Ga2O3 thin film manufacturing method

Abstract

To provide a manufacturing method of a Ga2O3 thin film.SOLUTION: The invention provides a high-quality α-Ga2O3 thin film using a suitable Ga2O3 thin film growth mode. More particularly, this invention uses a growth mode that is obtained by plotting a ratio (mmol / mmol) of a HCl amount in the support agent to an amount of GaCl3 in a raw material solution in an X-axis, and by plotting a number (TPR) that a film thickness of a Ga2O3 thin film is divided by a square root (RMS) of a surface roughness in a Y-axis.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a method for producing a GaO thin film and a GaO thin film produced by the method. More specifically, the present invention relates to a method for obtaining a high-quality α-GaO thin film using an optimal GaO thin film growth mode obtained by plotting the ratio (mmol / mmol) of the amount of HCl supplied in the support agent to the amount of GaCl supplied in the source solution on the horizontal axis and the value obtained by dividing the thickness of the GaO thin film by the root mean square (RMS) of the surface roughness (TPR), i.e., the ratio of the thickness to the surface roughness, on the vertical axis. [Background technology]

[0002] The invention of blue LEDs enabled LEDs to cover the entire visible spectrum, leading to the development of white LEDs, which in turn enabled LEDs to support our lives as lighting. LEDs are now expanding their applications beyond lighting.

[0003] For example, attention is being focused on the development of deep-ultraviolet light sources. Mercury lamps have been used as deep-ultraviolet light sources up until now, but these lamps have various disadvantages, such as high power consumption, the need for frequent maintenance, the large size of the equipment, and restrictions on their use due to environmental impact. Therefore, the development of deep-ultraviolet LEDs to replace mercury lamps is being actively carried out around the world.

[0004] The nitride material AlGaN is typically used as a deep-UV LED material. The band gap of AlGaN can be controlled between 3.3 and 6.3 eV by adjusting its composition ratio. However, the oxide material AlGaO has a larger band gap that can be controlled between 5.3 and 8.7 eV, making AlGaO an extremely attractive material for deep-UV LEDs from the perspective of band gap. In addition, because AlGaO is an oxide, it has stronger ionic bonding than nitrides and is thought to exhibit higher electrical durability than AlGaN.

[0005] The inventors fabricated an AlGaO light-emitting device with a structure in which three layers of α-Ga2O3 thin films were used as the light-emitting layer and sandwiched between AlGaO. However, although this device exhibited strong emission around 4.9 eV, the reproducibility was insufficient. In particular, the surface of the thin film, which showed good emission characteristics, was very rough, suggesting that the quantum well structure may not have been properly formed. Therefore, it was necessary to investigate the optimal conditions for thin film fabrication and fabricate higher-quality α-Ga2O3 thin films.

[0006] Gallium oxide, which has five phases, has attracted attention as a wide-bandgap material for applications in power and optical devices. Among the five phases, the metastable α-Ga2O3, which has a bandgap of 5.3 eV, is a promising material because its bandgap can be tuned by controlling the composition ratio of α-(MxGa1-x)2O3 (M = Fe, Cr, In, Al). This makes α-Ga2O3 an attractive material, and it can be fabricated by HVPE, ALD, MOCVD, and mist CVD methods.

[0007] Crystal quality and surface roughness are important factors for the fabrication of high-quality devices, and film deposition rate is also important from a commercial perspective. Generally, to improve these, a high film deposition temperature is required to obtain greater surface migration. However, mist CVD, a non-vacuum film deposition process, is expected to have greater surface migration because it makes good use of the characteristics of mist flow. Therefore, it is thought that mist CVD can produce thin films with high crystallinity and flat surfaces at lower temperatures than other methods. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Japanese Patent Application Laid-Open No. 2005-307238 [Patent Document 2] International Publication No. WO2016203595 Summary of the Invention [Problem to be solved by the invention]

[0009] The present invention aims to produce high-quality Ga2O3 thin films, particularly those with small surface roughness, at a low temperature of around 400°C, which are necessary for improving the performance of deep-ultraviolet light-emitting devices. [Means for solving the problem]

[0010] The inventors prepared α-Ga2O3 using the mist CVD method with the aid of HCl, investigated the effect of HCl on the preparation of α-Ga2O3, and established a method for producing Ga2O3 thin films with improved in-film purity and surface roughness in a low-temperature process at around 400°C.

