Ga2O3 BASED SINGLE CRYSTAL SUBSTRATE AND METHOD FOR MANUFACTURING Ga2O3 BASED SINGLE CRYSTAL SUBSTRATE

Abstract

To manufacture a Ga2O3 based single crystal and Ga2O3 based single crystal substrate without completely including twins and as a result, manufacture an optical device or an electric power device at a high yield using the Ga2O3 based single crystal substrate.SOLUTION: A single crystal without completely including twins is grown using a gallium oxide raw material having an impurity concentration controlled so that an impurity concentration included in the single crystal is 0.02 mol% or more and 0.15 mol% or less, and a Ga2O3 based single crystal substrate without completely having twins is manufactured from the single crystal.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a Ga2O3-based single crystal substrate and a method for manufacturing the Ga2O3-based single crystal substrate. [Background technology]

[0002] Recently, there has been active development of various semiconductor elements, such as optical devices and power devices, using Ga2O3-based single crystal substrates, which are new semiconductor substrates.

[0003] Generally, when forming various device structures on a single crystal substrate, if twins are present in the substrate, the laminated film grown on that portion will suffer from breakage, cracks, or peeling, and the laminated film will grow with a plane orientation different from the desired one, making it unusable as a device. Therefore, a twin-free single crystal substrate that does not contain any twins is required.

[0004] However, as explained in Patent Documents 1 and 2, Ga2O3-based single crystals have the problem that twins tend to occur during crystal growth. Therefore, as described in Patent Document 3, it is said that twins can be reduced to almost zero by using a seed crystal with the same width as the entire width of the die and growing the crystal without necking or spreading. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 6097989 [Patent Document 2] Patent No. 5879102 [Patent Document 3] Patent No. 5777756 Summary of the Invention [Problem to be solved by the invention]

[0006] However, even the method described in Patent Document 3 is insufficient because twins still occur in the newly crystallized portion from the seed crystal, and the method is not completely free of twins. One factor affecting the likelihood of twins occurring is the crystal system to which the single crystal belongs. Unlike the Si substrates, InP substrates, and GaN substrates currently used in the semiconductor industry, which belong to the cubic, cubic, and hexagonal crystal systems with good symmetry, and which produce single crystal substrates completely free of twins, Ga2O3-based single crystals belong to the monoclinic system, which has poor symmetry, and are rare crystals with extremely strong cleavage properties. Therefore, it is unclear whether it is possible to grow a single crystal completely free of twins and produce a completely twin-free substrate. Furthermore, the method described in Patent Document 3 does not involve necking or spreading, which results in the problem of easily generating crystal defects and poor crystallinity.

[0007] The present invention has been made in view of the above-mentioned problems, and aims to enable the production of Ga2O3-based single crystals and Ga2O3-based single crystal substrates that are completely free of twins and have good crystallinity, and ultimately to enable the production of optical devices and power devices that use Ga2O3-based single crystal substrates with good yields. [Means for solving the problem]

[0008] As a result of extensive research, the present inventors have found that the above problems can be solved by the present inventions described below in [1] to [6].

[0009] [1] A Ga2O3-based single crystal substrate with a total impurity concentration of 0.02 mol% or more and 0.15 mol% or less in the single crystal, and completely free of twins.

[0010] [2] The Ga2O3-based single crystal substrate according to [1] above, wherein the impurities are one or more of Si, Sn, C, Mg, N, Fe, P, Cu, Co, and Ni.

[0011] [3] The Ga2O3-based single crystal substrate according to [1] or [2] above, wherein the main surface of the substrate is any one of the (100), (010), (001), (-201), and (101) planes.

[0012] [4] The Ga2O3-based single crystal substrate according to [1] or [2] above, wherein the main surface is a plane inclined at an angle of 7° or less (excluding 0°) with respect to any one of the (100) plane, the (010) plane, the (001) plane, the (-201) plane, and the (101) plane.

[0013] [5] A method for manufacturing a Ga2O3-based single crystal substrate that is completely free of twins and has an impurity concentration of 0.02 mol% or more and 0.15 mol% or less, and is fabricated from a Ga2O3-based single crystal grown by an induction heating single crystal growth method.

