Crucible, method for producing beta-type digallium trioxide single crystal substrate using same, and beta-type digallium trioxide single crystal substrate

Abstract

A crucible for growing a beta-type digallium trioxide single crystal, wherein: the crucible thickness is 1-10mm, inclusive; the maximum inner diameter of the crucible is 100mm or more; the crucible composition is a stabilized zirconia containing yttrium oxide and / or calcium oxide; the surface on the inner-circumferential surface side of the crucible is coated with a sprayed film containing rhodium and / or platinum; the thickness of the sprayed film is 100-500μm, inclusive; and the stabilized zirconia at least contains 12.0-15.5 mass%, inclusive, of yttrium oxide or 10.2-11.4 mass%, inclusive, of calcium oxide.

Description

Crucible, method for producing beta-type digallium trioxide single crystal substrate using the same, and beta-type digallium trioxide single crystal substrate

[0001] The present disclosure relates to a crucible, a method for producing a beta-type digallium trioxide single crystal substrate using the crucible, and a beta-type digallium trioxide single crystal substrate.

[0002] Japanese Patent Laid-Open No. 2016-079080 (Patent Document 1), Japanese Patent Laid-Open No. 2017-193466 (Patent Document 2), Japanese Patent Laid-Open No. 2021-031367 (Patent Document 3), Japanese Patent Laid-Open No. 2021-031379 (Patent Document 4), Japanese Patent Laid-Open No. 2020-059633 (Patent Document 5), and Hoshikawa et al., Journal of the Japanese Society for Crystal Growth, Vol. 44, No. 4 (2017), 44-4-03 (Non-Patent Document 1) discloses a method for growing beta-type gallium trioxide single crystals (hereinafter also referred to as "beta-type GaO single crystals") by a vertical boat method using a crucible made of a platinum-rhodium alloy (hereinafter also referred to as "Pt-Rh alloy") or a crucible or die made of a platinum-iridium alloy (hereinafter also referred to as "Pt-Ir alloy"), or an edge-defined film-fed growth (EFG) method. JP 2000-129465 A (Patent Document 6) discloses a method for depositing platinum or a platinum-based alloy by thermal spraying onto the surface of a refractory substrate such as a ceramic.

[0003] JP 2016-079080 A JP 2017-193466 A JP 2021-031367 A JP 2021-031379 A JP 2020-059633 A JP 2000-129465 A

[0004] Hoshikawa et al., Journal of the Japanese Society for Crystal Growth, Vol. 44, No. 4 (2017), 44-4-03

[0005] The crucible according to the present disclosure is a crucible for growing beta-type gallium trioxide single crystals. The crucible has a thickness of 1 mm or more and 10 mm or less. The maximum inner diameter of the crucible is 100 mm or more. The crucible is composed of stabilized zirconia containing both or either of yttrium oxide and calcium oxide. The inner peripheral surface of the crucible is coated with a thermal sprayed film containing both or either of rhodium and platinum. The thickness of the thermal sprayed film is 100 μm or more and 500 μm or less. The stabilized zirconia contains at least 12.0 mass% to 15.5 mass% of the yttrium oxide or 10.2 mass% to 11.4 mass% of the calcium oxide.

[0006] FIG. 1 is a schematic diagram illustrating a single crystal growth apparatus used in a method for producing a beta-type GaO single crystal substrate according to this embodiment, and a main part of a first embodiment of a crucible used in the single crystal growth apparatus. FIG. 2 is an enlarged cross-sectional view illustrating a main part of a second embodiment of a crucible used in the single crystal growth apparatus of FIG. 1. FIG. 3 is an enlarged cross-sectional view illustrating a main part of a third embodiment of a crucible used in the single crystal growth apparatus of FIG. 1. FIG. 4 is an enlarged cross-sectional view illustrating a main part of a fourth embodiment of a crucible used in the single crystal growth apparatus of FIG. 1. FIG. 5 is an enlarged cross-sectional view illustrating a main part of a fifth embodiment of a crucible used in the single crystal growth apparatus of FIG. 1. FIG. 6 is a flowchart illustrating an example of a method for producing a beta-type GaO single crystal substrate according to this embodiment. FIG. 7 is a schematic view illustrating a beta-type GaO single crystal substrate according to this embodiment. FIG. 8 is an explanatory diagram illustrating a Hall measurement sample prepared using the central portion of a beta-type Ga2O3 single crystal substrate according to this embodiment in order to measure the carrier concentration in the substrate.

[0007] [Problem to be Solved by the Present Disclosure] As disclosed in Patent Documents 1 to 5 and Non-Patent Document 1, it is known to grow and obtain beta-type GaO single crystals using crucibles made of Pt—Rh alloys or Pt—Ir alloys. These crucibles made of Pt—Rh alloys, Pt—Ir alloys, etc. are expensive, and reducing their wall thickness is considered to reduce costs. However, crucibles made of Pt—Rh alloys, Pt—Ir alloys, etc. are prone to deformation due to thermal contraction and other factors. Therefore, they are prone to cracking or chipping due to the beta-type GaO single crystals present in the crucible during crystal growth and cooling after crystal growth. This has been pointed out as a problem, making it difficult to obtain the desired beta-type GaO single crystals with a high yield. Cracking of the crucible during crystal growth, in particular, is fatal to obtaining beta-type GaO single crystals. The method of depositing platinum or a platinum-based alloy by thermal spraying disclosed in Patent Document 6 is not intended to suppress cracking or chipping of the crucible, etc., and therefore there is no suggestion whatsoever regarding the action or effect of preventing cracking of the crucible during crystal growth. Therefore, a crucible using a thin film of a Pt—Rh alloy, Pt—Ir alloy, or the like that can at least suppress the occurrence of cracking, chipping, etc. during crystal growth and thereby produce beta-type GaO single crystals with a high yield has not yet been obtained, and its development is eagerly awaited.

[0008] In view of the above, an object of the present disclosure is to provide a crucible that can suppress the occurrence of cracks, chips, and the like during crystal growth, a method for manufacturing a beta-type digallium trioxide single crystal substrate using the same, and a beta-type digallium trioxide single crystal substrate.

[0009] [Effects of the Present Disclosure] According to the present disclosure, it is possible to provide a crucible that can suppress the occurrence of cracks, chips, and the like during crystal growth, a method for manufacturing a beta-type digallium trioxide single crystal substrate using the same, and a beta-type digallium trioxide single crystal substrate.

[0010] [Summary of the Embodiments] The following describes an overview of the embodiments of the present disclosure. The present inventors have conducted extensive research to solve the above-mentioned problems and have completed the present disclosure. First, the inventors focused on zirconia, a material with low thermal conductivity, stability against temperature changes, and resistance to deformation, as a material for a crucible used in the vertical boat method. In particular, the inner surface of the zirconia crucible was coated with a thin film containing both or either of rhodium and platinum, such as a thin film made of a Pt—Rh alloy containing Rh, which can withstand the temperatures required for growing beta-type GaO single crystals (approximately 1800°C). This resulted in the conceivable creation of a crucible that can at least suppress the occurrence of cracks, chips, and the like during crystal growth. In addition, the inventors discovered the appropriate thicknesses of the crucible and the thin film for obtaining the single crystals with a high yield, and arrived at the present disclosure.

[0011] Next, embodiments of the present disclosure will be described in detail. [1] A crucible according to one aspect of the present disclosure is a crucible for growing beta-type digallium trioxide single crystals. The crucible has a thickness of 1 mm or more and 10 mm or less. The maximum inner diameter of the crucible is 100 mm or more. The crucible is composed of stabilized zirconia containing both or either of yttrium oxide and calcium oxide. The inner peripheral surface of the crucible is coated with a thermal spray film containing both or either of rhodium and platinum. The thickness of the thermal spray film is 100 μm or more and 500 μm or less. The stabilized zirconia contains at least 12.0 mass% to 15.5 mass% of the yttrium oxide or 10.2 mass% to 11.4 mass% of the calcium oxide. A crucible having these characteristics can suppress cracking, chipping, and the like during crystal growth.

[0012] [2] In the crucible of [1] above, the sprayed film is preferably made of a platinum-rhodium alloy containing 10% by mass to 30% by mass of rhodium, thereby further suppressing cracking, chipping, and the like during crystal growth.

[0013] [3] In the crucible of [2] above, the sprayed film preferably has pores. The porosity, which is the volume ratio of the pores in the sprayed film, is preferably 30% by volume or more and 50% by volume or less. This makes it possible to further suppress the occurrence of cracks, chips, etc. during crystal growth.

[0014] [4] In the crucible of [2] above, the surface roughness Rz of the surface is preferably 300 μm or more and 500 μm or less. The sprayed film preferably has pores. The porosity, which is the volume ratio of the pores in the sprayed film, is preferably 10 vol% or more and less than 30 vol%. This can further suppress the occurrence of cracks, chips, etc. during crystal growth.

[0015] [5] In the crucible of [3] above, the surface roughness Rz of the surface is preferably 300 μm or more and 500 μm or less. This makes it possible to further suppress the occurrence of cracks, chips, etc. during crystal growth.

[0016] [6] In the crucible of [1] above, the sprayed film preferably comprises a first film and a second film. The first film preferably covers the surface. The first film preferably comprises rhodium or a platinum-rhodium alloy containing rhodium as a main component. The second film preferably covers the first film. The second film preferably comprises platinum or a platinum-rhodium alloy containing platinum as a main component. The total thickness of the sprayed film, including the first and second films, is preferably 100 μm or more and 500 μm or less. This makes it possible to suppress the incorporation of rhodium into the beta-type gallium trioxide single crystal.

[0017] [7] In the crucible of [6], it is preferable that both the first film and the second film have pores. The first film porosity, which is the volume ratio of the pores in the first film, and the second film porosity, which is the volume ratio of the pores in the second film, are both preferably 30% by volume or more and 50% by volume or less. This can further suppress the occurrence of cracks, chips, etc. during crystal growth.

[0018] [8] In the crucible of [6] above, the surface roughness Rz of the surface is preferably 300 μm or more and 500 μm or less. The first film and the second film preferably both have pores. The first film porosity, which is the volume ratio of the pores in the first film, and the second film porosity, which is the volume ratio of the pores in the second film, are both preferably 10% by volume or more and less than 30% by volume. This can further suppress the occurrence of cracks, chips, etc. during crystal growth.

[0019] [9] In the crucible of [7] above, the surface roughness Rz of the surface is preferably 300 μm or more and 500 μm or less. This makes it possible to further suppress the occurrence of cracks, chips, etc. during crystal growth.

[0020]

[10] A method for producing a beta-type digallium trioxide single crystal substrate according to one embodiment of the present disclosure is a method for producing a beta-type digallium trioxide single crystal substrate using the crucible described in any one of [1] to [9] above. The production method includes the steps of preparing the crucible, obtaining a beta-type digallium trioxide single crystal by a vertical boat method using the crucible, and processing the beta-type digallium trioxide single crystal to obtain a beta-type digallium trioxide single crystal substrate having a circular main surface. A production method having these characteristics can produce a beta-type digallium trioxide single crystal substrate with good yield and product yield.

[0021]

[11] A beta-type digallium trioxide single crystal substrate according to one embodiment of the present disclosure is a beta-type digallium trioxide single crystal substrate having a circular main surface. The diameter of the beta-type digallium trioxide single crystal substrate is 100 mm or more. The main surface is the (001) plane of the beta-type digallium trioxide single crystal. Alternatively, the main surface is a plane having an off-angle of more than 0° and not more than 10° from the (001) plane of the beta-type digallium trioxide single crystal, and an off-direction in the

[010] direction of the beta-type digallium trioxide single crystal or a direction perpendicular to the

[010] direction. The beta-type digallium trioxide single crystal substrate contains both rhodium and iridium. The rhodium concentration and the iridium concentration are both less than 3 ppm by mass by glow discharge mass spectrometry. A beta-type digallium trioxide single crystal substrate having these characteristics can have excellent electrical and optical properties.

[0022]

[12] In the beta-type gallium trioxide single crystal substrate of

[11] , the transmittance for light with a wavelength of 400 nm or more and 430 nm or less is preferably 70% or more. The carrier concentration measured at 25°C by the Van der Pauw Hall measurement is preferably 1×10 17 cm -3 Above 1.0 x 10 19 cm -3 It is preferable that the thickness is equal to or less than 100 nm, whereby both electrical and optical properties can be improved.

[0023] [Details of the embodiment] One embodiment according to the present disclosure (hereinafter also referred to as "the present embodiment") will be described in further detail below, but the present disclosure is not limited thereto. The following description may be made with reference to the drawings, and the same or corresponding elements in this specification and the drawings will be denoted by the same reference numerals, and the same description will not be repeated. Furthermore, the scale of the drawings has been adjusted appropriately to facilitate understanding of each component, and the scale of each component shown in the drawings does not necessarily coincide with the scale of the actual component.

[0024] In this specification, the expression "A to B" means the upper and lower limits of a range (i.e., A or more and B or less), and when no unit is specified for A and only a unit is specified for B, the units of A and B are the same. Furthermore, when a compound or the like is expressed in this specification by a chemical formula, unless the atomic ratio is particularly limited, it is understood to include any conventionally known atomic ratio, and should not necessarily be limited to only those within a stoichiometric range.

[0025] As used herein, "yield" refers to the percentage of beta-type gallium trioxide single crystals that can be grown to the desired thickness in the crucible without cracking or chipping in the crucible. As used herein, "product yield" refers to the percentage of the mass of a beta-type gallium trioxide single crystal ingot grown in the crucible, excluding regions where the crucible cracks or chips or the crystal cracks or chips during cooling, making it impossible to obtain the desired diameter when processed into a beta-type gallium trioxide single crystal substrate, and then evaluating the mass of the portion that can be used as a non-defective substrate using the evaluation method described below. The higher the "product yield" value of the single crystal, the less likely it is that cracks, chips, etc. occurred in the crucible in which the single crystal was grown. Furthermore, as used herein, "major component" refers to a component whose content exceeds 95% by mass in a composition such as an alloy.

[0026] In this specification, the "maximum inner diameter" of a crucible refers to the inner diameter of the crucible at the position where the inner diameter of the ring, which appears in a cross section perpendicular to the axial direction of the cylindrical crucible, is maximum when compared along the axial direction of the crucible. In the present disclosure, the crucible preferably has a structure including a cylindrical seed crystal accommodating portion, an increasing diameter portion connected to the seed crystal accommodating portion, and a straight body portion connected to the increasing diameter portion, as described below. In such a crucible, the "maximum inner diameter" refers to the inner diameter of the straight body portion.

[0027] In this specification, the "main surface" of a beta-type digallium trioxide single crystal substrate refers to both of the two circular faces of the beta-type digallium trioxide single crystal substrate. When at least one of the two faces of the beta-type digallium trioxide single crystal substrate satisfies the scope of the claims of the present disclosure, the substrate falls within the technical scope of the present disclosure. Furthermore, the "face" used in the term "in-plane" in this specification refers to the "main surface." Furthermore, when the diameter of a beta-type digallium trioxide single crystal substrate is described as "100 mm," this means that the diameter is approximately 100 mm (approximately 95 to 105 mm), or 4 inches. When the diameter is described as "150 mm," this means that the diameter is approximately 150 mm (approximately 145 to 155 mm), or 6 inches. The diameter can be measured using a conventionally known outer diameter measuring instrument such as a vernier caliper.