[0011] The method according to claim 1 of the present invention comprises: Ga with surface flatness and improved surface roughness 2 O 3 1. A method for producing a thin film, the method comprising: 3 By adjusting the supply amount of Ga and the supply amount of HCl in the support agent, 2 O 3 The formation of the thin film is controlled by applying the mixed raw material solution and supporting agent onto the substrate at 350-450°C. 2 O 3 A thin film is formed, the RMS of the surface roughness of the thin film is 0.10 to 2.0 nm, the mixing is performed by a mist mixer, the raw material solution and the supporting agent are each misted by ultrasonic waves, the raw material solution and the supporting agent are each supplied by a separate sprayer, and GaCl in the raw material solution is mixed with the GaCl 3 The ratio (mmol / mmol) of the amount of 2HCl supplied in the support agent to the amount of Ga 2 O 3 On the XY plane where the thickness of the thin film divided by the square root of the surface roughness (TPR) is plotted on the vertical axis, 2 O 3 2) X is in the range of 0 to 20 and Y is in the range of 0 to 40. 2 O 3 Thin film growth mode 2 or 3) Ga in the region where X is 0 to 15 and Y is 35 to 120 2 O 3 The growth of Ga films is performed in one of three modes. 2 O 3 It is a method for producing thin films , and is characterized by.

[0012] According to claim 2 of the present invention, the growth of the Ga2O3 thin film is carried out in 3) Ga2O3 thin film growth mode 3, where X is in the range of 0.0-1.7 and Y is in the range of 35-40.

[0013] According to claim 3 of the present invention, the raw material solution and the supporting agent are applied onto a substrate by a flow of a carrier gas and a dilution gas, the concentration of GaCl3 in the raw material solution is 0.010 to 0.50 mol / L, and the concentration of HCl in the supporting agent is 0.1 to 10%.

[0014] According to claim 4 of the present invention, the method includes the steps of supplying a raw material solution containing a GaCl3 aqueous solution and a supporting agent containing HCl diluted water, mixing the raw material solution and the supporting agent, and forming a Ga2O3 thin film, wherein the raw material solution and the supporting agent are supplied and mixed by the flow of a carrier gas and a dilution gas, and the concentration of GaCl3 in the raw material solution is 0.050-0.50 mol / L, and the concentration of HCl in the supporting agent is 0.1-10%.

[0016] The present invention Claim 5 According to GaCl in the raw material solution 3 The ratio of GaCl in the raw material solution to the Ga supply amount derived from the aqueous solution 3 the ratio of the Cl supply amount, which is the sum of Cl derived from the aqueous solution and Cl derived from the HCl-diluted water in the support agent (Cl / Ga supply amount ratio), does not fall within the range of 3.0 to 4.5; Claims 1 to 4 A Ga2O3 thin film produced by the method according to any one of claims 1 to 4 is provided.

[0017] According to claim 7 of the present invention, the RMS of the surface roughness is 0.10 to 2.0 nm. [Effects of the Invention]

[0018] According to the present invention, it is possible to fabricate α-Ga2O3 thin films with such good crystallinity that Laue fringes are visible, and with an extremely flat surface with an RMS surface roughness of 0.56 nm even at a low temperature of 400°C. If a quantum well structure is created using the high-quality α-Ga2O3 thin film obtained by the present invention, it will be possible to develop a deep-ultraviolet light source. [Brief explanation of the drawings]

[0019] [Figure 1] FIG. 1 shows the XRD measurement results of the crystal structure of α-Ga2O3 produced according to the present invention. [Figure 2] FIG. 2 shows the relationship between the deposition rate and (a) the Ga supply rate, (b) the HCl supply rate, and (c) the supply ratio HCl / Ga. [Figure 3]Figure 3 shows the relationship between the thickness per root-mean-square roughness (TPR) and (a) the Ga supply amount, (b) the HCl supply amount, and (c) the supply amount ratio HCl / Ga. [Figure 4] Figure 4 shows XPS measurements of α-Ga2O3 thin films grown using different growth modes. The XPS data were corrected using the C1s peak at 284.8 eV. Figures 4(a)–(c) show the O1s XPS measurements of samples 3, 4, and 11 grown using modes 1, 2, and 3. The O1s spectra were fitted with four peaks: the O-Ga bond in Ga2O3 (530 eV), the O-Ga bond in GaO or the bond of O adsorbed on the surface (531 eV), the O-C bond (532 eV), and the O=C bond (533 eV). GaO / Ga2O3 and Imp. / Ga2O3 in Figure 4 represent the peak intensity ratios Ga(GaO) / O-Ga(Ga2O3) and (O-C+O=C) / O-Ga(Ga2O3), respectively. DETAILED DESCRIPTION OF THE INVENTION

