Epitaxial process for growing (-201)-oriented pure-phase beta-Ga2O3 thick film on sapphire substrate by using HVPE

Abstract

The invention discloses an epitaxial process for growing a (-201)-oriented pure-phase beta-Ga2O3 thick film on a sapphire substrate by using HVPE (High Voltage Polyethylene). The epitaxial process comprises the following steps: depositing a pure-phase beta-Ga2O3 buffer layer on the sapphire substrate by using a magnetron sputtering method; a (-201) oriented pure phase beta-Ga2O3 thick film is epitaxially grown on a sapphire substrate deposited with a pure phase beta-Ga2O3 buffer layer through an HVPE method. The pure-phase beta-Ga2O3 thick film is epitaxially grown by adopting the HVPE method, the process is simple, the operation is easy, the controllability is strong, the finally obtained (-201) oriented beta-Ga2O3 thick film is smooth and compact in surface and uniform in thickness, the large-batch and large-scale production of the (-201) oriented beta-Ga2O3 thick film can be realized, and the device preparation requirements are met.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor materials, and particularly to an epitaxial process for growing a (-201)-oriented pure-phase β-Ga 2 O 3 thick film on a sapphire substrate by HVPE. Background Art

[0002] β-Ga 2 O 3 is an oxide semiconductor. Existing reports show that its bandgap is 4.7 - 4.9 eV. Such a large bandgap makes it exhibit ultra-high transparency even in the ultraviolet region, and its conductive properties can be modulated by doping with Si, Fe, Mg, Al, etc. These excellent characteristics enable β-Ga 2 O 3 to be used as a conductive substrate for GaN-based LEDs, a solar-blind ultraviolet detector, or the preparation of high-voltage and high-power devices.

[0003] β-Ga 2 O 3 Compared with other wide-bandgap semiconductor materials (such as SiC, GaN, etc.), the greatest advantage of β-Ga 2 O 3 is that it can grow single crystals by melt methods such as the FZ method (floating zone method), CZ method (Czochralski method), and EFG method (edge-defined film-fed growth method). Currently, although 2-inch and 4-inch β-Ga 2 O 3 single crystal substrates grown by the EFG method are commercially available, due to the fact that the EFG method requires expensive crucibles and molds made of iridium, the production cost of large-size β-Ga 2 O 3 single crystal substrates has increased sharply. A good solution is to use inexpensive sapphire as the substrate to epitaxially grow β-Ga 2 O 3 single crystal thick films, and then obtain β-Ga 2 O 3 single crystal substrates through a peeling technique. However, due to the in-plane rotational symmetry problem in heteroepitaxial growth of β-Ga 2 O 3 single crystals on a sapphire substrate is extremely difficult.

[0004] Regardless of the device to be fabricated, epitaxial growth is an essential step. β-Ga 2 O 3The epitaxial growth techniques mainly include MBE, MOCVD, magnetron sputtering, PLD, HVPE, etc. Among them, except for HVPE, the growth rates of other epitaxial growth techniques are all ≤ 1 μm / h. Since the preparation of high-voltage devices requires the strong support of thick epitaxial films and considering the development needs of industrialization, the HVPE epitaxial growth technique becomes the first choice. HVPE (Halide Vapor Phase Epitaxy), whose full name is halide vapor phase epitaxy, is an epitaxial growth method using halides (GaCl) as the main raw materials. The HVPE method was first used by the RCA research group in the United States in 1966 to grow compound semiconductors such as GaAsxP1-x. In 1974, researchers such as Matsumoto in Japan used this method to react GaCl generated by the reaction of gallium (Ga) and hydrogen chloride (HCl) with oxygen to successfully generate β-Ga 2 O 3 。