[0028] In the crystallographic descriptions in this specification, individual directions are represented by [ ], collective directions by < >, individual planes by ( ), and collective planes by {}. In addition, negative crystallographic indices are usually represented by placing a "- (bar)" above the number, but in this specification, a negative sign is placed before the number.

[0029] [Crucible] The crucible according to this embodiment is a crucible for growing beta-type gallium trioxide single crystals (beta-type Ga2O3 single crystals). The crucible has a thickness of 1 mm or more and 10 mm or less. The maximum inner diameter of the crucible is 100 mm or more. The crucible is composed of stabilized zirconia containing yttrium oxide and / or calcium oxide. The inner peripheral surface of the crucible is coated with a thermal spray film containing rhodium (Rh) and / or platinum (Pt). For example, the thermal spray film is preferably made of a platinum-rhodium alloy (Pt—Rh alloy) containing 10 mass % to 30 mass % Rh. The thickness of the thermal spray film is 100 μm to 500 μm. The stabilized zirconia contains at least 12.0% by mass to 15.5% by mass of the yttrium oxide or 10.2% by mass to 11.4% by mass of the calcium oxide. A crucible having such characteristics can suppress the occurrence of cracks, chips, etc. during crystal growth.

[0030] As described above, the crucible is a crucible for growing beta-type GaO single crystals. The crucible is applied to a single crystal growth apparatus, such as that shown in FIG. 1, for the purpose of growing and obtaining beta-type GaO single crystals. The crucible according to this embodiment will be described in detail below by explaining the single crystal growth apparatus shown in FIG. 1. FIG. 1 is a schematic diagram illustrating the single crystal growth apparatus used in the method for producing a beta-type GaO single crystal substrate according to this embodiment, and the main parts of a first embodiment of a crucible used in the single crystal growth apparatus.

[0031] 1, the single crystal growth apparatus 100 includes the above-mentioned crucible 5, a crucible holder 6 for holding the crucible 5, and a heating device 7 for heating the crucible 5. The single crystal growth apparatus 100 may further include a sealed container 9 for containing the single crystal growth apparatus 100 itself. The dimensions, material, etc. of the sealed container 9 are not particularly limited as long as it can contain the single crystal growth apparatus 100 and the like and has the function of preventing the intrusion of impurities from the outside.

[0032] The crucible 5 includes a cylindrical seed crystal accommodation portion 51, an increasing diameter portion 52 connected to the seed crystal accommodation portion 51, and a straight body portion 53 connected to the increasing diameter portion 52. The seed crystal accommodation portion 51 is cylindrical and has a hollow portion that opens on the side connected to the increasing diameter portion 52 and has a bottom wall formed on the side opposite the increasing diameter portion 52. The seed crystal accommodation portion 51 can accommodate and hold a seed crystal 8a in the hollow portion. The increasing diameter portion 52 has a truncated cone shape that widens upward in the axial direction of the crucible 5 and is connected to the seed crystal accommodation portion 51 on the smaller diameter side of the increasing diameter portion 52. The straight body portion 53 has a hollow cylindrical shape and is connected to the larger diameter side of the increasing diameter portion 52. The increasing diameter portion 52 and the straight body portion 53 function to hold a block of gallium trioxide bulk material (specifically, polycrystalline GaO; hereinafter, also referred to as "GaO bulk material") therein. The diameter increasing portion 52 and the cylindrical portion 53 have the function of solidifying the gallium trioxide melt to grow a beta type Ga2O3 single crystal as a crystal, as will be described later.

[0033] <Thickness and Maximum Inner Diameter> The crucible 5 has a thickness of 1 mm or more and 10 mm or less. More specifically, the side wall portions 5a of the seed crystal accommodating portion 51, the increased diameter portion 52, and the straight body portion 53 of the crucible 5 all have a thickness of 1 mm or more and 10 mm or less. It is preferable that the side wall portions 5a of the seed crystal accommodating portion 51, the increased diameter portion 52, and the straight body portion 53 of the crucible 5 all have a thickness of 5 mm or more and 10 mm or less. Furthermore, the maximum inner diameter of the crucible 5 is 100 mm or more. More specifically, it is preferable that the inner diameter of the straight body portion 53 of the crucible 5 is 100 mm or more. It is also preferable that the inner diameter of the straight body portion 53 of the crucible 5 is 150 mm or more. The upper limit of the maximum inner diameter of the crucible 5 is not particularly limited, but is, for example, 165 mm.

[0034] If the thickness of the crucible 5 is less than 1 mm, cracking and chipping of the crucible 5 during crystal growth may not be sufficiently suppressed. There is also a possibility that the crucible 5 may deform during crystal growth. If the thickness of the crucible 5 exceeds 10 mm, the adverse effect of increased cost of the crucible 5 may outweigh the cost reduction and other benefits obtained by suppressing cracking and chipping of the crucible 5 during crystal growth. By setting the maximum inner diameter of the crucible 5 to 100 mm or more, cracking and chipping of the crucible 5 can be suppressed when producing a large-diameter beta-type GaO single crystal substrate with a diameter of 4 inches or 6 inches.

[0035] <Crucible Composition: Stabilized Zirconia> The crucible 5 is composed of stabilized zirconia (hereinafter also referred to as "stabilized ZrO") containing either or both of yttrium oxide (yttria: YO) and calcium oxide (calcia: CaO). The crucible 5 is preferably composed of stabilized ZrO containing either YO or CaO. Specifically, the stabilized ZrO contains at least 12.0% by mass to 15.5% by mass of YO or 10.2% by mass to 11.4% by mass of CaO. By using stabilized ZrO, which has low thermal conductivity as described above, as the composition of the crucible 5, crystal defects that occur during crystal growth are more likely to be expelled to the outer periphery of the crystal, thereby preventing the beta-type GaO single crystal from becoming polycrystallized during crystal growth. "Stabilized ZrO2" means ZrO2 plus Y2O 3、 This refers to ZrO2 in which the high-temperature phase (typically a cubic or tetragonal solid solution) can be stably present down to room temperature by adding CaO, magnesium oxide (MgO), aluminum oxide (alumina: Al2O3), etc. The oxides that form a solid solution in stabilized ZrO2 are YO 3、 It is not limited to only CaO, MgO and Al2O3.

[0036] <Thermal Sprayed Film> (Composition) The inner peripheral surface of the crucible is coated with a thermal sprayed film containing both or either Rh and Pt. For example, the thermal sprayed film is preferably made of a Pt—Rh alloy containing 10% by mass to 30% by mass of Rh. For example, the crucible 5 of the first embodiment shown in FIG. 1 is coated with a thermal sprayed film 5b made of a platinum-rhodium alloy (Pt—Rh alloy) containing 10% by mass to 30% by mass of Rh. The thickness of the thermal sprayed film 5b is 100 μm to 500 μm. The thermal sprayed film 5b preferably covers the entire inner peripheral surface of the crucible 5. However, it would not depart from the scope of the present disclosure if a portion of the surface were not coated with the thermal sprayed film 5b or if the composition of the thermal sprayed film 5b were partially different.

[0037] The thermal spraying can be performed by a conventionally known method, such as plasma spraying. For example, the thermal spraying can be performed by heating the Pt—Rh alloy to form molten particles or particles similar to the molten particles (e.g., particle diameter: 45 to 300 μm), and supplying the spray material toward the inner circumferential surface of the side wall portion 5 a from a direction tilted at 30 to 45 degrees relative to the axial direction of the crucible 5 using a thermal spray nozzle. In this case, for example, the distance from the tip of the spray nozzle to the inner circumferential surface of the crucible 5 is preferably 20 to 120 mm along the direction in which the tip of the nozzle faces. Furthermore, the thickness of the sprayed film 5 b can be determined by controlling the supply rate of the spray material. For example, the supply rate of the spray material may be 50 to 75 g / min. The porosity, described below, can be determined by controlling the angle of the spray nozzle and the supply rate of the spray material. Increasing the particle diameter of the spray material can increase the surface roughness Rz, described below.

[0038] When the Rh content in the Pt—Rh alloy constituting the sprayed film 5b is 10 mass % or more, cracking and chipping of the crucible 5 during crystal growth can be more sufficiently suppressed. When the Rh content in the Pt—Rh alloy constituting the sprayed film 5b is 30 mass % or less, cracking and chipping of the crucible 5 during crystal growth can be sufficiently suppressed without increasing the cost of the crucible 5. It is more preferable that the sprayed film 5b be made of a Pt—Rh alloy containing 20 mass % to 30 mass % Rh.

[0039] If the thickness of the sprayed film 5b is less than 100 μm, the sprayed film 5b may peel off from the side wall 5a, and cracking and chipping of the crucible 5 during crystal growth may not be sufficiently suppressed. If the thickness of the sprayed film 5b exceeds 500 μm, the adverse effect of increased cost of the crucible 5 may outweigh the cost reduction and other benefits obtained by suppressing cracking and chipping of the crucible 5 during crystal growth. The thickness of the sprayed film 5b is preferably 200 μm or more and 500 μm or less.

[0040] The thickness of the thermal sprayed coating is measured in accordance with JIS H 8401:1999 (Testing method for thickness of thermal sprayed products). Specifically, the thickness can be measured by a direct method using a micrometer (for example, a product name (product number) of "U-shaped micrometer PMU100-25" manufactured by Mitutoyo Corporation, or a product name (product number) of "laser digital micrometer LSM-501S" manufactured by Mitutoyo Corporation) by determining the difference between the crucible thickness before and after thermal spraying. The Rh concentration in the Pt—Rh alloy can be determined when the thermal spray material is prepared.

[0041] (Porosity) Here, the sprayed film preferably has pores. The porosity, which is the volume ratio of pores in the sprayed film, is preferably 30% by volume or more and 50% by volume or less. This makes it possible to further suppress the occurrence of cracks, chips, etc. during crystal growth. Figure 2 is an enlarged cross-sectional view illustrating the main parts of a crucible of a second embodiment used in the single crystal growth apparatus of Figure 1. In the crucible of the second embodiment shown in Figure 2, the sprayed film 5b present on the inner peripheral surface side of the side wall portion 5a has pores 5c. The porosity, which is the volume ratio of pores 5c in this sprayed film 5b, is preferably 30% by volume or more and 50% by volume or less.

[0042] The porosity is measured in accordance with JIS K 7112:1999 Method A (underwater displacement method). Specifically, the density of the crucible is first measured before and after thermal spraying to calculate the measured density of the thermal sprayed film. The composition of the thermal sprayed film is then determined using an energy dispersive X-ray device (SEM-EDX: Scanning Electron Microscope-Energy Dispersive X-ray Spectroscopy) attached to a transmission electron microscope, and the ideal density is calculated from the composition. The porosity can be calculated by dividing the measured density by the ideal density x 100.

[0043] The crucible of the second embodiment is made of the stabilized ZrO2 described above, and therefore is not easily deformed by thermal contraction during crystal growth and cooling after crystal growth. However, even if the beta-type Ga2O3 single crystal present in the crucible compresses the sidewall 5a due to slight thermal contraction of the crucible, particularly during cooling after crystal growth, the pores 5c contained in the sprayed film 5b are crushed, thereby preventing cracking and chipping of the crucible. If the porosity is less than 30% by volume, the effect of suppressing cracking and chipping of the crucible due solely to the crushing of the pores 5c may not be sufficient. If the porosity is more than 50% by volume, it may be difficult to spray such a sprayed film 5b onto the sidewall 5a.

[0044] (Surface Roughness) The surface roughness Rz of the inner peripheral surface of the crucible is preferably 300 μm or more and 500 μm or less. Even in this case, the sprayed film preferably has pores. The porosity, which is the volume ratio of pores in the sprayed film, is preferably 10 vol% or more and less than 30 vol%. This further suppresses the occurrence of cracks, chips, and the like during crystal growth. FIG. 3 is an enlarged cross-sectional view illustrating essential parts of a crucible according to a third embodiment used in the single crystal growth apparatus of FIG. 1. In the crucible according to the third embodiment shown in FIG. 3, the surface roughness Rz of the inner peripheral surface of the side wall portion 5a is 300 μm or more and 500 μm or less. The sprayed film 5b present on the inner peripheral surface of the side wall portion 5a has pores 5c. The porosity, which is the volume ratio of pores 5c in the sprayed film 5b, is 10 vol% or more and less than 30 vol%. The surface roughness Rz of the inner peripheral surface of the side wall portion 5a is preferably 300 μm or more and 400 μm or less.

[0045] The surface roughness Rz of the inner peripheral surface of the side wall portion 5a is measured as follows. That is, the surface roughness Rz can be measured by determining the maximum height (Rz) of the inner peripheral surface of the side wall portion 5a as defined in JIS B0601:2001. For example, a surface roughness measuring instrument (product name (product number): "Surface Roughness Measuring Instrument SV-2100M4" manufactured by Mitutoyo Corporation, or product name (product number): "Surface Roughness Measuring Instrument SURFCOM TOUCH 550" manufactured by Tokyo Seimitsu Co., Ltd.) is used. The surface roughness Rz can be measured by setting a measuring unit inside the crucible and performing roughness measurements using a display / control unit. The porosity can be measured by the same method as the porosity of the thermal sprayed film of the crucible of the second embodiment.

[0046] The crucible of the third embodiment is made of the stabilized ZrO2 described above, and therefore is resistant to deformation due to thermal contraction during crystal growth and cooling after crystal growth. However, even if the beta-type Ga2O3 single crystal present in the crucible presses against the side wall 5a due to slight thermal contraction of the crucible, particularly during cooling after crystal growth, the surface roughness of the inner peripheral surface of the side wall 5a crushes any convex portions present, thereby preventing cracking, chipping, and the like of the crucible. Furthermore, the pores 5c contained in the sprayed film 5b are crushed, thereby preventing cracking, chipping, and the like of the crucible. If the surface roughness Rz is less than 300 μm, the effect of preventing cracking and chipping of the crucible due to crushing of convex portions may be insufficient. If the surface roughness Rz exceeds 500 μm, the strength of the crucible itself will decrease, which may cause the protrusions to break during crystal growth, leading to cracks and chips in the crucible. Furthermore, if the porosity is less than 10% by volume, the effect of suppressing cracks and chips in the crucible due to crushing of the pores 5 c may be insufficient.

[0047] Here, in the crucible of the second embodiment, the surface roughness Rz of the surface is preferably 300 μm or more and 500 μm or less. This allows the presence of the above-mentioned surface protrusions and voids 5c to further suppress the occurrence of cracks, chips, etc. during crystal growth. Having the surface roughness Rz of 300 μm or more can sufficiently suppress the cracks and chips of the crucible caused by the crushing of the protrusions. Having the surface roughness Rz of 500 μm or less can sufficiently suppress the cracks and chips of the crucible during crystal growth, etc., without reducing the strength of the crucible itself. In the crucible of the second embodiment, the surface roughness Rz of the surface is 300 μm or more and 500 μm or less can have the same configuration as the crucible of the third embodiment, in which the porosity is 30% by volume or more and 50% by volume or less.

