Method for growing (310) oriented beta-Ga2O3 single crystal thick film on sapphire substrate

Abstract

The invention provides a method for growing a (310) oriented beta-Ga2O3 single crystal thick film on a sapphire substrate. The method comprises the following steps: cleaning the sapphire substrate and then carrying out annealing treatment; and with hydrogen chloride gas, gallium metal and oxygen as reaction sources, epitaxially growing a (310) oriented beta-Ga2O3 single crystal thick film on the treated sapphire substrate by using a hydride vapor phase epitaxy method. According to the method for growing the (310) oriented beta-Ga2O3 single crystal thick film on the sapphire substrate, the process is simple, operation is easy, controllability is high, the obtained (310) oriented beta-Ga2O3 single crystal thick film is smooth in surface, compact and uniform in thickness, the crystallinity of the single crystal film layer is high, and the growth requirement of a single crystal epitaxial film layer of tens of micrometers can be met; in addition, the method provided by the invention can realize large-batch and large-scale production of the (310) oriented beta-Ga2O3 single crystal thick film, and meets the device preparation requirements.

Description

Technical Field

[0001] The present invention relates to the technical field of semiconductor materials, and in particular to a method for growing a (310)-oriented β-Ga2O3 single crystal thick film on a sapphire substrate. Background Art

[0002] Gallium oxide (Ga2O3) is a fourth-generation direct-bandgap, ultra-wide-bandgap oxide semiconductor material that has attracted widespread attention for its use in low-power power devices. Traditional power devices are made of silicon, but suffer from significant power losses during power control. To reduce these losses, various organizations are developing power devices made of SiC and GaN. Ga2O3 is a strong alternative to SiC and GaN, with a Baliga figure of merit (a measure of power loss) of 3444, ten times that of SiC, the third-generation semiconductor material currently used in high-power devices. Therefore, power devices based on fourth-generation semiconductor materials offer advantages such as smaller size, lower energy consumption, and higher power.

[0003] To date, Si, GaN, SiC, and α-Al2O3 have all been used as substrates for epitaxial growth of Ga2O3 films, but the lattice mismatch between them has prevented the formation of high-quality Ga2O3 films. Currently, the main methods for growing Ga2O3 films include metal organic vapor deposition, sol-gel, spray pyrolysis, magnetron sputtering, and molecular beam epitaxy. In related studies, the vast majority of Ga2O3 films are polycrystalline or grown in mixed crystal orientations. At the same time, the lattice mismatch between Ga2O3 and the substrate hinders the epitaxial growth of high-quality Ga2O3 films, which in turn greatly affects the performance of thin-film-based devices. High-quality epitaxial films are key to device performance.

[0004] While all of the aforementioned epitaxial growth techniques can produce high-quality gallium oxide films, their growth rates are slow, typically ≤1μm / h, making them suitable only for growing nanoscale Ga2O3 films for MOS devices. However, the epitaxial thickness required for producing gallium oxide-based high-voltage SBDs must reach several microns, making these techniques insufficient. Given the rapid growth of thick gallium oxide epitaxial films and the need for industrial development, halide vapor phase epitaxy (HVPE) has become an excellent alternative.

[0005] Halide vapor phase epitaxy (HVPE), a rapid method for growing thick films, has successfully demonstrated the growth of β-Ga2O3 on sapphire substrates. However, β-Ga2O3 grown by HVPE typically contains multiple orientations (particularly the coexistence of -201 and 310), which limits its application in high-performance devices. In particular, reports on (310)-oriented β-Ga2O3 single crystal thick films are limited, and the high cost of commercially available 2-inch and 4-inch β-Ga2O3 single crystal substrates further hinders their widespread application. Summary of the Invention

[0006] In view of this, the present invention proposes a method for growing a (310) oriented β-Ga2O3 single crystal thick film on a sapphire substrate, aiming to solve the above technical problems existing in the prior art.

[0007] The present invention provides a method for growing a (310)-oriented β-Ga2O3 single crystal thick film on a sapphire substrate, comprising the following steps:

[0008] Step 1: cleaning the sapphire substrate and then annealing it;

[0009] Step 2: Using hydrogen chloride gas, gallium metal and oxygen as reaction sources, epitaxially grow (310) oriented β-Ga2O3 single crystal thick film on the sapphire substrate processed in step 1 by using hydride vapor phase epitaxy method.

