JP4886722B2 - Method for producing nitride single crystal - Google Patents

Description

  The present invention relates to a method for producing a nitride single crystal.

Gallium nitride III-V nitride has attracted attention as an excellent blue light-emitting device, and has been put to practical use as a material for light-emitting diodes and semiconductor laser diodes. In the method described in Patent Document 1, a group III nitride single crystal is grown by a flux method. That is, a seed crystal substrate is placed in a uniformly heated flux to grow a single crystal.
WO2006-030718 A1

Disclosed is a method for growing a nitride semiconductor by combining methods such as swinging the apparatus and installing a stirring blade in the crucible so that a flow from the gas-liquid interface in contact with the source gas to the inside of the source liquid is generated. (Patent Document 2).
JP-A-2005-263622

In the methods described in Patent Documents 3 and 4, a low temperature part is provided at the bottom of the crucible (growth vessel), the seed crystal substrate is fixed on the bottom of the crucible, and the periphery of the seed crystal substrate is cooled to a solid liquid. Increase supersaturation near the interface to promote crystal growth.
WO96 / 15297 Patent No. 3087065

The present applicants disclosed in Patent Documents 5 and 6 that a seed crystal substrate is immersed in a melt in a crucible in a vertical direction and a nitride single crystal is grown on the surface of the seed crystal substrate by a flux method.
Japanese Patent Application No. 2007-081476 PCT / 2007/053853

  In Patent Documents 5 and 6, the lower part of the melt in the crucible is heated to a high temperature to generate upward convection and to stir the melt. However, it was found that by fixing the seed crystal substrate in the crucible, the seed crystal substrate becomes a kind of baffle plate, and there is still a region where melt convection is still insufficient on the surface of the seed crystal substrate. For this reason, the location which grew on the board | substrate laterally and maintained the smooth surface was limited.

  An object of the present invention is to promote convection of a melt near the surface of the entire surface of a seed crystal substrate when growing a nitride single crystal by a flux method, and to produce a smooth single crystal of good quality.

  In the production method according to the present invention, a seed crystal substrate is immersed in a melt containing a flux and a single crystal raw material in a growth vessel, a high temperature portion and a low temperature portion are provided on the bottom wall portion of the growth vessel, and the seed is formed on the high temperature portion. A crystal substrate is fixed, and a nitride single crystal is grown on the growth surface of the seed crystal substrate.

  The inventor has studied various melt flows when the bottom of the melt in the growth vessel is heated. When heating is performed from the bottom of the growth vessel, thermal convection occurs from the bottom to the top of the melt, and the melt is stirred. However, the flow is complicated because the melt rises upward from the chaotic origin at the bottom by thermal convection. For this reason, the contact between the melt and the seed crystal substrate becomes messy, and the single crystal film is considered to be difficult to grow in a layered and regular manner with good reproducibility. As a result, it was considered that the obtained single crystal film was likely to have non-uniform film thickness and defects.

  Based on this knowledge, the present inventor has a relatively high temperature portion 10b and a relatively high temperature portion 10b on the bottom wall portion 10 of the growth vessel 1, as schematically shown in FIGS. 1 (a) and 1 (b). And the low temperature part 10a. And when seed crystal substrate 5 was immersed in melt 2, it fixed so that seed crystal substrate 5 might be located on high temperature part 10b.

  As a result, an upward flow is generated along the growth surface 5a (or 5b) of the seed crystal substrate from the vicinity of the high temperature portion 10b as indicated by the arrow 6, and then flows toward the outside of the growth container near the gas-liquid interface, As shown by the arrow 8, a downward flow is generated along the inner wall surface of the growth vessel. In this case, the flow direction on the surface of the substrate is fixed as compared with the case where only the temperature gradient is provided above and below, and rectification is likely to occur. In addition, since convection can be efficiently performed, after the nitrogen is dissolved in the melt near the gas-liquid interface, the melt can be quickly supplied to the entire growth vessel. As a result, step flow growth occurred on the growth surface of the seed crystal substrate, and it was found that a smooth nitride single crystal of good quality could be formed, and the present invention was achieved.

  In this invention, a high temperature part and a low temperature part are provided in the bottom wall part of a growth container. The temperature of the high temperature part and the temperature of the low temperature part of the bottom wall part are measured as follows. That is, a thermocouple is installed so as to contact the bottom wall portion 10 of the growth vessel 1, and the temperature indicated by the thermocouple is measured.