[0014] [6] A method for producing a Ga2O3-based single crystal substrate according to the above [5], wherein the direction in which the Ga2O3-based single crystal is grown is the a-axis direction, the b-axis direction, the c-axis direction, or any direction tilted within a range of 7° (but excluding 0°) from each of the axes. [Effects of the Invention]

[0015] According to the present invention, it is possible to produce a Ga2O3-based single crystal substrate that is completely free of twins and has good crystallinity. [Brief explanation of the drawings]

[0016] [Figure 1] 1 is a schematic cross-sectional view illustrating a growth furnace in an example of a method for producing a Ga2O3-based single crystal by the EFG method according to the present invention. [Figure 2] 2 is an explanatory diagram of a method for producing a Ga2O3-based single crystal by the EFG method of FIG. 1. [Figure 3] 1A and 1B are a perspective view and a plan view, respectively, illustrating an example of a Ga2O3-based single crystal substrate according to an embodiment of the present invention; [Figure 4] FIG. 2 is a perspective view showing another example of a Ga2O3-based single crystal substrate according to an embodiment of the present invention. [Figure 5]Graph showing the Si impurity concentration [mol%] in the Ga2O3 single crystal according to Example 1 and Comparative Example 1 of the present invention, and the presence or absence of twins or grain boundaries. [Figure 6] Graph showing the Si impurity concentration [mol%] in the Ga2O3 single crystal according to Example 2 and Comparative Example 2 of the present invention, and the presence or absence of twins or grain boundaries.

Embodiments for Carrying Out the Invention

[0017] Hereinafter, this embodiment will be described with reference to FIGS. 1 to 3. In this embodiment, the Ga2O3 single crystal 13 is a Ga2O3 single crystal or a Ga2O3 crystal containing Al. When Al is included, the composition ratio is (Al (1-x) Ga x )2O3 (0 < X ≦ 1).

[0018] As an example of the production of the Ga2O3 single crystal from which the Ga2O3 single crystal substrate 16 or 21 is cut out, the growth of a β-type Ga2O3 single crystal (β-Ga2O3 single crystal) by the EFG (Edge-defined Film-fed Growth) method, which is a single crystal growth method of the induction heating type, can be mentioned. FIG. 1 is a schematic cross-sectional view showing the structure of a manufacturing apparatus 1 for a β-Ga2O3 single crystal using the EFG method. Note that the crystal growth method is not limited to the EFG method, and the CZ (Czochralski) method, the Bridgman method, or the like may also be used.

[0019] As shown in FIG. 1, inside the manufacturing apparatus 1, a crucible 3 for filling the raw material of the Ga2O3 single crystal and a die 5 provided with a slit are installed in the crucible 3. On the upper surface of the crucible 13, there is a lid 6 except for the upper surface of the die 5.

[0020] The raw material filled into the crucible 13 is high-purity Ga2O3 (gallium oxide) with a purity of 5N (99.999%) or higher. To maintain good crystallinity and prevent twinning during crystal growth, impurities are added so that their total content in the single crystal is 0.02 mol% to 0.15 mol%. This also ensures that the Ga2O3-based single crystal substrate has the desired semiconductor properties (e.g., electrical resistivity, carrier type, carrier density, mobility, etc.). Furthermore, the addition of impurities reduces the formation of polycrystals during crystal growth, improving crystallinity and increasing single crystal yield. However, excessively high impurity concentrations actually worsen crystallinity. Without the addition of impurities, polycrystals are more likely to form. Impurity elements include Si, Sn, C, N, P, Fe, Mg, Cu, Co, and Ni. When mixed with the starting gallium oxide raw material, these elements are used as simple substances or in the form of oxides or nitrides.

[0021] It is preferable that the raw material to be filled into the crucible 13 be a high density raw material so that as much as possible can be filled therein.

[0022] The growth apparatus heats the material to temperatures exceeding 1800°C, the melting point of β-Ga2O3. The crucible 13, die 5, and lid 6, which are exposed to the β-Ga2O3 melt and vapor, are made of materials that are resistant to reaction with the Ga2O3 melt and vapor and have a high melting point of over 1800°C. Currently, iridium is the most suitable material, and the growth atmosphere must therefore be an inert atmosphere containing 100 vol% inert gas such as argon or nitrogen, or up to 3 vol% oxygen. The crucible 3 may be pressurized to prevent evaporation of the raw materials.

[0023] The crucible 3 is induction-heated to a predetermined temperature by the heater unit 9 made of an induction coil, the raw material in the crucible 3 melts, and the melt rises through the slit 5A due to capillary action.

