Preparation method of high-quality beta-Ga2O3 film based on Van der Waals epitaxial growth

Abstract

The invention discloses a preparation method of a high-quality beta-Ga2O3 film based on Van der Waals epitaxial growth. The preparation method of the high-quality beta-Ga2O3 thin film comprises the following steps: S1, placing a fluorine crystal mica F-micro substrate in MOCVD (Metal Organic Chemical Vapor Deposition) equipment, and growing a gallium oxide low-temperature nucleating layer on the substrate at a first temperature by taking triethyl gallium as a gallium source and O2 as an oxygen source; s2, taking triethyl gallium as a gallium source and O2 as an oxygen source, and growing a gallium oxide high-temperature epitaxial layer on the gallium oxide low-temperature nucleating layer at a second temperature to obtain the high-quality beta-Ga2O3 thin film, the second temperature is higher than the first temperature. According to the beta-Ga2O3 thin film prepared by the method, the crystal quality is equivalent to that of a thin film obtained by a traditional rigid sapphire substrate, the problem that a high-quality gallium oxide thin film is difficult to prepare by an organic flexible substrate is solved, and the beta-Ga2O3 thin film is separated from the substrate and can be transferred to any target substrate; and the solar-blind ultraviolet photoelectric detector with high performance, flexibility and a vertical structure can be constructed.

Description

Technical Field

[0001] The invention relates to a method for preparing a high-quality beta-Ga2O3 film based on van der Waals epitaxial growth, and belongs to the technical field of optoelectronic functional materials. Background Art

[0002] In recent years, with the advancement of science and technology, mankind has gradually entered the electronic age. As the core of electronic technology, the semiconductor industry has become a pillar industry of the national economy and one of the fastest growing and most internationally competitive fields in the world today. From the first generation of semiconductor materials represented by Si and Ge to the second generation of semiconductor materials represented by GaAs, and now to the third generation of semiconductors represented by GaN and SiC, the bandgap width of semiconductor materials has been continuously improved and the application field has gradually expanded. Among them, semiconductor optoelectronic devices represented by light-emitting diodes and photodetectors have played an important role. In terms of photodetectors, with the increase of the bandgap width of materials, the detection field has gradually expanded from infrared to ultraviolet bands. Ultraviolet (UV) usually refers to the electromagnetic band with a wavelength of 10-400nm, which is specifically subdivided into the following bands: UVA (320-400nm), UVB (280-320nm), UVC (200-280nm), and VUV (10-200nm). Due to the strong absorption of deep ultraviolet rays by the atmospheric ozone layer, the surface of the earth can hardly receive sunlight in the UVC band, so the electromagnetic waves in this band are also called solar-blind ultraviolet light. Solar-blind ultraviolet light detection can effectively eliminate the interference of sunlight, and the signal comes entirely from the target object. Therefore, solar-blind ultraviolet photoelectric detection technology plays an important role in military and civilian fields such as missile tracking, confidential communications, fire warning, and ozone hole monitoring.

[0003] At present, there are four materials that can be used to prepare solar-blind ultraviolet photodetectors: Al x G a1-x N, Mg x Zn 1-x O, diamond, β-Ga2O3. By adjusting the ternary alloy Al x Ga 1-x N and Mg x Zn 1-x The element composition in O can change the bandgap of the material to achieve a continuous change in the detection band from the ultraviolet band to the solar-blind ultraviolet region. However, as the bandgap increases, the three alloys face some serious problems, such as the growth of Al with a high Al content. x Ga 1-x N thin films require a high temperature of more than 1350 degrees and have poor crystal quality; while Mg with high Mg content x Zn 1-xO has a serious phase separation phenomenon. Diamond material is limited by its fixed bandgap width, corresponding to an absorption edge of about 225nm, with a narrow application range and a lack of large-area single crystal films. Compared with the above three materials, β-Ga2O3 has a bandgap of about 4.9eV, has a natural solar-blind ultraviolet property, and a corresponding absorption edge of about 254nm, located in the middle of the solar-blind ultraviolet region, making it an ideal material for preparing solar-blind ultraviolet detectors. In addition, β-Ga2O3 has high chemical and thermal stability, and high-quality large-area single crystals can be obtained through a variety of technical methods.