[0005] It is very easy to epitaxially grow (-201)β-Ga on sapphire substrates using MBE, MOCVD [Patent No.: ZL202111423249.X] and magnetron sputtering method [Patent No.: ZL202111426791.0] 2 O 3 However, the growth rates of these three methods are all slow, and it is very difficult to achieve the thick film growth of β-Ga 2 O 3 Although the HVPE method can achieve the rapid growth of β-Ga 2 O 3 on sapphire substrates and form thick films, the β-Ga 2 O 3 formed by this method is polycrystalline containing two crystal orientations of (-201) and (310), which seriously affects the performance of β-Ga 2 O 3 -based devices. There are relevant reports suggesting that by cutting the sapphire at a certain angle, the growth of the (310) crystal orientation can be effectively suppressed. However, this method has extremely high processing requirements for sapphire substrates and has not completely solved the growth problem of (310)β-Ga 2 O 3 . Relatively speaking, the research on the rapid growth of pure-phase β-Ga 2 O 3 thick films on sapphire substrates is of great significance to this field. Summary of the Invention

[0006] The present invention provides a method for growing (-201)-oriented pure-phase β-Ga on a sapphire substrate using HVPE 2 O 3Thick film epitaxial process, capable of rapid epitaxial growth of pure phase β-Ga with (-201) orientation on sapphire substrate 2 O 3 Thick film.

[0007] The embodiment of the present invention provides a method for growing (-201) oriented pure phase β-Ga on a sapphire substrate using HVPE. 2 O 3 The thick film epitaxial process comprises the following steps: depositing pure phase β-Ga on a sapphire substrate by magnetron sputtering method 2 O 3 Buffer layer. In the deposition of pure phase β-Ga 2 O 3 On the sapphire substrate of the buffer layer, pure phase β-Ga with (-201) orientation was grown epitaxially by HVPE method. 2 O 3 Thick film.

[0008] Furthermore, in the case of the deposition of pure phase β-Ga 2 O 3 On the sapphire substrate of the buffer layer, pure phase β-Ga with (-201) orientation was grown epitaxially by HVPE method. 2 O 3 During the thick film process, hydrogen chloride gas, gallium metal and oxygen are used as reaction sources, the flow rate of hydrogen chloride gas is 5-20sccm, the flow rate of oxygen is 800-1200sccm, the working carrier gas is nitrogen, the working pressure is 400-760Torr, the growth temperature is 850-1100℃, and the rotation rate of the substrate is (10-50)±1r / min.

[0009] Furthermore, in the case of a pure phase β-Ga 2 O 3 On the sapphire substrate of the buffer layer, pure phase β-Ga with (-201) orientation was grown epitaxially by HVPE method. 2 O 3 During the thick film process, the flow rate of hydrogen chloride gas is 10 sccm, the flow rate of oxygen is 1000 sccm, the working carrier gas is nitrogen, the working pressure is 550 Torr, the growth temperature is 1000°C, and the rotation rate of the substrate is 20±1 r / min.

[0010] Furthermore, in the case of the deposition of pure phase β-Ga 2 O 3 On the sapphire substrate of the buffer layer, pure phase β-Ga with (-201) orientation was grown epitaxially by HVPE method. 2 O 3 During the thick film process, the pure phase β-Ga in the (-201) orientation 2 O 3The thickness of the thick film is 10 μm, and the roughness is 1.60 nm.

[0011] Further, on the sapphire substrate deposited with a pure-phase β-Ga 2 O 3 buffer layer, the (-201)-oriented pure-phase β-Ga 2 O 3 thick film is epitaxially grown by the HVPE method. After the epitaxial growth is completed, in-situ annealing is performed in an oxygen atmosphere for 10 - 20 min, and the pressure of the oxygen atmosphere is 400 - 760 Torr.

[0012] Further, on the sapphire substrate deposited with a pure-phase β-Ga 2 O 3 buffer layer, the (-201)-oriented pure-phase β-Ga 2 O 3 thick film is epitaxially grown by the HVPE method. After the epitaxial growth is completed, in-situ annealing is performed in an oxygen atmosphere for 15 min, and the pressure of the oxygen atmosphere is 550 Torr.

[0013] Further, during the deposition of the pure-phase β-Ga 2 O 3 buffer layer on the sapphire substrate by the magnetron sputtering method, the sapphire substrate is a (0006)-oriented sapphire wafer. The working pressure is 0.5 - 1.5 Pa, the substrate temperature is 500 - 800 °C, the sputtering power is 50 - 150 W, the distance between the target and the substrate is (5 - 10) ± 2 cm. The rotation rate of the substrate is (5 - 15) ± 1 r / min, and the growth time is 10 - 60 min.

