A method for growing an oriented ε-Ga2O3 epitaxial film

Abstract

This invention discloses a method for growing an ε-Ga2O3 epitaxial film with a (0002) orientation, comprising the following steps: removing inorganic contaminants, organic contaminants, moisture, and gas adsorption layers from the surface of a (0006) oriented sapphire substrate. Then, using hydrogen chloride gas, gallium metal, and oxygen as reaction sources, and nitrogen as the working carrier gas, an ε-Ga2O3 epitaxial film with a (0002) orientation is grown on the sapphire substrate. The ε-Ga2O3 epitaxial film is then annealed in situ under a nitrogen atmosphere. This invention results in high lattice matching, high crystal quality, good density, and tight inter-lattice bonding, making it suitable for growing thicker epitaxial films. This invention achieves the growth of ε-Ga2O3 epitaxial films using the HVPE method, which is simple, easy to operate, and highly controllable. The resulting ε-Ga2O3 epitaxial film has a smooth, dense, and uniform thickness, enabling large-scale production of ε-Ga2O3 epitaxial films.

Description

Technical Field

[0001] This invention relates to the field of semiconductor materials, and more particularly to a method for growing an ε-Ga2O3 epitaxial film with a (0002) orientation. Background Technology

[0002] With the continuous upgrading of demand for high-power, high-frequency, and high-temperature resistant electronic devices in fields such as new energy power systems, 5G communications, and aerospace, traditional silicon (Si)-based semiconductor materials, due to their inherent defects of narrow bandgap (1.1 eV) and low critical breakdown electric field (0.3 MV / cm), are no longer able to meet the performance requirements of devices under extreme operating conditions. Wide bandgap semiconductor materials, with their excellent electrical and thermal properties, have become the core direction for solving this technological bottleneck. Among them, gallium oxide (Ga2O3), as a representative of ultra-wide bandgap (4.7~5.4 eV) semiconductors, has a Baliga quality factor that is significantly higher than that of commercial wide bandgap materials such as SiC and GaN, showing irreplaceable application potential in fields such as high-power electronic devices, radio frequency resonators, and deep ultraviolet optoelectronic devices. Ga₂O₃ exists in various crystal forms, including α, β, γ, δ, and ε. Among them, ε-Ga₂O₃ exhibits the best overall performance due to its unique crystal structure: spontaneous polarization and high lattice symmetry enable the formation of extremely high two-dimensional electron gas (2DEG) mobility; it also demonstrates excellent breakdown voltage and strong piezoelectric effect, making it an ideal candidate material for both high-power electronic devices and high-frequency piezoelectric devices. Theoretical studies show that ε-Ga₂O₃ has a thermal stability exceeding 1000K, and its key parameters, such as longitudinal acoustic velocity and electromechanical coupling coefficient, meet the performance requirements of next-generation RF devices. In particular, it can achieve high-frequency response and low-loss characteristics above 1GHz in devices such as surface acoustic wave (SAW) and high-harmonic bulk acoustic resonators (HBAR). Furthermore, the compatibility of ε-Ga₂O₃ with silicon-based microelectronic processes makes it possible to achieve monolithic device integration and reduce manufacturing costs, further expanding its industrial application prospects. However, existing ε-Ga2O3 preparation technologies face multiple challenges: First, during epitaxial growth on mainstream c-plane sapphire substrates, interfacial lattice mismatch and energy competition easily lead to an increase in the half-width at half-maximum (FWHM) and surface roughness, making it difficult to obtain epitaxial films with high purity. Second, although silicon (Si) substrates have cost advantages and mature process compatibility, the Si surface is easily oxidized to form amorphous SiO. xThe epitaxial layer has a lattice mismatch of ~24% with ε-Ga2O3, resulting in disordered atomic arrangement and high defect density. Thirdly, existing chemical vapor deposition (CVD) and molecular beam epitaxy (MBE) processes lack precise means to control the growth thermodynamics and kinetics, and cannot effectively suppress the formation of secondary phases. Even by optimizing parameters such as temperature and oxygen partial pressure, it is difficult to stably obtain high-purity ε-Ga2O3 epitaxial films with high crystal quality. In gallium oxide epitaxial processes, halide vapor phase epitaxy (HVPE) technology possesses unique advantages in semiconductor material growth. Its equipment is relatively simple, with low installation and maintenance costs, while also offering high material growth rates and relatively low energy consumption. In recent years, HVPE technology has made some progress in the growth of β-Ga₂O₃ epitaxial films, attracting considerable attention from researchers and companies. Using the HVPE method, researchers have successfully grown high-quality β-Ga₂O₃ epitaxial layers with specific crystal orientations on homogeneous or heterogeneous substrates. However, research on the growth of ε-Ga₂O₃ using the HVPE method is relatively limited.