[0048] (First Film and Second Film) The sprayed film preferably comprises a first film and a second film. The first film preferably covers the surface. The first film preferably comprises Rh or a Pt-Rh alloy containing Rh as a main component. The second film preferably covers the first film. The second film preferably comprises Pt or a Pt-Rh alloy containing Pt as a main component. The total thickness of the sprayed film, including the first and second films, is preferably 100 μm or more and 500 μm or less. This not only has the effect of suppressing the occurrence of cracks, chips, etc. during crystal growth, but also makes it possible to suppress the incorporation of Rh into the beta-type Ga2O3 single crystal.

[0049] FIG. 4 is an enlarged cross-sectional view illustrating essential parts of a crucible according to a fourth embodiment used in the single crystal growth apparatus of FIG. 1. In the crucible according to the fourth embodiment shown in FIG. 4, the sprayed film comprises a first film 5b1 and a second film 5b2. The first film 5b1 covers the inner peripheral surface of the sidewall 5a. The first film 5b1 is made of Rh or a Pt—Rh alloy containing Rh as a main component, and is preferably made of Rh, for example. The second film 5b2 coats the first film 5b1. The second film 5b2 is made of Pt or a Pt—Rh alloy containing Pt as a main component, and is preferably made of Pt, for example. The total thickness of the sprayed film, including the first film 5b1 and the second film 5b2, is 100 μm or more and 500 μm or less. The total thickness of the sprayed film, including the first film 5b1 and the second film 5b2, is preferably 100 μm or more and 300 μm or less. If the total thickness of the first film 5b1 and the second film 5b2 is less than 100 μm, the first film 5b1 and the second film 5b2 may peel off from the sidewall 5a, and the effect of suppressing cracking and chipping of the crucible 5 during crystal growth, which is based on the sprayed film being composed of the first film 5b1 and the second film 5b2, may be insufficient. If the total thickness of the first film 5b1 and the second film 5b2 exceeds 500 μm, the adverse effect of increased cost of the crucible 5 may outweigh the cost reduction and other benefits obtained by suppressing cracking and chipping of the crucible 5 during crystal growth. The method for measuring the thickness of the first and second films may be the same as the method for measuring the thickness of the sprayed film of the crucible in the first embodiment.

[0050] As shown in Figure 4, both the first film 5b1 and the second film 5b2 preferably have pores 5c. The first film porosity, which is the volume ratio of the pores 5c in the first film 5b1, and the second film porosity, which is the volume ratio of the pores 5c in the second film 5b2, are preferably 30% by volume or more and 50% by volume or less. This allows the occurrence of cracks, chips, and the like during crystal growth to be further suppressed based on the above-mentioned effect of the pores 5c. The method for measuring the first film porosity and the second film porosity can be the same as the method for measuring the porosity of the sprayed film on the crucible in the second embodiment.

[0051] In the crucible of the fourth embodiment, the sprayed film comprises the first film 5b1 and the second film 5b2 described above. The first film 5b1 is made of Rh or a Pt—Rh alloy containing Rh as a main component, and the second film 5b2 is made of Pt or a Pt—Rh alloy containing Pt as a main component. The first film 5b1 covers the inner peripheral surface of the sidewall portion 5a, and the second film 5b2 covers the first film 5b1. Therefore, the Rh in the sprayed film does not come into direct contact with the beta-type GaO single crystal in the crucible, or if it does come into contact, the amount is very small, which prevents Rh from being mixed into the beta-type GaO single crystal during crystal growth, etc.

[0052] In the crucible of the fourth embodiment, the sprayed film comprises a first film 5b1 and a second film 5b2. Therefore, by considering the first film 5b1 and the second film 5b2 together, the sprayed film can be a Pt—Rh alloy containing 10% by mass or more and 30% by mass or less of Rh. For example, in the crucible of the fourth embodiment, the sprayed film can be configured to comprise a first film 5b1 made of Rh and a second film 5b2 made of Pt, with the thickness of the first film 5b1 being one-third of that of the second film 5b2. This allows the crucible of the fourth embodiment to include a Pt—Rh alloy containing 10% by mass or more and 30% by mass or less of Rh. As described above, the total thickness of the sprayed film, including the first film 5b1 and the second film 5b2, is 100 μm or more and 500 μm or less.

[0053] Furthermore, in a crucible in which the sprayed coating is composed of a first film and a second film, the surface roughness Rz of the inner peripheral surface is preferably 300 μm or more and 500 μm or less. Even in this case, both the first film and the second film preferably have pores. The first film porosity, which is the volume ratio of pores in the first film, and the second film porosity, which is the volume ratio of pores in the second film, are both preferably 10% by volume or more and less than 30% by volume. This further suppresses the occurrence of cracks, chips, and the like during crystal growth. Figure 5 is an enlarged cross-sectional view illustrating the main parts of a crucible according to a fifth embodiment used in the single crystal growth apparatus of Figure 1. In the crucible according to the fifth embodiment shown in Figure 5, the surface roughness Rz of the inner peripheral surface of the side wall portion 5a is 300 μm or more and 500 μm or less. The first membrane 5b1 and the second membrane 5b2 on the inner circumferential surface side of the side wall portion 5a each have pores 5c. The first membrane porosity and the second membrane porosity, which are the volume ratios of pores 5c in the first membrane 5b1 and the second membrane 5b2, are each 10% by volume or more and less than 30% by volume. The surface roughness Rz of the inner circumferential surface of the side wall portion 5a is preferably 300 μm or more and 400 μm or less.

[0054] According to the crucible of the fifth embodiment, like the crucible of the third embodiment, the occurrence of cracks, chips, etc. during crystal growth can be further suppressed due to the presence of the convex portions and voids 5c on the surface on the inner peripheral side. Furthermore, like the crucible of the fourth embodiment, the Rh in the sprayed film does not come into direct contact with the beta-type GaO single crystal in the crucible, or even if it does, the amount of contact is very small, so that it is possible to suppress the incorporation of Rh into the beta-type GaO single crystal during crystal growth, etc.

[0055] In the crucible of the fourth embodiment, the surface roughness Rz of the surface is preferably 300 μm or more and 500 μm or less. This allows the presence of the above-mentioned surface protrusions and pores 5c to further suppress the occurrence of cracks, chips, etc. during crystal growth. The crucible of the fourth embodiment, in which the surface roughness Rz of the surface is 300 μm or more and 500 μm or less, has the same configuration as the crucible of the fifth embodiment, in which the first membrane porosity and the second membrane porosity are each 30 vol% or more and 50 vol% or less.

[0056] <Crucible Holder> As shown in Fig. 1 , the single crystal growth apparatus 100 includes a crucible holder 6 that holds the crucible 5. The crucible holder 6 contacts the bottom of the crucible 5 to hold the crucible 5. The crucible holder 6 may have a cylindrical appearance. The material of the crucible holder 6 is not particularly limited, but may be, for example, quartz, alumina, zirconia, or silicon carbide. The outer diameter of the crucible holder 6 depends on the diameter of the crucible 5 it supports, but is, for example, 75 mm or more and 200 mm or less.

[0057] (Heating Device) The heating device 7 is installed for the purpose of heating the crucible 5. The heating device 7 may be, for example, a conventionally known electric heater (hereinafter simply referred to as "heater"). For example, two heaters may be provided, and these two heaters may be arranged to surround the outer periphery of the crucible 5. The heater output may be controlled independently for each heater. In particular, the heater may be divided into multiple sections perpendicular to the axis of the crucible 5, resulting in a multi-stage configuration. In this case, it is preferable to independently control the heater output for each of the multi-stage sections. This allows the temperature of the contents in the crucible 5 to be precisely adjusted along the axial direction of the crucible 5. For example, by independently controlling the heater output for each of the multi-stage sections to heat the enlarged diameter section 52 and the straight body section 53, the growth rates of the crystals grown in the enlarged diameter section 52 and the straight body section 53 can be stabilized.

[0058] Although not shown, the single crystal growth apparatus 100 may include a thermocouple capable of measuring the temperature of the crucible 5 heated by the heater. A plurality of thermocouples may be arranged outside the crucible 5 along the axial direction. For example, a known temperature monitor may be used as the thermocouple.

[0059] [Method for Manufacturing a Beta-Type Digallium Trioxide Single Crystal Substrate] The method for manufacturing a beta-type digallium trioxide single crystal substrate (beta-type GaO single crystal substrate) according to this embodiment preferably uses the crucible described above to produce a beta-type GaO single crystal substrate. That is, the manufacturing method preferably includes the steps of: preparing the crucible; obtaining a beta-type digallium trioxide single crystal (beta-type GaO single crystal) by a vertical boat method using the crucible; and processing the beta-type GaO single crystal to obtain a beta-type GaO single crystal substrate having a circular main surface. This manufacturing method for a beta-type GaO single crystal substrate having these characteristics reduces cracking and chipping of the crucible during crystal growth, thereby enabling the production of beta-type GaO single crystal substrates with a high yield.

[0060] Fig. 6 is a flowchart showing an example of a method for manufacturing a beta-type GaO single crystal substrate according to this embodiment. The method for manufacturing a beta-type GaO single crystal substrate according to this embodiment preferably includes a beta-type GaO single crystal manufacturing step S100 and a beta-type GaO single crystal substrate manufacturing step S200, as shown in the flowchart of Fig. 6. More specifically, as shown in Fig. 6, the method for manufacturing a beta-type GaO single crystal substrate according to this embodiment preferably includes, as the beta-type GaO single crystal manufacturing step S100, a step (first step: preparation step S110) of preparing a single crystal growth apparatus including at least a cylindrical crucible and a heating device disposed so as to surround the outer periphery of the crucible. In the preparation step S110, in addition to the single crystal growth apparatus and the crucible constituting the apparatus, a seed crystal and a massive GaO bulk body are preferably also prepared.

[0061] The beta-type GaO single crystal production process S100 preferably includes a step of placing the seed crystal at the bottom of the crucible and placing the GaO bulk body in the crucible above the seed crystal (second step: raw material charging step S120). In the raw material charging step S120, the GaO bulk body is preferably placed in the crucible above the seed crystal. The beta-type GaO single crystal production process S100 preferably includes a step of heating the crucible with the heating device to melt the GaO bulk body and a portion of the seed crystal to obtain a GaO melt, and bringing the GaO melt into contact with the remainder of the seed crystal (third step: raw material melting step S130). Furthermore, the beta-type GaO single crystal manufacturing process S100 preferably includes a step of growing a crystal from the GaO melt on the remaining portion of the seed crystal to obtain a beta-type GaO single crystal (fourth step: GaO single crystal growing process S140).

[0062] The method for manufacturing a beta-type GaO single crystal substrate according to this embodiment can include a cutting step, a peripheral grinding step, and a polishing step, which will be described later, as a beta-type GaO single crystal substrate manufacturing step S200. In the beta-type GaO single crystal substrate manufacturing step S200, the above steps are performed in this order to obtain a beta-type GaO single crystal substrate.

[0063] Hereinafter, each step included in the method for manufacturing a beta-type GaO single crystal substrate according to this embodiment will be described with reference to FIGS. 1 and 6. According to the method for manufacturing a beta-type GaO single crystal substrate, a beta-type GaO single crystal is first grown by the vertical boat method using a crucible 5 applicable to the single crystal growth apparatus 100 shown in FIG. 1. The crucible 5 may be any one of the crucibles described in the first to fifth embodiments. Hereinafter, the vertical boat method will be abbreviated as the VB method. The VB method includes the vertical Bridgman method and the vertical temperature gradient solidification method.

[0064] <Beta-type GaO single crystal manufacturing process S100> (Preparation process S110) As shown in FIGS. 1 and 6, the beta-type GaO single crystal manufacturing process S100 first includes a step (preparation process S110) of preparing a single crystal growth apparatus 100 including at least a cylindrical crucible 5 and a heating device 7 arranged to surround the outer periphery of the crucible 5. In the preparation process S110, in addition to the above-described single crystal growth apparatus 100 for manufacturing the beta-type GaO single crystal 81, it is preferable to also prepare a seed crystal 8a and a block-shaped GaO bulk body. The seed crystal 8a is made of a beta-type GaO single crystal. The GaO bulk body may be made of polycrystalline GaO. The seed crystal 8a and the block-shaped GaO bulk body may be prepared by a conventionally known method or by purchasing commercially available products.

[0065] In the preparation step S110, the crucible 5 is prepared as any one of the first to fifth embodiments described above. The crucibles of the first to fifth embodiments can all have the above-described features by using a conventionally known method. That is, a crucible 5 having a sidewall portion 5a with a thickness of 1 to 10 mm and an inner diameter of the body portion 53 of 100 mm or more can be manufactured by a conventionally known method. In this case, the composition of the crucible 5 can be, for example, stabilized ZrO containing at least 12.0% to 15.5% by mass of YO or 10.2% to 11.4% by mass of CaO.

[0066] Furthermore, by performing plasma spraying on the crucible 5 using a spray material prepared under the following conditions, for example, the inner peripheral surface of the side wall 5a can be coated with a sprayed film 5b: Spray material: Pt—Rh alloy containing 10 to 30 mass % Rh, Particle size of spray material: 45 to 300 μm, Supply rate of spray material: 50 to 75 g / min, Orientation of spray nozzle: 30 to 45 degrees with respect to the axial direction of the crucible, Distance between the spray nozzle and the inner peripheral surface of the side wall of the crucible: 20 to 120 mm.

[0067] By controlling the supply rate of the thermal spray material, the thickness of the thermal sprayed film 5b can be adjusted to, for example, 100 to 500 μm. By controlling the angle of the thermal spray nozzle and the supply rate of the thermal spray material, the porosity in the thermal sprayed film 5b can be adjusted to 10 to 50 volume %. By controlling the particle size of the thermal spray material, the surface roughness Rz of the inner peripheral surface of the side wall portion 5a of the crucible 5 can be adjusted to 300 to 500 μm.

[0068] When preparing the crucibles of the fourth and fifth embodiments, the following spray materials can be used: a first spray material made of Rh or a Pt—Rh alloy containing Rh as the main component and having a particle size of 45 to 300 μm; and a second spray material made of a Pt—Rh alloy containing Pt as the main component and having a particle size of 45 to 300 μm. In this case, by performing plasma spraying using the first spray material, the inner peripheral surface of the side wall portion 5 a of the crucible 5 can be coated with a first film. Furthermore, by performing plasma spraying using the second spray material, the first film can be coated with a second film. In this case, by controlling the supply speed of the first spray material and the second spray material, the angle of the spray nozzle, and the particle diameter of the first spray material and the second spray material, it is possible to adjust the thickness of the first film and the second film, the porosity of the first film, the porosity of the second film, and the surface roughness Rz of the surface on the inner surface side of the side wall portion 5 a of the crucible 5.

