Gallium oxide thin film material and epitaxial growth method thereof

Abstract

The application belongs to the technical field of semiconductor material preparation, and particularly relates to a gallium oxide thin film material and an epitaxial growth method thereof, which comprises a substrate and a gallium oxide epitaxial layer, and an indium oxide thin film layer is inserted between the substrate and the gallium oxide epitaxial layer; a layer of indium oxide thin film is grown on the substrate, since indium oxide and gallium oxide belong to the same group, the lattice mismatch between them is small, the mismatch stress between gallium oxide and the substrate can be relieved, and therefore the quality of the gallium oxide epitaxial thin film can be effectively improved; the metal organic chemical vapor deposition method used in the application has a relatively simple process, the growth thickness is accurately controllable, and the surface flatness of the grown sample is high, and the quality of the gallium oxide epitaxial thin film is further improved.

Description

Technical Field

[0001] This invention relates to the field of semiconductor material preparation technology, specifically to a gallium oxide thin film material and its epitaxial growth method. Background Technology

[0002] Gallium oxide (Ga2O3) is a novel ultra-wide bandgap semiconductor material with high breakdown field strength, high Barry's figure of merit, and good thermal stability. Its excellent material properties make it a promising candidate for next-generation high-power electronic devices. While homoepitaxy can produce high-quality Ga2O3 films, the substrates used are expensive. Heteroepitaxy allows for the use of cheaper substrates, but the significant lattice mismatch between Ga2O3 and the substrate during heteroepitaxy results in low-quality Ga2O3 films with high dislocation density and severe device leakage, limiting its application in power electronic systems.

[0003] Patent document CN117613131A discloses a solar-blind ultraviolet detector based on a gallium oxide / iron oxide heterojunction and its fabrication method. The device structure, from top to bottom, consists of a sapphire substrate, a gallium oxide thin film, and an iron oxide thin film. Due to the significant lattice mismatch between gallium oxide and sapphire, direct contact or direct epitaxy results in low quality of the gallium oxide thin film. Patent document CN119694887A discloses a gallium oxide thin film material structure and its epitaxial growth method. The epitaxial growth scheme involves: ultrasonically cleaning the substrate with acid and organic solution to remove impurities; growing an iron oxide thin film on the cleaned substrate surface using a sputtering device; annealing the material with the iron oxide thin film in an annealing furnace to transform the polycrystalline iron oxide film into an α-oriented single-crystal state; placing the annealed sample in an MOCVD reaction chamber and growing an α-oriented gallium oxide epitaxial film on top of the annealed iron oxide thin film using metal-organic chemical vapor deposition (MOCVD) to complete the epitaxial growth. This method effectively alleviates the mismatch stress between gallium oxide and the substrate by inserting an iron oxide layer between the substrate and the gallium oxide layer. However, its growth scheme is complex, requires numerous equipment, is unsuitable for large-scale production, and is prone to introducing unintentional external doping impurities, affecting the quality of the gallium oxide thin film. US Patent No. US2024015895 discloses a highly conductive α-gallium oxide thin film structure and its manufacturing method obtained by selective region growth using HVPE (High-Voltage Variation) growth. The method involves forming a nitride-based nitride film pattern on the α-gallium oxide thin film to expose only selected areas, and then performing HVPE regrowth only on the partially exposed areas. While this method uses a fast growth rate with HVPE epitaxy, it is difficult to achieve precise control of the film thickness, and the resulting surface roughness is relatively large, affecting the improvement of film quality. To address these issues, a heteroepitaxial growth method for gallium oxide is proposed. Summary of the Invention

[0004] The purpose of this invention is to provide a gallium oxide thin film material and its epitaxial growth method to solve the problems mentioned in the background art.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a gallium oxide thin film material, comprising a substrate and a gallium oxide epitaxial layer, wherein an indium oxide thin film layer is inserted between the substrate and the gallium oxide epitaxial layer.

[0006] Preferably, the substrate is made of sapphire, silicon, or other materials with a corundum or diamond structure.

[0007] Preferably, the thickness of the indium oxide thin film is 10nm-100nm.