[0003] In view of this, the present invention is hereby proposed. Summary of the Invention

[0004] This invention provides a method for growing (0002) oriented ε-Ga2O3 epitaxial films, which can grow high-quality (0002) crystal plane oriented ε-Ga2O3 epitaxial films.

[0005] An embodiment of the present invention provides a method for growing an ε-Ga2O3 epitaxial film with a (0002) orientation, comprising the following steps: removing inorganic contaminants, organic contaminants, moisture, and a gas adsorption layer from the surface of a (0006) oriented sapphire substrate. Then, using hydrogen chloride gas, gallium metal, and oxygen as reaction sources, and nitrogen as the working carrier gas, an ε-Ga2O3 epitaxial film with a (0002) orientation is grown on the sapphire substrate. The ε-Ga2O3 epitaxial film is then annealed in situ under a nitrogen atmosphere.

[0006] Furthermore, during the growth of (0002) oriented ε-Ga2O3 epitaxial film on a (0006) oriented sapphire substrate, the flow rate of hydrogen chloride gas was 5-20 sccm, the flow rate of oxygen was 100-250 sccm, the working pressure was 400-760 Torr, the growth temperature was 430-600℃, the rotation speed of the sapphire substrate was (10-50) ±1 r / min, and the growth time was 60 min.

[0007] Furthermore, the flow rate of hydrogen chloride gas is 10 sccm, the flow rate of oxygen is 150 sccm, the working pressure is 550 Torr, the growth temperature is 475℃, and the rotation speed of the sapphire substrate is 40±1 r / min.

[0008] Furthermore, during the in-situ annealing of ε-Ga2O3, the annealing time is 10-20 min and the pressure of the nitrogen atmosphere is 400-760 Torr.

[0009] Furthermore, the annealing time was 15 minutes, and the pressure of the nitrogen atmosphere was 550 Torr.

[0010] Furthermore, during the process of removing inorganic contaminants, organic contaminants, moisture and gas adsorption layers from the surface of the (0006) oriented sapphire substrate, the sapphire substrate is cleaned and then dried with dry nitrogen gas.

[0011] Furthermore, during the cleaning process of the sapphire substrate, the sapphire substrate was successively immersed in acetone and anhydrous ethanol and sonicated for 15 minutes, and then rinsed with running deionized water.

[0012] Furthermore, the ε-Ga2O3 epitaxial film has a thickness of 1 μm, a full width at half maximum (FWHM) of 0.45°, and a root mean square roughness of 1.8 nm.

[0013] The present invention has the following beneficial effects: 1. This invention removes inorganic contaminants, organic contaminants, moisture, and gas adsorption layers from the surface of a sapphire substrate to obtain a clean, flat, and uniform surface, providing favorable substrate conditions for the epitaxial growth of high-quality ε-Ga2O3 epitaxial films.

