the following formula:

[0018] in: N d This represents the theoretical doping concentration of germanium atoms, expressed in atoms / cm². 3 ; N Ga The Ga atom density in gallium nitride is 4.39 × 10⁻⁶. 22 atoms / cm 3 ; f1 represents the abundance of the Ga-69 isotope in gallium nitride, with a value of 0.604. f2 represents the abundance of the Ga-71 isotope in gallium nitride, with a value of 0.396. 1 represents the thermal neutron capture cross section of Ga-69, with a value of 1.68 × 10⁻⁶. -28 cm 2 ; 2 represents the thermal neutron capture cross section of Ga-71, with a value of 4.70 × 10⁻⁶. -28 cm 2 ; ψ represents the neutron flux of the irradiated neutron source, expressed in n / (cm²). 2•s); t is the reaction time of neutron irradiation, measured in seconds.

[0019] According to some embodiments of the method for preparing n-type gallium nitride self-supporting substrates described in this application, the neutron source used in the neutron irradiation process includes a reactor neutron source or an accelerator neutron source.

[0020] According to some embodiments of the method for fabricating n-type gallium nitride self-supporting substrates described in this application, the neutron flux of the neutron irradiation treatment is 10. 12 -10 16 n / (cm 2 •s).

[0021] According to some embodiments of the method for preparing an n-type gallium nitride self-supporting substrate described in this application, the ambient temperature of the neutron irradiation treatment is <100°C, and the gallium nitride stripping sheet is in a solid state during the neutron irradiation treatment.

[0022] According to some embodiments of the method for fabricating an n-type gallium nitride self-supporting substrate described in this application, the annealing process includes furnace tube annealing, rapid thermal annealing, or laser annealing.

[0023] According to some embodiments of the method for preparing an n-type gallium nitride self-supporting substrate described in this application, the annealing temperature is 700-900℃ and the time is 30-60min.

[0024] According to some embodiments of the method for fabricating an n-type gallium nitride self-supporting substrate described in this application, the annealing atmosphere is nitrogen or argon, preferably a nitrogen atmosphere.

[0025] The second aspect of this application provides a heavily doped gallium nitride substrate, which is prepared by the method for preparing an n-type gallium nitride self-supporting substrate described in the first aspect of this application.

[0026] According to some embodiments of the heavily doped gallium nitride substrate described in this application, the carrier concentration of the heavily doped gallium nitride substrate is 5 × 10⁻⁶. 15 / cm 3 -5×10 20 / cm 3 Preferably 5×10 18 / cm 3 -5×10 20 / cm 3 .

[0027] The third aspect of this application provides an application of the heavily doped gallium nitride substrate described in the second aspect of this application in vertical power devices, laser diodes, or Micro-LED display devices.

[0028] The beneficial effects of this application include: the method for preparing the n-type gallium nitride self-supporting substrate described in this application does not require external silicon or germanium dopants, and doping can be performed after the formation of gallium nitride strippers, and the doping amount and concentration of germanium can be precisely controlled, making it suitable for large-scale production.

[0029] The carrier concentration of the n-type gallium nitride self-supporting substrate described in this application can reach 5 × 10⁻⁶. 19 / cm 3 The above compares to the current technological level (the highest domestic level is 3×10). 18 / cm 3 This represents a 16.6-fold increase, breaking through the bottleneck of the highest doping concentration in existing technologies. It provides a feasible solution for high-power, low-loss vertical gallium nitride devices and high-performance optoelectronic devices, and has significant industrialization value. Attached Figure Description

[0030] Figure 1 This is a schematic flowchart of the method for fabricating an n-type gallium nitride self-supporting substrate as described in this application. Detailed Implementation

[0031] The embodiments of the present invention are described in detail below. These embodiments are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0032] In this invention, the terms "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to a specific feature, structure, material, or characteristic described in connection with that embodiment or example, which 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. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0033] This application provides a method for fabricating an n-type gallium nitride self-supporting substrate, including the following steps: (1) A buffer layer and a thick gallium nitride film are epitaxially grown sequentially on the original substrate; (2) Peel off the gallium nitride thick film to obtain a gallium nitride stripper sheet; (3) Based on the theoretical doping concentration of germanium atoms in the gallium nitride stripper, neutron irradiation treatment was performed on it to obtain germanium-doped gallium nitride stripper; (4) Anneal the germanium-doped gallium nitride strip to obtain an n-type gallium nitride self-supporting substrate.

[0034] Gallium nitride contains Ga-69 isotopes (60.4% natural abundance) and Ga-71 isotopes (39.6% natural abundance), whose nuclei undergo neutron absorption and subsequent reactions. 69 Ga(n, γ) 70 Ga and 71 Ga(n, γ) 72 Ga nucleus reaction.

[0035] 69 Ga + n → 70 Ga → 70 Ge+ β - + ν - (T 1 / 2 =21.1m) (Reaction 1) 71 Ga + n → 72 Ga → 72 Ge +β - +ν - (T 1 / 2 =14.1h) (Reaction 2) Through the neutron capture reactions of reaction 1 and reaction 2, Ga atoms in gallium nitride crystals are converted into Ge atoms. The characteristics of gallium nitride neutron transmutation doping are: (1) It is essentially a post-growth doping, which can be carried out at room temperature after the epitaxial growth of gallium nitride thick film is completed; (2) The doping concentration can be precisely controlled by controlling the process of neutron capture nuclear reaction; (3) No external doping element is required, and the doped Ge element is obtained by the conversion of Ga on the gallium nitride lattice.