[0020] <Detailed explanation> In one aspect, the present invention provides a method for producing a GaO thin film, comprising the steps of: providing a source solution containing a solution of a Ga-containing compound (e.g., but not limited to, GaCl, other Ga-containing ionic compounds, and Ga-containing complex compounds such as Ga(acac)), and a supporting agent containing HCl-diluted water; mixing the source solution and the supporting agent; and applying the mixed source solution and supporting agent onto a substrate to form a GaO thin film. The source solution is typically an aqueous solution, but any organic solvent known in the art can also be used. Examples of organic solvents include, but are not limited to, various polar and nonpolar solvents, including alcohols such as methanol and ethanol, ketones such as acetone, esters such as ethyl acetate, nitriles such as acetonitrile, aliphatic compounds such as hexane, aromatic compounds such as benzene, and chlorinated compounds such as chloroform, as well as mixtures thereof. High-purity solvents are preferred, and when water is used as the solvent, ultrapure water is preferred.

[0021] In one embodiment, the raw material solution and the supporting agent are each atomized by ultrasonic waves, and the raw material solution and the supporting agent are each supplied using separate sprayers, each of which is, for example, three (vibrators) with a diameter of 100 mm and a height of 140 mm, each with 24 V and 0.6 A per vibrator, but is not limited thereto.

[0022] In one embodiment, the source solution and the supporting agent are supplied, mixed, and applied onto a substrate by a flow of a carrier gas and a dilution gas.

[0023] In one embodiment, the mixing step is performed using a mist mixer. The amount of mist generated per unit time per atomizer is not limited, but is, for example, 2-3 mL / min. The total gas flow rate is 7 L / min. The mist mixer used here has a diameter of 200 mm and a height of 200 mm, but is not limited thereto.

[0024] The concentration of GaCl3 in the raw material solution can be varied depending on the film formation conditions and film formation rate, but is, for example, 0.010 to 0.50 mol / L, 0.020 to 0.40 mol / L, 0.030 to 0.30 mol / L, 0.040 to 0.20 mol / L, or 0.050 to 0.10 mol / L.

[0025] The concentration of HCl in the reactor is not limited because it can be adjusted by the gas flow, but the concentration of HCl in the supporting agent is 0.1 to 10% relative to H2O and 0.1 to 20 times relative to gallium.

[0026] Preferably, the concentration of GaCl3 in the raw material solution is 0.050 to 0.10 mol / L, and the concentration of HCl in the supporting agent is 0.1 to 10%.

[0027] Preferably, the carrier gas is flowed at a rate within a range of 0.0 to 20 L / min through a reaction channel having an inlet width of 30 mm and a height of 1 mm, and the dilution gas is flowed at a rate within a range of 0.0 to 20 L / min, and it is preferable to select an inert gas such as He, N2, or Ar.

[0028] Preferably, the ratio of the flow rate of the carrier gas for the raw material solution to the flow rate of the carrier gas for the supporting agent is in the range of 4:1 to 2:3.

[0029] Preferably, the step of forming a Ga2O3 thin film is carried out at 350° C. or higher, more preferably at 350 to 450° C. (the time can be selected depending on the target film thickness).

[0030] In another aspect, the present invention relates to a Ga2O3 thin film produced by the above method.

[0031] Preferably, the Ga2O3 thin films produced by the method of the present invention have improved surface roughness, with an RMS of the substrate level roughness or an RMS of the surface roughness of 0.10-2.0 nm, preferably 0.10-1.0 nm, or 0.10-0.8 nm.

[0032] The present invention relates to a method for producing Ga2O3 thin films using specific amounts of GaCl3 and HCl.

[0033] Preferably, the specific amounts of GaCl3 and HCl can be shown on an XY plane in which the ratio (mmol / mmol) of the supply amount of HCl in the supporting agent to the supply amount of Ga in the raw material solution is plotted on the horizontal axis, and the value (TPR) obtained by dividing the thickness of the Ga2O3 thin film by the square root of the surface roughness (RMS) is plotted on the vertical axis, and on this plane, 1) Growth mode 1 of Ga2O3 thin film, where X is in the range of 20-40 and Y is in the range of 0-40. 2) Growth mode 2 of Ga2O3 thin films, where X is in the range of 0 to 20 and Y is in the range of 0 to 40; or 3) Growth mode 3 of Ga2O3 thin films in the range of X 0 to 15 and Y 35 to 120 The growth of Ga2O3 thin films can be carried out in either of the following modes.

