P-type beta-Ga2O3 single crystal film and preparation method and application thereof

Abstract

The invention provides a P-type beta-Ga2O3 single crystal film as well as a preparation method and application thereof, and belongs to the technical field of gallium oxide materials. Vapor phase epitaxial film growth is carried out on the surface of a beta-Ga2O3 single crystal substrate to obtain the P-type beta-Ga2O3 single crystal film, and nitrogen is used as carrier gas and nitrogen oxide is used as an oxidizing agent in the vapor phase epitaxial film growth process. In the growth process of the vapor phase epitaxial thin film, an N element is in a thermodynamic unstable state in a gallium oxide crystal and is easy to volatilize from the gallium oxide crystal, so that after the carrier gas is changed into nitrogen, the concentration of the N element in the environment is increased, the volatilization of the N element in the gallium oxide thin film is inhibited, the N doping efficiency is improved, and the yield of the gallium oxide thin film is improved. According to the method, nitrogen oxide is used as an oxidizing agent, nitrogen is used as carrier gas, and the nitrogen doping concentration of the P-type beta-Ga2O3 single crystal thin film is improved under the combined action.

Description

Technical Field

[0001] The present invention relates to the technical field of gallium oxide materials, and in particular to a P-type β-Ga2O3 single crystal thin film and a preparation method and application thereof. Background Art

[0002] Gallium oxide (GaO) is an oxide semiconductor with an ultra-wide bandgap of 4.7–4.9 eV. Due to its significant advantages, such as high breakdown field strength (approximately 8 MeV / cm) and stable physicochemical properties, it holds broad application prospects in power devices and everyday ultraviolet detectors. Among ultra-wide bandgap semiconductors, gallium oxide (GaO) is the material most likely to be the first to achieve commercial application. High-quality single crystal growth and substrate development are crucial for the fabrication of high-performance GaO devices. Currently, a major obstacle hindering the large-scale application of β-Ga2O3 devices is the lack of p-type β-Ga2O3. This is due to the flat valence band top of β-Ga2O3, which results in a large effective mass for holes and hinders their migration. Furthermore, as an oxide semiconductor, oxygen vacancies are prone to form and act as donor impurities. Currently, heterojunction devices are typically designed using β-Ga2O3 with other materials, such as p-type NiO. However, the p-type conductivity of p-type NiO, which stems from Ni vacancies, is unstable under practical operating conditions, hindering its application in large-scale commercial production. Therefore, it is necessary to design a preparation path for p-type β-Ga2O3 to broaden the application scenarios of β-Ga2O3.

[0003] As a donor element, nitrogen is an excellent choice for achieving p-type β-Ga2O3, mainly due to the following three aspects: 1. N mainly replaces O atoms in β-Ga2O3. The radii of N atoms and O atoms are similar, so they can achieve effective replacement; 2. N has a valence of -3, compared with the valence of O of -2, and can act as a p-type dopant that captures electrons; 3. N is a shallow-energy p-type dopant that can be effectively excited in β-Ga2O3 to achieve the effect of p-type β-Ga2O3.

[0004] However, it is very difficult to introduce the N element into β-Ga2O3, mainly due to the following reasons: 1. At high temperatures during the single crystal growth process, Ga-O compounds are more stable than Ga-N compounds. Therefore, when growing β-Ga2O3 crystals by the melt method, it is impossible to introduce the N element into β-Ga2O3 by introducing nitrogen or nitrogen oxide gas; 2. At the temperature of epitaxial growth of β-Ga2O3, N2 is very stable. When nitrogen is introduced during the epitaxial growth of β-Ga2O3, nitrogen will always exist in the form of N2 molecules, making it difficult to enter the film in the form of atoms, and it is impossible to achieve the effect of N-doped p-type thin film. Related technology discloses the introduction of an organic gallium source and N2O, using argon as a carrier gas, and homoepitaxially growing a p-type gallium oxide material on the β-Ga2O3 single crystal substrate by an organic metal chemical vapor deposition method. However, there is still the problem of low nitrogen doping concentration in the P-type β-Ga2O3 single crystal film. Summary of the Invention

[0005] In view of this, the object of the present invention is to provide a P-type β-Ga2O3 single crystal thin film and its preparation method and application. The P-type β-Ga2O3 single crystal thin film prepared by the preparation method of the present invention has a high nitrogen doping concentration.