[0036] In some embodiments of this application, in step (1), the original substrate includes a sapphire substrate, a silicon carbide substrate, a silicon substrate, or a gallium nitride substrate; due to the lack of homogeneous substrates, heteroepitaxial growth remains the main choice for GaN crystal growth. Before epitaxial growth, the original substrate needs to be etched and surface-treated.

[0037] In some embodiments of this application, the diameter of the original substrate is 2 inches, 4 inches, 6 inches, 8 inches, or 12 inches.

[0038] In some embodiments of this application, the epitaxial growth method includes metal-organic chemical vapor deposition (MOCVD) or hydride vapor phase epitaxy (HVPE).

[0039] In some embodiments of this application, the buffer layer includes one or more of aluminum nitride, gallium nitride, indium nitride, and zinc oxide. Lattice and thermal mismatches exist between the heterogeneous substrate (such as sapphire, silicon carbide, and silicon substrates) and the GaN epitaxial layer, inevitably affecting the quality of the grown crystal and reducing the device's lifespan and reliability. Inserting one or more buffer layers between the heterogeneous substrate and the gallium nitride thick film can reduce the defect density (such as dislocations) within the grown crystal, improving crystal quality. The insertion of the buffer layer can also release thermal stress during cooling, preventing cracking of the gallium nitride thick film. Furthermore, the insertion of the buffer layer can prevent high-temperature diffusion of elements (O, Si, etc.) from the original substrate into the GaN epitaxial layer.

[0040] In some embodiments of this application, the thickness of the gallium nitride thick film is 300-5000 μm; for example, 300 μm, 500 μm, 1000 μm, 1200 μm, 1600 μm, 2300 μm, 2800 μm, 3200 μm, 3700 μm, 4500 μm, 5000 μm, etc.

[0041] In some embodiments of this application, the gallium nitride thick film has a hexagonal wurtzite structure and a space group of P63mc.

[0042] In some embodiments of this application, the stripping method used in step (2) includes laser stripping, automatic stripping, or chemical stripping. The gallium nitride stripping sheet is a whole gallium nitride thick film or 2-20 thin film sheets further processed from a gallium nitride thick film. In the subsequent neutron irradiation process, it is possible to irradiate the uncut whole gallium nitride thick film sheet and then cut it; or it is possible to first cut it into several thin film sheets (thickness of 300-500 micrometers) and then directly irradiate the cut thin film sheets with neutrons.

[0043] In some embodiments of this application, the theoretical germanium atom doping concentration of the gallium nitride stripper is calculated according to the following formula:

[0044] in: N d This represents the theoretical doping concentration of germanium atoms, expressed in atoms / cm². 3 ; N Ga The Ga atom density in gallium nitride is 4.39 × 10⁻⁶. 22 atoms / cm 3 ; f1 represents the abundance of the Ga-69 isotope in gallium nitride, with a value of 0.604. f2 represents the abundance of the Ga-71 isotope in gallium nitride, with a value of 0.396. 1 represents the thermal neutron capture cross section of Ga-69, with a value of 1.68 × 10⁻⁶. -28 cm 2 ; 2 represents the thermal neutron capture cross section of Ga-71, with a value of 4.70 × 10⁻⁶. -28 cm 2 ; ψ represents the neutron flux of the irradiated neutron source, expressed in n / (cm²). 2 •s); t is the reaction time of neutron irradiation, in seconds; In the above formula, the theoretical doping concentration of germanium atoms can be understood as the concentration to be doped, N d The value is approximately equal to the actual measured germanium doping concentration. In practice, its accuracy needs to be verified and corrected using data such as the germanium atom concentration, carrier concentration, mobility, and resistivity of the sample after neutron irradiation.

[0045] The purpose of semiconductor doping is to achieve precise control over carrier concentration and conductivity. Therefore, controlling the nuclear reaction process to precisely control the Ge doping concentration in gallium nitride is the focus and challenge of this invention. The atomic density of Ga in gallium nitride is an important parameter. Based on the gallium nitride crystal structure (hexagonal wurtzite), the applicant calculated the overall atomic density of gallium in the gallium nitride crystal, and the calculation process is as follows: Given conditions: (1) GaN lattice constant (room temperature 300K), a = 3.185 × 10⁻⁶ -9 cm; c=5.189×10 -9 cm. (2) GaN crystal structure: wurtzite (hexagonal), each unit cell contains 2 Ga atoms and 2 N atoms (i.e., 2 GaN molecular units); (3) The formula for calculating the volume of a hexagonal unit cell is:

[0046] Calculation steps: (1) Unit cell volume

[0047] (2) Gallium atomic density Each unit cell contains 2 Ga atoms: .

[0048] The applicant, based on 69 Ga and 71 Based on the atomic density of Ga and its cross-section in thermal neutron capture reaction, a theoretical formula for calculating the germanium doping concentration of gallium nitride under neutron irradiation was designed. The doping factor was verified and corrected using actual germanium doping concentration and carrier concentration data obtained from neutron irradiation.

[0049] In some embodiments of this application, the neutron source used in the neutron irradiation treatment includes a reactor neutron source or an accelerator neutron source.

[0050] In some embodiments of this application, the neutron flux of the neutron irradiation treatment is 10. 12 -10 16 n / (cm 2 •s).

[0051] In some embodiments of this application, the ambient temperature of the neutron irradiation treatment is <100°C, and the gallium nitride stripper is in a solid state during the neutron irradiation treatment.