[0069] (Raw Material Charging Step S120) The raw material charging step S120 is a step of placing the seed crystal at the bottom of the crucible and placing a massive GaO bulk body above the seed crystal in the crucible. In the raw material charging step S120, it is preferable that solid BO is also placed above the seed crystal 8a in the crucible 5 along with the massive GaO bulk body. The purpose of the raw material charging step S120 is to seal various raw materials into the crucible for crystal growth using the single crystal growth apparatus 100. In the raw material charging step S120, first, a seed crystal 8a consisting of a beta-type GaO single crystal is placed in the hollow portion of the seed crystal accommodation portion 51 of the crucible 5. Next, a plurality of GaO bulk masses made of polycrystalline GaO are loaded into the increased diameter portion 52 and the body portion 53 of the crucible 5 and stacked. In the raw material loading step S120, it is preferable to add a predetermined amount of Sn or Si when loading a plurality of GaO bulk masses into the crucible 5. As a result, a beta GaO single crystal substrate containing the Sn or Si as a dopant is obtained from the beta GaO single crystal 81 obtained by the beta GaO single crystal manufacturing step S100. When adding Sn or Si, the concentration of the dopant in the beta GaO single crystal substrate is set to, for example, 1.0 × 10 18 cm －3 (5.0 x 10 17 cm -3 Above 4.0 x 10 19 cm -3 It is preferable to adjust the amount of addition so that the following is satisfied:

[0070] (Raw Material Melting Step S130) The raw material melting step S130 involves heating the crucible with the heating device to melt the GaO bulk and a portion of the seed crystal to obtain a GaO melt, and bringing the GaO melt into contact with the remainder of the seed crystal. The purpose of the raw material melting step S130 is to melt the GaO bulk and a portion of the seed crystal 8a to bring the remainder of the seed crystal 8a into contact with the GaO melt 82 when growing a crystal using the single crystal growth apparatus 100. This allows a beta-type GaO single crystal 81 to grow on the remainder of the seed crystal 8a in the next step, the GaO single crystal growth step S140. Specifically, in the raw material melting step S130, the crucible 5 containing the seed crystal 8a and the GaO bulk is supported by the crucible holder 6. Thereafter, a current is supplied to the heating device 7 to heat the crucible 5. As a result, the GaO bulk melts to form a GaO melt 82. Next, a portion of the seed crystal 8a also melts, and the remainder of the seed crystal 8a and the GaO melt 82 come into contact with each other at the interface.

[0071] (GaO Single Crystal Growth Step S140) The GaO single crystal growth step S140 is a step of growing a crystal from the GaO melt onto the remaining portion of the seed crystal to obtain a beta-type GaO single crystal. In the GaO single crystal growth step S140, for example, the crucible 5 is gradually lowered along its axis (toward the seed crystal housing portion 51) relative to the heating device 7, thereby creating a temperature gradient in the crucible 5 such that the temperature on the seed crystal 8a side is lower and the temperature on the GaO melt 82 side is higher. This solidifies the GaO melt 82 in contact with the seed crystal 8a, allowing the beta-type GaO single crystal 81 to be continuously grown from the GaO melt 82 on the remaining portion of the seed crystal 8a. At this time, the temperature on the GaO melt 82 side is, for example, 1800 to 1820°C. The temperature gradient at the interface between the GaO melt 82 and the growing beta-type GaO single crystal 81 is, for example, 3 to 8°C / cm. The speed at which the crucible 5 is pulled downward along its axis is not particularly limited, but can be, for example, 0.1 to 2 mm / hour.

[0072] In the GaO single crystal growth step S140, the crucible 5 is pulled downward along its axis relative to the heating device 7, so that the interface between the beta GaO single crystal 81 and the GaO melt 82 rises toward the liquid BO side, and the GaO melt 82 is solidified as the beta GaO single crystal 81. As a result, the crystal growth of the beta GaO single crystal 81 continues until the solidification of the GaO melt 82 remaining in the straight body portion 53 of the crucible 5 is completed. In this manner, an ingot of the beta GaO single crystal 81 can be obtained.

[0073] <Beta-type GaO single crystal substrate manufacturing step S200> The method for manufacturing the beta-type GaO single crystal substrate includes a step (beta-type GaO single crystal substrate manufacturing step S200) of obtaining a beta-type GaO single crystal substrate having a circular main surface by processing the beta-type GaO single crystal obtained in the GaO single crystal growth step S140, as shown in Fig. 6. The beta-type GaO single crystal substrate manufacturing step S200 includes the following cutting step, outer periphery grinding step, and polishing step, and the beta-type GaO single crystal substrate can be obtained by performing these steps in this order.

[0074] The cutting step is a step of slicing the ingot made of a beta-type GaO single crystal removed from the crucible into wafers having a predetermined thickness to obtain a beta-type GaO single crystal substrate. Furthermore, the periphery grinding step is a step of grinding the periphery of the wafer to obtain a beta-type GaO single crystal substrate having a circular main surface. The periphery grinding step may include, for example, a chamfering step. Conventionally known cutting and periphery grinding methods can be used for the cutting step and the periphery grinding step. Furthermore, the polishing step is a step of polishing the center portion of the main surface to a mirror finish. Conventionally known polishing methods can be used for the polishing step. The polishing step can achieve a surface roughness Ra of 10 nm or less at the center portion, as specified in JIS B 0681-2:2018, for example.

[0075] <Effects> By carrying out the above steps, a beta-type GaO single crystal substrate according to this embodiment is manufactured. In the method for manufacturing a beta-type GaO single crystal substrate, the beta-type GaO single crystal is manufactured using the crucible according to any one of the first to fifth embodiments described above, which reduces cracking or chipping of the crucible during crystal growth, etc. Therefore, beta-type GaO single crystal substrates can be obtained with a high yield.

[0076] [Beta-type Digallium Trioxide Single Crystal Substrate] The beta-type digallium trioxide single crystal substrate (beta-type GaO single crystal substrate) according to this embodiment is a beta-type GaO single crystal substrate having a circular main surface. The diameter of the beta-type GaO single crystal substrate is 100 mm or more. The main surface is the (001) plane of the beta-type GaO single crystal. Alternatively, the main surface is a plane having an off-angle of more than 0° and not more than 10° from the (001) plane of the beta-type GaO single crystal, and an off-direction that is the

[010] direction of the beta-type GaO single crystal or a direction perpendicular to the

[010] direction. The beta-type GaO single crystal substrate contains both or either rhodium (Rh) and iridium (Ir). The Rh concentration and the Ir concentration are both less than 3 ppm by mass as determined by glow discharge mass spectrometry (GDMS). The beta-type GaO single crystal substrate having such characteristics can exhibit excellent electrical and optical properties due to the extremely small amounts of Rh and Ir contained therein.

[0077] The inventors focused on minimizing the concentrations of rhodium and iridium in a beta-type GaO single crystal substrate, which may be contained in the substrate and may inhibit the substrate's favorable electrical and optical properties because they are not homologous to gallium (Ga). Specifically, in producing a beta-type GaO single crystal to obtain a beta-type GaO single crystal substrate, Rh and Ir were prevented from coming into direct contact with the beta-type GaO single crystal and the GaO melt that served as its raw material. More specifically, a beta-type GaO single crystal was produced using, for example, the crucible of the fifth embodiment described above, and a beta-type GaO single crystal substrate was obtained from the beta-type GaO single crystal. This led to the development of a beta-type GaO single crystal substrate in which the Rh and Ir concentrations were both less than 3 ppm by mass, thereby completing the present disclosure.

[0078] <Diameter> Fig. 7 is a schematic diagram illustrating a beta-type GaO single crystal substrate according to this embodiment. The beta-type GaO single crystal substrate 1 shown in Fig. 7 has a diameter of 100 mm or more. In particular, the diameter of the beta-type GaO single crystal substrate 1 is preferably 100 mm or more and 155 mm or less. Specifically, the beta-type GaO single crystal substrate 1 having a diameter of 100 mm or more and 155 mm or less preferably has a diameter of 101.6 mm or 152.4 mm, in other words, a diameter of 4 inches or 6 inches. This allows a large-diameter beta-type GaO single crystal substrate having a diameter of 100 mm or more and 155 mm or less to have excellent electrical and optical properties. Here, the diameter of the beta-type GaO single crystal substrate is determined based on the circular shape before the formation of the orientation flat (hereinafter also referred to as "OF"), index flat (hereinafter also referred to as "IF"), etc., even if the main surface does not have a geometrically circular shape due to the influence of the orientation flat (hereinafter also referred to as "OF"), index flat (hereinafter also referred to as "IF"), etc. As mentioned above, the diameter of the beta-type GaO single crystal substrate can be measured using a conventionally known outer diameter measuring device such as a vernier caliper. The definition of "circular shape" representing the shape of the main surface in this specification will be given later.

[0079] <Main Surface> (Circular Shape) As described above, the beta-type GaO single crystal substrate 1 has a circular main surface 10. In this specification, the term "circular shape" used to describe the shape of the main surface includes not only a geometric circular shape but also a shape in which the main surface does not form a geometric circular shape due to the formation of at least one of a notch, OF, or IF on the periphery of the main surface 10. Here, "a shape in which the main surface does not form a geometric circular shape" refers to a shape in which, among line segments extending from any point on the periphery of the main surface 10 to the center of the main surface 10, the lengths of line segments extending from any point on the notch, OF, or IF to the center of the main surface are shorter. Furthermore, "a shape in which the main surface does not form a geometric circular shape" also includes a shape in which the lengths of all line segments extending from any point on the periphery of the main surface 10 to the center of the main surface 10 are not necessarily the same due to the shape of the beta-type GaO single crystal that is the raw material for the beta-type GaO single crystal substrate 1. In this case, the center of the main surface 10 refers to the position of the center of gravity, and the diameter of the beta-type GaO single crystal substrate 1 refers to the length of the longest line segment that passes through the center of the main surface 10 and extends from any point on the outer periphery of the beta-type GaO single crystal substrate 1 to another point on the outer periphery.

[0080] (The (001) plane of the beta-type GaO single crystal) The main surface 10 is the (001) plane of the beta-type GaO single crystal. Alternatively, the main surface 10 is a plane having an off-angle of more than 0° and not more than 10° from the (001) plane of the beta-type GaO single crystal, and an off-direction that is the

[010] direction of the beta-type GaO single crystal or a direction perpendicular to the

[010] direction. This makes it possible to provide a beta-type GaO single crystal substrate 1 whose main surface 10 is the (001) plane of a beta-type GaO single crystal that is widely used for forming optical devices, electronic devices, etc.

[0081] In this specification, the crystal plane of the main surface 10 is assumed to have an accuracy error of ±0.5°. For example, when the main surface 10 is said to be the "(001) plane" of a beta-type GaO single crystal, this means that the main surface 10 may be a (001) just plane, or may be a plane having an off-angle of -0.5 to +0.5° from the (001) plane. The off-angle and off-direction from the (001) plane at the main surface 10 of the beta-type GaO single crystal substrate 1 can be measured using a conventionally known crystal orientation measuring device (for example, the product name (product number) "FSASIII" manufactured by Rigaku Corporation).

[0082] <Rhodium (Rh) and Iridium (Ir)> The beta-type GaO single crystal substrate contains both or either of rhodium (Rh) and iridium (Ir). The Rh concentration and the Ir concentration are both less than 3 ppm by mass in GDMS. The Rh concentration and the Ir concentration are both preferably 1 ppm by mass or less, more preferably 0.1 ppm by mass or less, and even more preferably 0.01 ppm by mass or less in GDMS. The lower limits of the Rh concentration and the Ir concentration are such that they are not detectable in GDMS. The beta-type GaO single crystal substrate can exhibit excellent electrical and optical properties because the Rh and Ir contents are less than 3 ppm by mass.

[0083] The Rh and Ir are known elements that may be contained in the beta-type GaO single crystal substrate. Meanwhile, when the beta-type GaO single crystal substrate is obtained using the crucible of the fifth embodiment and the method for producing a beta-type GaO single crystal substrate, the Rh concentration and the Ir concentration can both be easily controlled to less than 3 ppm by mass in GDMS, based on the material of the crucible and the structure of the sprayed film consisting of the first and second films. Therefore, beta-type GaO single crystal substrates excellent in both electrical and optical properties can be obtained with a high yield.

[0084] (Glow Discharge Mass Spectrometry (GDMS)) A method for measuring the Rh and Ir concentrations in the beta-type GaO single crystal substrate using glow discharge mass spectrometry (GDMS) is described below. GDMS is a technique in which a glow discharge plasma is generated using the analytical sample as the cathode in a high-purity argon atmosphere, the surface of the analytical sample is sputtered in the plasma, and the ionized constituent elements of the analytical sample are measured using a mass spectrometer. This allows for qualitative and quantitative analysis of impurity elements, including Rh and Ir, other than Ga and O contained in the beta-type GaO single crystal substrate. Either a flat cell or a pin-shaped cell is used as the ion source for the GDMS. The pin-shaped cell is applicable to analytical samples that can be formed into strips approximately 2 mm square and 20 mm long. Specifically, it is used when analyzing Si single crystals, gallium arsenide (GaAs) single crystals, indium phosphide (InP) single crystals, and other materials that can be prepared by cleavage. The flat cell can be applied to analytical samples that can be formed into a disk shape with a diameter of about 10 mm, for example, when analyzing polycrystalline bodies. In any case, it is preferable to select either a flat cell or a pin-shaped cell as the GDMS ion source from the viewpoint of avoiding contamination of the analytical sample with external impurity elements. Since the beta-type GaO single crystal substrate can be cleaved longitudinally to prepare a pin-shaped analytical sample, it is preferable to prepare an analytical sample in the shape of a pin-shaped cell from the beta-type GaO single crystal substrate and use this as the GDMS ion source.

[0085] The GDMS can be performed, for example, as follows. First, a beta-type GaO single crystal substrate is obtained by the manufacturing method described below. The beta-type GaO single crystal substrate is then cleaved longitudinally to form a 2 mm square, 20 mm long, rectangular GaO analysis sample, which is then placed on the sample placement section of the apparatus described below. It is preferable to clean the sample placement section in accordance with a conventional method to prevent and remove foreign matter, and then pre-sputter for 60 minutes. The analytical value obtained during pre-sputtering serves as the background.

[0086] Next, GDMS can be performed on the GaO analysis sample placed on the sample placement surface under the following conditions. Regarding Rh and Ir, which are constituent elements of the GaO analysis sample other than Ga and O, semi-quantitative values ​​can be calculated by correcting the ion intensity ratio between Ga and Rh or the ion intensity ratio between Ga and Ir using the relative sensitivity factor (RSF). The relative sensitivity factor can be calculated using the value built into the software provided with the following instrument: Instrument: Glow discharge mass spectrometer (product name (product number): VG-9000, manufactured by VG Elemental); Ion source: Pin-shaped cell (cooled with liquid nitrogen during analysis); Discharge area: 10 mm diameter; Discharge gas: High-purity argon (6N grade); Discharge conditions: 2 mA, 1 kV (constant current mode); Detector: Faraday cup and multiplier; Mass resolution: 4000 m / Δm or higher (high resolution mode).

[0087] By analyzing the GaO analysis sample in the manner described above, it is possible to qualitatively and quantitatively determine the Rh and Ir contained in the beta-type GaO single crystal substrate. The detection limit of the GDMS is preferably 0.01 mass ppm.

[0088] (Transmittance and Carrier Concentration) In the beta-type GaO single crystal substrate, the transmittance for light having a wavelength of 400 nm or more and 430 nm or less is preferably 70% or more. The carrier concentration measured at 25° C. in the Hall measurement by the Van der Pauw method is 1×10 17 cm -3 Above 1.0 x 10 19 cm -3 It is preferable that the thickness is equal to or less than 100 nm, whereby both electrical and optical properties can be improved.