[0010] Furthermore, in the above method of growing a (310) oriented β-Ga2O3 single crystal thick film on a sapphire substrate, the sapphire substrate is a (0006) oriented sapphire wafer.

[0011] Furthermore, in the above-mentioned method for growing a (310)-oriented β-Ga2O3 single crystal thick film on a sapphire substrate, in step 1, H2SO4 with a mass concentration of 98% and H3PO4 with a mass concentration of 30% are mixed in a volume ratio of 3:1 to obtain an acid solution, and the sapphire substrate is immersed in the acid solution at 70-90°C. After the immersion is completed, it is rinsed with deionized water and then dried.

[0012] Furthermore, in the above-mentioned method of growing a (310)-oriented β-Ga2O3 single crystal thick film on a sapphire substrate, in step 1, when the sapphire substrate is annealed, the annealing atmosphere is nitrogen or oxygen, the working pressure is 500-700 Torr, the annealing temperature is 900-1100°C, and the annealing time is 60-180 min.

[0013] Furthermore, in the above-mentioned method of growing a (310)-oriented β-Ga2O3 single crystal thick film on a sapphire substrate, in step 1, when the sapphire substrate is annealed, the annealing atmosphere is nitrogen, the working pressure is 700 Torr, the annealing temperature is 1000°C, and the annealing time is 60 minutes.

[0014] Furthermore, in the above-mentioned method for growing a (310)-oriented β-Ga2O3 single crystal thick film on a sapphire substrate, in step 2, the flow rate of the hydrogen chloride gas is 5-20 sccm, the flow rate of the oxygen is 800-1200 sccm, the working carrier gas is nitrogen, the working pressure is 400-600 Torr, the reaction temperature of the hydrogen chloride gas and gallium metal is 800-900°C, the growth temperature of the β-Ga2O3 single crystal thick film is 1000-1200°C, and the rotation rate of the sapphire substrate is 10-50 r / min.

[0015] Furthermore, in the above-mentioned method for growing a (310)-oriented β-Ga2O3 single crystal thick film on a sapphire substrate, the flow rate of the hydrogen chloride gas is 10 sccm, the flow rate of the oxygen is 1000 sccm, the working carrier gas is nitrogen, the working pressure is 500 Torr, the reaction temperature of the hydrogen chloride gas and gallium metal is 850°C, the growth temperature of the β-Ga2O3 single crystal thick film is 1150°C, and the rotation rate of the sapphire substrate is 20 r / min.

[0016] Furthermore, in the above-mentioned method of growing a (310)-oriented β-Ga2O3 single crystal thick film on a sapphire substrate, the (310)-oriented β-Ga2O3 single crystal thick film obtained in step 2 has a thickness of 8.2 μm, a half-height width of 0.160°, and a roughness of 0.08 nm.

[0017] Furthermore, in the above method of growing a (310) oriented β-Ga2O3 single crystal thick film on a sapphire substrate, in step 2, after the epitaxial growth is completed, in-situ annealing is performed in a nitrogen atmosphere for 10-20 minutes, and the pressure of the nitrogen atmosphere is 400-600 Torr.

[0018] Furthermore, in the above method of growing a (310) oriented β-Ga2O3 single crystal thick film on a sapphire substrate, in step 2, after the epitaxial growth is completed, in-situ annealing is performed in a nitrogen atmosphere for 15 minutes, and the pressure of the nitrogen atmosphere is 500 Torr.