[0024] While resistance heating, commonly used in the CZ method for growing silicon crystals, is a popular heating method, induction heating is more suitable for growing Ga2O3-based crystals. Because Ga2O3 is highly susceptible to sublimation and evaporation, resistance heating, which requires raising the temperature of the entire hot zone, can cause sublimation and decomposition of the seed crystal and the grown crystal, resulting in thin, slender crystals and, in the worst case, complete loss. This can result in a decrease in crystal growth yield or even failure to grow crystals at all. In contrast, induction heating, which uses localized heating that heats only the iridium components, such as the crucible 3 and lid 6, allows the crystal to cool relatively easily, suppressing sublimation and decomposition from the crystal to a nearly negligible degree. Furthermore, because unnecessary heating is avoided, sublimation and evaporation from the crucible are also suppressed. As a result, raw material efficiency, which indicates the weight percentage of the raw material that becomes a single crystal, is improved.

[0025] The seed crystal 10 above the slit 5A is lowered until it partially contacts the die upper surface 5B where the melt is exposed. Then, the seed crystal 10 is pulled up at a predetermined speed, and crystallization begins from the part of the seed crystal that is in contact with the melt.

[0026] First, the seed crystal 10 is pulled up while adjusting the pulling speed at the highest possible temperature, and a thin neck is formed (necking 13a) to remove dislocations in the crystal. Specifically, at a temperature of 1800°C or higher, the neck thickness is set to approximately half or less of the seed crystal area in contact with the upper surface of the die, thereby reducing the dislocation density of the Ga2O3-based single crystal 13 to 1.0 × 10 5 pieces / cm 2 The following can be done: In terms of the principles of crystal growth, it is preferable that the seed crystal has as few dislocations as possible.

[0027] Next, the seed crystal holder 11 is raised at a predetermined rate, and a Ga2O3-based single crystal 13 is grown around the seed crystal 10 at a constant angle θ in the width direction of the die 5 (spreading 13b). Twins in gallium oxide single crystals occur during necking, spreading, and the growth of the straight body portion (described later), but are particularly frequent during the spreading stage. Twins grow and extend in a direction parallel to the (100) plane in the crystal, and do not disappear until they hit the edge of the crystal.

[0028] Generally, the rate at which twins occur depends on the size of θ. To prevent twins from occurring, it is preferable to make θ small and widen it slowly. The larger θ is made, the more rapidly the atoms in the melt line up and crystallize, resulting in more twins, which are a disorder in the atomic arrangement. Specifically, if θ is made 30° or less, twins will disappear and single crystals with high crystallinity can be grown. If θ is made larger than 30°, twins will occur.

[0029] However, regardless of the magnitude of the above θ, twinning does not occur when the impurity concentration in the single crystal is 0.02 mol% or more. Twinning occurs when the impurity concentration is lower than 0.02 mol%. However, if the impurity concentration is higher than 0.15 mol%, twinning does not occur, but grain boundaries occur and the crystallinity deteriorates. Therefore, it is preferable that the impurity concentration be 0.15 mol% or less.

[0030] Next, when the GaO-based single crystal 13 has been expanded to the full width of the die 5 (full spread), the portion (straight body portion 13c) having the same width as the full width of the die 5 is pulled up to an appropriate length. The length of the straight body portion is not particularly limited.

[0031] After the growth of the straight body portion is completed, the temperature is lowered to room temperature, and the crystal is then removed from the manufacturing equipment and the presence or absence of twins and the crystallinity are evaluated using a distortion detector and an X-ray diffractometer. If the impurity concentration in the single crystal is within the above-mentioned specified range, no twins are present. In addition, no grain boundaries are present. The above evaluation may also be performed after the removed crystal is processed into a substrate.

[0032] Furthermore, if the impurity concentration in the single crystal is within the above-mentioned predetermined range, a twin-free seed crystal having the same width as the entire width of the die 5 is used in growing the Ga2O3-based single crystal 13, and the necking and spreading described above are eliminated, even when the body portion is grown directly from the seed crystal, no twins are generated, and a twin-free single crystal with excellent crystallinity can be grown.

[0033] The pulling plane orientation can be set in various ways depending on the plane orientation of the main surface. The pulling direction is along the a-axis, b-axis, or c-axis, or along any direction tilted within ±7° (but not including 0°) relative to each axis. The pulling direction here refers to the crystal growth direction. The main surface 15 of the substrate 16 is preferably the (100), (010), (001), (101), or (-201) plane, or any plane tilted within an angle range of 7° (but not including 0°) relative to any of the (100), (010), (001), (101), or (-201) planes, which allows the formation of a semiconductor layer with good surface morphology and is suitable for the fabrication of semiconductor device structures such as ultraviolet LEDs.