[0052] In some embodiments of this application, the annealing process includes furnace tube annealing, rapid thermal annealing, or laser annealing.

[0053] In some embodiments of this application, the annealing temperature is 700-900℃, such as 700℃, 750℃, 800℃, 860℃, 900℃, etc., and the time is 30-60min, such as 30min, 40min, 50min, 60min, etc.

[0054] In some embodiments of this application, the annealing atmosphere is a nitrogen atmosphere or an argon atmosphere.

[0055] This application also provides an n-type heavily doped gallium nitride substrate, which is prepared by the n-type gallium nitride self-supporting substrate preparation method described in the first aspect of this application.

[0056] In some embodiments of this application, the carrier concentration of the n-type heavily doped gallium nitride substrate is 5 × 10⁻⁶. 18 / cm 3 -5×10 20 / cm 3 For example, 5×10 18 / cm 3 6×10 18 / cm 3 8×10 18 / cm 3 5×10 19 / cm 3 8×10 19 / cm 3 5×10 20 / cm 3 wait.

[0057] According to industry practice and device physics requirements, carrier concentrations higher than 5 × 10⁻⁶ are typically used. 18 / cm 3n-type GaN is defined as heavily doped. Heavily doped n-type gallium nitride self-supporting substrates have lower on-resistance, used to reduce the ohmic contact resistance of the drain in vertical structure devices (such as MOSFETs and optoelectronic devices), meeting the demand for extremely low substrate resistance in next-generation high-power, low-loss vertical GaN devices. Heavily doped substrates significantly reduce resistivity, which can reduce conduction losses, increase output power, and reduce ohmic contacts, making them widely used in vertical power devices, laser diodes (LDs), and novel Micro-LED display technologies.

[0058] This application also provides an application of the n-type heavily doped gallium nitride substrate described in the second aspect of this application in vertical power devices, laser diodes, or Micro-LED displays.

[0059] n-type gallium nitride (GaN) substrates are fundamental for fabricating high-performance GaN vertical power devices and solid-state optoelectronic devices. Accurately controlling the on-resistance and electrical properties of the substrate through the incorporation of shallow donor impurities is a crucial process. This application, through in-depth research on GaN self-supporting substrate fabrication technology and doping processes, discovered that silicon impurities under heavy doping conditions exhibit a severe anti-surfactant effect, leading to catastrophic cracking during GaN thin film growth, representing an insurmountable physical bottleneck. This application takes a unique approach, studying the mechanism of the neutron capture reaction between GaN crystals from a nuclear physics perspective. It introduces neutron irradiation and transmutation doping of germanium, precisely controlling the conversion concentration of germanium atoms by controlling the nuclear reaction process, achieving a germanium doping concentration of 5 × 10⁻⁶. 15 / cm 3 -5×10 20 / cm 3 The range is adjustable, enabling the fabrication of gallium nitride self-supporting substrates with doping concentrations exceeding those of existing technologies.

[0060] The technical solution of this application will be further described below with reference to specific embodiments.

[0061] Example 1 A method for fabricating an n-type gallium nitride self-supporting substrate, wherein the substrate is sapphire and the target carrier concentration of the gallium nitride self-supporting substrate is 1×10⁻⁶. 19 / cm 3 The neutron irradiation target is the entire thick film of gallium nitride.

[0062] Preparation method as follows Figure 1 As shown, it specifically includes: Step 1: Epitaxially grow a buffer layer and a thick gallium nitride film sequentially on a sapphire substrate (original substrate). S11 Raw substrate pretreatment: A 4-inch c-plane (0001) sapphire substrate is selected. The surface is cleaned using the standard wafer wet cleaning process to remove organic matter, metal ions and particulate contaminants from the surface. Then the raw substrate is placed on the substrate tray of the HVPE reaction chamber. Surface nitriding of S12 original substrate Hydrogen and ammonia with a purity of 99.999% were introduced into the hydride vapor phase epitaxy reaction chamber, and the H2 flow rate was controlled at 10 slm and the NH3 flow rate at 3 slm. The temperature of the hydride vapor phase epitaxy reaction chamber was raised to 1050℃ and the pressure was 600 Torr, and maintained for 15 min. Through surface nitriding, an extremely thin polycrystalline layer was formed on the sapphire surface, providing nucleation sites for the growth of the buffer layer.

[0063] S13 aluminum nitride buffer layer deposition Al metal (5N purity) was placed at the front end (source region) of the hydride vapor phase epitaxy reaction chamber. HCl gas was introduced using high-purity nitrogen as the carrier gas, and the source region temperature was set to 500℃. AlCl3 was produced in the source region through reaction. The temperature of the rear growth chamber was raised to 1150℃ and the pressure to 200 Torr. A group III source (HCl) and a group V source (NH3) were introduced, with the HCl flow rate controlled at 10 sccm and the NH3 flow rate at 2 slm (V / III ratio greater than 100). At the same time, a H2 / N2 mixed gas with a volume ratio of 1:9 was introduced as the carrier gas at a flow rate of 10 slm. The growth time was 10 min, resulting in an atomically flat aluminum nitride buffer layer with a thickness of approximately 100 nm, providing a template for subsequent GaN growth.