[0019] In the present invention, a method for growing a (310) oriented β-Ga2O3 single crystal thick film on a sapphire substrate comprises the following steps: cleaning the sapphire substrate to remove impurities and complexes on the surface of the sapphire substrate, while improving the surface roughness and flatness; further annealing the substrate to destroy the hexagonal symmetry of oxygen atoms within the sapphire substrate plane, thereby providing favorable substrate conditions for growing the (310) oriented β-Ga2O3 single crystal thick film; adopting the HVPE method, using hydrogen chloride gas, gallium metal and oxygen as reaction sources, growing the (310) oriented β-Ga2O3 single crystal thick film on the above substrate; the method is simple in process, easy to operate and highly controllable; the surface of the finally obtained (310) oriented β-Ga2O3 single crystal thick film is smooth, dense and uniform in thickness; the single crystal film layer has high crystallinity and can meet the growth requirements of tens of microns of single crystal epitaxial film layers; in addition, the method of the present invention can realize large-scale and large-scale production of (310) oriented β-Ga2O3 single crystal thick films, thereby meeting the requirements of device preparation. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Various other advantages and benefits will become apparent to those skilled in the art upon reading the detailed description of the preferred embodiment below. The accompanying drawings are for illustration purposes only and are not to be considered as limiting the present invention. The same reference symbols are used throughout the drawings to represent the same components. In the drawings:

[0021] Figure 1 The XRD patterns of the (0006) sapphire substrates of the present invention are those without pickling, pickling, and pickling followed by annealing.

[0022] Figure 2 The XRD patterns of the β-Ga2O3 epitaxial films grown on un-acid-washed and acid-washed sapphire substrates at a growth temperature of 1150° C. are shown in the figure.

[0023] Figure 3 The XRD patterns of the β-Ga2O3 epitaxial films grown on the acid-washed sapphire substrate under different growth temperature conditions in the present invention are shown;

[0024] Figure 4 XRD patterns of β-Ga2O3 epitaxial films grown under different growth temperature conditions on a sapphire substrate that has been acid-washed and annealed at 900°C in a nitrogen atmosphere for 60 min in the present invention;

[0025] Figure 5 is an XRD pattern of a β-Ga2O3 epitaxial film grown at a growth temperature of 1150°C on a sapphire substrate that has been acid-washed and annealed at 1000°C in a nitrogen atmosphere and an oxygen atmosphere, respectively;

[0026] Figure 6 is an XRD pattern of a β-Ga2O3 epitaxial film grown on a sapphire substrate that has been acid-washed and annealed at 1000°C in a nitrogen atmosphere for different times in the present invention;

[0027] Figure 7 is an XRC diagram of a β-Ga2O3 single crystal film grown on a sapphire substrate that has been pickled and annealed at 1000°C in a nitrogen atmosphere for different times in the present invention;

[0028] Figure 8 are AFM images of β-Ga2O3 single crystal films grown on sapphire substrates that were pickled and annealed at 1000°C in a nitrogen atmosphere for different times in the present invention;

[0029] Figure 9 This is an ellipsometric diagram of a β-Ga2O3 single crystal film grown at a growth temperature of 1150°C on a sapphire substrate that has been pickled and annealed at 1000°C in a nitrogen atmosphere in the present invention. DETAILED DESCRIPTION

[0030] The exemplary embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. Although exemplary embodiments of the present disclosure are shown in the accompanying drawings, it should be understood that the present disclosure can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided to enable a more thorough understanding of the present disclosure and to fully convey the scope of the present disclosure to those skilled in the art. It should be noted that, unless there is a conflict, the embodiments of the present disclosure and the features described in the embodiments can be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0031] In the epitaxial growth process of β-Ga2O3 on (0006)-oriented sapphire substrates using the HVPE method, the (-201) crystal plane of β-Ga2O3 and the (0006) plane of sapphire are parallel to each other, i.e., (-201)β-Ga2O3║(0006)Al2O3. This results in a hexagonal rotational symmetry between the (-201) crystal plane of β-Ga2O3 and the oxygen atoms within the (0006) plane of sapphire. Therefore, it is easy to grow a (-201)-oriented β-Ga2O3 epitaxial layer on a (0006)-oriented sapphire substrate. Furthermore, the (310) crystal plane of β-Ga2O3 and the oxygen atoms within the (0006) plane of sapphire exhibit trigonal symmetry, making it easy to form mixed crystals of (310) and (-201) crystal orientations on (0006)-oriented sapphire substrates.

[0032] An embodiment of the present invention provides a method for growing a (310)-oriented β-Ga2O3 single crystal thick film on a sapphire substrate, comprising the following steps:

[0033] Step 1: clean the sapphire substrate and then perform annealing treatment.

[0034] Specifically, the sapphire substrate is cleaned to remove surface impurities and contaminants; the cleaned sapphire substrate is annealed to improve the surface structure of the sapphire substrate and provide a suitable surface layer for the growth of (310) oriented β-Ga2O3 epitaxial film.

[0035] The sapphire substrate is a (0006) oriented sapphire wafer, or the (0006) surface of the sapphire is used as the substrate. The diameter of the sapphire substrate can be determined according to actual conditions, for example, 2 inches or 4 inches. The (0006) oriented sapphire wafer selected in this embodiment has the advantages of high crystallinity, low price, and easy availability.

[0036] In a specific implementation, an acid solution obtained by mixing H2SO4 with a mass concentration of 98% and H3PO4 with a mass concentration of 30% in a volume ratio of 3:1 is prepared, and the sapphire substrate is immersed in the acid solution at 70-90°C. After the immersion, the substrate is rinsed with deionized water and dried.

[0037] The temperature of the acid solution is preferably 80° C.; the immersion time of the sapphire substrate in the acid solution is 3-7 minutes, preferably 5 minutes.

[0038] In this embodiment, an acidic solution is used to chemically clean the sapphire substrate to remove organic residues and metal impurities. After the sapphire substrate is soaked, it is repeatedly rinsed with flowing deionized water and then flushed dry with dry nitrogen.

[0039] In step 1, when the sapphire substrate is annealed, the annealing atmosphere is nitrogen, the working pressure is 500-700 Torr, the annealing temperature is 900-1100° C., for example, 900, 1000, 1100° C.; and the annealing time is 60-180 min, for example, 60, 120, 180 min.

[0040] More specifically, the nitrogen flow rate during annealing is 1-3 slm, such as 1, 2, or 3 slm. Preferably, when annealing the sapphire substrate, the annealing atmosphere is nitrogen, the operating pressure is 700 Torr, the annealing temperature is 1000°C, and the annealing time is 60 minutes. High-temperature nitrogen annealing can destroy the hexagonal symmetry of the oxygen atoms within the sapphire substrate plane, while an appropriate annealing time does not destroy the trigonal symmetry of the oxygen atoms within the plane, thereby laying a good substrate foundation for growing high-quality (310)-oriented β-Ga2O3 single crystal thick films.

[0041] Step 2: Using hydrogen chloride gas, gallium metal and oxygen as reaction sources, epitaxially grow a (310) oriented β-Ga2O3 single crystal thick film on the sapphire substrate processed in step 1 by using the HVPE method.

[0042] Specifically, the purity of hydrogen chloride gas and oxygen is 99.999%, and the purity of gallium metal reaches 7N, ensuring the rapid growth of high-quality β-Ga2O3 epitaxial films on sapphire substrates. In this embodiment, the β-Ga2O3 film obtained after epitaxial growth on a sapphire substrate is referred to as an epitaxial film, and whether it is a single crystal film cannot be determined at this stage. It is only considered a single crystal film after XRD testing confirms that it is a single crystal ((310) orientation). It is only considered a single crystal thick film after its thickness is measured.

[0043] A HVPE device is used to epitaxially grow a (310) oriented β-Ga2O3 single crystal thick film. The HVPE device includes a reaction chamber and a growth chamber. The HVPE method for preparing a β-Ga2O3 single crystal thick film is divided into two steps: the first step is the reaction of hydrogen chloride gas with gallium metal to generate GaCl. The flow rate of hydrogen chloride gas is 5-20sccm, such as 5, 10, and 20sccm; taking a reaction time of 60 minutes as an example, the amount of gallium metal required can be: 1-4g. In practice, a certain amount of gallium metal (for example, 1 kg) is usually placed in the reaction device in advance. During the reaction process, hydrogen chloride gas is introduced into the reaction chamber and reacts with the gallium metal to generate GaCl. The working carrier gas is nitrogen; the working pressure is 400-600Torr, such as 400, 500, and 600Torr. The reaction temperature of hydrogen chloride gas and gallium (i.e., the reaction chamber temperature of the HVPE device) is 800-900°C, such as 800, 850, and 900°C. Preferably, the flow rate of hydrogen chloride gas is 10 sccm, the working pressure is 500 Torr, and the reaction temperature is 850°C.