[0034] Growth mode 1 of the Ga2O3 thin film exists in the region of 20 to 40 and Y of 0 to 40 on the XY plane where the horizontal axis is the HCl / Ga supply ratio (mmol / mmol) in the support solution and the vertical axis is the thickness of the Ga2O3 thin film divided by the square root of the surface roughness (TPR). In this mode 1, as the supply ratio of HCl / GaCl3 (mmol / mmol) in the support solution increases, the square root of the surface roughness (TPR) of the Ga2O3 thin film thickness remains almost unchanged, and the slope of the increasing line (TPR / (HCl / Ga supply ratio)) is approximately -0.5 to 0.5.

[0035] Growth mode 2 of the Ga2O3 thin film exists in the region of 0-20 and 0-40 on the XY plane, where the horizontal axis is the HCl / Ga supply ratio (mmol / mmol) in the support solution and the vertical axis is the thickness of the Ga2O3 thin film divided by the square root of the surface roughness (RMS) (TPR). In this mode 2, the thickness of the Ga2O3 thin film divided by the square root of the surface roughness (RMS) (TPR) increases monotonically with an increase in the HCl / GaCl3 supply ratio (mmol / mmol) in the support solution, and the slope of the increasing line (TPR / (HCl / Ga supply ratio)) is approximately 0.5-2.0.

[0036] Growth mode 3 of the Ga2O3 thin film exists in the region of 0-15 and Y-35-120 on the XY plane where the horizontal axis is the HCl / Ga supply ratio (mmol / mmol) in the support agent and the vertical axis is the thickness of the Ga2O3 thin film divided by the square root of the surface roughness (RMS) (TPR). In this mode 3, the thickness of the Ga2O3 thin film increases monotonically with the square root of the surface roughness (RMS) as the HCl / GaCl3 supply ratio (mmol / mmol) in the support agent increases, and the slope of the increasing line (TPR / (HCl / Ga supply ratio)) is approximately 2 or more.

[0037] More preferably, the growth mode of the Ga2O3 thin film is 3) growth mode 3 of the Ga2O3 thin film in which X is in the range of 0-15 and Y is in the range of 35-120.

[0038] The mist CVD method used in this invention will now be explained. Mist Chemical Vapor Deposition (hereinafter referred to as mist CVD) is a method in which a raw material solution is physically misted using ultrasound, transported to a reaction zone by gas, and a functional thin film is formed on a substrate by thermal decomposition. There are many thin film fabrication methods available, but compared to these, mist CVD has the following major features: (1) Atmospheric pressure process that does not require a vacuum (2) General-purpose reagents can be used as raw materials (3) Because it uses mist flow, it has a higher degree of freedom in operation than processes that use single-phase flow.

[0039] Thin film fabrication methods can be broadly divided into liquid phase growth and vapor phase growth. Liquid phase growth is a method for obtaining crystals or thick films from a solution without requiring a vacuum. Previously, the coating method, a type of liquid phase growth, was primarily used to fabricate optical devices. However, with the demand for higher performance and quantum effects, MOCVD (Metal Organic Chemical Vapor Deposition) and MBE (Molecular Beam Epitaxy) methods are now being used (Masao Mashita and Masatsugu Yoshida, eds., Thin Film Engineering Handbook, Kodansha). MOCVD and MBE are classified as vapor phase growth methods and can produce higher quality thin films than liquid phase growth methods. However, many of these require a vacuum to suppress the effects of external disturbances, which consumes a great deal of energy and requires complex equipment.

[0040] Mist CVD, positioned between liquid-phase growth and vapor-phase growth, has been developed as a low-environmental-impact technology capable of producing high-quality thin films without the use of a vacuum. Furthermore, the raw materials used in mist CVD are general-purpose reagents, making it relatively inexpensive and safe to operate. While any solution method can be used, mist CVD in particular allows for the proper control of solution behavior to supply the raw materials and multiple components used in this invention separately to prevent reaction outside the reactor. Furthermore, mist CVD has recently evolved into a technology that simultaneously achieves four goals: low environmental impact, large area deposition, uniform high-quality deposition, and composition control, by taking advantage of the greater operational flexibility of gaseous multiphase flow compared to single-phase flow.

[0041] The mist CVD apparatus configuration and substrate cleaning process used in the implementation of the present invention are described below.