[0014] 2. This invention grows a (0002) oriented ε-Ga2O3 epitaxial film on a (0006) oriented sapphire substrate, resulting in high lattice matching, high crystal quality, good density, and tight inter-lattice bonding, making it suitable for growing thicker epitaxial films. Furthermore, the (0006) oriented sapphire substrate has higher crystallinity, lower price, and is widely available in the market, reducing the cost of growing ε-Ga2O3 epitaxial films.

[0015] 3. This invention achieves the growth of ε-Ga2O3 epitaxial films using hydrogen chloride gas, gallium metal, and oxygen as reaction sources and the HVPE method. The process is simple, easy to operate, and highly controllable. The final ε-Ga2O3 epitaxial film has a smooth, dense, and uniform thickness, which can realize the mass production of ε-Ga2O3 epitaxial films without the need for secondary chemical mechanical polishing (CMP) to meet the requirements of device fabrication. Attached Figure Description

[0016] Figure 1 These are XRD patterns of Ga2O3 epitaxial films grown on (0006) oriented sapphire substrates at different growth temperatures when the oxygen flow rate is 150 sccm in this invention. Figure 2 This is the XRD pattern of Ga2O3 epitaxial film grown on a (0006) oriented sapphire substrate under different oxygen flow rates at a growth temperature of 475℃ in this invention. Figure 3 This is the XRD pattern of the Ga2O3 epitaxial film grown on a sapphire substrate without mixed acid immersion at an oxygen flow rate of 150 sccm and a growth temperature of 475°C in this invention. Figure 4 This is the XRD pattern of the Ga2O3 epitaxial film grown on a sapphire substrate soaked in mixed acid at an oxygen flow rate of 150 sccm and a growth temperature of 475°C in this invention. Figure 5 These are the XRC and AFM images of the ε-Ga2O3 epitaxial film grown on a sapphire substrate at an oxygen flow rate of 150 sccm and a growth temperature of 475°C in this invention. Figure 6 This is an ellipsoid of the ε-Ga2O3 epitaxial film grown on a sapphire substrate at a working pressure of 550 Torr and a growth temperature of 475°C in this invention. Detailed Implementation

[0017] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. Although exemplary embodiments of this disclosure are shown in the drawings, it should be understood that this disclosure can be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided to enable a more thorough understanding of this disclosure and to fully convey the scope of this disclosure to those skilled in the art. It should be noted that, unless otherwise specified, the embodiments and features described herein can be combined with each other. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0018] An embodiment of the present invention provides a method for growing an ε-Ga2O3 epitaxial film with a (0002) orientation, comprising the following steps: Step (1) removes inorganic contaminants, organic contaminants, moisture and gas adsorption layers from the surface of the (0006) oriented (i.e., crystal plane oriented) sapphire substrate.

[0019] In step (1) above, the (0006) oriented sapphire substrate is cleaned and then dried with dry nitrogen gas to remove inorganic contaminants, organic contaminants, moisture, and gas adsorption layers from the surface of the (0006) oriented sapphire substrate. This is achieved by sequentially immersing the (0006) oriented sapphire substrate in acetone and anhydrous ethanol, followed by ultrasonication for 15 minutes, and then rinsing with flowing deionized water. The (0006) oriented sapphire substrate can be a (0006) oriented sapphire wafer, which has the advantages of high crystallinity, low price, and easy availability; or the (0006) facet of the sapphire can be used as the substrate. The diameter of the (0006) oriented sapphire substrate can be determined according to the actual situation, for example, 2 inches or 4 inches.

[0020] It should be noted that since the (0002) crystal plane of ε-Ga2O3 and the (0006) plane of sapphire are both atomic planes perpendicular to their own crystal c-axis, they have a parallel interplane relationship, namely (0002)ε-Ga2O3║(0006)Al2O3. Furthermore, the oxygen atoms in the (0002) crystal plane of ε-Ga2O3 and the (0006) plane of sapphire (both are oxygen atom termination planes, and sapphire is a trigonal crystal system equivalent to a hexagonal close-packed plane) follow hexagonal symmetry (D6h point group) and satisfy the quasi-matching of in-plane translational symmetry (low lattice mismatch, about 4.8%). They belong to the same point group and the same coordination number of oxygen atom layer symmetry alignment relationship. Thus, the (0006) sapphire wafer provides a key structural basis for the epitaxial growth of high-quality ε-Ga2O3.