[0064] S14 GaN buffer layer (template layer) deposition In the front-end source region of the reaction chamber, Al metal was replaced with gallium metal (5N purity), the Al source supply was stopped, and the front-end temperature was raised to 850℃. At this time, HCl gas flowed through the gallium boat to generate GaCl. In the substrate reaction region at the rear end of the reaction chamber, the temperature was adjusted to 1050℃, the pressure to 650 Torr, and the V / III ratio was adjusted to 60. The flow rate of the H2 / N2 mixed carrier gas with a volume ratio of 1:9 was 20 slm. At this time, the growth rate of the GaN buffer layer was relatively slow, and after 20 minutes of growth, a gallium nitride deposition layer (second buffer layer) with a thickness of about 10 micrometers was obtained. The purpose of growing the GaN buffer layer is to achieve a smooth transition from AlN to GaN and obtain a GaN "seed layer" with low dislocations.

[0065] Rapid growth of S15 GaN bulk thick film To increase the partial pressure of GaCl, the HCl flow rate to the Ga source was increased at the front end of the reaction chamber. The V / III flow rate at the rear end of the reaction chamber was reduced to 20 μL, the growth temperature was increased to 1070 °C, and the flow rate of the 1:9 H2 / N2 mixed carrier gas was increased to 50 slm. At this point, the thick film growth rate was approximately 250 μm / h. After 8 hours of continuous growth, a 2 mm thick GaN film was obtained, exhibiting a hexagonal wurtzite structure with space group P63mc.

[0066] Step 2: Self-peeling of gallium nitride thick film and preparation of peeling sheet Cooling process and stress regulation of S21 GaN thick film First, the HCl supply is cut off, and the mixture is maintained for 10 minutes under the protection of NH3 and H2 / N2 mixed carrier gas to protect the GaN surface. Then, the reaction chamber temperature is reduced to 800℃ at a rate of 10℃ / min; then reduced to 400℃ at a rate of 3℃ / min; and finally reduced to room temperature at a rate of 10℃ / min.

[0067] Debonding of S22 GaN thick film from substrate The peeling method is spontaneous peeling: During the cooling process, huge thermal mismatch stress is concentrated at the GaN / sapphire substrate interface. When the interfacial adhesion is weaker than the stress, the GaN thick film automatically detaches from the original substrate, yielding the GaN thick film.

[0068] S23 subsequent processing The removed thick film blank surface (original substrate contact surface) is ground and polished to obtain a GaN stripped sheet with a thickness of about 2 mm.

[0069] Characterization of S24 GaN growth surface morphology Five regions (5 μm × 5 μm) were selected on the GaN thick film growth surface. The morphology of the growth surface of the GaN exfoliated sheet was characterized using a Bruker Dimension Icon atomic force microscope (AFM). The Ra value of each region was measured, and the average value of the five points was taken. The measurement results are shown in Table 1.

[0070] Step 3: Design the neutron irradiation process for GaN stripped sheets S31 Neutron Source Selection. The reactor was selected as the neutron irradiation source, with a neutron flux of 5.16 × 10⁻⁶ at the irradiation aperture. 14 n / (cm 2 •s); S32 determines the doping concentration of the sample. In this embodiment, the carrier concentration is determined to be 1 × 10⁻⁶. 19 / cm 3If the doped germanium atoms activate 100% of the contributing electron carriers, then the carrier concentration equals the germanium atom concentration. Studies have determined that the activation rate of neutron transmutation doped Ge in GaN is 80%, therefore the required target germanium atom doping concentration is 1.25 × 10⁻⁶. 19 / cm 3 .

[0071] S33 designed a neutron irradiation process based on the theoretical formula for calculating the germanium atom doping concentration of GaN under neutron irradiation.

[0072] The theoretical doping concentration of germanium atoms in GaN irradiated by neutrons is calculated as follows:

[0073] in, N d This represents the theoretical doping concentration of germanium atoms, expressed in atoms / cm². 3 ; N Ga The Ga atom density in gallium nitride is 4.39 × 10⁻⁶. 22 atoms / cm 3 ; f1 represents the abundance of the Ga-69 isotope in gallium nitride, with a value of 0.604. f2 represents the abundance of the Ga-71 isotope in gallium nitride, with a value of 0.396. 1 represents the thermal neutron capture cross section of Ga-69, with a value of 1.68 × 10⁻⁶. -28 cm 2 ; 2 represents the thermal neutron capture cross section of Ga-71, with a value of 4.70 × 10⁻⁶. -28 cm 2 ; ψ represents the neutron flux of the irradiated neutron source, in units of 5.16 × 10⁻⁶. 14 / n / (cm 2 •s); t is the reaction time of neutron irradiation, in seconds; Assuming the target germanium doping concentration is equal to the theoretical doping concentration, substituting the target germanium doping concentration into the above formula, the neutron irradiation process is designed as follows: neutron irradiation time 192000s (53.33h).

[0074] Step 4: Neutron irradiation treatment of the GaN stripped sheet The GaN stripped sheet was placed in the reactor irradiation aperture and irradiated for 192,000 s. The ambient temperature for neutron irradiation treatment was 77.9 °C. At this time, the GaN stripped sheet was in a solid state.

[0075] Step 5: Annealing and subsequent processing of neutron-irradiated strips S51 Annealing and Activation. A tube furnace annealing method was used. The neutron-irradiated GaN stripped sheet was placed in a vacuum tube furnace, and nitrogen gas was introduced into the furnace. Since gallium nitride precipitates nitrogen at temperatures above 900°C, the nitrogen atmosphere suppresses its volatilization. The furnace was slowly heated to 820°C at a rate of 20°C / min and held at that temperature for 45 minutes to repair defects and crystal damage caused by neutron irradiation, while simultaneously activating the germanium atoms doped in the sample. Finally, it was slowly cooled to room temperature at a rate of 20°C / min. This slow heating and cooling method prevents the crystal from cracking due to drastic temperature changes.