[0014] Further, during the deposition of the pure-phase β-Ga 2 O 3 buffer layer on the sapphire substrate by the magnetron sputtering method, the working pressure is 1.0 Pa, the substrate temperature is 675 °C, the sputtering power is 100 W, the distance between the target and the substrate is 7 ± 2 cm. The rotation rate of the substrate is 10 r ± 1 r / min, and the growth time is 30 min.

[0015] Further, during the deposition of the pure-phase β-Ga 2 O 3 buffer layer on the sapphire substrate by the magnetron sputtering method, after sputtering, in-situ annealing is performed in an oxygen atmosphere for 10 - 30 min, and the pressure of the oxygen atmosphere is 0.5 - 1.5 Pa.

[0016] Further, during the deposition of the pure-phase β-Ga 2 O 3During the process of the buffer layer, after sputtering, in-situ annealing is carried out in an oxygen atmosphere for 15 minutes, and the pressure of the oxygen atmosphere is 1.0 Pa.

[0017] The present invention has the following beneficial effects:

[0018] 1. In the present invention, a sapphire wafer with a (0006) orientation, which has a higher crystallinity, a lower price, and is generally commercially available, is used as a substrate. First, a β-Ga 2 O 3 buffer layer is epitaxially grown on the sapphire substrate by magnetron sputtering, and then by controlling the temperature and gas flow rate of the HVPE growth chamber, a (-201)-oriented β-Ga 2 O 3 thick film is rapidly grown on the above substrate.

[0019] 2. In the present invention, a uniformly distributed (-201)-oriented pure-phase β-Ga 2 O 3 thick film can be grown on a sapphire substrate with a (0006) orientation. The lattice matching degree is high, the quality of the crystal is high, the compactness is good, and the binding between the lattices is tight, which is suitable for the growth of thicker epitaxial film layers.

[0020] 3. In the present invention, the HVPE method is used to epitaxially grow a pure-phase β-Ga 2 O 3 thick film. The process is simple, easy to operate, and has strong controllability. The finally obtained (-201)-oriented β-Ga 2 O 3 thick film has a smooth, dense, and uniform thickness surface, and large-scale and mass production of the (-201)-oriented β-Ga 2 O 3 thick film can be realized to meet the device preparation requirements. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 is the XRD pattern of the β-Ga 2 O 3 buffer layer grown on a sapphire substrate with a (0006) orientation in the present invention;

[0022] Figure 2 is the AFM image of the β-Ga 2 O 3 buffer layer grown on a sapphire substrate with a (0006) orientation in the present invention;

[0023] Figure 3 is the XRD pattern of β-Ga 2 O 3 grown on the crystal surface of a sapphire substrate without a buffer layer under different pressure conditions at a growth temperature of 1000 °C in the present invention;

[0024] Figure 4 This is the AFM image of β-Ga 2 O 3 grown on the sapphire substrate surface without a buffer layer under different pressure conditions at a growth temperature of 1000 °C in the present invention;

[0025] Figure 5 This is the XRD image of the β-Ga 2 O 3 epitaxial layer grown on the (0006)-oriented sapphire substrate with or without a β-Ga 2 O 3 buffer layer at a growth temperature of 1000 °C and a pressure of 550 Torr in the present invention;

[0026] Figure 6 This is the XRC image of the β-Ga 2 O 3 epitaxial layer grown on the (0006)-oriented sapphire substrate with or without a β-Ga 2 O 3 buffer layer at a growth temperature of 1000 °C and a pressure of 550 Torr in the present invention;

[0027] Figure 7 This is the XRD image of β-Ga 2 O 3 grown on the sapphire substrate surface with a buffer layer under different growth temperature conditions at a pressure of 550 Torr in the present invention;

[0028] Figure 8 This is the XRC image of the (-201) peak of β-Ga 2 O 3 grown on the sapphire substrate surface with a buffer layer under different growth temperature conditions at a pressure of 550 Torr in the present invention;