  The difference between the temperature at the high temperature portion 10b and the temperature at the low temperature portion 10a of the bottom wall of the growth vessel is preferably 3 ° C. or higher, and more preferably 10 ° C. or higher, from the viewpoint of the effect of the present invention. . Further, if this temperature difference becomes too large, turbulent flow is likely to occur due to thermal convection, and the quality of the nitride single crystal may be lowered, so it is preferably 50 ° C. or less, and 30 ° C. or less. More preferably.

  From the viewpoint of promoting convection, the difference between the temperature at the gas-liquid interface 2b of the melt 2 and the temperature at the bottom wall 10b is more preferably 0.5 ° C./cm or more, and more preferably 1 ° C./cm or more. preferable. From the viewpoint of suppressing the generation of turbulent flow due to vertical thermal convection and preventing the generation of miscellaneous crystals near the gas-liquid interface due to the low temperature of the gas-liquid interface, The difference between the temperature at the gas-liquid interface 2a and the temperature of the high temperature part 10b is preferably 10 ° C./cm or less, and more preferably 5 ° C./cm° C. or less.

In the present invention, a method for forming a relatively high temperature high temperature portion on the bottom wall portion of the growth vessel is not particularly limited. For example, the following method can be illustrated.
(1) A support plate is provided under the growth container, and the support plate includes a high heat conduction portion and a low heat conduction portion. A high temperature part is provided on the high heat conduction part.
(2) A support plate is provided under the growth container, and the bottom wall portion includes a thick portion and a thin portion. The thick part is the high temperature part.
(3) A thermal control plate is provided under the growth vessel, and a through hole is formed in the thermal control plate. A high temperature portion of the bottom wall portion is provided on the through hole.

  FIG. 1 (a) is a cross-sectional view schematically showing a state where a single crystal is grown according to an embodiment of the present invention, and FIG. 1 (b) shows a seed crystal substrate 5, a support plate 9, a high temperature part 9b, It is a schematic diagram which shows the planar positional relationship of the low temperature part 9a.

  In this example, a support plate is provided under the growth container, and this support plate includes a high heat conduction portion and a low heat conduction portion. In this example, the growth container 1 is columnar, but the shape is not limited. For example, it is cylindrical. The melt 2 is accommodated in the growth container 1, and the seed crystal substrate 5 is immersed in the melt 2. The growth container 1 includes a side wall portion 4 and a bottom wall portion 10. A support plate 9 is installed under the bottom wall portion 10, and the bottom wall portion 10 and the support plate 9 are in contact with each other.

  The space temperature under the support plate 9 is higher than the ambient temperature of the growth vessel 1, so that the heat rises toward the support plate 9 as indicated by an arrow H. Here, the support plate 9 is provided with a high heat conduction portion 9b and a low heat conduction portion 9a. The high heat conduction portion 9b is a portion made of a material having a relatively high thermal conductivity in the support plate, and the low heat conduction portion 9a is a portion made of a material having a relatively low heat conductivity in the support plate. is there. As a result, the low temperature part 10a of the bottom wall part 9 is located on the low heat conduction part 9a, and the high temperature part 10b of the bottom wall part 9 is located on the high heat conduction part 9b.

  And the seed crystal substrate 5 is fixed on the high temperature part 10b. Then, convection occurs as indicated by an arrow 6 upward from the high temperature portion 10b. This flow is relatively rectified. Then, it flows in the vicinity of the gas-liquid interface toward the outside, and descends as indicated by an arrow 8 in the vicinity of the side wall portion 4 downward.

  In this case, since the starting point is determined as compared with the case where a temperature gradient is simply provided above and below, the direction of the flow on the substrate surface is fixed and rectification is likely to occur. In addition, since convection can be efficiently performed, after the nitrogen is dissolved in the melt near the gas-liquid interface, the melt can be quickly supplied to the entire growth vessel. As a result, step growth is likely to occur on the growth surface of the seed crystal substrate, and the film thickness of a wide area of the nitride single crystal can be easily reproduced and made uniform.