[0034] The pulling direction of the Ga2O3-based single crystal 13 and the setting direction of the seed crystal 10 are usually set so that the plane orientation of the face 20 of the Ga2O3-based single crystal 13 is as described above.

[0035] Next, a description will be given of a method for processing the grown Ga2O3-based single crystal 13 into a Ga2O3-based single crystal substrate 16. For example, a slicing machine, a diamond core drill, an ultrasonic processing machine, or the like is used to perform cutting processing into a square or circle to cut out a square or circular substrate of a predetermined shape.

[0036] Then, the outer shape of the substrate is finely adjusted and shaped using an end face grinder.

[0037] Furthermore, before or after the above-mentioned cutting process, an orientation flat may be formed on the substrate 16 or 21 as necessary.

[0038] The orientation flats are end faces where at least one of the orientation flats is perpendicular to the principal surface and parallel to the b-axis when the principal surface is a (100) plane or a plane tilted at an angle of 7° or less from the (100) plane. When the principal surface is other than a (100) plane or a plane tilted at an angle of 7° or less from the (100) plane, at least one of the orientation flats is an end face where at least one of the orientation flats is perpendicular to the principal surface and parallel to the intersection line between the principal surface and the (100) plane.

[0039] By forming the orientation flat in the above crystal orientation, cracks, chipping, and peeling can be prevented from occurring in the substrate during processing.

[0040] Next, one side of the fabricated substrate 16 is designated as the main surface 15, and at least this main surface 15 is subjected to polishing processes such as lapping and polishing to make the main surface 15 ultra-flat and at the same time adjust the thickness of the substrate 16. The back surface 19 is also polished as needed. Alumina abrasives are preferably used for lapping. Chemical mechanical polishing (CMP) is used for polishing, and colloidal silica is preferably used as the CMP abrasive.

[0041] As a result of the above, the surface roughness Ra of the main surface 15 is 3.0 nm or less, and the surface roughness Ra of the rear surface 19 is 0.1 nm or more as required.

[0042] After the above substrate processing is completed, the substrate is cleaned by organic cleaning with acetone, etc., followed by hydrofluoric acid cleaning and RCA cleaning to remove contaminants such as silica adhering to the substrate, remove residual processing distortion, and form a clean oxide layer on the substrate surface.

[0043] Furthermore, in the substrate processing step, heat treatment may be performed as appropriate to remove residual thermal strain, residual processing strain, and coloration, as well as to improve electrical properties, as is common to those skilled in the art of processing single-crystal substrates such as Si, InP, and sapphire. The atmospheric gas for the heat treatment may be any of nitrogen, carbon dioxide, argon, oxygen, and air, excluding reducing gases such as hydrogen gas, and may be combined as appropriate. The processing temperature is 500°C to 1600°C, preferably 700°C to 1400°C. Pressure may also be applied.

[0044] By going through the above steps, a Ga2O3-based single crystal substrate with excellent crystallinity and no twins or grain boundaries on the main surface is produced.

[0045] The planar shape of the substrate is rectangular, circular, or rectangular or circular with an orientation flat. In order to precisely control the shape, ensure the rigidity of a self-standing substrate, have strength sufficient for easy handling, and prevent cracks and burrs, it is preferable that the rectangular shape have a long side of 15 mm or more and 150 mm or less, and that the circular shape have a diameter of φ25 mm or more and φ160 mm or less.

[0046] Furthermore, for the above reasons, the substrate thickness is preferably 0.1 mm or more and 2.0 mm or less.

[0047] The dislocation density of the substrate 16 cut from the single crystal grown by the necking and spreading of the EFG method and processed into a substrate was 1.0×10 5 pieces / cm 2 The reason is as follows: By suppressing the dislocation density low, it is possible to improve the light emission efficiency and the device life in optical devices, and to improve the power conversion efficiency and the device life in power devices.

[0048] The dislocation density can be substituted by, for example, the density of point-like etch pits when the substrate is etched, and is evaluated by etching with a KOH etchant.

[0049] Examples of the present invention will be described below, but the present invention is not limited to only the following examples. [Example]

[0050] Here, we will explain the case of crystal growth using the EFG method, which involves necking and spreading. First, for the gallium oxide raw material to be placed in the crucible, a Ga2O3 powder raw material with a purity of 6N mixed with Si impurities at the concentrations shown in Table 1 for each of Example Samples 1 to 4 was sintered and pulverized. Then, each of the high-density raw materials was placed in the crucible for each crystal growth, and thereafter, each crystal was grown and polished in the same manner to produce a substrate. Note that SiO2, an oxide, was used as the Si impurity.