[0029] Figure 9 This is the AFM image of β-Ga 2 O 3 grown on the sapphire substrate surface with a buffer layer under different growth temperature conditions at a pressure of 550 Torr in the present invention;

[0030] Figure 10 This is the ellipsometry image of β-Ga 2 O 3 grown on the sapphire substrate surface with a buffer layer at a pressure of 550 Torr and a growth temperature of 1000 °C in the present invention. Detailed implementation manners

[0031] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0032] In the technology of growing β-Ga 2 O 3 on a sapphire substrate with (0006) orientation by the HVPE method, due to the fact that the arrangement of oxygen atoms in the (-201) crystal plane of β-Ga 2 O 3 and the oxygen atoms in the (0006) plane of sapphire both have a six-fold rotational symmetry structure, and the arrangement of oxygen atoms in the (310) crystal plane of β-Ga 2 O 3 and the oxygen atoms in the (0006) plane of sapphire can simultaneously form a triangular symmetry, it is easy to generate a mixed crystal with (310) and (-201) crystal orientations on the (0006)-oriented sapphire substrate. Although there is research on bevel-cutting the (0006) sapphire substrate and suppressing the growth of β-Ga 2 O 3 with (310) orientation to a certain extent, due to the difficulties in processing the bevel-cut sapphire substrate and the problem of special requirements, this research fails to completely obtain the film layer of β-Ga 2 O 3 with (-201) orientation. On this basis, in order to obtain β-Ga 2 O 3 with (-201) orientation, especially a pure-phase β-Ga 2 O 3 thick film on a (0006)-oriented sapphire substrate, the present invention conducts research and exploration. The embodiments of the present invention provide an epitaxial process for growing a pure-phase β-Ga 2 O 3 thick film with (-201) orientation on a sapphire substrate by HVPE, including the following steps:

[0033] (1) Depositing a pure-phase β-Ga 2 O 3 buffer layer on the sapphire substrate by magnetron sputtering.

[0034] In the above steps, the sapphire substrate is a sapphire wafer with a (0006) orientation, or in other words, the (0006) plane of sapphire is used as the substrate. The working pressure is 0.5 - 1.5 Pa, such as 0.5, 1, 1.5 Pa. The substrate temperature is 500 - 800 °C, such as 500, 600, 800 °C. Preferably, the substrate temperature is 650 - 800 °C, such as 650, 700, 800 °C. The sputtering power is 50 - 150 W, such as 50, 100, 150 W. The distance between the target and the substrate is (5 - 10) ± 2 cm, such as 5, 8, 10 cm. The rotation rate of the substrate is (5 - 15) ± 1 r / min, such as 5, 10, 15 r / min. The growth time is 10 - 60 min, such as 10, 40, 60 min. Optionally, the working pressure is 1.0 Pa. The substrate temperature is 675 °C. The sputtering power is 100 W. The distance between the target and the substrate is 7 ± 2 cm. The rotation rate of the substrate is 10 r ± 1 r / min. The growth time is 30 min. Under the above conditions, pure phase β-Ga 2 O 3 The thickness of the buffer layer is 150 nm. Pure phase β-Ga 2 O 3 The roughness of the buffer layer is 3.25 nm. Pure phase β-Ga 2 O 3 The buffer layer is in the (-201) orientation.

[0035] After sputtering, in-situ annealing is carried out in an oxygen atmosphere for 10 - 30 min, such as 10, 20, 30 min. The pressure of the oxygen atmosphere is 0.5 - 1.5 Pa, such as 0.5, 1, 1.5 Pa. Optionally, after sputtering, in-situ annealing is carried out in an oxygen atmosphere for 15 min. The pressure of the oxygen atmosphere is 1.0 Pa.

[0036] By using the magnetron sputtering method with the above parameters, the growth of a pure phase β-Ga 2 O 3 buffer layer on the sapphire substrate is achieved. The presence or absence of the buffer layer directly affects the growth of the (-201) orientation pure phase β-Ga 2 O 3 thick film in the subsequent HVPE method.

[0037] (2) On the sapphire substrate deposited with a pure phase β-Ga 2 O 3 buffer layer, a (-201) orientation pure phase β-Ga 2 O 3 thick film is epitaxially grown by the HVPE method.