[0076] After the gallium nitride stripper is activated at high temperature, the free electrons of Ge atoms are activated into conductive charge carriers, which increases the charge carrier concentration in GaN.

[0077] S52 Subsequent processing: The annealed gallium nitride stripper is cut into several films with a thickness of about 450 micrometers by laser cutting. The films are then ground and polished to obtain a GaN self-supporting substrate.

[0078] One GaN self-supporting substrate was selected as the test sample, denoted as A1.

[0079] The surface roughness of the A1 sample after irradiation was characterized using a Bruker Dimension Icon atomic force microscope. The germanium doping concentration in the irradiated substrate sample was measured using a CAMECA IMS-4F SIMS instrument (the detection limit for germanium impurities was 2 × 10⁻⁶). 15 cm -3 The carrier concentration of the irradiated substrate samples was measured using a Semilab MCV-530L mercury probe microanalyzer. The characterization and measurement results are shown in Table 1.

[0080] Example 2 The difference between the n-type gallium nitride self-supporting substrate fabrication method in Example 2 and Example 1 is that the target carrier concentration of the gallium nitride self-supporting substrate is set to 5 × 10⁻⁶ during the fabrication process in Example 2. 19 / cm 3 The neutron irradiation time was calculated to be 960,000 s (266.67 h) using the theoretical doping concentration formula of germanium atoms in GaN irradiated by neutrons. The resulting GaN self-supporting substrate was denoted as sample A2.

[0081] The surface roughness of the A2 sample before and after irradiation was characterized using a Bruker Dimension Icon atomic force microscope. The germanium doping concentration in the irradiated substrate sample was measured using a CAMECA IMS-4F SIMS instrument (the lower limit of germanium impurity detection was 2 × 10⁻⁶). 15 cm -3 The carrier concentration of the irradiated substrate samples was measured using a Semilab MCV-530L mercury probe microanalyzer. The characterization and measurement results are shown in Table 1.

[0082] Example 3 A method for fabricating an n-type gallium nitride self-supporting substrate, wherein the substrate is sapphire and the target carrier concentration of the gallium nitride self-supporting substrate is 1×10⁻⁶. 19 / cm 3 The neutron irradiation target was a thin sheet of gallium nitride thick film after laser cutting.

[0083] Preparation method as follows Figure 1 As shown, the specific preparation method includes: Step 1: Epitaxially grow a buffer layer and a thick gallium nitride film sequentially on a sapphire substrate (original substrate); S11 Raw substrate pretreatment: A 4-inch c-plane (0001) sapphire substrate is selected. The surface is cleaned using the standard wafer wet cleaning process to remove organic matter, metal ions and particulate contaminants from the surface. Then the raw substrate is placed on the substrate tray of the HVPE reaction chamber. Surface nitriding of S12 original substrate Hydrogen and ammonia with a purity of 99.999% were introduced into the hydride vapor phase epitaxy reaction chamber, and the H2 flow rate was controlled at 10 slm and the NH3 flow rate at 3 slm. The temperature of the hydride vapor phase epitaxy reaction chamber was raised to 1050℃ and the pressure was 600 Torr, and maintained for 15 min. Through surface nitriding, an extremely thin polycrystalline layer was formed on the sapphire surface, providing nucleation sites for the growth of the buffer layer.

[0084] S13 aluminum nitride buffer layer deposition Al metal (5N purity) was placed at the front end (source region) of the hydride vapor phase epitaxy reaction chamber. High-purity nitrogen was used as the carrier gas, and HCl gas was introduced. The source region temperature was set to 500℃, and AlCl3 was generated in the source region through reaction. The temperature of the rear growth chamber was raised to 1150℃ and the pressure to 200 Torr. A group III source (HCl) and a group V source (NH3) were introduced, and the HCl flow rate was controlled at 10 sccm and the NH3 flow rate at 2 slm (V / III ratio greater than 100). At the same time, a H2 / N2 mixed gas (volume ratio of 1:9) was introduced as the carrier gas at a flow rate of 10 slm. The growth time was 10 min, and an atomically flat aluminum nitride buffer layer with a thickness of about 100 nm was obtained, providing a template for the subsequent GaN growth.

[0085] S14 GaN buffer layer (template layer) deposition In this embodiment, only one buffer layer is grown, omitting the step of growing the GaN buffer layer.

[0086] Rapid growth of S15 GaN bulk thick film To increase the partial pressure of GaCl, the HCl flow rate to the Ga source was increased at the front end of the reaction chamber. The V / III flow rate at the rear end of the reaction chamber was reduced to 20, the growth temperature was increased to 1070℃, and the H2 / N2 mixed carrier gas flow rate (volume ratio 1:9) was increased to 50 slm. At this point, the thick film growth rate was approximately 250 μm / h. After continuous growth for 8 h, a GaN thick film with a thickness of 2 mm was obtained.

[0087] Step 2: Self-peeling of gallium nitride thick film and preparation of peeling sheet Cooling process and stress regulation of S21 GaN thick film First, the HCl supply is cut off, and the mixture is maintained for 10 minutes under the protection of a carrier gas mixture of NH3 and H2 / N2 (volume ratio of 1:9) to protect the GaN surface. Then, the reaction chamber temperature is reduced to 800℃ at a rate of 10℃ / min, then to 400℃ at a rate of 3℃ / min, and finally to room temperature at a rate of 10℃ / min.