[0004] At present, metal organic vapor deposition (MOCVD), low pressure chemical vapor deposition (LPCVD), halide vapor phase epitaxy (HVPE), molecular beam epitaxy (MBE), pulsed laser deposition (PLD), plasma enhanced atomic layer deposition (PEALD), magnetron sputtering and other technologies have been used to prepare technical β-Ga2O3 films. According to whether the substrate is flexible, it can be divided into rigid substrates (sapphire substrates, Si, SiC, etc.) and flexible substrates (PI, PET, etc.). Since single crystal gallium oxide substrates are expensive and the lattice mismatch between sapphire substrates and gallium oxide is low, sapphire substrates are usually used for epitaxial growth of high-quality gallium oxide films. However, due to the strong covalent bond between the two, gallium oxide films are difficult to separate from the substrate, which is not conducive to the preparation of flexible, vertical structure and other optoelectronic devices. Traditional flexible substrates represented by PET do not have high temperature stability (decompose above 300 degrees), and can only prepare amorphous gallium oxide films, with poor crystal quality and general device performance. Therefore, how to prepare high-quality β-Ga2O3 films on flexible substrates is a technical problem that needs to be solved urgently. Summary of the invention

[0005] To solve the above problems, the purpose of the present invention is to provide a method for preparing high-quality β-Ga2O3 film based on van der Waals epitaxial growth. The method selects layered material fluorphlogopite mica (F-mica) as the epitaxial substrate, adopts MOCVD technology, and prepares high-quality β-Ga2O3 film by a two-step growth method of a low-temperature buffer layer and a high-temperature epitaxial layer. Not only is the crystal quality equivalent to that of the film obtained by a traditional rigid sapphire substrate, but it also solves the problem that it is difficult to prepare high-quality gallium oxide films on organic flexible substrates, realizes the separation of the β-Ga2O3 film from the substrate and can be transferred to any target substrate, which is conducive to the construction of high-performance flexible, vertical structure Schottky diode type, pn heterojunction type and other solar-blind ultraviolet photoelectric detection devices.

[0006] To achieve the above object, the present invention adopts the following technical solution:

[0007] In a first aspect, the present invention provides a method for preparing a high-quality β-Ga2O3 thin film, comprising the following steps:

[0008] S1, placing a fluorophlogopite mica substrate in an MOCVD device, using triethylgallium as a gallium source and O2 as an oxygen source, and growing a gallium oxide low-temperature nucleation layer on the substrate at a first temperature;

[0009] S2, using triethylgallium as a gallium source and O2 as an oxygen source, at a second temperature, growing a gallium oxide high-temperature epitaxial layer on the gallium oxide low-temperature nucleation layer to obtain the high-quality β-Ga2O3 film;

[0010] The second temperature is greater than the first temperature.

[0011] In the above-mentioned method for preparing high-quality β-Ga2O3 thin film, as an example, the first temperature is 600°C;

[0012] The second temperature is 800-900°C. As an example, the second temperature is 830°C.

[0013] In the above-mentioned method for preparing high-quality β-Ga2O3 thin film, as an example, the growth time of the gallium oxide low-temperature nucleation layer is 3 minutes, and the growth thickness is 10 nm;

[0014] As an example, the growth time of the gallium oxide high temperature epitaxial layer is 30 minutes, and the growth thickness is 210 nm.

[0015] In the above-mentioned method for preparing high-quality β-Ga2O3 thin film, as an example, in step S1, the oxygen flow rate is 500 sccm, argon is used as the carrier gas, the argon flow rate is 1000 sccm, and the growth pressure is 60 Torr;

[0016] As an example, in step S2, the oxygen flow rate is 800 sccm, argon is used as the carrier gas, the argon flow rate is 1000 sccm, and the growth pressure is 60 Torr.

[0017] In the above-mentioned method for preparing high-quality β-Ga2O3 film, preferably, in step S1, the fluorophlogopite mica substrate includes the following pre-treatment steps: ultrasonically cleaning the fluorophlogopite mica substrate with acetone, ethanol, and deionized water in sequence, and then drying it with nitrogen.

[0018] In a second aspect, the present invention provides a high-quality β-Ga2O3 thin film with fluorophlogopite F-mica as a substrate obtained by any of the preparation methods described above.