[0044] The second step is that GaCl and oxygen enter the growth chamber and react to form a β-Ga2O3 epitaxial film. The operating pressure of the growth chamber is 400-600Torr, such as 400, 500, and 600Torr. The growth temperature of the β-Ga2O3 epitaxial film (i.e., the growth chamber temperature of the HVPE equipment) is 1000-1200°C, such as 1000, 1050, 1100, and 1150°C. The oxygen flow rate is 800-1200sccm, such as 800, 1000, and 1200sccm; preferably 1000sccm; the rotation rate of the sapphire substrate is 10-50r / min, such as 10, 30, and 50r / min; the allowable deviation is ±1r / min.

[0045] Preferably, the growth pressure of the β-Ga2O3 epitaxial film is 500 Torr, the flow rate of oxygen is 1000 sccm, the growth temperature is 1150°C, the rotation rate of the sapphire substrate is 20 r / min, and the allowable deviation is ±1 r / min. The deposition rate is 8.2 μm / h and the growth time is 60 min. Under the above conditions, a high-quality β-Ga2O3 epitaxial film with a (310) orientation is grown on the sapphire substrate. The thickness of the (310) oriented β-Ga2O3 single crystal epitaxial film obtained is 8.2 μm, the half-height width of the (310) peak is only 0.160°, and the roughness is 0.08 nm. All parameters are in an optimal state. In addition, by adjusting the growth temperature and the annealing time of the sapphire substrate, it is found that the growth temperature and the substrate annealing time have a crucial influence on the crystallization quality of the β-Ga2O3 epitaxial film.

[0046] In this embodiment, after the epitaxial growth is completed, an in-situ annealing is performed in a nitrogen atmosphere for 10-20 minutes, such as 10, 15, or 20 minutes. The pressure of the nitrogen atmosphere is 400-600 Torr, such as 400, 500, or 600 Torr. Alternatively, after the epitaxial growth is completed, an in-situ annealing is performed in a nitrogen atmosphere for 15 minutes, and the pressure of the nitrogen atmosphere is 500 Torr.

[0047] In an embodiment of the present invention, in-situ annealing is performed after growth is completed to fully react the GaCl remaining in the growth chamber and simultaneously release the stress of the β-Ga2O3 epitaxial film on the sapphire substrate, rendering it Ga-rich, thereby improving the crystal quality of the final β-Ga2O3 product. The immediate in-situ annealing not only improves the crystallinity of the β-Ga2O3 epitaxial film but also effectively controls the crystal orientation of the β-Ga2O3 epitaxial film, ensuring that it grows primarily along the (310) direction. This results in the formation of a high-quality (310)-oriented β-Ga2O3 single crystal thick film on the sapphire substrate during the epitaxial growth process.

[0048] It can be clearly concluded that by adopting the HVPE method with the above parameters, a uniformly distributed (310) oriented high-quality β-Ga2O3 single crystal thick film can be obtained. The process is simple, easy to operate, and highly controllable. The sapphire only needs to be pickled and annealed in a nitrogen atmosphere. In addition, the obtained β-Ga2O3 film has a smooth, dense surface, a thick thickness, and a very fast deposition rate.

[0049] By adopting the above-mentioned epitaxial process, high-quality (310)-oriented β-Ga2O3 single crystal thick films can be grown on (0006)-oriented sapphire substrates. The lattice matching is high, the crystals are of high quality and compactness, and the lattice bonding is tight, making them suitable for the growth of thicker epitaxial films. Ultimately, epitaxial growth of high-quality (310)-oriented β-Ga2O3 single crystal thick films was achieved using (0006)-oriented sapphire substrates, which have higher crystallinity and lower cost. The resulting β-Ga2O3 thick films have high crystallinity and fast growth rates, and can be grown to thicknesses ranging from micrometers to tens of micrometers.

[0050] The present invention is described in detail below in conjunction with specific embodiments:

[0051] Example 1

[0052] (1) A 2-inch diameter (0006) oriented sapphire substrate was immersion cleaned using an acid solution consisting of 98% sulfuric acid (H2SO4) and 30% phosphoric acid (H3PO4) in a volume ratio of 3:1. The acid solution temperature was maintained at 80°C and the sapphire substrate was immersed for 5 minutes. After immersion, the substrate was thoroughly rinsed with running deionized water and blown dry with dry nitrogen.

[0053] (2) The acid-washed sapphire substrate was placed in a nitrogen atmosphere for annealing. The annealing conditions were: nitrogen flow rate of 2 slm (standard liters per minute), working pressure of 700 Torr, annealing temperature of 1000°C, and annealing time of 60 min.

[0054] (3) The sapphire substrate that has been acid-washed and annealed in a nitrogen atmosphere is placed in the growth chamber of the HVPE equipment, and β-Ga2O3 epitaxial film is rapidly grown on the sapphire substrate using 99.999% pure hydrogen chloride gas, oxygen and 7N gallium metal as reaction sources. The reaction conditions are as follows: the temperature of the reaction chamber is set to 850°C, and the pressure of the reaction chamber is adjusted to 500 Torr; the sapphire substrate in the growth chamber is heated to 1150°C, and the pressure is stabilized at 500 Torr for 20 minutes; then oxygen is introduced at a flow rate of 1000 sccm (standard cubic centimeters per minute) while maintaining the pressure of the growth chamber at 500 Torr; 1 minute later, hydrogen chloride gas is introduced at a flow rate of 10 sccm to start growing a β-Ga2O3 epitaxial film on the sapphire substrate. During the growth process, the sapphire substrate is kept at a rotation rate of 20 r / min, and the growth time is 60 minutes; after the growth is completed, the hydrogen chloride gas is first turned off, and then nitrogen gas is continued to be introduced, maintaining the pressure at 500 Torr, and the grown β-Ga2O3 epitaxial film is subjected to in-situ annealing for 15 minutes.

[0055] Example 2

[0056] The only difference from Example 1 is that no annealing treatment is performed in step (2).

[0057] Example 3

[0058] The only difference from Example 1 is that the annealing time in step (2) is 120 min.

[0059] Example 4

[0060] The only difference from Example 1 is that the annealing time in step (2) is 180 min.

[0061] Example 5

[0062] The only difference from Example 1 is that the annealing temperature in step (2) is 900°C.

[0063] Comparative Example 1

[0064] The only difference from Example 1 is that the pickling and annealing treatments of the sapphire substrate in steps (1) and (2) are omitted, and a (0006) oriented sapphire wafer is directly used as the substrate.

[0065] Comparative Example 2

[0066] The only difference from Comparative Example 1 is that the sapphire substrate is pickled in step (1), the annealing treatment of the pickled sapphire substrate in step (2) is omitted, and the growth temperature in step (3) is 1000°C.

[0067] Comparative Example 3

[0068] The only difference from Comparative Example 1 is that the sapphire substrate is pickled in step (1), the annealing treatment of the pickled sapphire substrate in step (2) is omitted, and the growth temperature in step (3) is 1050°C.

[0069] Comparative Example 4

[0070] The only difference from Comparative Example 1 is that the sapphire substrate is pickled in step (1), the annealing treatment of the pickled sapphire substrate in step (2) is omitted, and the growth temperature in step (3) is 1100°C.

[0071] Comparative Example 5

[0072] The only difference from Comparative Example 1 is that the sapphire substrate is pickled in step (1), the annealing treatment of the pickled sapphire substrate in step (2) is omitted, and the growth temperature in step (3) is 1150°C.

[0073] Comparative Example 6

[0074] The only difference from Comparative Example 1 is that the gas atmosphere for annealing the pickled sapphire substrate in step (2) is oxygen.

[0075] Test example

[0076] To verify the effectiveness of the present invention, the following characterization techniques were used to analyze the characteristics of the sapphire substrates and the resulting β-Ga2O3 single crystal thick films under different processing conditions. Specifically, they include:

[0077] X-ray diffraction (XRD): used to evaluate the changes in crystal orientation of (0006) sapphire substrates without acid cleaning, acid cleaning, and acid cleaning and annealing (see Figure 1 ); XRD technology is also used to evaluate the crystal orientation of β-Ga2O3 epitaxial films grown under different substrate processing conditions and different growth temperatures (see Figure 2-Figure 6 ).