[0088] Debonding of S22 GaN thick film from substrate The stripping method is laser stripping: the GaN thick film is stripped from the original substrate using a KrF excimer laser (248nm) and further cut into 4 strips with a thickness of about 450μm.

[0089] Five regions (5 μm × 5 μm) were selected on the growth surface of the GaN stripped wafer. The morphology of the growth surface was characterized using a Bruker Dimension Icon atomic force microscope (AFM). The Ra value of each region was measured, and the average value of the five points was taken. The measurement results are shown in Table 1.

[0090] S23 Subsequent processing The stripped sheets were ground and polished to obtain GaN stripped sheets with a thickness of approximately 400 μm.

[0091] Step 3: Design the neutron irradiation process for GaN stripped sheets S31 Neutron Source Selection. The reactor was selected as the neutron irradiation source, with a neutron flux of 5.16 × 10⁻⁶ at the irradiation aperture. 14 n / (cm 2 •s); S32 determines the doping concentration of the sample. In this embodiment, the carrier concentration is determined to be 1 × 10⁻⁶. 19 / cm 3 Research has determined that the activation rate of neutron transmutation doping with Ge in GaN is 80%, therefore the required target doping concentration of germanium atoms is 1.25 × 10⁻⁶. 19 / cm 3 .

[0092] S33 designed a neutron irradiation process based on the theoretical formula for calculating the germanium atom doping concentration of GaN under neutron irradiation.

[0093] The theoretical doping concentration of germanium atoms in GaN irradiated by neutrons is calculated as follows:

[0094] in, N d This represents the theoretical doping concentration of germanium atoms, expressed in atoms / cm². 3 ; N Ga The Ga atom density in gallium nitride is 4.39 × 10⁻⁶. 22 atoms / cm 3 ; f1 represents the abundance of the Ga-69 isotope in gallium nitride, with a value of 0.604. f2 represents the abundance of the Ga-71 isotope in gallium nitride, with a value of 0.396. 1 represents the thermal neutron capture cross section of Ga-69, with a value of 1.68 × 10⁻⁶. -28 cm 2 ; 2 represents the thermal neutron capture cross section of Ga-71, with a value of 4.70 × 10⁻⁶. -28 cm 2 ; ψ represents the neutron flux of the irradiated neutron source, in units of 5.16 × 10⁻⁶. 14 n / (cm 2 •s); t is the reaction time of neutron irradiation, in seconds; Assuming the target germanium doping concentration is equal to the theoretical doping concentration, substituting the target germanium doping concentration into the above formula, the neutron irradiation process is designed as follows: neutron irradiation time 192000 s (53.33h).

[0095] Step 4: Neutron irradiation treatment of the GaN stripped sheet The GaN stripped sheet was placed in the reactor irradiation aperture and irradiated for 192,000 s. The ambient temperature for neutron irradiation treatment was 77.9 °C. At this time, the GaN stripped sheet was in a solid state.

[0096] Step 5: Annealing and subsequent processing of neutron-irradiated strips S51 Annealing and Activation. A tube furnace annealing method was used. The neutron-irradiated GaN stripped sheet was placed in a vacuum tube furnace, and nitrogen gas was introduced into the furnace. Since nitrogen precipitates at temperatures above 900°C, the nitrogen atmosphere suppresses its volatilization. The furnace was slowly heated to 800°C at a rate of 20°C / min and held at that temperature for 45 minutes to repair defects and crystal damage caused by neutron irradiation, while simultaneously activating the germanium atoms doped in the sample. Finally, the sample was slowly cooled to room temperature at a rate of 20°C / min. This slow heating and cooling method prevents the crystal from cracking due to drastic temperature changes.

[0097] After the gallium nitride stripper is activated at high temperature, the free electrons of Ge atoms are activated into conductive charge carriers, which increases the charge carrier concentration in GaN.

[0098] S52 subsequent processing The thin film was further ground and polished to obtain a GaN self-supporting substrate.

[0099] One GaN self-supporting substrate was selected as the test sample, denoted as A3.

[0100] The surface roughness of sample A3 was characterized using a Bruker Dimension Icon atomic force microscope; the germanium doping concentration in the above substrate samples was measured using a CAMECA IMS-4F SIMS instrument (the detection limit for germanium impurities was 2 × 10⁻⁶). 15 The carrier concentration of the above substrate samples was measured using a Semilab MCV-530L mercury probe microanalyzer (cm⁻³). The characterization and measurement results are shown in Table 1.

[0101] Example 4 The difference between the n-type gallium nitride self-supporting substrate fabrication method in Example 4 and Example 3 is that the target carrier concentration of the gallium nitride self-supporting substrate is set to 5 × 10⁻⁶ during the fabrication process in Example 4.19 / cm 3 The neutron irradiation time was calculated to be 960,000 s (266.67 h) using the theoretical doping concentration formula of germanium atoms in GaN irradiated by neutrons. The resulting GaN self-supporting substrate was denoted as sample A4.

[0102] The surface roughness of the A4 sample before and after irradiation was characterized using a Bruker Dimension Icon atomic force microscope. The germanium doping concentration in the irradiated substrate sample was measured using a CAMECA IMS-4F SIMS instrument (the detection limit for germanium impurities was 2 × 10⁻⁶). 15 cm -3 The carrier concentration of the irradiated substrate samples was measured using a Semilab MCV-530L mercury probe microanalyzer. The characterization and measurement results are shown in Table 1.