[0051] The gas atmosphere in the crystal growth furnace was nitrogen at atmospheric pressure, and the iridium crucible was heated by induction heating.

[0052] First, once the specified temperature was reached, the seed crystal was lowered and the tip of the seed crystal was brought into contact with the die to melt it. In the necking process, the growth temperature was raised to 1850°C or higher, and the seed crystal pulling speed was started at 10 mm / hr or higher. The temperature rate was then adjusted appropriately so that the neck diameter became φ4 mm.

[0053] Next, in the spreading step, the pulling speed was set to 10 mm / hr, the growth temperature was slowly lowered so that θ became 50°, and the die was fully spread to a die width of 55 mm and a die thickness of 10 mm.

[0054] After full spreading, the temperature rate is adjusted appropriately to grow a straight body length of 55 mm.

[0055] Thereafter, the temperature was lowered to room temperature and the crystal was taken out of the growth apparatus. When the crystal was evaluated with a distortion detector, it was found that the crystals obtained in each example sample were single crystals completely free of twins.

[0056] The widest surface of the pulled single crystal is the surface that will become the main surface of the substrate, and in this case the seed crystal was set so that it would be the (-201) surface, and was pulled up in the b-axis direction to grow.

[0057] After the crystal growth was completed, the crystals from which each sample was cut were examined using a distortion detector and an X-ray diffractometer, and it was found that none of the crystals contained twins or grain boundaries.

[0058] Next, to process the grown single crystal into a substrate, two end faces were first formed using a slicing machine: one end face parallel to the b-axis direction and the other parallel to the [10-1] direction.Then, a diamond core drill was used to cut out a round shape with a diameter of 2 inches.

[0059] Next, after heat treatment at 1000°C for 5 hours in a nitrogen gas atmosphere, the main surface of the substrate was subjected to lapping and polishing. The back surface was only subjected to lapping. After polishing, the above-mentioned cleaning procedures were carried out, and then evaluation was performed using a distortion tester and an X-ray diffractometer. It was found that for all example samples, completely twin-free φ2-inch substrates were obtained. Furthermore, there were no grain boundaries and the crystallinity was excellent.

[0060] [Table 1]

[0061] (Comparative Example 1) Comparative Examples Samples 5 and 6 were also prepared in the same manner as in Example 1. However, the concentration of the Si impurity mixed into the raw material and contained in the crystal was different from that of the Example Samples, as shown in Table 2.

[0062] [Table 2]

[0063] After the crystal growth was completed, the original crystals from which each sample was cut were evaluated using a distortion detector and an X-ray diffraction device. Twin crystals were found to be present in the original crystal from which Sample 5 was cut. Although no twin crystals were found in the original crystal from which Sample 6 was cut, grain boundaries were observed.

[0064] Furthermore, when the substrates of the comparative samples 5 and 6 were evaluated using a distortion detector and an X-ray diffractometer, twin crystals were found in sample 5, while no twin crystals were found in sample 6. However, only sample 6 had grain boundaries, indicating poor crystallinity.

[0065] The results of Example 1 and Comparative Example 1 are summarized in Figure 5. By adjusting the Si impurity concentration in the single crystal that produced necking or spreading to 0.02 mol% to 0.15 mol%, a single crystal and substrate with excellent crystallinity and no twins or grain boundaries were obtained. [Example]

[0066] This section describes crystal growth using the EFG method, which uses a seed crystal with the same width as the entire width of the die 5 and omits necking and spreading. First, for the gallium oxide raw material to be placed in the crucible, Ga2O3 powder raw material with a purity of 6N was mixed to achieve the Si impurity concentration shown in Table 3 for each of Example Samples 7 to 10, and then sintered and pulverized. Then, each of the high-density raw materials was placed in the crucible for each crystal growth. Thereafter, each crystal was grown and polished in the same manner as in Example 1 to produce a substrate. Note that SiO2, an oxide, was used as the Si impurity. The single crystal was a (-201) plane pulled along the b-axis.

[0067] The gas atmosphere in the crystal growth furnace was nitrogen at atmospheric pressure, and the iridium crucible was heated by induction heating.

[0068] First, once the specified temperature is reached, the seed crystal is lowered and the tip of the seed crystal is brought into contact with the die to melt it. The growth temperature is set to 1800°C or higher and the seed crystal pulling speed is set to 50 mm / hr or less. The temperature and speed are adjusted as needed to prevent the melt from running out between the seed crystal and the die, and a straight body length of 55 mm is grown.