[0078] from Figure 1 It can be seen that no obvious crystal orientation change occurs on the (0006) oriented sapphire substrate, regardless of whether it undergoes pickling and annealing treatment. This indicates that the (0006) oriented sapphire substrate and β-Ga2O3 have good lattice matching and interface quality, which can ensure the quality of the β-Ga2O3 single crystal thick film.

[0079] from Figure 2-Figure 3 It can be seen from the figure that with the increase of temperature, the crystal quality gradually improves. When the growth temperature is 1150℃, in addition to the (310) oriented β-Ga2O3 on the sapphire substrate after acid washing, there is only a small impurity peak at the position of 2θ≈32°, indicating that the acid washing treatment of the substrate effectively removes impurities and defects on the surface of the sapphire substrate, making the diffraction peak of the (310) oriented β-Ga2O3 purer and the crystal quality better.

[0080] from Figure 4 It can be seen that when the annealing atmosphere is oxygen, the epitaxial film layer appears as a mixed crystal with two orientations, (-201) and (310); while when annealed in a nitrogen atmosphere, the β-Ga2O3 grown on the sapphire substrate forms a single crystal film layer with a single (310) orientation. This indicates that annealing the sapphire substrate in a nitrogen atmosphere destroys the hexagonal symmetry of the oxygen atoms in its plane, retaining only the trigonal symmetry of the oxygen atoms in the substrate plane, so that the β-Ga2O3 epitaxial film tends to form a structure with high crystalline quality and a single orientation.

[0081] from Figure 5It can be seen from the figure that after the sapphire substrate is pickled, when the annealing temperature is 900℃ and the annealing time is 60min, as the temperature increases, the epitaxial film tends to a single (310) orientation, but the (-201), (-402) and (-603) peaks cannot be completely eliminated. This shows that the 900℃ nitrogen atmosphere annealing treatment on the substrate is too low and the hexagonal symmetry of the oxygen atoms on the sapphire surface cannot be effectively destroyed, thus failing to obtain a substrate surface layer that is more conducive to (310) growth.

[0082] from Figure 6 It can be seen that after the sapphire substrate is pickled, the annealing temperature is 1000℃ and the annealing time is 60min, and the β-Ga2O3 grown thereon is a (310) oriented single crystal film layer. Except for the substrate peak, no other peaks appear, indicating that the grown β-Ga2O3 single crystal film has a high degree of crystal purity and orientation consistency.

[0083] X-ray rocking curve (XRC): used to further analyze the crystal quality of β-Ga2O3 single crystal films grown on sapphire substrates after acid washing and annealing at 1000℃ in nitrogen atmosphere for different times (see Figure 7 ).

[0084] from Figure 7 It can be seen that when the sapphire substrate is pickled and then annealed at a temperature of 1000°C and an annealing time of 60 minutes, the (310) oriented β-Ga2O3 single crystal film has the best crystallinity, with a half-height width of only 0.160°.

[0085] Atomic force microscopy (AFM): used to observe the surface morphology and roughness of β-Ga2O3 single crystal films grown on sapphire substrates that were pickled and annealed at 1000℃ in a nitrogen atmosphere for different times (see Figure 8 ).

[0086] from Figure 8 It can be seen that when the sapphire substrate is pickled and then annealed at a temperature of 1000°C and an annealing time of 60 minutes, the surface roughness of the (310) oriented β-Ga2O3 single crystal film is only 0.08 nm.

[0087] Ellipsometry: used to characterize the thickness of β-Ga2O3 single crystal films grown on sapphire substrates that were pickled and annealed at 1000°C in a nitrogen atmosphere (see Figure 9 ).

[0088] from Figure 9 The fitting results show that under the growth conditions, when the growth time is 60 min, the thickness of the single crystal thick film is about 8.2 μm (8272.9 nm).

[0089] Combine Figure 2-9 The XRD patterns, XRC patterns and AFM patterns of β-Ga2O3 grown on sapphire substrates with or without pickling, annealing, different annealing times and different growth temperatures show that when the HVPE method is used on a (0006) oriented sapphire substrate that has been pickled and annealed at 1000℃ in a nitrogen atmosphere for 60min, and the growth temperature is 1150℃, all the parameters of the epitaxially grown β-Ga2O3 film are in the optimal state. The thickness of the film is 8.2μm, which meets the thickness requirements in practical applications. The half-height width of the (310) peak is only 0.160°, which is much better than the half-height width of the existing process, showing extremely high crystal quality. The surface roughness is only 0.08nm, indicating that the film is smooth, which is conducive to completing steps such as photolithography during device preparation.