[0103] Comparative Example 1 n-type gallium nitride self-supporting substrates were prepared using silicon dopant (SiH4) (representing prior art, intended for comparative analysis with embodiments of this application).

[0104] Step 1: Epitaxially grow a buffer layer and a thick gallium nitride film sequentially on a sapphire substrate (original substrate); S11 Raw substrate pretreatment: A 4-inch c-plane (0001) sapphire substrate is selected. The surface is cleaned using the standard standard wafer wet cleaning process to remove organic matter, metal ions and particulate contaminants from the surface. Then the raw substrate is placed on the substrate tray of the HVPE reaction chamber. Surface nitriding of S12 original substrate Hydrogen and ammonia with a purity of 99.999% were introduced into the hydride vapor phase epitaxy reaction chamber, and the H2 flow rate was controlled at 10 slm and the NH3 flow rate at 3 slm. The temperature of the hydride vapor phase epitaxy reaction chamber was raised to 1050℃ and the pressure was 600 Torr, and maintained for 15 min. Through surface nitriding, an extremely thin polycrystalline layer was formed on the sapphire surface, providing nucleation sites for the growth of the buffer layer.

[0105] S13 aluminum nitride buffer layer deposition Al metal (5N purity) was placed at the front end (source region) of the hydride vapor phase epitaxy reaction chamber. HCl gas was introduced using high-purity nitrogen as the carrier gas, and the source region temperature was set to 500℃. AlCl3 was produced in the source region through reaction. The temperature of the rear growth chamber was raised to 1150℃ and the pressure to 200 Torr. A group III source (HCl) and a group V source (NH3) were introduced, with the HCl flow rate controlled at 10 sccm and the NH3 flow rate at 2 slm (V / III ratio greater than 100). At the same time, a H2 / N2 mixed gas (volume ratio 1:9) was introduced as the carrier gas at a flow rate of 10 slm. The growth time was 10 min, resulting in an atomically flat aluminum nitride buffer layer with a thickness of approximately 100 nm, providing a template for subsequent GaN growth.

[0106] S14 Silicon-doped GaN thick film growth To increase the partial pressure of GaCl, the flow rate of HCl to the Ga source was increased at the front end of the hydride vapor phase epitaxy reaction chamber. A mixture of silane (SiH4) and N2 (SiH4 concentration of 0.01%) was introduced into the gas nozzle at the rear end of the reaction chamber. The flow rate of V / III at the rear end of the reaction chamber was reduced to 40, the growth temperature was increased to 1070℃, and the flow rate of H2 / N2 mixed carrier gas (volume ratio 1:9) was increased to 50 slm. After continuous growth for 2 hours, a GaN thick film with a thickness of about 400 μm was obtained.

[0107] Step 2: Self-peeling of gallium nitride thick film and preparation of peeling sheet Cooling process and stress regulation of S21 GaN thick film First, the supply of HCl and SIH4 gases is cut off, and the mixture is maintained for 10 minutes under the protection of NH3 and H2 / N2 mixed carrier gas to protect the GaN surface. Then, the reaction chamber temperature is reduced to 800℃ at a rate of 10℃ / min; then reduced to 400℃ at a rate of 3℃ / min; and finally reduced to room temperature at a rate of 10℃ / min.

[0108] Debonding of S22 GaN thick film from substrate The peeling method was spontaneous peeling: during the cooling process, huge thermal mismatch stress was concentrated at the GaN / sapphire substrate interface. When the interfacial bonding force was weaker than the stress, the GaN thick film automatically detached from the original substrate, yielding an n-type silicon-doped GaN thick film, which was used as a comparative sample and denoted as sample A0. Visual observation of the growth surface of A0 revealed clearly visible protrusions, depressions, and textures.

[0109] Five regions (5μm×5μm) were selected on the growth surface of the A0 sample. The morphology of the growth surface of the GaN exfoliated sheet was characterized using a Bruker Dimension Icon atomic force microscope (AFM). The Ra value of each region was measured and the average value of the five points was taken.

[0110] S23 Subsequent processing The A0 blank surface (original substrate contact surface) after stripping was ground and polished to obtain an n-type silicon-doped GaN self-supporting substrate with a thickness of approximately 400 μm. The carrier concentration of the substrate sample was measured using a Semilab MCV-530L mercury probe microanalyzer. The measurement results are shown in Table 1.

[0111] Table 1

[0112] As can be seen from Table 1: (1) The surface morphology of the samples in the examples did not change before and after neutron irradiation. Before neutron irradiation, the samples in Examples 1-4 of this application had a smooth surface morphology and a low Ra value, between 0.3-0.5 nm, because no n-type donor impurities were incorporated. After neutron irradiation, a higher concentration of donor impurity Ge was incorporated, but the Ra value of the samples in each example did not change. This indicates that neutron irradiation and transmutation doping do not change the surface morphology of gallium nitride thick film crystals, that is, they do not have a negative impact on the crystal quality of gallium nitride self-supporting substrates.