[0042] Fine Channel Reactor There are several types of mist CVD methods, each differing in reactor design. In this study, we used a Fine Channel (FC) reactor. This reactor is equipped with a raw material supply section, where the raw material solution is converted into mist using ultrasound. This mist is transported to the FC reactor on the right by a carrier gas (cg) and a dilution gas (dg). The FC reactor was designed to achieve two goals: 1) increasing reaction efficiency by pressing the mist against the substrate, and 2) increasing thermal conductivity. The mist transported from the raw material supply section is thermally decomposed as it passes through this FC structure, forming a thin film on the substrate (T. Kawaharamura: Ph.D. Thesis, Kyoto University, Kyoto (2008) [in Japanese]).

[0043] In the present invention, CuKα1 (1.540561 Å) was used as the incident X-ray, and the evaluation was carried out using a high-output, high-precision five-axis X-ray diffractometer ATX-G manufactured by Rigaku.

[0044] In this study, an Oxford Instruments Cypher ES AFM and an Oxford Instruments AC160TSA cantilever were used to evaluate the surface shape and roughness. The scan size was 2.0 μm vertically and horizontally. [Example]

[0045] Example 1 Preparation of α-Ga2O3 thin film with excellent surface flatness 1 1-1 Preparation conditions In this example, α-Ga2O3 films were deposited on c-plane sapphire substrates using the third-generation mist CVD method. This method utilizes multiple atomizers to allow the use of multiple solutions, and the mist was supplied to a fine-channel reactor via a mist mixer. The supply rate was controlled by varying the nitrogen gas flow rate. The total flow rate (flow rate through the reactor) was 7.0 L / min. GaCl3 was used as the Ga precursor, dissolved in ultrapure water, to form a raw solution with a concentration of 50–300 mmol / L. HCl diluted with ultrapure water was used as the Cl source, with a concentration of 570 mmol / L. The Ga and HCl supply rates were controlled by the carrier gas (cg) flow rate. The experimental conditions are listed in Table 1, and detailed gas flow conditions are listed in Table 2. The crystal structure was evaluated using X-ray diffraction (XRD) 2θ / ω scans, and the thin film surface roughness was evaluated using atomic force microscopy (AFM). X-ray photoelectron spectroscopy was used to evaluate the chemical bonding state of the α-Ga2O3 thin film. The film thickness was calculated from the Laue fringe of the XRD measurement, and the amount of Ga and HCl supplied was calculated from the weight difference from the start to the end of film formation.

[0046] [Table 1]

[0047] [Table 2]

[0048] 1-2 rating Figure 1 shows the XRD measurement results. Under all conditions, peaks originating from α-Ga2O3 (0006) and Laue fringes were observed, indicating the formation of highly crystalline α-Ga2O3. Figures 2(a)-(c) show the relationship between the deposition rate and the Ga supply rate, HCl supply rate, and HCl / Ga supply ratio. In these figures, C1, C2, C3, and C4 are plotted with ●, ▲, ■, and ×, respectively. The plot color represents the HCl supply rate. An HCl supply rate of 0.22 mmol / min is black (0,0,0), 2.29 mmol / min is red (255,0,0), and intermediate values ​​are represented by black-red (127,0,0) (represented by single diagonal lines) and red-black (190,0,0) (represented by double diagonal lines). Figure 2(a) shows that there is no correlation between the film formation rate and the Ga supply rate, and therefore, when the Ga supply rate is greater than 0.060 mmol / min, α-Ga2O3 is a reaction-determining process. Figure 2(b) shows that the film formation rate increases as the HCl supply rate increases. This indicates that HCl plays a significant role in the formation of α-Ga2O3 using the mist CVD method. The numerical data for each plot in Figure 2 is shown below.

[0049] [Table 3]