[0008] Preferably, the thickness of the gallium oxide thin film is 300 nm-10 μm.

[0009] Preferably, a 5-100 nm diameter is optionally inserted between the indium oxide thin film and the gallium oxide thin film. Gradient layer.

[0010] An epitaxial growth method for gallium oxide thin film material, the specific steps of which are as follows: Step 1: Place the substrate in the MOCVD chamber and introduce high-purity oxygen. Set the pressure to 20mbar-150mbar, the temperature to 1000-1200℃, and the time to 3-10min to remove impurities from the substrate; Step 2: Introduce an indium source and an oxygen source to epitaxially grow the indium oxide layer on the cleaned substrate surface; the epitaxial growth of the indium oxide layer shall satisfy at least one of the following conditions; Step 3: After in-situ heating, continue to introduce gallium source and oxygen source to continue growing gallium oxide film on indium oxide film; epitaxially grow the gallium oxide layer to satisfy at least one of the following conditions; Step 4: Turn off the gallium source and perform annealing in an oxygen source environment. The annealing temperature is 600℃-800℃, the pressure is 40mbar-200mbar, and the annealing time is 1min-10min.

[0011] Preferably, the conditions to be met in step two include: using a high-purity oxygen source, including... or or One or more of the following are used: a high-purity indium source including one or both of TMIn and TEIn; hydrogen, nitrogen, or argon as the carrier gas; an epitaxial growth temperature of 600℃-800℃; an epitaxial growth pressure of 20mbar-150mbar; a flow rate of 10sccm-200sccm for the indium source; a flow rate of 10sccm-100sccm for the oxygen source; an epitaxial growth time of 1s-100s; and an indium oxide buffer layer thickness of 10nm-100nm.

[0012] Preferably, in step three, the following conditions need to be met: A high-purity oxygen source is used, including... or or One or more of the following are used: a high-purity gallium source, including one or two of TEGa or TMGa, and hydrogen, nitrogen or argon as the carrier gas; the reaction chamber growth temperature is set at 500℃-800℃, the pressure is 40mbar-200mbar, and the molar flow ratio of gallium source to oxygen source is 1:5000-1:200, and a gallium oxide thin film with a thickness of 300nm-10μm is grown on top of an indium oxide thin film by metal-organic chemical vapor deposition.

[0013] Preferably, an intercalation can be made between the indium oxide thin film and the gallium oxide thin film. A gradient transition layer with a thickness of 5nm-100nm, wherein the In composition gradually changes from 0.3 to 0.

[0014] Compared with the prior art, the beneficial effects of the present invention are: 1) In this invention, an indium oxide thin film is grown on a substrate. Since indium oxide and gallium oxide belong to the same group, the lattice mismatch between them is small, which can alleviate the mismatch stress between gallium oxide and the substrate, thus effectively improving the quality of gallium oxide epitaxial film. 2) The metal-organic chemical vapor deposition method used in this invention has a relatively simple process, the growth thickness is precisely controllable, and the surface flatness of the grown sample is high, which further improves the quality of gallium oxide epitaxial films. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the structure of the material of the present invention; Figure 2 This is a schematic diagram of the process for producing the material of this invention. Detailed Implementation

[0016] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0017] Example:

[0018] Please see Figure 1-2 The present invention provides a technical solution: A gallium oxide thin film material includes a substrate 1 and a gallium oxide epitaxial layer 3. An indium oxide thin film layer 2 is inserted between the substrate 1 and the gallium oxide epitaxial layer 3. The inserted layer can effectively alleviate the mismatch stress between gallium oxide and the substrate, thereby improving the quality of the gallium oxide epitaxial film.

[0019] The substrate 1 is made of sapphire, silicon, or other materials with a corundum or diamond structure.

[0020] The thickness of the indium oxide thin film 2 is 10nm-100nm.

[0021] The thickness of the gallium oxide thin film 3 is 300nm-10μm.

[0022] Optionally, a 5-100 nm diameter is inserted between the indium oxide thin film 2 and the gallium oxide thin film 3. The gradient layer further alleviates mismatch stress and thermal expansion stress.