[0089] As described above, the transmittance of a beta-type GaO single crystal substrate for light with a wavelength of 400 nm or more and 430 nm or less is preferably 70% or more. The transmittance is more preferably 75% or more, and even more preferably 80% or more. The upper limit of the transmittance is the ideal value of 100%. The transmittance can be determined by measuring the light transmittance of the beta-type GaO single crystal substrate using an ultraviolet-visible-infrared spectrophotometer or the like. A specific procedure for determining the transmittance will be described below with reference to FIG. 7.

[0090] First, one beta-type GaO single crystal substrate 1 is obtained, for example, based on the manufacturing method described above. A rectangular slice 10a (e.g., 600 μm thick) measuring 20 mm long and 20 mm wide and centered at its center O (e.g., the center O of the main surface 10) is prepared from this beta-type GaO single crystal substrate 1, thereby obtaining a sample for transmittance measurement. Next, using an ultraviolet-visible-infrared spectrophotometer (product name (product number): "U-4000", manufactured by Hitachi High-Tech Corporation), light with a wavelength of 400 nm to 430 nm (e.g., 427 nm) is incident perpendicularly onto the center of the rectangular slice 10a. This allows the transmittance of the light through the beta-type GaO single crystal substrate 1 to be measured.

[0091] (Carrier Concentration) In this embodiment, the carrier concentration measured at 25° C. by the Hall measurement using the Van der Pauw method is 1×10 17 cm -3 Above 1.0 x 10 19 cm -3 Specifically, the carrier concentration determined at 25° C. by Hall measurement using the Van der Pauw method with the center of the beta-type GaO single crystal substrate as the measurement object is 1×10 17 cm -3 Above 1.0 x 10 19 cm -3 It is preferable that the carrier concentration is 1.0×10 or less. 17 cm -3If the carrier concentration is less than 1.0×10, when a semiconductor device is fabricated, current may not flow and the device may not operate. 19 cm -3 When the amount of inactive impurities in the crystal exceeds 1.0 × 10 19 cm -3 This suggests that the carrier concentration is 5.0×10 or more, which may have a negative effect on the operation of the device. 17 cm -3 3.8 x 10 18 cm -3 It is more preferable that the carrier concentration is less than 100%. This allows the n-type beta-type GaO single crystal substrate to have good electrical properties that enable it to be used for various electronic and optical devices. The carrier concentration can be determined by the following measurement method.

[0092] The procedure for determining the carrier concentration will be described in detail below with reference to FIGS. 7 and 8. FIG. 8 is an explanatory diagram illustrating a Hall measurement sample prepared using the central portion of a beta-type GaO single crystal substrate according to this embodiment in order to measure the carrier concentration in the substrate. First, as shown in FIG. 7, a single beta-type GaO single crystal substrate 1 is obtained, for example, using the manufacturing method described above. From the central portion of this single beta-type GaO single crystal substrate 1, a rectangular slice 10a (e.g., 600 μm thick) measuring 4 mm long and 4 mm wide is prepared, centered on its center O (e.g., the center O of the main surface 10). Next, as shown in FIG. 8, electrodes 21 made of an alloy containing gold and titanium are formed on the four corners of the rectangular slice 10a (the surface to be measured), thereby obtaining a Hall measurement sample. The shape of the electrode 21 is not limited to the rectangular shape shown in the figure, but may be a sector or a circle. The carrier concentration can be determined by applying Hall measurement by the Van der Pauw method to the rectangular slice 10a provided with such electrodes 21 in an atmosphere at 25° C. In this specification, the carrier concentration obtained by using the above-mentioned rectangular slice as the measurement object is defined as the carrier concentration of the beta-type GaO single crystal substrate measured at 25° C. in Hall measurement by the Van der Pauw method.

[0093] <Applications> The beta-type GaO single crystal substrate according to this embodiment has excellent electrical and optical properties, and therefore can be used as a substrate for forming optical devices and electronic devices. In particular, the beta-type GaO single crystal substrate is preferably used as a substrate for forming electronic devices based on its excellent electrical properties.

[0094] The present disclosure will be described in more detail below with reference to examples, but the present disclosure is not limited to these examples. In these examples, a single crystal manufacturing apparatus as shown in FIG. 1 and crucibles having essential configurations as shown in FIGS. 2 to 5 were used to manufacture beta-type GaO single crystal substrates according to the flowchart shown in FIG. 6. In the following description, Samples 101 to 115, Samples 201 to 213, and Samples 301 to 313 are examples. Samples 10A to 10C and Samples 20A to 20C are comparative examples.

[0095] Here, the "crystal outer diameter" of the beta-type GaO single crystal in each of the following samples refers to the crystal outer diameter determined by the following method: the outer diameter of the beta-type GaO single crystal ingot taken out of the crucible was determined at three points: a position corresponding to the boundary between the increased diameter portion and the straight body portion (hereinafter also referred to as "measurement point 1"), a position 10 mm below the crystal growth termination side of the ingot (hereinafter also referred to as "measurement point 2"), and an intermediate position between measurement points 1 and 2 (hereinafter also referred to as "measurement point 3"), and the average value thereof was defined as the "crystal outer diameter."

[0096] [Manufacturing of GaO Single Crystal Substrate] <Sample 10A> Following the method disclosed in Patent Document 1, an attempt was made to manufacture a beta-type GaO single crystal with the growth direction in the

[001] direction by using the vertical Bridgman (VB) method. A crucible made of a Pt—Rh alloy containing 30 mass% Rh was used to obtain the beta-type GaO single crystal. The inner diameter of the crucible's straight body was 105 mm. Furthermore, the thickness of the crucible's sidewall was 0.2 μm, and the surface roughness Rz of the inner peripheral surface of the sidewall was 20 μm. However, because the crucible cracked during crystal growth, the beta-type GaO single crystal could not be obtained, and thus the beta-type GaO single crystal substrate of Sample 10A could not be obtained.

[0097] <Sample 10B> A beta-type GaO single crystal was produced with the growth direction set to the

[001] direction using the same method as for obtaining the beta-type GaO single crystal substrate of Sample 10A. No cracks were observed in the crucible in this test example. The outer diameter of the beta-type GaO single crystal was 120 mm. The beta-type GaO single crystal was then subjected to the cutting, outer peripheral grinding, and polishing processes described above, in that order. This resulted in the beta-type GaO single crystal substrate of Sample 10B. The diameter of the beta-type GaO single crystal substrate of Sample 10B was 101.6 mm and the thickness was 650 μm. The Rh concentration in the beta-type GaO single crystal substrate of Sample 10B was 25 ppm by mass in the above-mentioned GDMS, and the Ir concentration in the above-mentioned GDMS was 0.02 ppm by mass.

[0098] <Sample 10C> A beta-type GaO single crystal was produced with the growth direction set to the

[001] direction using the same method as for obtaining the beta-type GaO single crystal substrate of Sample 10A, except that the thickness of the crucible sidewall was set to 1.0 mm. No cracks were observed in the crucible in this test example. The outer diameter of the beta-type GaO single crystal was 108 mm. The beta-type GaO single crystal was then subjected to the cutting, outer peripheral grinding, and polishing processes described above, in that order. This resulted in the beta-type GaO single crystal substrate of Sample 10C. The diameter of the beta-type GaO single crystal substrate of Sample 10C was 101.6 mm and the thickness was 650 μm. The Rh concentration in the beta-type Ga2O3 single crystal substrate of Sample 10C was 45 mass ppm in the above-mentioned GDMS, and the Ir concentration in the above-mentioned GDMS was 0.02 mass ppm.

[0099] <Sample 101> (Preparation Step S110) First, a single crystal growth apparatus 100, a seed crystal 8a consisting of a beta-type GaO single crystal, and bulk GaO polycrystals were prepared by a conventional method or by commercially available products. The crucible 5 constituting the single crystal growth apparatus 100 was made of stabilized ZrO with a purity of 89.2% by mass and containing 10.8% by mass of CaO. The crucible had a 3 mm-thick sidewall 5a and a 500 μm-thick thermally sprayed coating 5b. More specifically, the inner diameter of the straight body of the crucible 5 was 105 mm. Furthermore, the surface roughness Rz of the inner peripheral surface of the sidewall 5a was 20 μm. The thermally sprayed coating 5b was a Pt—Rh alloy containing 30% by mass of Rh, and the porosity of the thermally sprayed coating 5b was 10%.

[0100] (Raw Material Charging Step S120 and Raw Material Melting Step S130) Next, by a conventionally known method, a seed crystal 8a was placed in the seed crystal accommodation portion 51 of the crucible 5, and a chunk of GaO polycrystal was placed above the seed crystal 8a. Specifically, multiple chunks of GaO polycrystal were placed and stacked in the increased diameter portion 52 and the straight body portion 53. Next, the crucible 5 containing the seed crystal 8a and the chunk of GaO polycrystal was supported by the crucible holder 6. Thereafter, an electric current was supplied to the heating device 7 to heat the crucible 5, and the GaO polycrystal and a portion of the seed crystal 8a were melted, thereby preparing a GaO melt 82. Next, the remaining portion of the seed crystal 8a and the GaO melt 82 were brought into contact at their interface.

[0101] (GaO Single Crystal Growth Step S140) Next, the crucible 5 was gradually pulled downward (toward the bottom) along its axis relative to the heating device 7, creating a temperature gradient such that the temperature on the seed crystal 8a side of the crucible 5 was lower and the temperature on the GaO melt 82 side was higher. This resulted in a crystal growing from the GaO melt 82 onto the remaining portion of the seed crystal 8a side, with the growth direction being the

[001] direction, to obtain a beta-type GaO single crystal 81. This operation was continued until the pulling-down distance reached 100 mm. The temperature at the interface between the growing beta-type GaO single crystal 81 and the GaO melt 82 was 1800 to 1820°C. The temperature gradient at the interface was 5°C / cm. The speed at which the crucible 5 was pulled downward along its axis was 1 mm / hour. In this manner, a beta-type GaO single crystal ingot was obtained. The outer diameter of the beta-type GaO single crystal was 105.8 mm. Although no cracks were observed in the crucible 5 during the crystal growth, cracks were observed during cooling after the crystal growth.

[0102] (GaO single crystal substrate manufacturing process S200) Finally, the beta-type GaO single crystal ingot obtained in the GaO single crystal growth process S140 was processed in the cutting process, periphery grinding process, and polishing process to obtain a beta-type GaO single crystal substrate. First, in the cutting process, the ingot was sliced ​​into wafers having a thickness of 700 μm using a conventionally known method. In the periphery grinding process, the wafer was ground to chamfer the periphery using a conventionally known method to obtain wafers having main surfaces consisting of a central portion and an outer periphery surrounding the periphery of the central portion. Furthermore, in the polishing process, the central portion was polished using a conventionally known polishing method to obtain a surface roughness Ra of 8 nm at the central portion, as specified in JIS B 0681-2:2018, for example.

[0103] In this manner, a beta-type GaO single crystal substrate was produced as sample 101. The diameter of the beta-type GaO single crystal substrate of sample 101 was 101.6 mm, and the thickness was 650 μm. The Rh concentration in the beta-type GaO single crystal substrate of sample 101 was 15 ppm by mass in the above-mentioned GDMS, and the Ir concentration in the above-mentioned GDMS was less than 0.01 ppm by mass.

[0104] <Sample 102> A beta-type GaO single crystal ingot was obtained in the same manner as the method for obtaining the beta-type GaO single crystal substrate of Sample 101, except that in the preparation step, a crucible was prepared in which the sprayed film 5b covering the inner peripheral surface of the sidewall portion 5a had a porosity of 20%. The outer diameter of the beta-type GaO single crystal was 105.8 mm. Furthermore, the beta-type GaO single crystal substrate of Sample 102 was obtained from the beta-type GaO single crystal. The diameter of the beta-type GaO single crystal substrate of Sample 102 was 101.6 mm and the thickness was 650 μm. The Rh concentration in the beta-type GaO single crystal substrate of Sample 102 was 20 ppm by mass in the above-mentioned GDMS, and the Ir concentration in the above-mentioned GDMS was 0.01 ppm by mass. Regarding crucible 5, no cracks were observed during the crystal growth, but cracks were observed during cooling after the crystal growth.

[0105] <Sample 103> A beta-type GaO single crystal ingot was obtained in the same manner as the method for obtaining the beta-type GaO single crystal substrate of Sample 101, except that in the preparation step, a crucible was prepared in which the sprayed film 5b covering the inner peripheral surface of the sidewall portion 5a had a porosity of 30%. The outer diameter of the beta-type GaO single crystal was 105.8 mm. Furthermore, a beta-type GaO single crystal substrate of Sample 103 was obtained from the beta-type GaO single crystal. The diameter of the beta-type GaO single crystal substrate of Sample 103 was 101.6 mm and the thickness was 650 μm. The Rh concentration in the beta-type GaO single crystal substrate of Sample 103 was 18 ppm by mass in the above-mentioned GDMS, and the Ir concentration in the above-mentioned GDMS was 0.01 ppm by mass.

[0106] <Sample 104> A beta-type GaO single crystal ingot was obtained in the same manner as the beta-type GaO single crystal substrate of Sample 101, except that a crucible with a 200 μm-thick sprayed film 5b coating the inner peripheral surface of the sidewall 5a was prepared in the preparation step. The outer diameter of the beta-type GaO single crystal was 105.8 mm. Furthermore, a beta-type GaO single crystal substrate of Sample 104 was obtained from the beta-type GaO single crystal. The diameter of the beta-type GaO single crystal substrate of Sample 104 was 101.6 mm and the thickness was 650 μm. The Rh concentration in the beta-type GaO single crystal substrate of Sample 104 was 17 ppm by mass in the above-mentioned GDMS, and the Ir concentration was less than 0.01 ppm by mass in the above-mentioned GDMS. Regarding crucible 5, no cracks were observed during the crystal growth, but cracks were observed during cooling after the crystal growth.

[0107] <Sample 105> A beta-type GaO single crystal ingot was obtained in the same manner as the method for obtaining the beta-type GaO single crystal substrate of Sample 102, except that a crucible with a 200 μm-thick sprayed film 5b covering the inner peripheral surface of the sidewall 5a was prepared in the preparation step. The outer diameter of the beta-type GaO single crystal was 105.8 mm. Furthermore, the beta-type GaO single crystal substrate of Sample 105 was obtained from the beta-type GaO single crystal. The diameter of the beta-type GaO single crystal substrate of Sample 105 was 101.6 mm and the thickness was 650 μm. The Rh concentration in the beta-type GaO single crystal substrate of Sample 105 was 25 ppm by mass in the above-mentioned GDMS, and the Ir concentration was less than 0.01 ppm by mass in the above-mentioned GDMS. Regarding crucible 5, no cracks were observed during the crystal growth, but cracks were observed during cooling after the crystal growth.

[0108] <Sample 106> A beta-type GaO single crystal ingot was obtained in the same manner as the beta-type GaO single crystal substrate of Sample 103, except that a crucible with a 200 μm-thick thermal sprayed film 5b coating the inner peripheral surface of the sidewall 5a was prepared in the preparation step. The outer diameter of the beta-type GaO single crystal was 105.8 mm. Furthermore, a beta-type GaO single crystal substrate of Sample 106 was obtained from the beta-type GaO single crystal. The diameter of the beta-type GaO single crystal substrate of Sample 106 was 101.6 mm and the thickness was 650 μm. The Rh concentration in the beta-type GaO single crystal substrate of Sample 106 was 40 ppm by mass in the above-mentioned GDMS, and the Ir concentration was less than 0.01 ppm by mass in the above-mentioned GDMS.