[0050] Example 2: Preparation of α-Ga2O3 thin film with excellent surface flatness. Examination of the relationship between the amount of 2-Ga supply, the amount of HCl supply, and the surface roughness. To investigate the effect of HCl on the formation of α-Ga2O3 thin films in more detail, we investigated the relationship between the Ga supply amount, HCl supply amount, and surface roughness. To evaluate the surface roughness of thin films with different thicknesses, we used the thickness per root-mean-square roughness (TPR) as the root-mean-square roughness. A larger TPR indicates a higher surface flatness relative to the film thickness and thus better quality. Figures 3(a)–(c) show the relationship between TPR and the Ga supply amount, HCl supply amount, and the HCl / Ga supply ratio. Figure 3(a) shows no correlation between TPR and the Ga supply amount. Figure 3(b) shows a trend for each Ga supply amount. When the Ga supply amount is low (C1), the TPR remains low and constant even as the HCl supply amount increases. When the Ga supply amount increases (C2, C3, and C4), the TPR increases with increasing HCl supply amount. Figure 3(c) shows the TPR plotted against the HCl / Ga supply ratio. Figure 3(c) clearly shows three trends, suggesting that α-Ga2O3 has three growth modes depending on the HCl / Ga supply ratio. When the HCl / Ga supply ratio is large, the TPR remains low and constant, or increases only slightly (mode 1). As the Ga supply increases and the HCl / Ga supply ratio decreases, the growth mode changes to mode 2 or mode 3, where the TPR increases with increasing HCl / Ga supply ratio. In mode 2, the TPR increases linearly with the HCl / Ga supply ratio, and the plot points lie on a straight line regardless of the experimental conditions. Unlike mode 2, in mode 3, the TPR increases with the HCl / Ga supply ratio at a steeper slope than in mode 2. However, in mode 3, the TPR increases similarly with each Ga supply, but the transition from mode 2 to mode 3 shifts toward smaller HCl / Ga supply ratios as the Ga supply increases. The numerical data for each plot in Figure 3 are shown below.

[0051] [Table 4]

[0052] XPS measurements were performed to investigate the differences in α-Ga2O3 thin films grown using different growth modes. The XPS data were corrected using the C1s peak at 284.8 eV. Figures 4(a)–(c) show the O1s XPS results for samples 3, 4, and 11 grown using modes 1, 2, and 3. The O1s spectra were fitted with four peaks: the O-Ga bond in Ga2O3 (530 eV), the O-Ga bond in GaO or the bond of O adsorbed on the surface (531 eV), the O-C bond (532 eV), and the O=C bond (533 eV). GaO / Ga2O3 and Imp. / Ga2O3 in Figure 4 represent the peak intensity ratios Ga(GaO) / O-Ga(Ga2O3) and (O-C+O=C) / O-Ga(Ga2O3), respectively. In the order of samples No. 3, 4, and 11 (modes 1, 2, and 3), Imp. / Ga2O3 decreased from 0.168 to 0.054, and GaO / Ga2O3 decreased from 0.432 to 0.223, indicating that the purity of the α-Ga2O3 thin film improved.

[0053] Here, we consider the mechanism by which the results obtained with HCl assistance were obtained. Since the Ga source is an ionic binder, it is thought to be sufficiently dissociated and ionized in the solution. If we consider that an increase in HCl does not have a significant effect on the state of the raw material, it is thought to contribute to the surface reaction. For example, the bonds such as C and OH adsorbed or bonded on the surface and excess Ga are dissociated by Cl. - By supplying O 2- The domain appears and Ga 3+ O 2- On the other hand, when the Ga supply is insufficient compared to the HCl supply, C atoms are easily adsorbed to the surface O. 2- It is thought that the surface roughness did not improve as a result of the recombination of the particles (mode 1).

[0054] summary It was found that HCl support affects the film formation rate, impurity content, and surface roughness. When the Ga supply rate is 0.060 mmol / min or higher, the film formation rate increases as the HCl supply rate increases, regardless of the Ga supply amount. In addition, by changing the HCl / Ga supply ratio and Ga supply amount and considering the TPR, it was found that three growth modes of α-Ga2O3 can be observed. It was found that the α-Ga2O3 thin film grown in each mode has improved α-Ga2O3 purity in the film. This is because by supporting HCl during film formation in the mist CVD method, surface residues are washed away and O is left on the surface. 2- It is thought that the appearance of domains may have improved the film formation rate, the purity in the film, and the surface roughness. [Industrial Applicability]

[0055] According to the present invention, it is possible to produce high-quality Ga2O3 thin films, which lead to the development of high-performance deep-ultraviolet light-emitting devices.

Claims

[Claim 1] Ga with surface flatness and improved surface roughness ２ O ３ A method for producing a thin film, comprising: The method comprises: spraying a source solution containing GaCl 3 and a support agent containing HCl onto a substrate at 350-450°C; The step of spraying onto the substrate includes: A step of placing the raw material solution and the supporting agent in separate sprayers; a step of misting the raw material solution and the supporting agent by ultrasonic waves; a step of mixing the mist-formed raw material solution and the supporting agent; spraying a mist of the mixed raw material solution and the supporting agent onto the substrate; The raw material solution contains GaCl ３ The concentration of is 100 to 500 mmol / L. Ga ２ O ３ A method for producing a thin film.

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