[0038] In the above steps, hydrogen chloride gas, gallium metal, and oxygen are used as reaction sources. The flow rate of hydrogen chloride gas is 5 - 20 sccm, such as 5, 10, 20 sccm. The flow rate of oxygen is 800 - 1200 sccm, such as 800, 1000, 1200 sccm. The working carrier gas is nitrogen. The working pressure is 400 - 760 Torr, such as 400, 600, 760 Torr. The growth temperature (i.e., the growth chamber temperature of HVPE) is 850 - 1100 °C, such as 850, 1000, 1100 °C. The rotation rate of the substrate is (10 - 50) ± 1 r / min, such as 10, 30, 50 r / min. Optionally, the flow rate of hydrogen chloride gas is 10 sccm. The flow rate of oxygen is 1000 sccm. The working carrier gas is nitrogen. The working pressure is 550 Torr. The growth temperature is 1000 °C. The rotation rate of the substrate is 20 ± 1 r / min. The deposition rate is 10 μm / h, and the growth time is 60 min. Specifically, a (-201)-oriented pure-phase β-Ga 2 O 3 thick film is epitaxially grown by the HVPE method. In the first step of the process, hydrogen chloride gas reacts with metallic gallium to generate GaCl / GaCl 3 . Among them, the working pressure of the reaction chamber is 550 Torr, the flow rate of hydrogen chloride gas introduced is 10 sccm, and the temperature of the reaction chamber is 850 °C. In the second step, GaCl / GaCl 3 and oxygen enter the growth chamber and react to form β-Ga 2 O 3 . Among them, the working pressure of the growth chamber is 550 Torr, the flow rate of oxygen introduced is 1000 sccm, the temperature of the growth chamber is 1000 °C, the rotation rate of the substrate is 20 ± 1 r / min, the deposition rate is 10 μm / h, and the growth time is 60 min. Under the above conditions, a (-201)-oriented pure-phase β-Ga 2 O 3 thick film is epitaxially grown on a sapphire substrate. The thickness of the (-201)-oriented pure-phase β-Ga 2 O 3 thick film is 10 μm, and the roughness is 1.60 nm, both of which are in relatively good parameters. In addition, by adjusting the pressure and temperature, it is found that both the pressure and temperature have a crucial impact on the crystallization quality of the β-Ga 2 O 3 epitaxial film. Optionally, the working pressure is 550 Torr. The growth temperature is 1000 °C.

[0039] After the epitaxial growth is completed, in-situ annealing is carried out in an oxygen atmosphere for 10 - 20 min, such as 10, 15, 20 min. The pressure of the oxygen atmosphere is 400 - 760 Torr, such as 400, 600, 760 Torr. Optionally, after the epitaxial growth is completed, in-situ annealing is carried out in an oxygen atmosphere for 15 min, and the pressure of the oxygen atmosphere is 550 Torr. In-situ annealing is carried out after the growth to fully react the residual GaCl in the growth chamber and fully oxidize the β-Ga 2 O 3 on the sapphire substrate, so as to improve the crystal quality of the obtained β-Ga 2 O 3 . Under the above conditions, a high-quality (-201)-oriented pure-phase β-Ga 2 O 3 thick film is epitaxially grown on the sapphire substrate.

[0040] By using the HVPE method with the above parameters, a uniformly distributed (-201)-oriented pure-phase β-Ga 2 O 3 thick film can be obtained. The process is simple, easy to operate, highly controllable, the sapphire does not need to be obliquely cut, and the obtained β-Ga 2 O 3 film has a smooth, dense surface and a relatively thick thickness, and the deposition rate is very fast.

[0041] By using the above epitaxial process, a high-quality (-201)-oriented pure-phase β-Ga 2 O 3 thick film can be grown on a (0006)-oriented sapphire substrate. The lattice matching degree is high, the crystal quality is high, the compactness is good, and the binding between lattices is tight, which is suitable for the growth of relatively thick epitaxial film layers. Finally, under the condition of using a (0006)-oriented sapphire with higher crystallinity and lower price as the substrate, the epitaxial growth of a (-201)-oriented pure-phase β-Ga 2 O 3 thick film is realized, and the obtained β-Ga 2 O 3 thick film has a high degree of purity, a fast growth rate, and the thickness of the film can be grown from the micron level to the tens of micron level.