[0006] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions: The present invention provides a method for preparing a P-type β-Ga2O3 single crystal thin film, comprising the following steps: Vapor phase epitaxial thin film growth is performed on the surface of a β-Ga2O3 single crystal substrate to obtain the P-type β-Ga2O3 single crystal thin film. During the vapor phase epitaxial thin film growth process, nitrogen is used as a carrier gas and nitrogen oxide is used as an oxidant.

[0007] Preferably, the flow rate of the nitrogen gas is 100-5000 sccm.

[0008] Preferably, the flow rate of the nitrogen gas is 500-4000 sccm.

[0009] Preferably, the nitrogen oxides include one or more of NO, N2O, NO2, N2O3, N2O4 and N2O5.

[0010] Preferably, the vapor phase epitaxial thin film growth time is 0.5 to 48 hours.

[0011] Preferably, the vapor phase epitaxial thin film is grown by metal organic vapor phase epitaxy (MOVPE) or halide vapor phase epitaxy (HVPE).

[0012] Preferably, the conditions of the metal organic vapor phase epitaxy method include: a growth temperature of 550-1200° C., a pressure of 10-100 mbar, trimethylgallium as a gallium source, a flow rate of the trimethylgallium of 10-150 sccm, and a flow rate of nitrogen oxide of 1000-10000 sccm.

[0013] Preferably, the conditions of the halide vapor phase epitaxy method include: a growth temperature of 600-1200° C., a growth pressure of 10-500 Torr, an HCl flow rate of 10-150 sccm, and a nitrogen oxide flow rate of 100-5000 sccm.

[0014] The present invention also provides a P-type β-Ga2O3 single crystal thin film prepared by the preparation method described in the above technical solution.

[0015] The present invention also provides the application of the P-type β-Ga2O3 single crystal thin film described in the above technical solution in the field of gallium oxide devices.

[0016] The present invention provides a method for preparing a P-type β-Ga2O3 single crystal thin film, comprising the following steps: performing vapor phase epitaxial thin film growth on the surface of a β-Ga2O3 single crystal substrate to obtain the P-type β-Ga2O3 single crystal thin film, wherein nitrogen is used as a carrier gas and nitrogen oxide is used as an oxidant during the vapor phase epitaxial thin film growth process.

[0017] Compared with the prior art, the present invention has the following beneficial effects: During the growth of vapor phase epitaxial thin films, the nitrogen element is in a thermodynamically unstable state in the gallium oxide crystal and is easily volatilized from the gallium oxide crystal. Therefore, after replacing the carrier gas with nitrogen, the concentration of the nitrogen element in the environment is increased, and the volatilization of the nitrogen element in the gallium oxide film is suppressed, thereby improving the efficiency of nitrogen doping. The present invention uses nitrogen oxide as an oxidant and combines it with nitrogen as a carrier gas to jointly increase the nitrogen doping concentration of the P-type β-Ga2O3 single crystal film.

[0018] Furthermore, the growth temperature of the vapor phase epitaxial thin film of the present invention is low.

[0019] The present invention also provides a P-type β-Ga2O3 single crystal thin film prepared by the preparation method described in the above technical solution, which has a high nitrogen doping concentration and has high hole concentration, mobility and low resistivity. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 is an AFM image of the P-type β-Ga2O3 single crystal thin film in Example 1; Figure 2 This is the AFM image of the P-type β-Ga2O3 single crystal thin film in Example 6. DETAILED DESCRIPTION

[0021] The present invention provides a method for preparing a P-type β-Ga2O3 single crystal thin film, comprising the following steps: Vapor phase epitaxial thin film growth is performed on the surface of a β-Ga2O3 single crystal substrate to obtain the P-type β-Ga2O3 single crystal thin film. During the vapor phase epitaxial thin film growth process, nitrogen is used as a carrier gas and nitrogen oxide is used as an oxidant.

[0022] In the present invention, it is preferred to first grow a high-quality bulk β-Ga2O3 crystal, and then process the bulk β-Ga2O3 crystal to obtain the β-Ga2O3 single crystal substrate.