[0023] An epitaxial growth method for gallium oxide thin film material, the specific steps of which are as follows: Step 1: Place the substrate in the MOCVD chamber and introduce high-purity oxygen. Set the pressure to 20mbar-150mbar, the temperature to 1000-1200℃, and the time to 3-10min to remove impurities from the substrate; High temperature and high purity of 1000-1200℃ The reducing atmosphere can quickly remove adsorbed water vapor, organic contaminants, and particulate impurities from the substrate surface, while simultaneously reducing the natural oxide layer on the substrate surface. This prevents impurities from becoming heterogeneous nucleation sites for subsequent thin film growth, reducing point defects, dislocations, and other defect sources in the epitaxial layer. At high temperatures... Baking enables slight reconstruction of the substrate surface, improving surface flatness and reducing surface roughness, ensuring uniform contact between the subsequent indium oxide buffer layer and the substrate, and avoiding uneven film thickness and local cracking caused by uneven substrate surface. The low-pressure environment of 20mbar-150mbar is consistent with the pressure range of subsequent film growth, eliminating the need for significant adjustments to the reaction chamber pressure, reducing gas flow field disturbances caused by sudden changes in process parameters, and ensuring stable transmission of source gas. The processing time of 3-10 minutes removes impurities while avoiding lattice distortion on the substrate surface caused by prolonged high-temperature baking, thus ensuring the integrity of the substrate lattice.

[0024] Step 2: Introduce an indium source and an oxygen source to epitaxially grow the indium oxide layer on the cleaned substrate surface; the epitaxial growth of the indium oxide layer shall satisfy at least one of the following conditions; Gallium oxide has a high lattice mismatch with traditional substrates, and direct growth is prone to generating a large number of dislocations and stress defects. In contrast, indium oxide has lattice parameters that are closer to those of gallium oxide. As a buffer layer, it can achieve a gradient transition of lattice mismatch, disperse the interfacial stress between the substrate and gallium oxide, reduce dislocation extension in the gallium oxide film, and improve its crystal quality. At the same time, the thermal expansion coefficient of indium oxide is between that of the substrate and gallium oxide, which can alleviate the cracking and peeling of the film caused by thermal stress during subsequent growth and cooling processes. The growth temperature of 600℃-800℃ and the pressure of 20mbar-150mbar fall within the low-temperature and low-pressure growth range of MOCVD, which is suitable for the slow and uniform nucleation of thin buffer layers, avoiding the excessively fast nucleation rate caused by high temperature and high pressure, thus forming a loose and porous buffer layer. With indium source (TMIn / TEIn) and oxygen source flow rates ranging from 10-200 sccm to 10-100 sccm, the film formation rate can be precisely controlled. Short growth time of 1s-100s enables the fabrication of thin buffer layers of 10nm-100nm. If the buffer layer is too thick, it will affect the main performance of the gallium oxide film. If it is too thin, it will not be able to effectively relieve stress. This thickness range achieves a balance between "stress buffering" and "performance non-interference". With dual-source indium and multi-source oxygen options, the film formation characteristics can be adjusted according to the substrate type to adapt to the growth requirements of different substrates and improve process compatibility. The dense and uniform indium oxide buffer layer has a high surface flatness and no obvious defects, and can be used as a "virtual substrate" for gallium oxide thin films to ensure uniform nucleation of gallium oxide epitaxial layers and improve the in-plane uniformity of the thin films.

[0025] Step 3: After in-situ heating, continue to introduce gallium source and oxygen source to continue growing gallium oxide film on indium oxide film; epitaxially grow the gallium oxide layer to satisfy at least one of the following conditions.

[0026] Step 4: Turn off the gallium source and perform annealing in an oxygen source environment. The annealing temperature is 600℃-800℃, the pressure is 40mbar-200mbar, and the annealing time is 1min-10min. With the gallium source turned off and only the oxygen source retained, oxygen atoms can diffuse fully into the gallium oxide film at a temperature of 600℃-800℃, filling the oxygen vacancies formed during the growth process that were not completely oxidized, reducing intrinsic defects, and improving the electrical performance stability of the film (such as reducing leakage current and increasing breakdown field strength). The annealing temperature of 600℃-800℃ is consistent with the film growth temperature range, which is a mild annealing. It can promote grain rearrangement of gallium oxide films, merge small grains into large grains, improve the crystallinity and preferred orientation of the film, and avoid grain coarsening and film surface morphology deterioration caused by high temperature annealing. Short annealing time of 1-10 minutes can achieve defect repair while avoiding over-annealing that could cause interdiffusion at the indium oxide / gallium oxide interface, thereby damaging the interface structure and ensuring the integrity of the interlayer interface.