[0042] The following is a detailed description in combination with specific embodiments:

[0043] Example 1

[0044] (1) Deposit pure-phase β-Ga 2 O 3Buffer layer. Among them, the sapphire substrate is a sapphire wafer with (0006) orientation, the working pressure is 1.0 Pa, the substrate temperature is 675 °C, the sputtering power is 100 W, the distance between the target and the substrate is 7 ± 2 cm, the rotation rate of the substrate is 10 r ± 1 r / min, the growth time is 30 min, and after sputtering, in-situ annealing is carried out in an oxygen atmosphere for 15 min, and the pressure of the oxygen atmosphere is 1.0 Pa.

[0045] (2) On the sapphire substrate deposited with the pure-phase β-Ga 2 O 3 buffer layer, epitaxially grow a pure-phase β-Ga 2 O 3 thick film with (-201) orientation by the HVPE method. Specifically, take a sapphire substrate with a size of 2 inches deposited with the pure-phase β-Ga 2 O 3 buffer layer and put it into the growth chamber of the HVPE equipment. Using hydrogen chloride gas with a purity of 99.999%, oxygen, and 7N gallium metal as reaction sources, rapidly grow β-Ga 2 O 3 on the sapphire substrate. Among them, stabilize the pressure of the growth chamber to the preset pressure of 550 Torr. After the sapphire substrate is heated to the preset temperature of 1000 °C and stabilized for 20 min; then introduce oxygen with a flow rate of 1000 sccm, and at the same time keep the pressure of the growth chamber at the preset pressure of 550 Torr; after 1 min, introduce hydrogen chloride gas with a flow rate of 10 sccm, and start to grow β-Ga 2 O 3 on the sapphire substrate. The substrate maintains a rotation rate of 20 r / min during the growth process, and the growth time is 60 min; then close the hydrogen chloride gas and continue to introduce oxygen, and the pressure still remains at the preset pressure of 550 Torr, and perform in-situ annealing on the grown Ga 2 O 3 for 15 min.

[0046] Example 2

[0047] The difference from Example 1 is only that in step (2), the preset pressure is 400 Torr.

[0048] Example 3

[0049] The difference from Example 1 is only that in step (2), the preset pressure is 500 Torr.

[0050] Example 4

[0051] The difference from Example 1 is only that in step (2), the preset pressure is 600 Torr.

[0052] Example 5

[0053] It is only different from Example 1 in that the preset pressure in step (2) is 700 Torr.

[0054] Example 6

[0055] It is only different from Example 1 in that the preset temperature in step (2) is 900 °C.

[0056] Example 7

[0057] It is only different from Example 1 in that the preset temperature in step (2) is 950 °C.

[0058] Example 8

[0059] It is only different from Example 1 in that the preset temperature in step (2) is 1050 °C.

[0060] Comparative Example 1

[0061] It is only different from Example 1 in that step (1) is omitted, and a sapphire substrate without a deposited pure-phase β-Ga 2 O 3 buffer layer is used, that is, a sapphire wafer with an (0006) orientation is used.

[0062] Comparative Example 2

[0063] It is only different from Comparative Example 1 in that the preset pressure in step (2) is 400 Torr.

[0064] Comparative Example 3

[0065] It is only different from Comparative Example 1 in that the preset pressure in step (2) is 500 Torr.

[0066] Comparative Example 4

[0067] It is only different from Comparative Example 1 in that the preset pressure in step (2) is 600 Torr.

[0068] Comparative Example 5

[0069] It is only different from Comparative Example 1 in that the preset pressure in step (2) is 700 Torr.

[0070] Test Example

[0071] Refer to Figure 1-2 , Figure 1-2 β-Ga grown on a sapphire substrate with an (0006) orientation 2 O 3XRD and AFM diagrams of the buffer layer show that β-Ga grown on a sapphire substrate with (0006) orientation by magnetron sputtering method 2 O 3 The buffer layer has a crystal orientation of (-201), and the average roughness of the buffer layer is 3.25 nm.