[0113] (2) Compared with the comparative example, the embodiment exhibits good crystal quality of the gallium nitride self-supporting substrate under n-type heavy doping. The comparative example uses Si as the doping element, with a doping density of 1.6 × 10⁻⁶. 18 / cm 3 At certain carrier concentrations, the gallium nitride crystal surface deteriorates, with Ra values ​​reaching as high as 7.2 nm. This is attributed to the anti-surfactant effect of the Si dopant, which leads to a decrease in crystal growth quality at higher doping concentrations. In contrast, the example samples A2 and A4 show a Ra value of 5.2 × 10⁻⁶ nm. 19 / cm 3 and 5.3×10 19 / cm 3 With a carrier concentration (heavy doping level), the Ra value is 0.3-0.5 nm, indicating that the crystal of the gallium nitride self-supporting substrate can still maintain good crystal quality. At the same time, it means that the solution of this application can overcome the bottleneck of the existing technology that cannot prepare n-type heavily doped gallium nitride self-supporting substrates, and provides possibilities for new application scenarios.

[0114] It should be noted that the carrier concentration in the embodiments provided in this application is at a heavily doped level (doping concentration 1×10⁻⁶). 19 -5×10 19 / cm 3 The purpose is to verify that the technical solution of this invention can overcome the bottleneck of the highest doping concentration in existing technologies. In practice, the carrier concentration can also be controlled at a lower level (1×10⁻⁶) by controlling the neutron irradiation process. 15 -1×10 19 / cm 3 ).

[0115] Although the above embodiments have been shown and described, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Any changes, modifications, substitutions and variations made to the above embodiments by those skilled in the art are within the protection scope of the present invention.

Claims

1. A method for fabricating an n-type gallium nitride self-supporting substrate, characterized in that, Includes the following steps: (1) A buffer layer and a thick gallium nitride film are epitaxially grown sequentially on the original substrate; (2) Peel off the gallium nitride thick film to obtain a gallium nitride stripper sheet; (3) Based on the theoretical doping concentration of germanium atoms in the gallium nitride stripper, neutron irradiation treatment was performed on it to obtain germanium-doped gallium nitride stripper; (4) Anneal the germanium-doped gallium nitride strip to obtain an n-type gallium nitride self-supporting substrate.

2. The method for fabricating an n-type gallium nitride self-supporting substrate according to claim 1, characterized in that, In step (1), the original substrate includes a sapphire substrate, a silicon carbide substrate, a silicon substrate, or a gallium nitride substrate; And / or, the diameter of the original substrate is 2 inches, 4 inches, 6 inches, 8 inches, or 12 inches; And / or, the epitaxial growth method includes metal-organic chemical vapor deposition (MOCVD) or hydride vapor phase epitaxy (HVPE). And / or, the buffer layer comprises one or more of aluminum nitride, gallium nitride, indium nitride, and zinc oxide; And / or, the thickness of the gallium nitride thick film is 300-5000 μm; And / or, the gallium nitride thick film has a hexagonal wurtzite structure with a space group of P63mc.

3. The method for fabricating an n-type gallium nitride self-supporting substrate according to claim 1, characterized in that, In step (2), the stripping methods include laser stripping, spontaneous stripping and chemical stripping.

4. The method for fabricating an n-type gallium nitride self-supporting substrate according to claim 1, characterized in that, The theoretical germanium atom doping concentration of the gallium nitride stripper is calculated according to the following formula: in: N d This represents the theoretical doping concentration of germanium atoms, expressed in atoms / cm². 3 ; N Ga The Ga atom density in gallium nitride is 4.39 × 10⁻⁶. 22 atoms / cm 3 ; f1 represents the abundance of the Ga-69 isotope in gallium nitride, with a value of 0.

604. f2 represents the abundance of the Ga-71 isotope in gallium nitride, with a value of 0.

396. 1 represents the thermal neutron capture cross section of Ga-69, with a value of 1.68 × 10⁻⁶. -28 cm 2 ; 2 represents the thermal neutron capture cross section of Ga-71, with a value of 4.70 × 10⁻⁶. -28 cm 2 ; ψ represents the neutron flux of the irradiated neutron source, expressed in n / (cm²). 2 •s); t is the reaction time of neutron irradiation, measured in seconds.

5. The method for fabricating an n-type gallium nitride self-supporting substrate according to claim 1, characterized in that, The neutron source used in the neutron irradiation treatment includes a reactor neutron source or an accelerator neutron source; Preferably, the neutron flux of the neutron irradiation treatment is 10. 12 -10 16 n / (cm 2 •s); Preferably, the ambient temperature of the neutron irradiation treatment is <100°C, and the gallium nitride stripper is in a solid state during the neutron irradiation treatment.

6. The method for fabricating an n-type gallium nitride self-supporting substrate according to claim 1, characterized in that, The annealing process includes furnace tube annealing, rapid thermal annealing, or laser annealing.

7. The method for fabricating an n-type gallium nitride self-supporting substrate according to claim 1, characterized in that, The annealing temperature is 700-900℃, and the time is 30-60 minutes; And / or, the annealing atmosphere is nitrogen or argon, preferably nitrogen.

8. A heavily doped gallium nitride substrate, characterized in that, It is prepared by the method for preparing an n-type gallium nitride self-supporting substrate according to any one of claims 1-7.

9. The heavily doped gallium nitride substrate according to claim 8, characterized in that, The carrier concentration of the heavily doped gallium nitride substrate is 5 × 10⁻⁶. 15 / cm 3 -5×10 20 / cm 3 Preferably 5×10 18 / cm 3 -5×10 20 / cm 3 .

10. The use of the heavily doped gallium nitride substrate according to any one of claims 8-9 in vertical power devices, laser diodes or Micro-LED display devices.

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