[0023] In the present invention, the growth method is preferably a Czochralski method, a guided mold method, a casting method, a floating zone method or a vertical Bridgman method. The present invention has no special limitation on the growth parameters and can adopt methods familiar to those skilled in the art.

[0024] In the present invention, the flow rate of the nitrogen gas is preferably 100-5000 sccm, more preferably 500-4000 sccm, and specifically can be 100, 500, 1000, 1500, 2000, 2500, 3000, 3500, 4000, 4500 or 5000 sccm.

[0025] In the present invention, the nitrogen oxide preferably includes one or more of NO, N2O, NO2, N2O3, N2O4 and N2O5. The higher the valence state of N in the nitrogen oxide, the easier it is for N to obtain electrons in the reaction, the stronger the oxidizing property, and the more conducive to the growth of epitaxial gallium oxide.

[0026] In the present invention, the time for the vapor phase epitaxial thin film growth is preferably 0.5 to 48 hours, specifically 0.5, 1, 3, 5, 10, 15, 20, 25, 30, 35, 40, 45 or 48 hours.

[0027] In the present invention, the vapor phase epitaxial thin film growth is preferably a metal organic vapor phase epitaxy method or a halide vapor phase epitaxy method.

[0028] In the present invention, the conditions of the metal organic vapor phase epitaxy method preferably include: a growth temperature of 550-1200°C, specifically 550, 600, 700, 800, 900, 1000, 1100 or 1200°C, a pressure of 10-100 mbar, specifically 10, 25, 30, 40, 50, 60, 70, 80, 90 or 100 mbar, trimethylgallium is used as the gallium source, the flow rate of trimethylgallium is 10-150 sccm, specifically 10, 50, 100 or 150 sccm, and the flow rate of nitrogen oxide is 1000-10000 sccm, specifically 1000, 2000, 3000, 4000, 5000, 6000, 7000, 8000, 9000 or 10000 sccm.

[0029] In the present invention, the conditions of the halide vapor phase epitaxy method preferably include: a growth temperature of 600-1200°C, specifically 600, 650, 700, 800, 1000 or 1200°C, a growth pressure of 10-500 Torr, specifically 10, 50, 100, 150, 200, 250, 300, 350, 400, 450 or 500 Torr, an HCl flow rate of 10-150 sccm, specifically 10, 50, 100 or 150 sccm, and a nitrogen oxide flow rate of 100-5000 sccm, specifically 100, 500, 1000, 2000, 3000, 4000 or 5000 sccm.

[0030] In the present invention, since the nitrogen element is in a thermodynamically unstable state in the gallium oxide crystal at the high temperature of epitaxy and is easily volatilized from the crystal, replacing the carrier gas with nitrogen increases the concentration of the nitrogen element in the environment, suppresses the volatilization of the nitrogen element in the gallium oxide film, and thus improves the efficiency of nitrogen doping. In addition, the temperature for the vapor phase epitaxial film growth of the present invention is low, and nitrogen oxides are generally easy to decompose at high temperatures. Taking N2O as an example, it begins to decompose above 300°C, decomposes significantly at 500°C, and completely decomposes into nitrogen and oxygen above 900°C. Therefore, lowering the temperature helps to avoid the decomposition of nitrogen oxides during the epitaxial film growth process, thereby improving the utilization rate of nitrogen oxides and the nitrogen doping concentration.

[0031] The present invention also provides a P-type β-Ga2O3 single crystal film prepared by the preparation method described in the above technical solution. The present invention uses nitrogen oxide as an oxidant and combines it with nitrogen as a carrier gas to jointly increase the nitrogen doping concentration of the P-type β-Ga2O3 single crystal film. The P-type β-Ga2O3 single crystal film has a high nitrogen doping concentration and has a high hole concentration, mobility and low resistivity.

[0032] The present invention also provides the application of the P-type β-Ga2O3 single crystal thin film described in the above technical solution in the field of gallium oxide devices.

[0033] The present invention has no particular limitation on the specific manner of the application, and any manner familiar to those skilled in the art may be used.

[0034] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions of the present invention. Obviously, the embodiments described are only some of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0035] Example 1 Preparation of a P-type β-Ga2O3 single crystal thin film, comprising the following steps: 1. First, high-quality bulk β-Ga2O3 crystals are grown using the Czochralski method and then processed into β-Ga2O3 single crystal substrates.

[0036] 2. Metal organic vapor phase epitaxy was used for epitaxial film growth at a growth temperature of 600°C, a pressure of 25 mbar, a trimethylgallium flow rate of 50 sccm, an N2O flow rate of 1000 sccm, N2 was used as the carrier gas, the carrier gas flow rate was 500 sccm, and the growth time was 0.5 h to produce a P-type β-Ga2O3 single crystal thin film.

[0037] Example 2 Preparation of a P-type β-Ga2O3 single crystal thin film, comprising the following steps: 1. First, high-quality bulk β-Ga2O3 crystals are grown using the Czochralski method and then processed into β-Ga2O3 single crystal substrates.

[0038] 2. Metal organic vapor phase epitaxy was used for epitaxial film growth at a growth temperature of 600°C, a pressure of 25 mbar, a trimethylgallium flow rate of 50 sccm, an N2O flow rate of 5000 sccm, and N2 as the carrier gas with a carrier gas flow rate of 500 sccm. The growth time was 0.5 h to produce a P-type β-Ga2O3 single crystal thin film.

[0039] Example 3 Preparation of a P-type β-Ga2O3 single crystal thin film, comprising the following steps: 1. First, high-quality bulk β-Ga2O3 crystals are grown using the Czochralski method and then processed into β-Ga2O3 single crystal substrates.

[0040] 2. Metal organic vapor phase epitaxy was used for epitaxial film growth at a growth temperature of 600°C, a pressure of 25 mbar, a trimethylgallium flow rate of 50 sccm, an N2O flow rate of 10,000 sccm, N2 was used as the carrier gas, the carrier gas flow rate was 500 sccm, and the growth time was 0.5 h to produce a P-type β-Ga2O3 single crystal thin film.

[0041] Comparative Example 1 The same as Example 1, the only difference is that N2 is replaced by argon.

[0042] Example 4 The same as Example 1, the only difference is that N2O is replaced by N2O3.

[0043] Example 5 The same as Example 1, the only difference is that N2O is replaced by N2O5.

[0044] Example 6 The same as Example 1, the only difference is that the growth temperature is 550°C.

[0045] Example 7 The same as Example 1, the only difference is that the growth temperature is 650°C.

[0046] Example 8 Preparation of a P-type β-Ga2O3 single crystal thin film, comprising the following steps: 1. First, high-quality bulk β-Ga2O3 crystals are grown using the Czochralski method and then processed into β-Ga2O3 single crystal substrates.

[0047] 2. P-type β-Ga2O3 single crystal thin film was obtained by halide vapor phase epitaxy with a growth temperature of 700°C, a growth pressure of 200 Torr, an HCl flow rate of 10 sccm, an N2O flow rate of 100 sccm, N2 as the carrier gas, a flow rate of 2000 sccm, and a growth time of 3 h, followed by chemical mechanical polishing.

[0048] Example 9 Preparation of a P-type β-Ga2O3 single crystal thin film, comprising the following steps: 1. First, high-quality bulk β-Ga2O3 crystals are grown using the Czochralski method and then processed into β-Ga2O3 single crystal substrates.

[0049] 2. P-type β-Ga2O3 single crystal thin film was obtained by halide vapor phase epitaxy with a growth temperature of 700°C, a growth pressure of 200 Torr, an HCl flow rate of 10 sccm, an N2O flow rate of 1000 sccm, N2 as the carrier gas, a flow rate of 2000 sccm, and a growth time of 3 h.

[0050] Example 10 Preparation of a P-type β-Ga2O3 single crystal thin film, comprising the following steps: 1. First, high-quality bulk β-Ga2O3 crystals are grown using the Czochralski method and then processed into β-Ga2O3 single crystal substrates.

[0051] 2. P-type β-Ga2O3 single crystal thin film was obtained by halide vapor phase epitaxy with a growth temperature of 700°C, a growth pressure of 200 Torr, an HCl flow rate of 10 sccm, an N2O flow rate of 5000 sccm, N2 as the carrier gas, a flow rate of 2000 sccm, and a growth time of 3 h.

[0052] Example 11 The same as Example 9, the only difference is that the growth temperature is 650°C.

[0053] Example 12 The same as Example 9, the only difference is that the growth temperature is 600°C.

[0054] Example 13 The same as Example 1, except that the flow rate of the carrier gas is 100 sccm.

[0055] Example 14 The same as Example 1, the only difference is that the flow rate of the carrier gas is 4000 sccm.

[0056] Example 15 The same as Example 1, except that the flow rate of the carrier gas is 5000 sccm.

[0057] Comparative Example 2 The same as Example 9, the only difference is that N2 is replaced by argon.

[0058] Figure 1 This is the AFM image of the P-type β-Ga2O3 single crystal thin film in Example 1, with a roughness of 1.5 nm. Figure 2 This is the AFM image of the P-type β-Ga2O3 single crystal film in Example 6, with a roughness of 0.6 nm. It can be seen that the surface roughness of the P-type β-Ga2O3 single crystal film prepared by the present invention is good.

[0059] Table 1 shows the test results of the P-type β-Ga2O3 single crystal films prepared in the examples and comparative examples. It can be seen that the present invention uses nitrogen oxide as an oxidant in combination with nitrogen as a carrier gas, which together increase the nitrogen doping concentration of the P-type β-Ga2O3 single crystal film. The P-type β-Ga2O3 single crystal film has a high nitrogen doping concentration and a small half-width at half-maximum of the rocking curve. The P-type β-Ga2O3 single crystal film has an ordered crystal structure, good quality, good performance, high hole concentration, mobility and low resistivity. In addition, the higher the valence state of N in the nitrogen oxide, the easier it is for N to obtain electrons in the reaction, the stronger the oxidizing property, and the more conducive to the growth of epitaxial gallium oxide. The growth temperature of the present invention is as low as 550°C.

[0060] Table 1 Test results of P-type β-Ga2O3 single crystal thin films prepared in Examples and Comparative Examples

[0061] The above description is merely a preferred embodiment of the present invention and does not constitute any limitation thereto. It should be noted that those skilled in the art may make various improvements and modifications without departing from the principles of the present invention, and such improvements and modifications shall also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a P-type β-Ga2O3 single crystal thin film, characterized in that: The following steps are involved: Vapor phase epitaxial thin film growth is performed on the surface of a β-Ga2O3 single crystal substrate to obtain the P-type β-Ga2O3 single crystal thin film. During the vapor phase epitaxial thin film growth process, nitrogen is used as a carrier gas and nitrogen oxide is used as an oxidant.

2. The preparation method according to claim 1, characterized in that The flow rate of the nitrogen gas is 100-5000 sccm.

3. The preparation method according to claim 1, characterized in that The flow rate of the nitrogen gas is 500-4000 sccm.

4. The preparation method according to claim 1, characterized in that The nitrogen oxides include one or more of NO, N2O, NO2, N2O3, N2O4 and N2O5.

5. The preparation method according to claim 1, characterized in that The time for the vapor phase epitaxial thin film growth is 0.5 to 48 hours.

6. The preparation method according to claim 1 or 2, characterized in that The vapor phase epitaxial thin film is grown by metal organic vapor phase epitaxy or halide vapor phase epitaxy.

7. The preparation method according to claim 6, characterized in that The conditions of the metal organic vapor phase epitaxy method include: a growth temperature of 550-1200° C., a pressure of 10-100 mbar, trimethyl gallium as a gallium source, a flow rate of the trimethyl gallium of 10-150 sccm, and a flow rate of nitrogen oxide of 1000-10000 sccm.

8. The preparation method according to claim 6, characterized in that The conditions of the halide vapor phase epitaxy method include: a growth temperature of 600-1200° C., a growth pressure of 10-500 Torr, an HCl flow rate of 10-150 sccm, and a nitrogen oxide flow rate of 100-5000 sccm.

9. A P-type β-Ga2O3 single crystal thin film prepared by the preparation method according to any one of claims 1 to 8.

10. Use of the P-type β-Ga2O3 single crystal thin film according to claim 9 in the field of gallium oxide devices.

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