From the viewpoint of the present invention, the difference between the thermal conductivity of the material constituting the low thermal conductive portion 9a and the thermal conductivity of the material constituting the high thermal conductive portion 9b is 10 W · m ⁻¹ · K ⁻¹ or more. It is preferably 30 W · m ⁻¹ · K ⁻¹ or more. Further, the difference between the thermal conductivity of the material constituting the low thermal conductive portion 9a and the thermal conductivity of the material constituting the high thermal conductive portion 9b is preferably 500 W · m ⁻¹ · K ⁻¹ or less, 350 W More preferably, m ⁻¹ · K ⁻¹ or less.

  In the present invention, the seed crystal substrate is placed on the high temperature portion of the bottom wall portion of the growth vessel. At this time, it is preferable that the entire seed crystal substrate exists in the high-temperature space E. Although it is not essential that the entire seed crystal substrate exists in the high-temperature space E, it is preferable that 30% or more of the area of the growth surface of the seed crystal substrate is located in the space E.

  FIG. 2 is a perspective view schematically showing a state in which a single crystal is grown on a seed crystal substrate in a growth container in another embodiment, and FIG. 3 shows the support plate 9A, the growth container 2, and high heat conduction. It is a figure which shows the planar positional relationship of the part 9b, the low heat conductive part 9a, and the seed crystal substrate 5. FIG.

  In this example, similarly to the example of FIG. 1, a support plate 9A is provided under the growth container 1, and the support plate 9A includes a high heat conduction portion 9b and a low heat conduction portion 9a. The melt 2 is accommodated in the growth container 1, and the seed crystal substrate 5 is immersed in the melt 2. The growth container 1 includes a side wall portion 4 and a bottom wall portion 10. A support plate 9A is installed under the bottom wall portion 10, and the bottom wall portion 10 and the support plate 9A are in contact with each other.

  The space temperature under the support plate 9A is higher than the ambient temperature of the growth vessel 1, and the heat rises toward the support plate 9A. Here, the support plate 9A is provided with a high heat conduction portion 9b and a low heat conduction portion 10a. The high heat conduction portion 9b is a portion made of a material having a relatively high thermal conductivity in the support plate, and the low heat conduction portion 9a is a portion made of a material having a relatively low heat conductivity in the support plate. is there. As a result, the low temperature part 10a of the bottom wall part 10 is located on the low heat conduction part 9a, and the high temperature part 10b of the bottom wall part 10 is located on the high heat conduction part 9b. In the present example, the high heat conducting portion 9b extends substantially along the diagonal line of the support plate 9A.

  And the seed crystal substrate 5 is fixed on the high temperature part 10b. Then, convection occurs as indicated by an arrow 6 upward from the high temperature portion 10b. This flow is relatively rectified. Then, it flows in the vicinity of the gas-liquid interface toward the outside, and flows in the vicinity of the side wall portion 4 as indicated by the arrow 8 in the downward direction.

  FIG. 4 is a cross-sectional view schematically showing a state where a single crystal is grown according to an embodiment of the present invention. In this example, a support plate 9B is provided under the growth container 1A, and the bottom wall portion 10 includes a thick portion 10b and a thin portion 10a.

  The melt 2 is accommodated in the growth container 1, and the seed crystal substrate 5 is immersed in the melt 2. The growth container 1 includes a side wall portion 4 and a bottom wall portion 10. A support plate 9B is installed under the bottom wall portion 10, and the bottom wall portion 10 and the support plate 9B are in contact with each other. The support plate 9B may be made of a single material in this example.

  The space temperature under the support plate 9B is higher than the ambient temperature of the growth vessel 1, so that the heat rises toward the support plate 9B as indicated by the arrow H. Here, the thick part 10b of the bottom wall part 10 is in contact with the support plate 9B. The thin portion 10a is not in contact with the support plate 9B, and a gap 12 is formed between them. The heat H rising from below the support plate 9B preferentially conducts heat through the thick portion 10b. Therefore, the thick part 10b becomes a high temperature part, and the thin part 10a becomes a low temperature part.

  And the seed crystal substrate 5 is fixed on the high temperature part 10b. Then, convection occurs as indicated by unmarked 6 upward from the high temperature portion 10b. This flow is relatively rectified. Then, it flows in the vicinity of the gas-liquid interface toward the outside, and flows in the vicinity of the side wall portion 4 as indicated by the arrow 8 in the downward direction.

  FIG. 5 is a cross-sectional view schematically showing a state where a single crystal is grown according to an embodiment of the present invention. In this example, a heat control plate 9C is provided under the growth container 1, and a through hole 18 is formed in the heat control plate 9C. The high temperature portion 10 b of the bottom wall portion 10 is provided on the through hole 18.