[0069] The crystals were then cooled to room temperature and removed from the growth furnace. The crystals were evaluated using a distortion detector and an X-ray diffractometer, and it was found that each example sample had a single crystal with no twins. Furthermore, no grain boundaries were observed.

[0070] Next, the grown single crystals were processed into substrates in the same manner as in Example 1, and each example sample was evaluated using a distortion detector and an X-ray diffraction device. As a result, a φ2-inch substrate with excellent crystallinity was obtained for each sample, which was completely twin-free and had no grain boundaries.

[0071] [Table 3]

[0072] (Comparative Example 2) Comparative Examples Samples 11 and 12 were also prepared in the same manner as in Example 2. However, the concentration of the Si impurity mixed into the crystal at the time of starting material was different from that in Example 2, and was as shown in Table 4.

[0073] [Table 4]

[0074] After the crystal growth was completed, the original crystals from which each sample was cut were removed from the growth apparatus and evaluated using a distortion detector and an X-ray diffraction device. Twins were found to be present in the original crystal from sample 11. Sample 12 had no twins at all, but grain boundaries were present.

[0075] Sample 11, which was processed into a substrate from the above crystal, contained twin crystals, while Sample 12 contained no twin crystals at all. However, only Sample 12 had grain boundaries, and the crystallinity was poor.

[0076] The results of Example 2 and Comparative Example 2 are summarized in Figure 6. When the Si impurity concentration in the single crystal produced without necking or spreading is set to 0.02 mol% to 0.15 mol%, the single crystal and substrate can be obtained with excellent crystallinity, with no twins or grain boundaries.

[0077] As described above, according to this embodiment, if the crystal contains 0.02 to 0.15 mol % of Si, a single crystal with excellent crystallinity and absolutely no twins can be grown, and by processing the single crystal into a substrate, a twin-free substrate with excellent crystallinity and absolutely no grain boundaries can be produced.

[0078] The present invention is not limited to the above-described embodiments and examples, and many modifications can be made by a person having ordinary skill in the art within the technical concept of the present invention.

[0079] And the scope of the present invention shall be determined to the fullest extent permitted by law by the broadest permissible interpretation of the claims and their equivalents, and shall not be limited or restricted by the foregoing detailed description. [Explanation of symbols]

[0080] 1. Growth furnace 2. Ga2O3-containing melt 3 Crucible 4 Support stand 5 Die 5A Slit 5B opening 6 Lid 7 Thermocouples 8. Insulation 9 Heater section 10 seed crystals 11 Seed crystal holder 12 shafts 13 Ga2O3-based single crystals 13a Neck 13b Spreading 13c Straight body part 15 Main surface of Ga2O3-based single crystal substrate 16, 21 Ga2O3-based single crystal substrate 19 Backside of Ga2O3-based single crystal substrate 20 Ga2O3 single crystal faces t Thickness of Ga2O3-based single crystal substrate θ Spreading angle

Claims

【Request Item 1】 The total concentration of impurities contained in the single crystal is 0.02 mol% or more and 0.15 mol% or less, and there are no twins. 2 O 3 Single crystal substrate. 【Request Item 2】 2. The Ga as claimed in claim 1, wherein the impurities are any one or more of the elements Si, Sn, C, Mg, N, Fe, P, Cu, Co, and Ni. 2 O 3 Single crystal substrate. 【Request Item 3】 3. The GaAs substrate according to claim 1, wherein the primary surface of the substrate is any one of the (100), (010), (001), (-201), and (101) planes. 2 O 3 Single crystal substrate. 【Request Item 4】 3. The GaAs crystal according to claim 1, wherein the primary surface is a surface inclined at an angle of ±7° (excluding 0°) with respect to any of the (100), (010), (001), (-201), and (101) planes. 2 O 3 Single crystal substrate. 【Request Item 5】 Ga grown by induction heating single crystal growth method 2 O 3 The substrate is processed from a Ga-based single crystal, and the impurity concentration is between 0.02 mol% and 0.15 mol%. 2 O 3 A method for manufacturing a silicon-based single crystal substrate. 【Request Item 6】 The Ga 2 O 3 6. The Ga-based single crystal according to claim 5, wherein the direction in which the Ga-based single crystal is grown is the a-axis direction, the b-axis direction, the c-axis direction, or a direction tilted within a range of ±7° (excluding 0°) from each of the axes. 2 O 3 A method for manufacturing a silicon-based single crystal substrate.

Images