[0090] Obviously, those skilled in the art may make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if such changes and modifications fall within the scope of the claims and their equivalents, the present invention is intended to include such changes and modifications.

Claims

1. A method for growing a (310) oriented β-Ga2O3 single crystal thick film on a sapphire substrate, characterized in that: The following steps are involved: Step 1: cleaning the sapphire substrate and then annealing it; Step 2: Using hydrogen chloride gas, gallium metal and oxygen as reaction sources, epitaxially grow (310) oriented β-Ga2O3 single crystal thick film on the sapphire substrate processed in step 1 by using hydride vapor phase epitaxy method.

2. The method for growing a (310)-oriented β-Ga2O3 single crystal thick film on a sapphire substrate according to claim 1, characterized in that The sapphire substrate is a sapphire wafer with a (0006) orientation.

3. The method for growing a (310)-oriented β-Ga2O3 single crystal thick film on a sapphire substrate according to claim 1, characterized in that In step 1, H2SO4 with a mass concentration of 98% and H3PO4 with a mass concentration of 30% are mixed in a volume ratio of 3:1 to obtain an acid solution, and the sapphire substrate is immersed in the acid solution at 70-90°C. After the immersion, it is rinsed with deionized water and dried.

4. The method for growing a (310)-oriented β-Ga2O3 single crystal thick film on a sapphire substrate according to claim 1, characterized in that In the step 1, when the sapphire substrate is annealed, the annealing atmosphere is nitrogen or oxygen, the working pressure is 500-700 Torr, the annealing temperature is 900-1100° C., and the annealing time is 60-180 min.

5. The method for growing a (310)-oriented β-Ga2O3 single crystal thick film on a sapphire substrate according to claim 4, characterized in that: In the step 1, when the sapphire substrate is annealed, the annealing atmosphere is nitrogen, the working pressure is 700 Torr, the annealing temperature is 1000° C., and the annealing time is 60 min.

6. The method for growing a (310)-oriented β-Ga2O3 single crystal thick film on a sapphire substrate according to claim 1, characterized in that In step 2, the flow rate of the hydrogen chloride gas is 5-20 sccm, the flow rate of the oxygen is 800-1200 sccm, the working carrier gas is nitrogen, the working pressure is 400-600 Torr, the reaction temperature of the hydrogen chloride gas and gallium metal is 800-900°C, the growth temperature of the β-Ga2O3 single crystal thick film is 1000-1200°C, and the rotation rate of the sapphire substrate is 10-50 r / min.

7. The method for growing a (310)-oriented β-Ga2O3 single crystal thick film on a sapphire substrate according to claim 6, characterized in that: The flow rate of the hydrogen chloride gas is 10 sccm, the flow rate of the oxygen is 1000 sccm, the working carrier gas is nitrogen, the working pressure is 500 Torr, the reaction temperature of the hydrogen chloride gas and gallium metal is 850°C, the growth temperature of the β-Ga2O3 single crystal thick film is 1150°C, and the rotation rate of the sapphire substrate is 20 r / min.

8. The method for growing a (310)-oriented β-Ga2O3 single crystal thick film on a sapphire substrate according to claim 1, characterized in that The (310) oriented β-Ga2O3 single crystal thick film obtained in step 2 has a thickness of 8.2 μm, a half-height width of 0.160°, and a roughness of 0.08 nm.

9. The method for growing a (310)-oriented β-Ga2O3 single crystal thick film on a sapphire substrate according to claim 1, characterized in that: In the step 2, after the epitaxial growth is completed, in-situ annealing is performed in a nitrogen atmosphere for 10-20 minutes, and the pressure of the nitrogen atmosphere is 400-600 Torr.

10. The method for growing a (310)-oriented β-Ga2O3 single crystal thick film on a sapphire substrate according to claim 9, characterized in that: In the step 2, after the epitaxial growth is completed, in-situ annealing is performed in a nitrogen atmosphere for 15 minutes, and the pressure of the nitrogen atmosphere is 500 Torr.

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