[0021] Step (2) Using hydrogen chloride gas, gallium metal and oxygen as reaction sources and nitrogen as working carrier gas, an ε-Ga2O3 epitaxial film with (0002) orientation is grown on a sapphire substrate.

[0022] In step (2) above, the flow rate of hydrogen chloride gas is 5-20 sccm (that is, standard cubic centimeters per minute), the flow rate of oxygen is 100-250 sccm, the working pressure is 400-760 Torr, the growth temperature (that is, the temperature of the HVPE growth chamber, which is also the temperature of the sapphire substrate) is 430-600℃, the rotation speed of the sapphire substrate is (10-50) ±1 r / min, and the growth time is 60 min.

[0023] The hydrogen chloride gas and oxygen gas have a purity of 99.999%. The gallium metal has a purity of 7N. These settings ensure the growth of high-quality ε-Ga₂O₃ epitaxial films.

[0024] The flow rate of hydrogen chloride gas can be 5 sccm, 10 sccm, 20 sccm, etc., preferably 10 sccm. The flow rate of oxygen can be 100 sccm, 150 sccm, 200 sccm, 250 sccm, etc., preferably 150 sccm. The working pressure can be 400 Torr, 600 Torr, 760 Torr, etc., preferably 550 Torr. The growth temperature can be 430℃, 450℃, 475℃, 500℃, 550℃, 600℃, etc., preferably 475℃. The rotation speed of the sapphire substrate can be 10±1 r / min, 30±1 r / min, 50±1 r / min, etc., preferably 40±1 r / min.

[0025] It should be noted that the above steps utilize the HVPE method to grow ε-Ga₂O₃ epitaxial films. The first step involves the reaction of hydrogen chloride gas with metallic gallium to generate GaCl / GaCl₃. The operating pressure of the reaction chamber is 550 Torr, the flow rate of hydrogen chloride gas is 10 sccm, and the temperature of the reaction chamber is 650℃. The second step involves GaCl / GaCl₃ reacting with oxygen in the growth chamber to generate ε-Ga₂O₃. The operating pressure of the growth chamber is 550 Torr, the flow rate of oxygen is 150 sccm, the temperature of the growth chamber is 475℃, the substrate rotation speed is 40 ± 1 r / min, the deposition rate is 1 μm / h, and the growth time is 60 min.

[0026] The practical application of ε-Ga₂O₃ is limited by a core bottleneck in its growth technology: as a metastable crystalline phase, ε-Ga₂O₃ has a higher formation energy than the stable phase β-Ga₂O₃, making it prone to competitive nucleation during growth, leading to the formation of α-ε or ε-β miscible phases, severely compromising the crystal integrity and performance consistency of the epitaxial film. This invention improves the crystallinity of the ε-Ga₂O₃ epitaxial film by adjusting the aforementioned parameters, such as temperature and oxygen flow rate.

[0027] The ε-Ga2O3 epitaxial film has a thickness of 1 μm, a full width at half maximum (FWHM) of 0.45°, and a root mean square roughness of 1.8 nm, all of which are within the optimal parameters.

[0028] Step (3) The ε-Ga2O3 epitaxial film is annealed in situ under a nitrogen atmosphere.

[0029] In step (3) above, the annealing time is 10-20 min, and the pressure of the nitrogen atmosphere is 400-760 Torr. The above settings prevent excessive oxygen from causing some ε-Ga2O3 to be converted into α-Ga2O3, while allowing the stress between the ε-Ga2O3 lattice to be fully released, thereby improving the crystal quality of the ε-Ga2O3 epitaxial film.