[0109] <Sample 107> A beta-type GaO single crystal ingot was obtained in the same manner as the beta-type GaO single crystal substrate of Sample 104, except that a crucible with a surface roughness Rz of 100 μm on the inner peripheral surface of the sidewall portion 5a was prepared in the preparation step. The crystal outer diameter of the beta-type GaO single crystal was 105.8 mm. Furthermore, a beta-type GaO single crystal substrate of Sample 107 was obtained from the beta-type GaO single crystal. The diameter of the beta-type GaO single crystal substrate of Sample 107 was 101.6 mm and the thickness was 650 μm. The Rh concentration in the beta-type GaO single crystal substrate of Sample 107 was 28 ppm by mass in the above-mentioned GDMS, and the Ir concentration was less than 0.01 ppm by mass in the above-mentioned GDMS. Regarding crucible 5, no cracks were observed during the crystal growth, but cracks were observed during cooling after the crystal growth.

[0110] <Sample 108> A beta-type GaO single crystal ingot was obtained in the same manner as the method for obtaining the beta-type GaO single crystal substrate of Sample 105, except that a crucible with a surface roughness Rz of 100 μm on the inner peripheral surface of the sidewall portion 5a was prepared in the preparation step. The crystal outer diameter of the beta-type GaO single crystal was 105.8 mm. Furthermore, the beta-type GaO single crystal substrate of Sample 108 was obtained from the beta-type GaO single crystal. The diameter of the beta-type GaO single crystal substrate of Sample 108 was 101.6 mm and the thickness was 650 μm. The Rh concentration in the beta-type GaO single crystal substrate of Sample 108 was 15 ppm by mass in the above-mentioned GDMS, and the Ir concentration was less than 0.01 ppm by mass in the above-mentioned GDMS. Regarding crucible 5, no cracks were observed during the crystal growth, but cracks were observed during cooling after the crystal growth.

[0111] <Sample 109> A beta-type GaO single crystal ingot was obtained in the same manner as the method for obtaining the beta-type GaO single crystal substrate of Sample 104, except that a crucible with a surface roughness Rz of 300 μm on the inner peripheral surface of the sidewall portion 5a was prepared in the preparation step. The outer diameter of the beta-type GaO single crystal was 105.8 mm. Furthermore, a beta-type GaO single crystal substrate of Sample 109 was obtained from the beta-type GaO single crystal. The diameter of the beta-type GaO single crystal substrate of Sample 109 was 101.6 mm and the thickness was 650 μm. The Rh concentration in the beta-type GaO single crystal substrate of Sample 109 was 22 ppm by mass in the above-mentioned GDMS, and the Ir concentration was less than 0.01 ppm by mass in the above-mentioned GDMS.

[0112] <Sample 110> In the preparation step, a crucible having a surface roughness Rz of 300 μm on the inner peripheral surface of the sidewall portion 5a was prepared. A beta-type GaO single crystal ingot was obtained in the same manner as the method for obtaining the beta-type GaO single crystal substrate of Sample 105. The outer diameter of the beta-type GaO single crystal was 105.8 mm. Furthermore, the beta-type GaO single crystal substrate of Sample 110 was obtained from the beta-type GaO single crystal. The diameter of the beta-type GaO single crystal substrate of Sample 110 was 101.6 mm and the thickness was 650 μm. The Rh concentration in the beta-type GaO single crystal substrate of Sample 110 was 25 ppm by mass in the above-mentioned GDMS, and the Ir concentration in the above-mentioned GDMS was 0.02 ppm by mass.

[0113] <Sample 111> A beta-type GaO single crystal ingot was obtained in the same manner as the method for obtaining the beta-type GaO single crystal substrate of Sample 106, except that a crucible with a surface roughness Rz of 300 μm on the inner peripheral surface of the sidewall portion 5a was prepared in the preparation step. The crystal outer diameter of the beta-type GaO single crystal was 105.8 mm. Furthermore, a beta-type GaO single crystal substrate of Sample 111 was obtained from the beta-type GaO single crystal. The diameter of the beta-type GaO single crystal substrate of Sample 111 was 101.6 mm and the thickness was 650 μm. The Rh concentration in the beta-type GaO single crystal substrate of Sample 111 was 27 ppm by mass in the above-mentioned GDMS, and the Ir concentration was less than 0.01 ppm by mass in the above-mentioned GDMS.

[0114] <Sample 112> A beta-type GaO single crystal ingot was obtained in the same manner as the beta-type GaO single crystal substrate of Sample 111. The outer diameter of the beta-type GaO single crystal was 105.8 mm. Furthermore, a beta-type GaO single crystal substrate of Sample 112 was obtained from the beta-type GaO single crystal. The diameter of the beta-type GaO single crystal substrate of Sample 112 was 101.6 mm and the thickness was 650 μm. The Rh concentration in the beta-type GaO single crystal substrate of Sample 112 was 20 ppm by mass in the above-mentioned GDMS, and the Ir concentration was less than 0.01 ppm by mass in the above-mentioned GDMS.

[0115] <Sample 113> A beta-type GaO single crystal ingot was obtained in the same manner as the method for obtaining the beta-type GaO single crystal substrate of Sample 109, except that a crucible was prepared in the preparation step, in which the inner peripheral surface of the side wall portion 5a was coated with a sprayed film consisting of the following first film 5b1 and second film 5b2. That is, in the preparation step of this test example, a first spray material was sprayed onto the inner peripheral surface of the side wall portion 5a of the crucible 5, thereby coating the surface with a first film 5b1 made of Rh, having a first film porosity of 30%, and having a thickness of 50 μm. Further, a second spray material was sprayed onto the first film 5b1, thereby coating the first film 5b1 with a second film 5b2 made of Pt, having a second film porosity of 30%, and having a thickness of 150 μm.

[0116] The outer crystal diameter of the beta-type GaO single crystal obtained in this manner was 105.8 mm. Furthermore, a beta-type GaO single crystal substrate of Sample 113 was obtained from the beta-type GaO single crystal. The diameter of the beta-type GaO single crystal substrate of Sample 113 was 101.6 mm and the thickness was 650 μm. The Rh concentration in the beta-type GaO single crystal substrate of Sample 113 was less than 0.01 ppm by mass in the above-mentioned GDMS, and the Ir concentration was less than 0.01 ppm by mass in the above-mentioned GDMS.

[0117] <Sample 114> A beta-type GaO single crystal ingot was obtained in the same manner as the beta-type GaO single crystal substrate of Sample 113. The outer diameter of the beta-type GaO single crystal was 105.8 mm. Furthermore, a beta-type GaO single crystal substrate of Sample 114 was obtained from the beta-type GaO single crystal. The diameter of the beta-type GaO single crystal substrate of Sample 114 was 101.6 mm and the thickness was 650 μm. The Rh concentration in the beta-type GaO single crystal substrate of Sample 114 was 0.08 ppm by mass in the above-mentioned GDMS, and the Ir concentration was less than 0.01 ppm by mass in the above-mentioned GDMS.

[0118] <Sample 115> A beta-type GaO single crystal ingot was obtained in the same manner as the beta-type GaO single crystal substrate of Sample 113. The outer diameter of the beta-type GaO single crystal was 105.8 mm. Furthermore, a beta-type GaO single crystal substrate of Sample 115 was obtained from the beta-type GaO single crystal. The diameter of the beta-type GaO single crystal substrate of Sample 115 was 101.6 mm and the thickness was 650 μm. The Rh concentration in the beta-type GaO single crystal substrate of Sample 115 was 2.9 ppm by mass in the above-mentioned GDMS, and the Ir concentration in the above-mentioned GDMS was 0.01 ppm by mass.

[0119] <Samples 20A and 20B> An attempt was made to manufacture the beta-type GaO single crystal substrates of Samples 20A and 20B in the same manner as the method for obtaining the beta-type GaO single crystal substrates of Samples 10A and 10B, except that the inner diameter of the straight body of the crucible used to obtain the GaO single crystals was set to 156 mm. However, the crucible broke during crystal growth, and the beta-type GaO single crystal substrates of Samples 20A and 20B could not be obtained.

[0120] <Sample 20C> A beta-type GaO single crystal was produced with the growth direction set to the

[001] direction using the same method as for obtaining the beta-type GaO single crystal substrates of Samples 20A and 20B, except that the thickness of the crucible sidewall was set to 1.0 mm. No cracks were observed in the crucible in this test example. The outer diameter of the beta-type GaO single crystal was 165 mm. The beta-type GaO single crystal was then subjected to the cutting, outer peripheral grinding, and polishing processes described above, in that order. This resulted in the beta-type GaO single crystal substrate of Sample 20C. The diameter of the beta-type GaO single crystal substrate of Sample 20C was 152.4 mm and the thickness was 650 μm. The Rh concentration in the beta-type Ga2O3 single crystal substrate of Sample 20C was 38 mass ppm in the above-mentioned GDMS, and the Ir concentration was 0.01 mass ppm in the above-mentioned GDMS.

[0121] <Sample 201> A beta-type GaO single crystal ingot was obtained in the same manner as the method for obtaining the beta-type GaO single crystal substrate of Sample 101, except that a crucible with an inner diameter of the straight body of 156 mm was prepared in the preparation step. The outer crystal diameter of the beta-type GaO single crystal was 157.1 mm. Furthermore, the beta-type GaO single crystal substrate of Sample 201 was obtained from the beta-type GaO single crystal. The beta-type GaO single crystal substrate of Sample 201 had a diameter of 152.4 mm and a thickness of 650 μm. The Rh concentration in the beta-type GaO single crystal substrate of Sample 201 was 15 ppm by mass in the above-mentioned GDMS, and the Ir concentration was 0.01 ppm by mass in the above-mentioned GDMS. Regarding crucible 5, no cracks were observed during crystal growth, but cracks were observed upon cooling after crystal growth.

[0122] <Sample 202> A beta-type GaO single crystal ingot was obtained in the same manner as the method for obtaining the beta-type GaO single crystal substrate of Sample 201, except that in the preparation step, a crucible was prepared in which the sprayed film 5b covering the inner peripheral surface of the sidewall portion 5a had a porosity of 20%. The outer diameter of the beta-type GaO single crystal was 157.1 mm. Furthermore, the beta-type GaO single crystal substrate of Sample 202 was obtained from the beta-type GaO single crystal. The diameter of the beta-type GaO single crystal substrate of Sample 202 was 152.4 mm and the thickness was 650 μm. The Rh concentration in the beta-type GaO single crystal substrate of Sample 202 was 20 ppm by mass in the above-mentioned GDMS, and the Ir concentration was less than 0.01 ppm by mass in the above-mentioned GDMS. Regarding crucible 5, no cracks were observed during the crystal growth process when it was heated, but cracks were observed during cooling after the crystal growth.

[0123] <Sample 203> A beta-type GaO single crystal ingot was obtained in the same manner as the method for obtaining the beta-type GaO single crystal substrate of Sample 201, except that in the preparation step, a crucible was prepared in which the sprayed film 5b covering the inner peripheral surface of the sidewall portion 5a had a porosity of 30%. The outer diameter of the beta-type GaO single crystal was 157.1 mm. Furthermore, the beta-type GaO single crystal substrate of Sample 203 was obtained from the beta-type GaO single crystal. The diameter of the beta-type GaO single crystal substrate of Sample 203 was 152.4 mm and the thickness was 650 μm. The Rh concentration in the beta-type GaO single crystal substrate of Sample 203 was 23 ppm by mass in the above-mentioned GDMS, and the Ir concentration in the above-mentioned GDMS was 0.01 ppm by mass.

[0124] <Sample 204> A beta-type GaO single crystal ingot was obtained in the same manner as the beta-type GaO single crystal substrate of Sample 201, except that a crucible with a 200 μm-thick thermal sprayed film 5b coating the inner peripheral surface of the sidewall 5a was prepared in the preparation step. The outer diameter of the beta-type GaO single crystal was 157.1 mm. Furthermore, a beta-type GaO single crystal substrate of Sample 204 was obtained from the beta-type GaO single crystal. The diameter of the beta-type GaO single crystal substrate of Sample 204 was 152.4 mm and the thickness was 650 μm. The Rh concentration in the beta-type GaO single crystal substrate of Sample 204 was 27 ppm by mass in the above-mentioned GDMS, and the Ir concentration was less than 0.01 ppm by mass in the above-mentioned GDMS. Regarding crucible 5, no cracks were observed during the crystal growth, but cracks were observed during cooling after the crystal growth.

[0125] <Sample 205> A beta-type GaO single crystal ingot was obtained in the same manner as the beta-type GaO single crystal substrate of Sample 202, except that a crucible with a 200 μm-thick thermal sprayed film 5b coating the inner peripheral surface of the sidewall 5a was prepared in the preparation step. The outer diameter of the beta-type GaO single crystal was 157.1 mm. Furthermore, a beta-type GaO single crystal substrate of Sample 205 was obtained from the beta-type GaO single crystal. The diameter of the beta-type GaO single crystal substrate of Sample 205 was 152.4 mm and the thickness was 650 μm. The Rh concentration in the beta-type GaO single crystal substrate of Sample 205 was 15 ppm by mass in the above-mentioned GDMS, and the Ir concentration in the above-mentioned GDMS was 0.02 ppm by mass. Regarding crucible 5, no cracks were observed during the crystal growth, but cracks were observed during cooling after the crystal growth.

[0126] <Sample 206> A beta-type GaO single crystal ingot was obtained in the same manner as the beta-type GaO single crystal substrate of Sample 203, except that a crucible with a 200 μm-thick thermal sprayed film 5b coating the inner peripheral surface of the sidewall 5a was prepared in the preparation step. The outer diameter of the beta-type GaO single crystal was 157.1 mm. Furthermore, a beta-type GaO single crystal substrate of Sample 206 was obtained from the beta-type GaO single crystal. The diameter of the beta-type GaO single crystal substrate of Sample 206 was 152.4 mm and the thickness was 650 μm. The Rh concentration in the beta-type GaO single crystal substrate of Sample 206 was 35 ppm by mass in the above-mentioned GDMS, and the Ir concentration was less than 0.01 ppm by mass in the above-mentioned GDMS.

[0127] <Sample 207> A beta-type GaO single crystal ingot was obtained in the same manner as the beta-type GaO single crystal substrate of Sample 204, except that a crucible with a surface roughness Rz of 100 μm on the inner peripheral surface of the sidewall portion 5a was prepared in the preparation step. The crystal outer diameter of the beta-type GaO single crystal was 157.1 mm. Furthermore, a beta-type GaO single crystal substrate of Sample 207 was obtained from the beta-type GaO single crystal. The diameter of the beta-type GaO single crystal substrate of Sample 207 was 152.4 mm and the thickness was 650 μm. The Rh concentration in the beta-type GaO single crystal substrate of Sample 207 was 18 ppm by mass in the above-mentioned GDMS, and the Ir concentration in the above-mentioned GDMS was 0.01 ppm by mass. Regarding crucible 5, no cracks were observed during the crystal growth, but cracks were observed during cooling after the crystal growth.