[0072] Refer to Figure 3-4 , Figure 3-4 XRD and AFM diagrams of β-Ga 2 O 3 grown on the crystal plane of a sapphire substrate without a buffer layer under different pressure conditions at a growth temperature of 1000 °C show that when the pressure is 550 Torr, there are no other impurity peaks except for β-Ga 2 O 3 with crystal orientations of (-201) and (310), and the epitaxial layer has the best crystallinity, no obvious defect pits, and the surface roughness of the mixed-orientation crystal is only 0.31 nm.

[0073] Refer to Figure 5-6 , Figure 5-6 XRD and XRC diagrams of the β-Ga 2 O 3 epitaxial layer grown on a (0006)-oriented sapphire substrate with and without a β-Ga 2 O 3 buffer layer at a growth temperature of 1000 °C and a pressure of 550 Torr show that when grown on a (0006)-oriented sapphire substrate without a β-Ga 2 O 3 buffer layer, β-Ga 2 O 3 with crystal orientations of (-201) and (310) grows, indicating that the β-Ga 2 O 3 grown on this substrate has a mixed crystal orientation, and there are two shoulder peaks in the XRC diagram of the (-201) diffraction peak; while on the sapphire substrate with a β-Ga 2 O 3 buffer layer, only β-Ga 2 O 3 with a crystal orientation of (-201) grows, indicating that the β-Ga 2 O 3 grown on this substrate is a pure-phase crystal with good crystallinity, and the full width at half maximum of the (-201) diffraction peak is 0.97°.

[0074] Refer to Figure 7 , Figure 7For the XRD pattern of β-Ga 2 O 3 grown on the sapphire substrate with a buffer layer at different growth temperatures under a pressure of 550 Torr, it can be seen that in the growth temperature range of 900 - 1050 °C on the sapphire substrate with a buffer layer, there are exactly three diffraction peaks of (-201), (-402), and (-603) in the (-201) crystal orientation of β-Ga 2 O 3 . And as the temperature increases, the intensity of the diffraction peaks increases, indicating that all the epitaxial layers on this substrate surface are β-Ga 2 O 3 grown epitaxially along the (-201) crystal orientation.

[0075] Refer to Figure 8 , Figure 8 For the XRC pattern of the (-201) peak of β-Ga 2 O 3 grown on the sapphire substrate with a buffer layer at different growth temperatures under a pressure of 550 Torr. It can be seen that when the growth temperature is 1000 °C, the full width at half maximum of the (-201) peak is the narrowest, only 0.97°.

[0076] Refer to Figure 9 , Figure 9 For the AFM image of β-Ga 2 O 3 grown on the sapphire substrate with a buffer layer at different growth temperatures under a pressure of 550 Torr. It can be seen that when the growth temperature is 1000 °C, the surface roughness of the pure-phase β-Ga 2 O 3 in the (-201) orientation is the smallest, only 1.60 nm.

[0077] Refer to Figure 10 , Figure 10 For the ellipsometry image of β-Ga 2 O 3 grown on the sapphire substrate with a buffer layer at a pressure of 550 Torr and a growth temperature of 1000 °C. It can be seen that under this growth condition, when the growth time is 60 min, the thickness of the epitaxial layer is ~10 μm.

[0078] Combined with Figure 3-9 the XRD patterns, XRC patterns, and AFM images of β-Ga 2 O 3 grown on sapphire substrates with different pressures, different growth temperatures, and with or without a buffer layer in 2 O 3On the (0006)-oriented sapphire substrate of the buffer layer, when the growth temperature is 1000 °C, epitaxial growth of β-Ga 2 O 3 The thick film has the highest crystallization quality, the full width at half maximum of the (-201) peak is only 0.97°, and the surface roughness is only 1.60 nm.

[0079] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. An epitaxial process for growing a (-201) oriented pure phase β-Ga2O3 thick film on a sapphire substrate using HVPE, characterized in that: The following steps are involved: A pure phase β-Ga2O3 buffer layer was deposited on a sapphire substrate by magnetron sputtering; On the sapphire substrate on which the pure phase β-Ga2O3 buffer layer is deposited, a pure phase β-Ga2O3 thick film with a (-201) orientation is epitaxially grown by the HVPE method.

2. The epitaxial process according to claim 1, characterized in that: In the process of epitaxially growing a (-201) oriented pure phase β-Ga2O3 thick film on a sapphire substrate deposited with the pure phase β-Ga2O3 buffer layer by the HVPE method, hydrogen chloride gas, gallium metal and oxygen are used as reaction sources, the flow rate of the hydrogen chloride gas is 5-20sccm, the flow rate of the oxygen is 800-1200sccm, the working carrier gas is nitrogen, the working pressure is 400-760Torr, the growth temperature is 850-1100℃, and the rotation rate of the substrate is (10-50)±1r / min.

3. The epitaxial process according to claim 2, characterized in that: In the process of epitaxially growing a (-201) oriented pure phase β-Ga2O3 thick film on a sapphire substrate deposited with the pure phase β-Ga2O3 buffer layer by the HVPE method, the flow rate of the hydrogen chloride gas is 10sccm, the flow rate of the oxygen is 1000sccm, the working carrier gas is nitrogen, the working pressure is 550Torr, the growth temperature is 1000℃, and the rotation rate of the substrate is 20±1r / min.

4. The epitaxial process according to claim 3, characterized in that: In the process of epitaxially growing a (-201) oriented pure phase β-Ga2O3 thick film on a sapphire substrate with the pure phase β-Ga2O3 buffer layer deposited thereon by the HVPE method, the thickness of the (-201) oriented pure phase β-Ga2O3 thick film was 10 μm and the roughness was 1.60 nm.

5. The epitaxial process according to claim 1, characterized in that: In the process of epitaxially growing a (-201) oriented pure phase β-Ga2O3 thick film on a sapphire substrate deposited with the pure phase β-Ga2O3 buffer layer by the HVPE method, after the epitaxial growth is completed, in-situ annealing is performed in an oxygen atmosphere for 10-20 minutes, and the pressure of the oxygen atmosphere is 400-760Torr.

6. The epitaxial process according to claim 5, characterized in that: In the process of epitaxially growing a (-201) oriented pure phase β-Ga2O3 thick film on a sapphire substrate deposited with the pure phase β-Ga2O3 buffer layer by the HVPE method, after the epitaxial growth is completed, in-situ annealing is performed in an oxygen atmosphere for 15 minutes, and the pressure of the oxygen atmosphere is 550 Torr.

7. The epitaxial process according to claim 1, characterized in that: In the process of depositing a pure phase β-Ga2O3 buffer layer on a sapphire substrate by a magnetron sputtering method, the sapphire substrate is a (0006) oriented sapphire wafer; the working pressure is 0.5-1.5 Pa, the substrate temperature is 500-800°C, the sputtering power is 50-150 W, the distance between the target and the substrate is (5-10) ±2 cm; the rotation rate of the substrate is (5-15) ±1 r / min, and the growth time is 10-60 min.

8. The epitaxial process according to claim 7, characterized in that: In the process of depositing a pure phase β-Ga2O3 buffer layer on a sapphire substrate by magnetron sputtering, the working pressure was 1.0 Pa, the substrate temperature was 675°C, the sputtering power was 100 W, the distance between the target and the substrate was 7±2 cm; the rotation rate of the substrate was 10r±1r / min, and the growth time was 30 min.

9. The epitaxial process according to claim 1, characterized in that: In the process of depositing a pure phase β-Ga2O3 buffer layer on a sapphire substrate by a magnetron sputtering method, after the sputtering is completed, in-situ annealing is performed in an oxygen atmosphere for 10-30 minutes, and the pressure of the oxygen atmosphere is 0.5-1.5Pa.

10. The epitaxial process according to claim 9, characterized in that: In the process of depositing a pure phase β-Ga2O3 buffer layer on a sapphire substrate by a magnetron sputtering method, after the sputtering is completed, in-situ annealing is performed in an oxygen atmosphere for 15 minutes, and the pressure of the oxygen atmosphere is 1.0Pa.

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