  The melt 2 is accommodated in the growth container 1, and the seed crystal substrate 5 is immersed in the melt 2. The growth container 1 includes a side wall portion 4 and a bottom wall portion 10. The bottom wall portion 10 and the heat control plate 9C may be in contact with each other or may not be in contact with each other. The heat control plate 9C may be made of a single material in this example.

  The space temperature under the heat control plate 9C is higher than the ambient temperature of the growth vessel 1, so that the heat rises toward the plate 9C as indicated by the arrow H. Here, heat passes preferentially through the through-hole 18 and is easily transmitted toward the bottom wall portion 10. As a result, the through hole 18 becomes the high temperature part 10b, and the others become the low temperature part 10a.

  And the seed crystal substrate 5 is fixed on the high temperature part 10b. Then, convection occurs as indicated by an arrow 6 upward from the high temperature portion 10b. This flow is relatively rectified. Then, it flows in the vicinity of the gas-liquid interface toward the outside, and flows in the vicinity of the side wall portion 4 as indicated by the arrow 8 in the downward direction.

  In the present invention, as shown in FIG. 6, the seed crystal substrate may be installed in an inclined state. In a preferred embodiment, the angle θ formed by the gas-liquid interface 2a of the melt and the growth surface 5a of the seed crystal substrate 5 is set to 30 ° or more and 150 ° or less. Preferably, θ is set to 60 ° or more and 120 ° or less. Particularly preferably, the gas-liquid interface of the melt and the growth surface of the seed crystal are substantially perpendicular. This makes it difficult for the miscellaneous crystals to adhere to the single crystal.

  In a preferred embodiment, as schematically shown in FIG. 7, a plurality of heating elements 26A, 26B, 26C, 26D, 26E, 26F, and 26G are installed in the vertical and horizontal directions, and the heating value for each heating element. Are controlled independently. That is, multi-zone control is performed in the vertical direction and the horizontal direction. When each heating element is heated, a nitrogen-containing atmosphere is passed through the gas tank 21, the pressure control device 22, and the piping 23 to the growth vessel 1 in the atmosphere control vessel 14, and heated and pressurized. All dissolve and form a melt.

  In the present invention, the material of the heating element is not particularly limited, but an alloy heating element such as iron-chromium-aluminum or nickel-chromium, a refractory metal heating element such as platinum, molybdenum, tantalum or tungsten, silicon carbide, molybdenum Non-metallic heating elements such as silicite and carbon can be exemplified.

  In the single crystal growth apparatus of the present invention, the apparatus for heating the raw material mixture to generate a melt is not particularly limited. This apparatus is preferably a hot isostatic pressing apparatus, but other atmospheric pressure heating furnaces may be used.

  The flux for generating the melt is not particularly limited, but one or more metals selected from the group consisting of alkali metals and alkaline earth metals or alloys thereof are preferable. Examples of the metal include lithium, sodium, potassium, rubidium, cesium, beryllium, magnesium, calcium, strontium, and barium. Lithium, sodium, and calcium are particularly preferable, and sodium is most preferable.

Examples of the substance that forms an alloy with one or more metals selected from the group consisting of alkali metals and alkaline earth metals include the following metals.
Gallium, aluminum, indium, boron, zinc, silicon, tin, antimony, bismuth.

For example, the following single crystals can be suitably grown by the growing method of the present invention.
GaN, AlN, InN, mixed crystals thereof (AlGaInN), BN.

  The heating temperature and pressure in the single crystal growth step are not particularly limited because they are selected depending on the type of single crystal. The heating temperature can be set to, for example, 800 to 1500 ° C. Preferably it is 800-1200 degreeC, More preferably, it is 800-1100 degreeC. The pressure is not particularly limited, but the pressure is preferably 1 MPa or more, and more preferably 2 MPa or more. The upper limit of the pressure is not particularly defined, but can be, for example, 200 MPa or less, and preferably 100 MPa or less.

  The material of the growth container for carrying out the reaction is not particularly limited as long as the material is durable under the intended heating and pressurizing conditions. Examples of such materials include refractory metals such as tantalum, tungsten, and molybdenum, oxides such as alumina, sapphire, and yttria, nitride ceramics such as aluminum nitride, titanium nitride, zirconium nitride, and boron nitride, tungsten carbide, tantalum carbide, and the like. And pyrolytic products such as p-BN (pyrolytic BN) and p-Gr (pyrolytic graphite).

Hereinafter, more specific single crystals and their growth procedures will be exemplified.
(Gallium nitride single crystal growth example)
Using the present invention, a gallium nitride single crystal can be grown using a flux containing at least sodium metal. In this flux, the gallium source material is dissolved. As the gallium source material, a gallium simple metal, a gallium alloy, and a gallium compound can be applied, but a gallium simple metal is also preferable in terms of handling.

  This flux can contain metals other than sodium, such as lithium. The use ratio of the gallium source material and the flux source material such as sodium may be appropriate, but in general, it is considered to use an excess amount of sodium. Of course, this is not limiting.

  In this embodiment, a gallium nitride single crystal is grown under a pressure of a total pressure of 1 MPa or more and 200 MPa or less in an atmosphere composed of a mixed gas containing nitrogen gas. By setting the total pressure to 1 MPa or more, it was possible to grow a good quality gallium nitride single crystal in a high temperature region of, for example, 800 ° C. or higher, more preferably in a high temperature region of 900 ° C. or higher.

  In a preferred embodiment, the nitrogen partial pressure in the growth atmosphere is 1 MPa or more and 200 MPa or less. By setting the nitrogen partial pressure to 1 MPa or higher, for example, in a high temperature region of 800 ° C. or higher, dissolution of nitrogen into the flux was promoted, and a high-quality gallium nitride single crystal could be grown. From this viewpoint, it is more preferable that the nitrogen partial pressure of the atmosphere is 2 MPa or more. Moreover, it is preferable that nitrogen partial pressure shall be 100 Mpa or less practically.

A gas other than nitrogen in the atmosphere is not limited, but an inert gas is preferable, and argon, helium, and neon are particularly preferable. The partial pressure of a gas other than nitrogen is a value obtained by subtracting the nitrogen gas partial pressure from the total pressure.
In a preferred embodiment, the growth temperature of the gallium nitride single crystal is 800 ° C. or higher, preferably 800 ° C. or higher, and more preferably 1000 ° C. or higher. Even in such a high temperature region, a good quality gallium nitride single crystal can be grown. Moreover, there is a possibility that productivity can be improved by growing at high temperature and high pressure.

  The upper limit of the growth temperature of the gallium nitride single crystal is not particularly limited. However, if the growth temperature is too high, the crystal is difficult to grow. Therefore, the temperature is preferably set to 1500 ° C. or lower. From this viewpoint, the temperature is further set to 1200 ° C. or lower. preferable.

The material of the growth substrate for epitaxially growing the gallium nitride crystal is not limited, but sapphire, AlN template, GaN template, silicon single crystal, SiC single crystal, MgO single crystal, spinel (MgAl ₂ O ₄ ), LiAlO ₂ , LiGaO ₂ , perovskite complex oxides such as LaAlO ₃ , LaGaO ₃ , and NdGaO ₃ can be exemplified. The composition formula _{[A 1-y (Sr 1-} x Ba x) y ] _{[(Al 1-z Ga z)} 1-u · D u ] _O 3 (A is a rare earth element; D is niobium and One or more elements selected from the group consisting of tantalum; y = 0.3-0.98; x = 0-1; z = 0-1; u = 0.15-0.49; x + z = 0 .1 to 2) cubic perovskite structure composite oxides can also be used. SCAM (ScAlMgO ₄ ) can also be used.

(Example of growing AlN single crystal)
The present invention has been confirmed to be effective even when growing an AlN single crystal by pressurizing a melt containing a flux containing at least aluminum and an alkaline earth in a nitrogen-containing atmosphere under specific conditions. .

(Preliminary experiment)
A growing apparatus as shown in FIGS. 2 and 3 was prepared and installed in the apparatus as shown in FIG. The size of the growth container was 35 mm × 40 mm × 70 mm. The size of the seed crystal substrate was 2 inches. Water was accommodated in the growth container, and polyester as a tracer was added. Convection was generated in the water by heating the growth vessel from below. When convection was visualized by irradiating laser light from the side wall, desired convection as shown in FIGS. 2 and 3 was observed.

Example 1
According to the method described with reference to FIGS. 2 and 3, a GaN single crystal was grown by the Na flux method. Specifically, 74 g of metal Na, 50 g of metal, and 100 mg of carbon as an additive were weighed in a vacuum glove box and placed in an alumina crucible 1 having an inner diameter of 16 × 55 mm × height of 75 mm. A GaN template substrate having a diameter of 2 inches was used as the seed crystal substrate 5 and leaned at an angle of about 80 degrees from approximately vertical to horizontal on the diagonal line of the crucible. The crucible 1 was accommodated in the container 14 shown in FIG. At this time, as shown in FIGS. 2 and 3, the material of the high temperature portion 9b is aluminum nitride ceramics, and the material of the low temperature portion 9a is alumina ceramics. The thermal conductivity of aluminum nitride ceramics is 150 W · m ⁻¹ · K ⁻¹ , and the thermal conductivity of alumina ceramics is 32 W · m ⁻¹ · K ⁻¹ .

  Next, the pressure was increased to 4.5 MPa with nitrogen gas, the temperature in the furnace was increased to 850 ° C. in 45 minutes, and maintained at 850 ° C. for 200 hours for crystal growth. During this period, the bottom of the container was controlled to be 880 ° C. with a separate heater. Then it was cooled to room temperature. When the flux was treated with ethanol and the crystal was taken out, a GaN crystal having a thickness of about 1 mm was grown on the seed substrate. The surface of the crystal was entirely smooth on the seed substrate, and steps were observed. The impurity band emission was small, and the crystal color was almost colorless and transparent.

(Comparative Example 1)
A GaN single crystal was grown in the same manner as in Example 1. However, the support plate 9A was not installed under the crucible 1. As a result, a crystal of about 1 mm grew on the seed crystal substrate, but the surface of the crystal was smooth, but there were three-dimensionally grown portions in some places. In addition, in that portion, the crystals were colored brown to black, and impurity band emission was strongly observed. This suggests that the convection of the melt on the seed crystal substrate 5 was insufficient.

(A) is sectional drawing which shows typically the state which has grown the single crystal in one Embodiment of this invention, (b) is the seed crystal substrate 5, the support plate 9, the high heat conductive part 9b, and low heat It is a figure which shows typically the planar positional relationship of the conduction | electrical_connection part 9a. It is a perspective view which shows typically the state which has grown the single crystal in other embodiment. In FIG. 2, it is a figure which shows typically the planar positional relationship of the growth container 1, the seed crystal substrate 5, the high heat conduction part 9b, and the low heat conduction part 9a. Furthermore, it is sectional drawing which shows typically the state which has grown the single crystal in other embodiment. Furthermore, it is sectional drawing which shows typically the state which has grown the single crystal in other embodiment. It is a schematic diagram which shows a solute convection when a seed crystal is placed vertically. It is a schematic diagram of the cultivation apparatus which can be used by this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1, 1A Growth container 2 Melt 2a Gas-liquid interface 2b Bottom part of melt 4 Side wall part 5 Seed crystal substrate 5a Growth surface 6, 6A, 6B, 6C Upflow from high temperature part 8 Downflow 9, 9A, 9B, 9C Support plate 9a Low heat conduction part 9b High heat conduction part 10 Bottom wall part 10a Low temperature part 10b High temperature part 12 Air gap E Region on high temperature part H Heat flow θ Angle formed by growth surface and gas-liquid interface

Claims (5)

  A seed crystal substrate is immersed in a melt containing a flux and a single crystal raw material in a growth vessel, a high temperature portion and a low temperature portion are provided on the bottom wall portion of the growth vessel, and the seed crystal substrate is fixed on the high temperature portion. A method for producing a nitride single crystal, comprising growing a nitride single crystal on a growth surface of the seed crystal substrate.   A support plate is provided under the growth container, the support plate includes a high heat conduction portion and a low heat conduction portion, and the high temperature portion of the bottom wall portion is provided on the high heat conduction portion. The method of claim 1.   The support plate is provided under the said growth container, The said bottom wall part is equipped with the thick part and the thin part, The said thick part has comprised the said high temperature part, The said high temperature part is characterized by the above-mentioned. the method of.   A heat control plate is provided under the growth vessel, a through hole is formed in the heat control plate, and the high temperature portion of the growth vessel is provided on the through hole. The method according to 1.   The angle formed by the gas-liquid interface of the melt and the growth surface of the seed crystal substrate is 30 ° or more and 150 ° or less, according to any one of claims 1 to 4. Method.

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