[0128] <Sample 208> A beta-type GaO single crystal ingot was obtained in the same manner as the beta-type GaO single crystal substrate of Sample 205, except that a crucible with a surface roughness Rz of 100 μm on the inner peripheral surface of the sidewall portion 5a was prepared in the preparation step. The outer diameter of the beta-type GaO single crystal was 157.1 mm. Furthermore, a beta-type GaO single crystal substrate of Sample 208 was obtained from the beta-type GaO single crystal. The diameter of the beta-type GaO single crystal substrate of Sample 208 was 152.4 mm and the thickness was 650 μm. The Rh concentration in the beta-type GaO single crystal substrate of Sample 208 was 25 ppm by mass in the above-mentioned GDMS, and the Ir concentration was less than 0.01 ppm by mass in the above-mentioned GDMS. Regarding crucible 5, no cracks were observed during the crystal growth, but cracks were observed during cooling after the crystal growth.

[0129] <Sample 209> A beta-type GaO single crystal ingot was obtained in the same manner as the beta-type GaO single crystal substrate of Sample 204, except that a crucible with a surface roughness Rz of 300 μm on the inner peripheral surface of the sidewall portion 5a was prepared in the preparation step. The outer diameter of the beta-type GaO single crystal was 157.1 mm. Furthermore, a beta-type GaO single crystal substrate of Sample 209 was obtained from the beta-type GaO single crystal. The diameter of the beta-type GaO single crystal substrate of Sample 209 was 152.4 mm and the thickness was 650 μm. The Rh concentration in the beta-type GaO single crystal substrate of Sample 209 was 32 ppm by mass in the above-mentioned GDMS, and the Ir concentration was less than 0.01 ppm by mass in the above-mentioned GDMS.

[0130] <Sample 210> A beta-type GaO single crystal ingot was obtained in the same manner as the beta-type GaO single crystal substrate of Sample 205, except that a crucible with a surface roughness Rz of 300 μm on the inner peripheral surface of the sidewall portion 5a was prepared in the preparation step. The crystal outer diameter of the beta-type GaO single crystal was 157.1 mm. Furthermore, a beta-type GaO single crystal substrate of Sample 210 was obtained from the beta-type GaO single crystal. The diameter of the beta-type GaO single crystal substrate of Sample 210 was 152.4 mm and the thickness was 650 μm. The Rh concentration in the beta-type GaO single crystal substrate of Sample 210 was 26 ppm by mass in the above-mentioned GDMS, and the Ir concentration in the above-mentioned GDMS was 0.02 ppm by mass.

[0131] <Sample 211> A beta-type GaO single crystal ingot was obtained in the same manner as the method for obtaining the beta-type GaO single crystal substrate of Sample 209, except that a crucible was prepared in the preparation step, in which the inner peripheral surface of the side wall portion 5a was coated with a sprayed film consisting of the following first film 5b1 and second film 5b2. That is, in the preparation step of this test example, a first spray material was sprayed onto the inner peripheral surface of the side wall portion 5a of the crucible 5, thereby coating the surface with a first film 5b1 made of Rh, having a first film porosity of 30%, and having a thickness of 50 μm. Further, a second spray material was sprayed onto the first film 5b1, thereby coating the first film 5b1 with a second film 5b2 made of Pt, having a second film porosity of 30%, and having a thickness of 150 μm.

[0132] The outer crystal diameter of the beta-type GaO single crystal obtained in this manner was 157.1 mm. Furthermore, a beta-type GaO single crystal substrate of sample 211 was obtained from the beta-type GaO single crystal. The diameter of the beta-type GaO single crystal substrate of sample 211 was 152.4 mm and the thickness was 650 μm. The Rh concentration in the beta-type GaO single crystal substrate of sample 211 was 0.02 ppm by mass in the above-mentioned GDMS, and the Ir concentration in the above-mentioned GDMS was less than 0.01 ppm by mass.

[0133] <Sample 212> A beta-type GaO single crystal ingot was obtained in the same manner as the beta-type GaO single crystal substrate of Sample 211. The outer diameter of the beta-type GaO single crystal was 157.1 mm. Furthermore, a beta-type GaO single crystal substrate of Sample 212 was obtained from the beta-type GaO single crystal. The diameter of the beta-type GaO single crystal substrate of Sample 212 was 152.4 mm and the thickness was 650 μm. The Rh concentration in the beta-type GaO single crystal substrate of Sample 212 was less than 0.01 ppm by mass in the above-mentioned GDMS, and the Ir concentration was less than 0.01 ppm by mass in the above-mentioned GDMS.

[0134] <Sample 213> A beta-type GaO single crystal ingot was obtained in the same manner as the method for obtaining the beta-type GaO single crystal substrate of Sample 211. The outer crystal diameter of the beta-type GaO single crystal was 157.1 mm. Furthermore, a beta-type GaO single crystal substrate of Sample 213 was obtained from the beta-type GaO single crystal. The diameter of the beta-type GaO single crystal substrate of Sample 213 was 152.4 mm and the thickness was 650 μm. The Rh concentration in the beta-type GaO single crystal substrate of Sample 213 was 2.8 ppm by mass in the above-mentioned GDMS, and the Ir concentration in the above-mentioned GDMS was 0.01 ppm by mass.

[0135] <Sample 301> In the preparation step S110, the crucible 5 constituting the single crystal growth apparatus 100 was made of stabilized ZrO2 with a purity of 86.2% by mass containing 13.8% by mass of YO. The sidewall 5a had a thickness of 9 mm, and the sprayed film 5b covering the inner surface of the sidewall 5a of the crucible 5 was a Pt—Rh alloy containing 11% by mass of Rh. A beta-type GaO3 single crystal ingot was obtained in the same manner as the beta-type GaO3 single crystal substrate of Sample 101. The outer diameter of the beta-type GaO3 single crystal was 105.8 mm. Furthermore, the beta-type GaO3 single crystal substrate of Sample 301 was obtained from the beta-type GaO3 single crystal. The beta-type GaO single crystal substrate of sample 301 had a diameter of 101.6 mm and a thickness of 650 μm. The Rh concentration in the beta-type GaO single crystal substrate of sample 301 was 14 ppm by mass in the above-mentioned GDMS, and the Ir concentration in the above-mentioned GDMS was less than 0.01 ppm by mass. Note that no cracks were observed in crucible 5 during crystal growth, but cracks were observed during cooling after crystal growth.

[0136] <Sample 302> In the preparation step S110, the crucible 5 constituting the single crystal growth apparatus 100 was made of stabilized ZrO2 with a purity of 86.2% by mass containing 13.8% by mass of YO. The sidewall 5a had a thickness of 9 mm, and the sprayed film 5b covering the inner surface of the sidewall 5a of the crucible 5 was a Pt—Rh alloy containing 11% by mass of Rh. A beta-type GaO3 single crystal ingot was obtained in the same manner as the beta-type GaO3 single crystal substrate of Sample 102. The outer diameter of the beta-type GaO3 single crystal was 105.8 mm. Furthermore, the beta-type GaO3 single crystal substrate of Sample 302 was obtained from the beta-type GaO3 single crystal. The beta-type GaO single crystal substrate of sample 302 had a diameter of 101.6 mm and a thickness of 650 μm. The Rh concentration in the beta-type GaO single crystal substrate of sample 302 was 21 ppm by mass in the above-mentioned GDMS, and the Ir concentration in the above-mentioned GDMS was 0.01 ppm by mass. Note that no cracks were observed in crucible 5 during crystal growth, but cracks were observed during cooling after crystal growth.

[0137] <Sample 303> In the preparation step S110, the crucible 5 constituting the single crystal growth apparatus 100 was made of stabilized ZrO2 with a purity of 86.2% by mass containing 13.8% by mass of YO. The sidewall 5a had a thickness of 9 mm, and the sprayed film 5b covering the inner surface of the sidewall 5a of the crucible 5 was a Pt—Rh alloy containing 11% by mass of Rh. A beta-type GaO3 single crystal ingot was obtained in the same manner as the beta-type GaO3 single crystal substrate of Sample 103. The outer diameter of the beta-type GaO3 single crystal was 105.8 mm. Furthermore, the beta-type GaO3 single crystal substrate of Sample 303 was obtained from the beta-type GaO3 single crystal. The beta-type GaO single crystal substrate of sample 303 had a diameter of 101.6 mm and a thickness of 650 μm. The Rh concentration in the beta-type GaO single crystal substrate of sample 303 was 19 ppm by mass in the above-mentioned GDMS, and the Ir concentration in the above-mentioned GDMS was less than 0.01 ppm by mass.

[0138] <Sample 304> In the preparation step S110, the crucible 5 constituting the single crystal growth apparatus 100 was made of stabilized ZrO2 with a purity of 86.2% by mass containing 13.8% by mass of YO, and the side wall 5a had a thickness of 9 mm. The sprayed film 5b covering the inner surface of the side wall 5a of the crucible 5 was a Pt—Rh alloy containing 11% by mass of Rh. A beta-type GaO3 single crystal ingot was obtained in the same manner as the beta-type GaO3 single crystal substrate of Sample 104. The outer diameter of the beta-type GaO3 single crystal was 105.8 mm. Furthermore, the beta-type GaO3 single crystal substrate of Sample 304 was obtained from the beta-type GaO3 single crystal. The beta-type GaO single crystal substrate of sample 304 had a diameter of 101.6 mm and a thickness of 650 μm. The Rh concentration in the beta-type GaO single crystal substrate of sample 304 was 18 ppm by mass in the above-mentioned GDMS, and the Ir concentration in the above-mentioned GDMS was less than 0.01 ppm by mass. Note that no cracks were observed in crucible 5 during crystal growth, but cracks were observed during cooling after crystal growth.

[0139] <Sample 305> In the preparation step S110, the crucible 5 constituting the single crystal growth apparatus 100 was made of stabilized ZrO2 with a purity of 86.2% by mass containing 13.8% by mass of YO. The sidewall 5a had a thickness of 9 mm, and the sprayed film 5b covering the inner surface of the sidewall 5a of the crucible 5 was a Pt—Rh alloy containing 11% by mass of Rh. A beta-type GaO3 single crystal ingot was obtained in the same manner as the beta-type GaO3 single crystal substrate of Sample 105. The outer diameter of the beta-type GaO3 single crystal was 105.8 mm. Furthermore, the beta-type GaO3 single crystal substrate of Sample 305 was obtained from the beta-type GaO3 single crystal. The beta-type GaO single crystal substrate of sample 305 had a diameter of 101.6 mm and a thickness of 650 μm. The Rh concentration in the beta-type GaO single crystal substrate of sample 305 was 24 ppm by mass in the above-mentioned GDMS, and the Ir concentration in the above-mentioned GDMS was less than 0.01 ppm by mass. Note that no cracks were observed in crucible 5 during crystal growth, but cracks were observed during cooling after crystal growth.

[0140] <Sample 306> In the preparation step S110, the crucible 5 constituting the single crystal growth apparatus 100 was made of stabilized ZrO2 with a purity of 86.2% by mass containing 13.8% by mass of YO. The sidewall 5a had a thickness of 9 mm, and the sprayed film 5b covering the inner surface of the sidewall 5a of the crucible 5 was a Pt—Rh alloy containing 10% by mass of Rh. A beta-type GaO single crystal ingot was obtained in the same manner as the beta-type GaO single crystal substrate of Sample 106. The outer diameter of the beta-type GaO single crystal was 105.8 mm. Furthermore, the beta-type GaO single crystal substrate of Sample 306 was obtained from the beta-type GaO single crystal. The beta-type GaO single crystal substrate of sample 306 had a diameter of 101.6 mm and a thickness of 650 μm. The Rh concentration in the beta-type GaO single crystal substrate of sample 306 was 22 ppm by mass in the above-mentioned GDMS, and the Ir concentration in the above-mentioned GDMS was less than 0.01 ppm by mass.

[0141] <Sample 307> In the preparation step S110, the crucible 5 constituting the single crystal growth apparatus 100 was made of stabilized ZrO2 with a purity of 86.2% by mass containing 13.8% by mass of YO. The sidewall 5a had a thickness of 9 mm, and the sprayed film 5b covering the inner surface of the sidewall 5a of the crucible 5 was a Pt—Rh alloy containing 10% by mass of Rh. A beta-type GaO3 single crystal ingot was obtained in the same manner as the beta-type GaO3 single crystal substrate of Sample 107. The outer diameter of the beta-type GaO3 single crystal was 105.8 mm. Furthermore, the beta-type GaO3 single crystal substrate of Sample 307 was obtained from the beta-type GaO3 single crystal. The beta-type GaO single crystal substrate of sample 307 had a diameter of 101.6 mm and a thickness of 650 μm. The Rh concentration in the beta-type GaO single crystal substrate of sample 307 was 25 ppm by mass in the above-mentioned GDMS, and the Ir concentration in the above-mentioned GDMS was less than 0.01 ppm by mass. Note that no cracks were observed in crucible 5 during crystal growth, but cracks were observed during cooling after crystal growth.

[0142] <Sample 308> In the preparation step S110, the crucible 5 constituting the single crystal growth apparatus 100 was made of stabilized ZrO2 with a purity of 86.2% by mass containing 13.8% by mass of YO, and the sidewall 5a had a thickness of 9 mm. The sprayed film 5b covering the inner surface of the sidewall 5a of the crucible 5 was a Pt—Rh alloy containing 10% by mass of Rh. A beta-type GaO single crystal ingot was obtained in the same manner as the beta-type GaO single crystal substrate of Sample 108. The outer diameter of the beta-type GaO single crystal was 105.8 mm. Furthermore, the beta-type GaO single crystal substrate of Sample 308 was obtained from the beta-type GaO single crystal. The beta-type GaO single crystal substrate of sample 308 had a diameter of 101.6 mm and a thickness of 650 μm. The Rh concentration in the beta-type GaO single crystal substrate of sample 308 was 17 ppm by mass in the above-mentioned GDMS, and the Ir concentration in the above-mentioned GDMS was less than 0.01 ppm by mass. Note that no cracks were observed in crucible 5 during crystal growth, but cracks were observed during cooling after crystal growth.

[0143] <Sample 309> In the preparation step S110, the crucible 5 constituting the single crystal growth apparatus 100 was made of stabilized ZrO2 with a purity of 86.2% by mass containing 13.8% by mass of YO, and the side wall 5a had a thickness of 9 mm. The sprayed film 5b covering the inner surface of the side wall 5a of the crucible 5 was a Pt—Rh alloy containing 10% by mass of Rh. A beta-type GaO3 single crystal ingot was obtained in the same manner as the beta-type GaO3 single crystal substrate of Sample 109. The outer diameter of the beta-type GaO3 single crystal was 105.8 mm. Furthermore, the beta-type GaO3 single crystal substrate of Sample 309 was obtained from the beta-type GaO3 single crystal. The beta-type GaO single crystal substrate of Sample 309 had a diameter of 101.6 mm and a thickness of 650 μm. The Rh concentration in the beta-type GaO single crystal substrate of Sample 309 was 21 ppm by mass in the above-mentioned GDMS, and the Ir concentration in the above-mentioned GDMS was less than 0.01 ppm by mass.