[0030] The annealing time can be 10 min, 15 min, 20 min, etc., with 15 min being preferred. The pressure of the nitrogen atmosphere can be 400 Torr, 600 Torr, 760 Torr, etc., with 550 Torr being preferred.

[0031] The present invention has the following beneficial effects: 1. This invention removes inorganic contaminants, organic contaminants, moisture, and gas adsorption layers from the surface of a sapphire substrate to obtain a clean, flat, and uniform surface, providing favorable substrate conditions for growing high-quality ε-Ga2O3 epitaxial films.

[0032] 2. This invention grows a (0002) oriented ε-Ga2O3 epitaxial film on a (0006) oriented sapphire substrate, resulting in high lattice matching, high crystal quality, good density, and tight inter-lattice bonding, making it suitable for growing thicker epitaxial films. Furthermore, the (0006) oriented sapphire substrate has higher crystallinity, lower price, and is widely available in the market, reducing the cost of growing ε-Ga2O3 epitaxial films.

[0033] 3. This invention achieves the growth of ε-Ga2O3 epitaxial films using hydrogen chloride gas, gallium metal, and oxygen as reaction sources and the HVPE method. The process is simple, easy to operate, and highly controllable. The final ε-Ga2O3 epitaxial film has a smooth, dense, and uniform thickness, which can realize the mass production of ε-Ga2O3 epitaxial films without the need for secondary chemical mechanical polishing (CMP) to meet the requirements of device fabrication.

[0034] In particular, the present invention enables the obtained ε-Ga2O3 to have high purity, fast growth rate, and film thickness that can be grown from micrometers to tens of micrometers.

[0035] The following detailed description is provided with reference to specific embodiments: Example 1 A 2-inch diameter (0006) oriented sapphire wafer was sequentially soaked in acetone and anhydrous ethanol and sonicated for 15 minutes, then rinsed with running deionized water and finally dried with dry nitrogen gas. The sapphire wafer obtained in step (1) was then placed in the growth chamber of an HVPE apparatus. A reaction source of 99.999% pure hydrogen chloride gas, 99.999% pure oxygen gas, and 7N pure gallium metal was used, with nitrogen gas as the working carrier gas. The temperature of the reaction chamber was set to 650°C, and the working pressure was adjusted to 550 Torr. The sapphire wafer in the growth chamber was heated to 475°C. The working pressure of the growth chamber was stabilized at 550 Torr and maintained for 20 min. Then, oxygen was introduced at a flow rate of 150 sccm while maintaining the working pressure of the growth chamber at 550 Torr. After 1 min, hydrogen chloride gas was introduced at a flow rate of 10 sccm to grow an ε-Ga2O3 epitaxial film with (0002) orientation on the sapphire wafer. The sapphire wafer was rotated with the sample tray at a speed of 40 r / min for 60 min. Then, the introduction of hydrogen chloride and oxygen gas was stopped, and nitrogen gas was introduced and the pressure of the nitrogen atmosphere was maintained at 550 Torr. The annealing was carried out in situ under the nitrogen atmosphere for 15 min.

[0036] Example 2 The only difference from Example 1 is that in step (2), the sapphire wafer in the growth chamber is heated to 430°C.

[0037] Example 3 The only difference from Example 1 is that in step (2), the sapphire wafer in the growth chamber is heated to 450°C.

[0038] Example 4 The only difference from Example 1 is that in step (2), the sapphire wafer in the growth chamber is heated to 500°C.

[0039] Example 5 The only difference from Example 1 is that in step (2), the sapphire wafer in the growth chamber is heated to 550°C.

[0040] Example 6 The only difference from Example 1 is that in step (2), the sapphire wafer in the growth chamber is heated to 600°C.

[0041] Example 7 The only difference from Example 1 is that oxygen is introduced at a flow rate of 100 sccm in step (2).

[0042] Example 8 The only difference from Example 1 is that oxygen is introduced at a flow rate of 200 sccm in step (2).

[0043] Example 9 The only difference from Example 1 is that oxygen is introduced at a flow rate of 250 sccm in step (2).

[0044] Comparative Example 1 The only difference from Example 1 is that in step (1), the 2-inch diameter (0006) oriented sapphire wafer was soaked in acetone and anhydrous ethanol and sonicated for 15 minutes. Then, a mixed acid was prepared by mixing 98% H2SO4 and 30% H3PO4 in a volume ratio of 3:1. The temperature of the mixed acid was maintained at 80°C. The sapphire wafer was soaked in the mixed acid for 5 minutes and then rinsed with running deionized water.

[0045] Experimental Example 1 Reference Figure 1 , Figure 1 The XRD patterns of Ga2O3 epitaxial films grown on sapphire substrates with a (0006) orientation at different growth temperatures with an oxygen flow rate of 150 sccm are shown. It can be seen that at an oxygen flow rate of 150 sccm and a growth temperature of 430 to 450 °C, the epitaxial film is a mixed crystal of α-Ga2O3 and ε-Ga2O3. As the temperature increases, the diffraction peak intensity of the α-Ga2O3 (003) crystal plane decreases, while the diffraction peak intensity of the ε-Ga2O3 (0002) crystal plane significantly increases. When the growth temperature is 475 °C, the epitaxial film is a single ε-Ga2O3 crystal; and after the temperature rises to 500 °C, the epitaxial film is a mixed crystal of β-Ga2O3 and ε-Ga2O3. This indicates that at a growth temperature of 475 °C, the preferred orientation of the epitaxial film is the ε-Ga2O3 (0002) crystal plane.

[0046] Reference Figure 2 , Figure 2 The XRD patterns of Ga2O3 epitaxial films grown on a (0006) oriented sapphire substrate under different oxygen flow rates at a growth temperature of 475℃ are shown. It can be seen that when the growth temperature is 475℃ and the oxygen flow rate is 150 sccm, there are no other impurity peaks except for the two parallel plane diffraction peaks of ε-Ga2O3 (0002) and (0004). Moreover, the diffraction peaks are sharp, the peak intensity is high, and the background is low, indicating that the crystallinity of the epitaxial layer is very good. However, with the increase or decrease of oxygen content, the epitaxial film will become α-Ga2O3 or a mixed crystal of β-Ga2O3 and ε-Ga2O3.

[0047] Reference Figure 3 , 4 , Figure 3The image shows the XRD pattern of a Ga2O3 epitaxial film grown on a sapphire substrate without mixed acid immersion at an oxygen flow rate of 150 sccm and a growth temperature of 475 °C. Figure 4 The XRD pattern shows the Ga2O3 epitaxial film grown on a sapphire substrate soaked in mixed acid at an oxygen flow rate of 150 sccm and a growth temperature of 475℃. It can be seen that at an oxygen flow rate of 150 sccm and a growth temperature of 475℃, on the (0006) oriented sapphire substrate soaked in mixed acid, in addition to ε-Ga2O3 with the (0002) crystal plane orientation, α-Ga2O3 with the (006) crystal plane orientation also grew, indicating that the epitaxial film grown on this substrate is a mixed crystal of α-Ga2O3 and ε-Ga2O3. On the (0006) oriented sapphire substrate that was not soaked in mixed acid, only ε-Ga2O3 crystals grew. The diffraction peaks in the XRD pattern are (0002), (0004) and (0006) crystal planes, respectively. Moreover, the diffraction peaks are sharp, the peak intensity is high, and the background is low, indicating that the ε-Ga2O3 grown on this substrate is a pure phase crystal with good crystallinity.

[0048] Reference Figure 5 , Figure 5 The XRC and AFM images of the ε-Ga2O3 epitaxial film grown on a sapphire substrate at an oxygen flow rate of 150 sccm and a growth temperature of 475℃ are shown. It can be seen that at an oxygen flow rate of 150 sccm and a growth temperature of 475℃, the full width at half maximum (FWHM) of the (0002) peak of ε-Ga2O3 is the narrowest, at only 0.45°, and the surface roughness is only 1.8 nm. Therefore, the device fabrication requirements can be met without secondary chemical mechanical polishing.

[0049] Reference Figure 6 , Figure 6 The image shows an ellipsometry of an ε-Ga2O3 epitaxial film grown on a sapphire substrate at a working pressure of 550 Torr and a growth temperature of 475℃. It can be seen that the thickness of the epitaxial film is ~1 μm when the growth time is 60 min.

[0050] Combination Figure 1-5 The XRD, XRC, and AFM images of Ga2O3 grown on sapphire substrates with different oxygen flow rates, different growth temperatures, and whether or not they have been soaked in mixed acid show that, using the HVPE method, the ε-Ga2O3 grown on the (0006) oriented sapphire substrate has the highest crystal quality at an oxygen flow rate of 150 sccm and a growth temperature of 475℃. The full width at half maximum (FWHM) of the (0002) peak is only 0.45° and the surface roughness is only 1.8 nm.

[0051] In summary, the method of this invention can precisely control the phase formation process, suppress the generation of mixed phases, and is compatible with mainstream commercial substrates. It breaks through the bottlenecks of phase purity and crystal quality in existing processes, and is of great significance for promoting the practical application of ultra-wide bandgap semiconductor devices and filling related technological gaps.

[0052] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for growing an ε-Ga2O3 epitaxial film with a (0002) orientation, characterized in that, Includes the following steps: Inorganic contaminants, organic contaminants, moisture and gas adsorption layer on the surface of a (0006) oriented sapphire substrate are removed; then, using hydrogen chloride gas, gallium metal and oxygen as reaction sources and nitrogen as working carrier gas, an ε-Ga2O3 epitaxial film with a (0002) orientation is grown on the sapphire substrate. The ε-Ga2O3 epitaxial film was annealed in situ under a nitrogen atmosphere.

2. The growth method as described in claim 1, characterized in that, During the growth of a (0002) oriented ε-Ga2O3 epitaxial film on a (0006) oriented sapphire substrate, the flow rate of the hydrogen chloride gas is 5-20 sccm, the flow rate of the oxygen gas is 100-250 sccm, the working pressure is 400-760 Torr, the growth temperature is 430-600℃, the rotation speed of the sapphire substrate is (10-50) ±1 r / min, and the growth time is 60 min.

3. The growth method as described in claim 2, characterized in that, The flow rate of the hydrogen chloride gas is 10 sccm, the flow rate of the oxygen gas is 150 sccm, the working pressure is 550 Torr, the growth temperature is 475℃, and the rotation speed of the sapphire substrate is 40±1 r / min.

4. The growth method as described in claim 1, characterized in that, During the in-situ annealing of the ε-Ga2O3, the annealing time is 10-20 min, and the pressure of the nitrogen atmosphere is 400-760 Torr.

5. The growth method as described in claim 4, characterized in that, The annealing time is 15 minutes, and the pressure of the nitrogen atmosphere is 550 Torr.

6. The growth method as described in claim 1, characterized in that, In the process of removing inorganic contaminants, organic contaminants, moisture and gas adsorption layer from the surface of the (0006) oriented sapphire substrate, the sapphire substrate is cleaned and then dried with dry nitrogen gas.

7. The growth method as described in claim 6, characterized in that, During the cleaning process of the sapphire substrate, the sapphire substrate is immersed in acetone and anhydrous ethanol in sequence and sonicated for 15 minutes, and then rinsed with running deionized water.

8. The growth method as described in claim 1, characterized in that, The ε-Ga2O3 epitaxial film has a thickness of 1 μm, a full width at half maximum (FWHM) of 0.45°, and a root mean square roughness of 1.8 nm.

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