[0019] In a third aspect, the present invention provides a method for peeling and transferring a high-quality β-Ga2O3 film, comprising the following steps:

[0020] 1) using a thermal release tape to closely adhere to one side of the β-Ga2O3 film in the high-quality β-Ga2O3 film with fluorphlogopite mica F-mica as the substrate, and then using a knife to cut into the middle of the substrate in a direction parallel to the F-mica substrate to divide it into two, leaving one side of the β-Ga2O3 film with the thermal release tape attached, so as to achieve rough thinning of the F-mica substrate;

[0021] 2) using a mechanical stripping method, continuously using an adhesive tape to finely thin the F-mica substrate in the high-quality β-Ga2O3 film with fluorophlogopite mica F-mica as the substrate that has been roughly thinned in step 1), until the F-mica substrate is completely stripped;

[0022] 3) The thermal release tape with the β-Ga2O3 film obtained in step 2) is attached to the target substrate, and heated until the thermal release tape loses its stickiness, and the β-Ga2O3 film is then transferred to the target substrate.

[0023] In the above-mentioned high-quality β-Ga2O3 film peeling transfer method, the heat release temperature is 120-130°C, such as 125°C.

[0024] In the above-mentioned peeling transfer method of high-quality β-Ga2O3 thin film, the target substrate can be an organic flexible substrate, such as a PET substrate, or any other substrate, such as a sapphire substrate, a Si / SiO2 substrate, etc.

[0025] In a fourth aspect, the present invention provides a solar-blind ultraviolet photoelectric detection device, comprising a target substrate obtained by transfer using the stripping transfer method of a high-quality β-Ga2O3 film as described in any of the above items and a high-quality β-Ga2O3 film on the target substrate.

[0026] The solar-blind ultraviolet photoelectric detection device mentioned above may specifically be a Schottky diode type or a PN heterojunction type.

[0027] In the above-mentioned solar-blind ultraviolet photoelectric detection device, the target substrate is a flexible substrate, such as a PET substrate.

[0028] The present invention has the following beneficial effects:

[0029] (1) In order to realize the preparation of high-quality β-Ga2O3 thin films on flexible substrates, the present invention uses an artificially synthesized F-mica substrate, whose good heat resistance and high melting point increase its operating temperature to 1200 degrees Celsius, which is conducive to the preparation of high-crystalline quality β-Ga2O3 thin films at high temperatures.

[0030] (2) The present invention adopts MOCVD technology and a two-step method of low temperature + high temperature to effectively alleviate lattice mismatch, reduce defect density, and achieve high-quality growth of thin films. High-crystalline quality β-Ga2O3 thin films are prepared on F-mica substrates, which are comparable to the quality of heteroepitaxial films obtained on sapphire substrates.

[0031] (3) F-mica also has excellent chemical stability and transparency, and good substrate cleavage provides atomic-level surface flatness, which can be used as a van der Waals epitaxial bonding interface to facilitate the peeling of the upper gallium oxide epitaxial film. The present invention realizes the peeling transfer of the epitaxial film, which is conducive to the subsequent preparation of flexible, vertical Schottky diode-type, PN heterojunction-type and other solar-blind ultraviolet photoelectric detection devices based on β-Ga2O3 film.

[0032] (4) The stripping and transfer method of the high-quality β-Ga2O3 film of the present invention is simple to operate and low in cost. The F-mica substrate can be reused after rough stripping. The crystal quality does not change after stripping, and the stripping process will not affect the film. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 This is a comparison of the XRD spectra of β-Ga2O3 films on F-mica substrate and sapphire substrate and the corresponding (-201) crystal plane FWHM. It can be seen from the figure that β-Ga2O3 grows preferentially along the {-201} crystal plane.

[0034] Figure 2 This is a comparison of the FWHM of the (-201) crystal plane of β-Ga2O3 film on F-mica substrate and sapphire substrate. It can be seen that the crystal quality of the β-Ga2O3 film obtained by F-mica is comparable to that of sapphire, and the position of the crystal plane diffraction peak is closer to the theoretical value.

[0035] Figure 3 This is an AFM photo of β-Ga2O3 film on F-mica substrate.

[0036] Figure 4 This is the O1s XPS spectrum of β-Ga2O3 film on F-mica substrate.

[0037] Figure 5 This is an optical photograph of the β-Ga2O3 film after it was peeled off and transferred to a PET substrate. The red dotted frame in the figure is a gallium oxide film with a size of about 1cm*1cm.

[0038] Figure 6 This is the XRD comparison diagram of β-Ga2O3 film before and after peeling. DETAILED DESCRIPTION

[0039] The present invention is further described in detail below in conjunction with specific embodiments, and the examples provided are only for illustrating the present invention, rather than for limiting the scope of the present invention. The examples provided below can be used as a guide for further improvements by those of ordinary skill in the art, and do not constitute a limitation of the present invention in any way.

[0040] The methods used in the following examples, unless otherwise specified, are all conventional methods, carried out according to the techniques or conditions described in the literature in the art or according to the product instructions. The materials, reagents, etc. used in the following examples, unless otherwise specified, can all be obtained from commercial sources.

[0041] Example 1: High-quality β-Ga2O3 thin film produced by MOCVD

[0042] Prepare high quality β-Ga2O3 thin films according to the following steps:

[0043] Step 1: The F-mica substrate with a specification of 10*10*0.2 mm purchased from Changchun Taiyuan Fluorphlogopite Co., Ltd. was cleaned by acetone, ethanol, and deionized water ultrasonic cleaning for 10 minutes, and then dried by nitrogen.

[0044] Step 2: Prepare gallium oxide epitaxial film. Use MOCVD technology to prepare β-Ga2O3 film in two steps of low-temperature nucleation layer + high-temperature epitaxial layer. High-purity triethylgallium and oxygen are selected as gallium source and oxygen source, and Ar is used as carrier gas.

[0045] S1. A gallium oxide low temperature nucleation layer is grown on an F-mica substrate. The growth parameters of the gallium oxide low temperature nucleation layer are as follows: temperature 600°C, pressure 60 Torr, growth time 3 min, gallium oxide low temperature nucleation layer thickness 10 nm, oxygen flow rate 500 sccm, argon flow rate 1000 sccm.

[0046] S2. growing a gallium oxide high temperature epitaxial layer on the gallium oxide low temperature nucleation layer. The growth parameters of the gallium oxide high temperature epitaxial layer are as follows: temperature 830° C., pressure 60 Torr, growth time 30 min, gallium oxide high temperature epitaxial layer thickness 210 nm, oxygen flow rate 800 sccm, argon flow rate 1000 sccm;

[0047] Finally, a high-quality β-Ga2O3 film with a thickness of 220nm was obtained.

[0048] Comparative Example 1

[0049] The preparation method is the same as that in Example 1, except that the substrate is replaced with a sapphire substrate.

[0050] Figure 1It is a comparison diagram of the XRD spectra of the β-Ga2O3 film on the F-mica substrate of Example 1 and the sapphire substrate of Comparative Example 1 and the corresponding (-201) crystal plane FWHM. It can be seen from the figure that the β-Ga2O3 grows preferentially along the {-201} crystal plane.

[0051] Figure 2 This is a comparison diagram of the (-201) crystal plane FWHM of the β-Ga2O3 film on the F-mica substrate of Example 1 and the sapphire substrate of Comparative Example 1. It can be seen that the crystal quality of the β-Ga2O3 film obtained by F-mica is equivalent to that of sapphire, and the position of the crystal plane diffraction peak is closer to the theoretical value.

[0052] Figure 3 This is an AFM photo of the β-Ga2O3 film on the F-mica substrate. The film surface is flat and smooth with an RMS roughness of 4.57nm.

[0053] Figure 4 This is the O1s XPS spectrum of the β-Ga2O3 film on the F-mica substrate, in which the OII (oxygen vacancy) content accounts for about 10.4% of the total oxygen content, indicating that the defect content in the film is low and the crystal quality is good.

[0054] Therefore, it can be seen that the present invention prepares high-crystalline quality β-Ga2O3 films on F-mica substrates, which are comparable to the quality of heteroepitaxial films obtained on sapphire substrates.

[0055] Example 2: Peel-off transfer of gallium oxide thin film

[0056] The β-Ga2O3 film obtained in Example 1 was transferred onto a PET flexible substrate according to the following steps:

[0057] 1) Rough thinning of F-mica substrate: Use medium-viscosity thermal release tape produced by Boer Technology to fit tightly to one side of the β-Ga2O3 film, then use a scalpel to cut along the middle of the F-mica substrate, split it into two, leaving one side of the film with the thermal release tape, to achieve rough thinning of the F-mica substrate.

[0058] 2) Fine thinning of F-mica substrate: Use 3M's model #810 Scotch Magic Tape to fit the F-mica substrate tightly. Use the mechanical peeling method to continuously use Scotch tape to finely thin the F-mica substrate, thinning it by about 10μm each time. After several times, the F-mica substrate can be completely peeled off.

[0059] 3) Bonding of β-Ga2O3 film to target substrate: Bond the thermal release tape with β-Ga2O3 film to the PET target substrate, heat the baking tray to 125°C, the thermal release tape loses its stickiness, and the β-Ga2O3 film is successfully transferred to the PET substrate.

[0060] Figure 5 This is an optical photograph of the β-Ga2O3 film after peeling and transferring to the PET substrate.

[0061] Figure 6 This is the XRD comparison diagram of the β-Ga2O3 film before and after stripping. It can be seen from the figure that no diffraction peak of the F-mica substrate is found after stripping, indicating that the substrate has been stripped cleanly. In addition, the {-201} crystal plane diffraction peak of the β-Ga2O3 film can still be seen after stripping, the crystal quality has not changed, and the stripping process has no effect on the film.

[0062] The present invention has been described in detail above. For those skilled in the art, without departing from the purpose and scope of the present invention, can implement the present invention in a wider range under equivalent parameters, concentrations and conditions. Although the present invention provides specific embodiments, it should be understood that the present invention can be further improved. In a word, according to the principle of the present invention, the application is intended to include any changes, uses or improvements to the present invention, including departing from the disclosed scope in the application and the changes made with conventional techniques known in the art.

Claims

1. A method for preparing high-quality β-Ga2O3 thin film, characterized in that: The steps include: S1, placing a fluorophlogopite mica substrate in an MOCVD device, using triethylgallium as a gallium source and O2 as an oxygen source, and growing a gallium oxide low-temperature nucleation layer on the substrate at a first temperature; S2, using triethylgallium as a gallium source and O2 as an oxygen source, at a second temperature, growing a gallium oxide high-temperature epitaxial layer on the gallium oxide low-temperature nucleation layer to obtain the high-quality β-Ga2O3 film; The second temperature is greater than the first temperature.

2. The method for preparing a high-quality β-Ga2O3 thin film according to claim 1, characterized in that: The first temperature is 600° C. The second temperature is 800-900°C, preferably 830°C.

3. The method for preparing a high-quality β-Ga2O3 thin film according to any one of claims 1-2, characterized in that: The growth time of the gallium oxide low temperature nucleation layer is 3 minutes, and the growth thickness is 10 nm; The growth time of the gallium oxide high temperature epitaxial layer is 30 minutes, and the growth thickness is 210 nm.

4. The method for preparing a high-quality β-Ga2O3 thin film according to any one of claims 1 to 3, characterized in that: In step S1, the oxygen flow rate is 500 sccm, argon is used as the carrier gas, the argon flow rate is 1000 sccm, and the growth pressure is 60 Torr; In step S2, the oxygen flow rate is 800 sccm, argon is used as the carrier gas, the argon flow rate is 1000 sccm, and the growth pressure is 60 Torr.

5. The method for preparing a high-quality β-Ga2O3 thin film according to any one of claims 1 to 4, characterized in that: In step S1, the fluorophlogopite mica substrate includes the following pre-treatment steps: ultrasonically cleaning the fluorophlogopite mica substrate with acetone, ethanol, and deionized water in sequence, and then drying it with nitrogen.

6. A high-quality β-Ga2O3 thin film with fluorophlogopite F-mica as substrate obtained by the preparation method according to any one of claims 1 to 5.

7. A method for peeling and transferring high-quality β-Ga2O3 thin films, characterized in that: The steps include: 1) using a thermal release tape to closely adhere to one side of the β-Ga2O3 film in the high-quality β-Ga2O3 film with fluorphlogopite mica F-mica as the substrate as claimed in claim 6, and then using a knife to cut into the middle of the substrate in a direction parallel to the F-mica substrate to divide it into two, leaving one side of the β-Ga2O3 film with the thermal release tape attached, so as to achieve rough thinning of the F-mica substrate; 2) using a mechanical stripping method, continuously using an adhesive tape to finely thin the F-mica substrate in the high-quality β-Ga2O3 film with fluorophlogopite mica F-mica as the substrate that has been roughly thinned in step 1), until the F-mica substrate is completely stripped; 3) The thermal release tape with the β-Ga2O3 film obtained in step 2) is attached to the target substrate, and heated until the thermal release tape loses its stickiness, and the β-Ga2O3 film is then transferred to the target substrate.

8. The method for peeling and transferring high-quality β-Ga2O3 thin film according to claim 7, characterized in that: The heat release temperature is 120-130°C.

9. A solar-blind ultraviolet photoelectric detection device, characterized in that: It comprises a target substrate obtained by transfer using the peeling transfer method of a high-quality β-Ga2O3 film according to any one of claims 7 to 8, and a high-quality β-Ga2O3 film on the target substrate.

10. The solar-blind ultraviolet photoelectric detection device according to claim 9, characterized in that: The target substrate is a PET substrate.

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