[0027] In step two, the conditions that need to be met include: using a high-purity oxygen source, including... or or One or more of the following; using a high-purity indium source, including one or both of TMI and TEIn, with hydrogen, nitrogen, or argon as the carrier gas; the epitaxial growth temperature is 600℃-800℃; the epitaxial growth pressure is 20mbar-150mbar; the flow rate of the indium source (including one or both of TMI and TEIn) is 10sccm-200sccm; the oxygen source (including...) / / The flow rate of one or more of the following is 10 sccm-100 sccm; the epitaxial growth time is 1s-100s; and the thickness of the indium oxide buffer layer is 10nm-100nm.

[0028] In step three, the following conditions must be met: A high-purity oxygen source must be used, including... or or One or more of the following are used: a high-purity gallium source, including one or two of TEGa or TMGa, and hydrogen, nitrogen or argon as the carrier gas; the reaction chamber growth temperature is set at 500℃-800℃, the pressure is 40mbar-200mbar, and the molar flow ratio of gallium source to oxygen source is 1:5000-1:200, and a gallium oxide thin film with a thickness of 300nm-10μm is grown on top of an indium oxide thin film by metal-organic chemical vapor deposition.

[0029] Optional intercalation between indium oxide thin films and gallium oxide thin films A gradient transition layer with a thickness of 5nm-100nm, wherein the In composition gradually changes from 0.3 to 0.

[0030] There is no need to remove the substrate from the MOCVD reaction chamber. Gallium oxide can be grown directly in situ by heating. This avoids the indium oxide buffer layer surface being exposed to air and being oxidized and contaminated. It also eliminates problems such as decreased interlayer bonding and increased interface defects caused by interface impurities, thus achieving a clean heterogeneous interface of indium oxide / gallium oxide and reducing the interface barrier. High-purity oxygen and high-purity gallium sources are used to reduce impurity doping in the source gas, prevent impurities from becoming deep-level defect centers in gallium oxide films, and ensure their electrical (such as carrier mobility) and optical (such as transmittance) properties. The dual gallium source selection can adapt to different growth requirements: TMGa has high reactivity and is suitable for rapid growth of thick films; TEGa has a mild reaction and is suitable for slow growth to improve crystal quality. Combined with a wide thickness range of 300nm-10μm, it can meet the needs of different device applications. The carrier gas selected is H2 / N2 / Ar. As a reducing carrier gas, it can suppress the gas-phase pre-oxidation of gallium source. N2 / Ar is an inert carrier gas with a stable flow field. Both can prevent impurity particles generated by gas-phase side reactions from depositing on the film surface.

[0031] The growth temperature is 500℃-800℃ and the pressure is 40mbar-200mbar, which is highly compatible with the temperature and pressure range of the indium oxide buffer layer. This avoids sudden changes in temperature / pressure that could cause a sudden increase in internal stress in the film. At the same time, the low-pressure environment is conducive to the diffusion of source gas and the desorption of reaction products, reducing defects such as pores and inclusions in the film.

[0032] Gallium / oxygen molar ratio (1:5000-1:200): Ensures sufficient oxidation and reduces intrinsic defects: The design of a large excess of oxygen source can ensure that the gallium source is fully oxidized, avoids the formation of low-valence gallium oxides, and ensures the ideal stoichiometry of gallium oxide film; at the same time, the excess oxygen source can fill the oxygen vacancy defects (the main intrinsic defects of gallium oxide) generated during film growth, reducing the impact of defects on the electrical properties of the film.

[0033] Additional benefits of optional gradient transition layer (In composition 0.3→0): Inserting a 5nm-100nm In composition gradient transition layer between indium oxide and gallium oxide achieves a continuous gradient of lattice / composition, further alleviating the stress caused by the lattice abrupt change from indium oxide to pure gallium oxide, and minimizing the generation and extension of dislocation defects; at the same time, the composition gradient can avoid band abrupt changes at the interface, eliminate the interface barrier, and improve the carrier transport performance of gallium oxide thin films, making it suitable for gallium oxide devices with high electrical performance requirements.

[0034] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or basic characteristics. Therefore, the embodiments should be considered exemplary and non-limiting in all respects. The scope of the invention is defined by the appended claims rather than the foregoing description. Therefore, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention, and no reference numerals in the claims should be construed as limiting the scope of the claims.

[0035] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A gallium oxide thin film material, characterized in that, It includes a substrate (1) and a gallium oxide epitaxial layer (3), with an indium oxide thin film layer (2) inserted between the substrate (1) and the gallium oxide epitaxial layer (3).

2. The gallium oxide thin film material according to claim 1, characterized in that: The substrate (1) is made of sapphire, silicon, or other materials with a corundum or diamond structure.

3. The gallium oxide thin film material according to claim 1, characterized in that: The thickness of the indium oxide thin film (2) is 10nm-100nm.

4. The gallium oxide thin film material according to claim 1, characterized in that: The thickness of the gallium oxide thin film (3) is 300nm-10μm.

5. A gallium oxide thin film material according to claim 1, characterized in that: Optionally, a 5-100 nm diameter is inserted between the indium oxide thin film (2) and the gallium oxide thin film (3). Gradient layer.

6. An epitaxial growth method for gallium oxide thin film material according to any one of claims 1-5, characterized in that: The specific steps of this epitaxial growth method are as follows: Step 1: Place the substrate in the MOCVD chamber and introduce high-purity oxygen. Set the pressure to 20mbar-150mbar, the temperature to 1000-1200℃, and the time to 3-10min to remove impurities from the substrate; Step 2: Introduce an indium source and an oxygen source to epitaxially grow the indium oxide layer on the cleaned substrate surface; the epitaxial growth of the indium oxide layer shall satisfy at least one of the following conditions; Step 3: After in-situ heating, continue to introduce gallium source and oxygen source to continue growing gallium oxide film on indium oxide film; epitaxially grow the gallium oxide layer to satisfy at least one of the following conditions; Step 4: Turn off the gallium source and perform annealing in an oxygen source environment. The annealing temperature is 600℃-800℃, the pressure is 40mbar-200mbar, and the annealing time is 1min-10min.

7. The epitaxial growth method for gallium oxide thin film material according to claim 6, characterized in that: In step two, the conditions that need to be met include: using a high-purity oxygen source, including... or or One or more of the following are used: a high-purity indium source including one or both of TMIn and TEIn; hydrogen, nitrogen, or argon as the carrier gas; an epitaxial growth temperature of 600℃-800℃; an epitaxial growth pressure of 20mbar-150mbar; a flow rate of 10sccm-200sccm for the indium source; a flow rate of 10sccm-100sccm for the oxygen source; an epitaxial growth time of 1s-100s; and an indium oxide buffer layer thickness of 10nm-100nm.

8. The epitaxial growth method of gallium oxide thin film material according to claim 6, characterized in that: In step three, the following conditions must be met: A high-purity oxygen source must be used, including... or or One or more of the following are used: a high-purity gallium source, including one or two of TEGa or TMGa, and hydrogen, nitrogen or argon as the carrier gas; the reaction chamber growth temperature is set at 500℃-800℃, the pressure is 40mbar-200mbar, and the molar flow ratio of gallium source to oxygen source is 1:5000-1:200, and a gallium oxide thin film with a thickness of 300nm-10μm is grown on top of an indium oxide thin film by metal-organic chemical vapor deposition.

9. The epitaxial growth method for gallium oxide thin film material according to claim 6, characterized in that: Optional intercalation between indium oxide thin films and gallium oxide thin films A gradient transition layer with a thickness of 5nm-100nm, wherein the In composition gradually changes from 0.3 to 0.

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