[0144] <Sample 310> In the preparation step S110, the crucible 5 constituting the single crystal growth apparatus 100 was made of stabilized ZrO2 with a purity of 86.2% by mass containing 13.8% by mass of YO. The sidewall 5a had a thickness of 9 mm, and the sprayed film 5b covering the inner surface of the sidewall 5a of the crucible 5 was a Pt—Rh alloy containing 10% by mass of Rh. A beta-type GaO3 single crystal ingot was obtained in the same manner as the beta-type GaO3 single crystal substrate of Sample 110. The outer diameter of the beta-type GaO3 single crystal was 105.8 mm. Furthermore, the beta-type GaO3 single crystal substrate of Sample 310 was obtained from the beta-type GaO3 single crystal. The beta-type GaO single crystal substrate of sample 310 had a diameter of 101.6 mm and a thickness of 650 μm. The Rh concentration in the beta-type GaO single crystal substrate of sample 310 was 26 ppm by mass in the above-mentioned GDMS, and the Ir concentration in the above-mentioned GDMS was 0.01 ppm by mass.

[0145] <Sample 311> In the preparation step S110, the crucible 5 constituting the single crystal growth apparatus 100 was made of stabilized ZrO2 with a purity of 86.2% by mass containing 13.8% by mass of YO. The sidewall 5a had a thickness of 9 mm, and the sprayed film 5b covering the inner surface of the sidewall 5a of the crucible 5 was a Pt—Rh alloy containing 10% by mass of Rh. A beta-type GaO3 single crystal ingot was obtained in the same manner as the beta-type GaO3 single crystal substrate of Sample 111. The outer diameter of the beta-type GaO3 single crystal was 105.8 mm. Furthermore, the beta-type GaO3 single crystal substrate of Sample 311 was obtained from the beta-type GaO3 single crystal. The beta-type GaO single crystal substrate of sample 311 had a diameter of 101.6 mm and a thickness of 650 μm. The Rh concentration in the beta-type GaO single crystal substrate of sample 311 was 14 ppm by mass in the above-mentioned GDMS, and the Ir concentration in the above-mentioned GDMS was less than 0.01 ppm by mass.

[0146] <Sample 312> A beta-type GaO single crystal ingot was obtained in the same manner as the beta-type GaO single crystal substrate of Sample 311. The outer diameter of the beta-type GaO single crystal was 105.8 mm. Furthermore, a beta-type GaO single crystal substrate of Sample 312 was obtained from the beta-type GaO single crystal. The diameter of the beta-type GaO single crystal substrate of Sample 312 was 101.6 mm and the thickness was 650 μm. The Rh concentration in the beta-type GaO single crystal substrate of Sample 312 was 13 ppm by mass in the above-mentioned GDMS, and the Ir concentration was less than 0.01 ppm by mass in the above-mentioned GDMS.

[0147] <Sample 313> A beta-type GaO single crystal ingot was obtained in the same manner as the method for obtaining the beta-type GaO single crystal substrate of Sample 309, except that a crucible was prepared in the preparation step, in which the inner peripheral surface of the side wall portion 5a was coated with a thermal sprayed film consisting of the following first film 5b1 and second film 5b2. That is, in the preparation step of this test example, a first thermal spray material was sprayed onto the inner peripheral surface of the side wall portion 5a of the crucible 5, thereby coating the surface with a first film 5b1 made of Rh, having a first film porosity of 30%, and having a thickness of 50 μm. Further, a second thermal spray material was sprayed onto the first film 5b1, thereby coating the first film 5b1 with a second film 5b2 made of Pt, having a second film porosity of 30%, and having a thickness of 150 μm.

[0148] The outer crystal diameter of the beta-type GaO single crystal obtained in this manner was 105.8 mm. Furthermore, a beta-type GaO single crystal substrate of Sample 313 was obtained from the beta-type GaO single crystal. The diameter of the beta-type GaO single crystal substrate of Sample 313 was 101.6 mm and the thickness was 650 μm. The Rh concentration in the beta-type GaO single crystal substrate of Sample 313 was less than 0.01 ppm by mass in the above-mentioned GDMS, and the Ir concentration in the above-mentioned GDMS was less than 0.01 ppm by mass.

[0149] Tables 1, 2, and 3 show the configurations of the crucibles (inner diameter of the straight body, composition, surface roughness Rz, thickness of the sidewall, composition, porosity, thickness, etc.) used to produce the beta-type GaO single crystal substrates of Samples 10A to 10C, 101 to 115, 20A to 20C, 201 to 213, and 301 to 313. In Tables 1 to 3, when the sprayed film is a single layer, its composition, porosity, and thickness are shown in the column "sprayed film (innermost layer; second film)."

[0150]

[0151]

[0152]

[0153] [Evaluation] <Product Yield> The product yield was determined by the following method for the beta-type GaO single crystals used to obtain the beta-type GaO single crystal substrates of Samples 10B to 10C, Samples 101 to 115, Sample 20C, Samples 201 to 213, and Samples 301 to 313. As described above, "product yield" refers to the percentage of the mass of a beta-type GaO single crystal ingot grown in a crucible, excluding regions where the crucible cracks or chips or the crystal cracks or chips during cooling, making it impossible to obtain the desired diameter when processed into a beta-type gallium trioxide single crystal substrate, and which is evaluated as being capable of being a non-defective substrate by the evaluation method described below. The better the product yield of the single crystal, the less likely it is that cracks, chips, etc. occurred in the crucible used to grow the single crystal.

[0154] First, a disk-shaped measurement sample (thickness: 1 mm) having a (001) plane as its main surface was cut out from the beta-type GaO single crystal ingot of each sample taken out of the crucible at the measurement points 1 and 2, which are the positions for measuring the crystal outer diameter. Further, the main surfaces of the measurement samples were polished and then etched with conventionally known molten potassium hydroxide.

[0155] Next, the entire surface of the measurement sample was observed with a differential interference microscope (product name (model number): "LV-150", manufactured by Nikon Corporation), and the number of crystal defects that appeared in one visual field of the differential interference microscope was counted for each visual field, and it was determined whether or not polycrystallization had occurred. In this case, the observation with the differential interference microscope was carried out at a magnification of 10 times. As a result, one visual field of the differential interference microscope was 10 mm x 10 mm in size, and the number of crystal defects per visual field was directly converted into the density (cm -2 ) was calculated. The above crystal defects refer to "etch pits" that appear as corrosion holes on the main surface due to the above etching. Although the above etch pits are not academically synonymous with dislocations, they can be considered equivalent to dislocations in this technical field. Furthermore, the above "dislocations" refer to "threading dislocations" that exist inside beta-type Ga2O3 single crystals, and the above threading dislocations are known as one type of crystal defect.

[0156] Next, if no polycrystallization was observed in the measurement sample, the measurement sample was evaluated as a good product. On the other hand, if at least polycrystallization was observed in the measurement sample, the measurement sample was evaluated as defective. For the ingot from which the measurement sample evaluated as defective was cut, a new measurement sample was cut at a position 10 mm toward measurement point 3 from measurement point 1 or measurement point 2, where the measurement sample was cut, and the new measurement sample was observed as described above using the differential interference microscope. This operation was repeated until the measurement sample was determined to be good.

[0157] Finally, the volume of the ingot was calculated from the length (height) of the ingot sandwiched between the cut-out portions of the measurement samples judged to be non-defective and the diameter of the beta-type GaO single crystal substrate of each sample (i.e., 101.6 mm or 152.4 mm). The mass of the ingot that could be used as a product (hereinafter also referred to as "non-defective mass") was calculated from the volume. Next, the proportion of the non-defective mass in the mass of the region of the ingot sandwiched between measurement points 1 and 2 was calculated, and this was taken as the "product yield." The results are shown in Tables 4, 5, and 6.

[0158] [Measurement of Activation Ratio] The carrier concentration of each sample was determined by performing the above-described measurement method on a Hall measurement sample prepared using the center portion of each beta-type GaO single crystal substrate (Samples 10B to 10C, 101 to 115, 20C, 201 to 213, and 301 to 313). Furthermore, the Sn or Si impurity concentration in the beta-type GaO single crystal substrate was determined using glow discharge mass spectrometry (GDMS). The activation ratio of each sample was calculated by dividing the carrier concentration by the impurity concentration determined by GDMS. The results are shown in Tables 4, 5, and 6.

[0159] [Transmittance Measurement] The transmittance of light with a wavelength of 427 nm for each sample was determined by carrying out the above-mentioned measurement method on transmittance measurement samples prepared using the central portions of the beta-type GaO single crystal substrates of Samples 10B to 10C, Samples 101 to 115, Sample 20C, Samples 201 to 213, and Samples 301 to 313. The results are shown in Tables 4, 5, and 6.

[0160]

[0161]

[0162]

[0163] [Discussion] According to Table 4, the product yields of the beta-type GaO single crystal substrates of Samples 101 to 115 were better than those of the beta-type GaO single crystal substrates of Samples 10B to 10C. Therefore, it can be evaluated that the crucibles for producing the beta-type GaO single crystal substrates of Samples 101 to 115 are more likely to suppress cracking and chipping during crystal growth than those for producing the beta-type GaO single crystal substrates of Samples 10B to 10C. According to Table 5, the product yields of the beta-type GaO single crystal substrates of Samples 201 to 213 were better than those for the beta-type GaO single crystal substrate of Sample 20C. Therefore, it can be evaluated that the crucibles for producing the beta-type GaO single crystal substrates of Samples 201 to 213 are more likely to suppress cracking and chipping during crystal growth than those for producing the beta-type GaO single crystal substrate of Sample 10C. According to Table 6, the product yields of the beta-type GaO single crystal substrates of Samples 301 to 313 were good, similar to those of the beta-type GaO single crystal substrates of Samples 101 to 115. Therefore, it can be evaluated that the crucibles for producing the beta-type GaO single crystal substrates of Samples 301 to 313 can suppress the occurrence of cracks and chips during crystal growth.

[0164] In particular, the beta-type GaO single crystal substrates of Samples 113 to 115, and the beta-type GaO single crystal substrates of Samples 211 to 213, and Sample 313 were superior in activation ratio and transmittance compared to the other samples. Therefore, the beta-type GaO single crystal substrates of Samples 113 to 115, Samples 211 to 213, and Sample 313 are evaluated as being capable of being provided as compound semiconductor substrates excellent in both electrical and optical properties.

[0165] Although the embodiments and examples of the present disclosure have been described above, it is also planned from the beginning that the configurations of the above-described embodiments and examples may be appropriately combined.

[0166] The embodiments and examples disclosed herein are illustrative in all respects and should not be considered limiting. The scope of the present invention is defined by the claims, not by the embodiments and examples described above, and is intended to include meanings equivalent to the claims and all modifications within the scope of the claims.

[0167] 100 Single crystal growth apparatus, 5 Crucible, 51 Seed crystal accommodation section, 52 Diameter increasing section, 53 Straight body section, 5a Side wall section, 5b Sprayed film, 5b1 First film, 5b2 Second film, 5c Hole, 6 Crucible holder, 7 Heating device, 8a Seed crystal, 81 Beta-type GaO single crystal, 82 Digallium trioxide melt (GaO melt), 9 Sealed container, 1 Beta-type digallium trioxide single crystal substrate (Beta-type GaO single crystal substrate), 10 Main surface, 10a Rectangular slice, O Center, OF Orientation flat, 21 Electrode, S100 Beta-type GaO single crystal manufacturing process, S110 Preparation process, S120 Raw material accommodation process, S130 Raw material melting process, S140 Ga2O3 single crystal growth process, S200 Beta type Ga2O3 single crystal substrate manufacturing process.

Claims

1. A crucible for growing beta-type gallium trioxide single crystals, the crucible having a thickness of 1 mm or more and 10 mm or less, the maximum inner diameter of the crucible being 100 mm or more, the composition of the crucible being stabilized zirconia containing both or either of yttrium oxide and calcium oxide, the surface on the inner peripheral side of the crucible being coated with a sprayed film containing both or either of rhodium and platinum, the thickness of the sprayed film being 100 μm or more and 500 μm or less, the stabilized zirconia containing at least 12.0 mass % or more and 15.5 mass % or less of the yttrium oxide or 10.2 mass % or more and 11.4 mass % or less of the calcium oxide.

2. The crucible according to claim 1, wherein the sprayed coating is made of a platinum-rhodium alloy containing 10% by mass or more and 30% by mass or less of rhodium.

3. The crucible according to claim 2, wherein the sprayed film has pores, and the porosity, which is the volume ratio of the pores in the sprayed film, is 30 volume % or more and 50 volume % or less.

4. The crucible according to claim 2, wherein the surface roughness Rz of the surface is 300 μm or more and 500 μm or less, the thermal sprayed film has pores, and the porosity, which is the volume ratio of the pores in the thermal sprayed film, is 10 volume % or more and less than 30 volume %.

5. The crucible according to claim 3, wherein the surface roughness Rz of the surface is 300 μm or more and 500 μm or less.

6. The crucible according to claim 1, wherein the sprayed coating comprises a first film and a second film, the first film covers the surface, the first film is made of rhodium or a platinum-rhodium alloy mainly composed of rhodium, the second film covers the first film, the second film is made of platinum or a platinum-rhodium alloy mainly composed of platinum, and the thickness of the sprayed coating, the total thickness of the first film and the second film, is 100 μm or more and 500 μm or less.

7. The crucible described in claim 6, wherein the first film and the second film both have pores, and a first film porosity which is the volume ratio of the pores in the first film, and a second film porosity which is the volume ratio of the pores in the second film, are both 30 volume % or more and 50 volume % or less.

8. The crucible described in claim 6, wherein the surface roughness Rz of the surface is 300 μm or more and 500 μm or less, the first film and the second film both have pores, and a first film porosity which is the volume ratio of the pores in the first film and a second film porosity which is the volume ratio of the pores in the second film are both 10 vol. % or more and less than 30 vol. %.

9. The crucible according to claim 7, wherein the surface roughness Rz of the surface is 300 μm or more and 500 μm or less.

10. A method for producing a beta-type digallium trioxide single crystal substrate using the crucible according to any one of claims 1 to 9, comprising the steps of: preparing the crucible; obtaining a beta-type digallium trioxide single crystal by a vertical boat method using the crucible; and processing the beta-type digallium trioxide single crystal to obtain a beta-type digallium trioxide single crystal substrate having a circular main surface.

11. A beta-type digallium trioxide single crystal substrate having a circular main surface, wherein the diameter of the beta-type digallium trioxide single crystal substrate is 100 mm or more, the main surface is a (001) plane of the beta-type digallium trioxide single crystal, or a plane having an off angle of more than 0° and not more than 10° from the (001) plane of the beta-type digallium trioxide single crystal, and an off direction in the [010] direction of the beta-type digallium trioxide single crystal or a direction perpendicular to the [010] direction, the beta-type digallium trioxide single crystal substrate contains both or either one of rhodium and iridium, and the concentrations of the rhodium and the iridium are both less than 3 ppm by mass in glow discharge mass spectrometry.

12. The transmittance for light having a wavelength of 400 nm or more and 430 nm or less is 70% or more, and the carrier concentration measured at 25°C by the Van der Pauw Hall measurement is 1 x 10 17 cm -3 Above 1.0 x 10 19 cm -3The beta-type gallium trioxide single crystal substrate according to claim 11, wherein: