WO2009157347A1

WO2009157347A1 - Method for growing nitride single crystal

Info

Publication number: WO2009157347A1
Application number: PCT/JP2009/060978
Authority: WO
Inventors: 今井克宏; 岩井真; 東原周平; 市村幹也
Original assignee: 日本碍子株式会社
Priority date: 2008-06-26
Filing date: 2009-06-10
Publication date: 2009-12-30
Also published as: JPWO2009157347A1; JP5361884B2

Abstract

Disclosed is a method for growing a nitride single crystal by a flux process in a nitrogen-containing non-oxidizing atmosphere. Nitrogen is dissolved into a melt (3A) in a container (1). Then, the level (H2) of the melt (3A) is raised by immersing a jig (8), at least the surface of which is composed of a material not reactive with the molten raw material, into the melt, and seed crystals (4A, 4B) are immersed into the melt (3A). A nitride single crystal is grown on the seed crystals (4A, 4B), while setting the angle between the gas-liquid interface of the melt (3A) and the growing surface of each seed crystal at not less than 45˚ but not more than 135˚C.

Description

Specification

Method of growing nitride single crystal TECHNICAL FIELD

The present invention relates to a method of growing a nitride single crystal by a flux method.

Background art

Gallium nitride ιπ-ν nitride has attracted attention as an excellent material for blue light emitting devices, and has been put to practical use in light emitting diodes and blue-violet semiconductor lasers for optical pickups. The Na flux method is known as one of the group I nitride single crystal growth methods. In WO 2 0 0 4 0 8 3 4 9 8 A 1, a seed crystal is placed horizontally at the bottom of the vessel, and while the vessel containing the melt is rotated or rocked, the nitride single crystal is grown. It has been described that. Also, in WO 2 0 07/1 0 2 0 6 0 1, a seed crystal is placed horizontally on the bottom of the vessel, and while the vessel containing the melt is rotated or shaken, a nitride single crystal is formed. It is stated that the fostering of Moreover, at this time, it is described that the stirring is promoted by immersing a plurality of balls in the melt and moving the balls in the melt.

In the group III nitride single crystal growth method using Na flux, the group III metal is filled with the Na metal in a vessel for crystal growth to form a mixed melt, and nitrogen is melted from the gas phase through the gas-liquid interface. It is supplied into. Crystal growth starts only when the amount of nitrogen dissolved in the melt reaches the saturation concentration of Group III nitride. In other words, crystal growth on the seed substrate does not progress until nitrogen of the required concentration dissolves in the melt and is transported to the periphery of the seed substrate by diffusion or convection. Also, the growth rate after the start of crystal growth is limited by the dissolution rate of nitrogen at the gas-liquid interface. In order to make the nitrogen concentration in the melt reach the saturation concentration more quickly, it is important that (1) the rate of nitrogen dissolution at the gas-liquid interface be fast, and (2) the absolute amount of melt be small. is there. (1) In order to increase the dissolution rate of nitrogen at the gas-liquid interface, there are methods such as (la) increasing the gas-liquid interface area and (lb) increasing the nitrogen pressure. In order to increase the gas-liquid interface area while keeping the absolute amount of melt small, it is desirable to lower the height of the melt relative to the diameter of the growth vessel. In other words, it is preferable to reduce the distance from the gas-liquid interface of the melt to the bottom of the vessel.

In order to make the melt shallow, it is conceivable to use a large diameter growth vessel and place the seed substrate horizontally on the bottom of the growth vessel. As a result, it should be possible to grow gallium nitride (GaN) crystal with a small amount of melt. However, in this method, GaN crystals grew on the seed substrate in a relatively short time, but the surface shape tends to be uneven, crystals tend to be colored, and microcrystals (miscellaneous crystals) generated in the melt grow. It has been found that there are problems such as sticking to the crystals and causing cracks.

Therefore, in WO 2007/112856 A1, the present applicant places the seed crystal substrate vertically in the melt, and in this state the nitride single crystal is formed on the growth surface of the seed crystal substrate. Was disclosed to grow. It was found that when the seed substrate is placed vertically, the surface shape tends to be smooth, it is difficult to be colored, and the adhesion of miscellaneous crystals tends to be suppressed. Disclosure of the invention

However, when seed crystals are arranged vertically in the melt of the growth vessel, it is necessary to raise the liquid level of the melt more than when arranged at the bottom of the vessel. For example, as shown in FIG. 12 (a), when melt 3 B is produced in container 1 A and seed crystal 4 is immersed in melt 3 B, the liquid level of melt 3 B becomes seed crystal 4. Need to be higher than. That is, when the seed crystal 4 is vertically disposed to produce a crystal with a large diameter, it is necessary to increase the liquid level of the melt and to increase the liquid depth by increasing the amount of the melt 3B.

However, in this case, since it takes a long time for the nitrogen concentration in the melt 3B to increase to the concentration necessary for crystal growth, the productivity is low and the manufacturing process becomes long. In addition, since it takes time for the nitrogen concentration in melt 3B to rise to the concentration necessary for crystal growth, the seed substrate is melted (melted back) in the melt before growth starts, and Crystals sometimes do not grow.

Furthermore, when the single crystal is taken out after completion of crystal growth, the grown nitride single crystal is taken into the solidified flux. Heating and cooling are required to take it out. However, there was a case that a crack was generated in the nitride single crystal during such heating and cooling.

On the other hand, as shown in Fig.12 (b), it is also conceivable to use a vessel with a small cross-sectional area to reduce the amount of melt. However, in this case, the gas-liquid interface area of the melt 3 B also decreases in proportion to the decrease in the amount of melt, so the time taken for the dissolution of nitrogen in the melt is not shortened.

It is an object of the present invention to provide a method of growing a nitride single crystal by a flux method in a nitrogen-containing non-oxidizing atmosphere, wherein the seed crystal is placed vertically in the melt to grow the nitride single crystal. By shortening the time taken for dissolution in the melt, the productivity is improved and the meltback of the seed crystals is prevented.

The present invention is a method of growing a nitride single crystal by a flux method in a nitrogen-containing non-oxidizing atmosphere,

Nitrogen dissolving process for dissolving nitrogen in the melt in the vessel;

Then, by immersing in the melt a jig whose material is at least the surface of the molten raw material and non-reactive material, the liquid level of the melt is raised, and the seed crystal is immersed in the melt. Soaking liquid level rising process; and

Having a single crystal growth process to grow a nitride single crystal on a seed crystal in a state where the angle between the gas-liquid interface of the melt and the growth surface of the seed crystal is 45 ° or more and 135 ° or less The present invention relates to a method of growing a nitride single crystal, which is characterized. According to the present invention, the nitride single crystal is grown on the seed crystal in a state where the angle between the gas-liquid interface of the melt and the growth surface of the seed crystal is 45 ° or more and 135 ° or less. It is hard to attach miscellaneous crystals and can suppress single crystal defects. Then, after dissolving nitrogen to a saturation concentration in the melt in the container, the jig is made by immersing in the melt a jig whose surface is made of a material that is not reactive with the molten raw material, so that the melt is melted. Raise the base and immerse the seed crystal in the melt to grow a single crystal.

Therefore, in the nitrogen dissolution step, the dissolution of nitrogen in the melt is completed in a short time because the amount of melt is small due to the low degree of stagnation. This can reduce the time required to produce single crystals. In addition, since the seed crystals are not immersed in the melt at the stage of the nitrogen dissolution step, it is possible to prevent the meltback of the seed crystals into the melt and to prevent the crystal defects caused by the meltback.

Further, in the present invention, after growing the nitride single crystal, the jig is separated from the melt, thereby reducing the height of the melt to melt the seed crystal and the nitride single crystal on the seed crystal. Can be exposed from In this case, since the grown nitride single crystal is not taken into the solidified flux, it is possible to prevent a crack which occurs when the nitride single crystal is taken out from the solidified flux. However, it is not always necessary to expose seed crystals and nitride single crystals from the melt. Brief description of the drawings

FIG. 1 is a cross-sectional view schematically showing a state in which melt 3 and seed crystals 4 and 4 are contained in container 1. FIG. 2 is a cross-sectional view schematically showing the lid 6 to which the jig 8 is attached. FIG. 3 is a cross-sectional view schematically showing a state in which the lid 6 is combined with the container 1.

FIG. 4 is a cross-sectional view schematically showing a state in which the jig 8 is immersed in the melt 3A. FIG. 5 is a cross-sectional view schematically showing a single crystal-attached seed crystal separated from the melt.

FIG. 6 is a cross-sectional view schematically showing a jig 8 to which a seed crystal is attached. FIG. 7 is a cross-sectional view schematically showing a state in which the lid 6 is combined with the container 1.

FIG. 8 is a cross-sectional view schematically showing a state in which the jig and the seed crystal are immersed in the melt.

FIG. 9 is a cross-sectional view schematically showing a jig 18 having a large width portion 1 8 a and a narrow width portion 1 8 b.

FIG. 10 is a cross-sectional view schematically showing a state in which the jig 18 and the seed crystal are immersed in the melt.

FIG. 11 is a cross-sectional view schematically showing the state in which the seed crystal is immersed in the melt. Fig. 12 (a) and Fig. 12 (b) are diagrams schematically showing a state in which the seed crystal 4 is immersed in the melt 3B of the containers 1A and 1B, respectively. BEST MODE FOR CARRYING OUT THE INVENTION

In a preferred embodiment, the container is moved in the seed crystal growing step. As a result, stirring and convection of the melt can be promoted, defects of the nitride single crystal can be prevented, and the film thickness can be made uniform. Such movement is not particularly limited, but peristalsis and rotation are preferable.

Hereinafter, the present invention will be described in more detail with reference to the drawings as appropriate.

Fig. 1 schematically shows the state in which the melt 3 and the seed crystals 4A and 4B are contained in the container 1. It is sectional drawing shown to. The metal source material and the source material of the flux are enclosed in a non-oxidative atmosphere glove box, and enclosed in the non-oxidative atmosphere in the inner space 5 of the container 1 as shown in the figure. Fix the seed crystal 2Α and 2 2 on the appropriate place of the container 1, for example, the side wall, and fix the seed crystals 4Α and 4Β on the 2Α and 2Β respectively.

The vessel 1 is placed in a pressure vessel such as a HIP (hot isotropic pressure press) apparatus, for example, and the vessel 1 is heated and pressurized in the pressure vessel. Then, all the raw materials are dissolved in the container 1 to form a mixed melt 3. Here, nitrogen is stably supplied into the mixed melt 3 from the space 5 in the container 1 and dissolved (nitrogen dissolving step). At this stage, the height H I of the melt is reduced so that the seed crystals 4 A and 4 B do not contact the melt 3.

FIG. 2 is a cross-sectional view schematically showing the lid 6 to which the jig 8 is attached. A jig 8 is attached so as to protrude into the inner space 7 of the lid 6. At least the surface of the jig 8 is made of a material non-reactive with the melt 3.

FIG. 3 is a cross-sectional view schematically showing a state in which the lid 6 is combined with the container 1. In this example, the lid 6 is placed on the platform 9 and fixed. Container 1 is attached to shaft 10. The axis 10 can move up and down like arrows A and B, and can rotate like arrow C. By raising the shaft 10 as shown by the arrow A, the container 1 is lifted from the state of FIG. 1 and charged into the inner space 7 of the lid 6. During this time, axis 10 may be kept rotating as shown by arrow C. At the time of FIG. 3, the jig 8 is not immersed in the melt 3 and the liquid level H 1 of the melt 3 does not change.

FIG. 4 is a cross-sectional view schematically showing a state in which the jig 8 is immersed in the melt 3A. Jig 8 is immersed in the melt by further raising axis 10 as shown by arrow A. As a result, the liquid level of the melt 3 A rises to H 2, and the seed crystals 4 A and 4 B are immersed in the melt 3 A. In this state, the nitrogen pressure required for nitride single crystal growth And when holding time, as shown in FIG. 5, nitride single crystals 12 A and 12 B grow on the growth surface 20 of the seed crystals 4 A and 4 B. At this time, the angle 0 between the gas-liquid interface 21 and the growth surface 20 is set to 45 ° to 35 °.

Next, the axis 10 is lowered as shown by arrow B, and the jig 8 is separated from the melt 3 as shown in FIG. The liquid level of Melt 3 drops and becomes slightly lower than the first liquid level H I. In this state, various crystals 4 A, 4 B and single crystals 12 A, 12 B are exposed from melt 3.

In a preferred embodiment, a seed crystal is attached to the jig. In this case, when the jig is lowered to immerse in the melt, the seed crystal attached to the jig is simultaneously immersed in the melt. In addition, when the jig is lifted and separated from the melt, the seed crystal and the single crystal thereon can also be separated from the melt at the same time.

6 to 8 relate to this embodiment. FIG. 6 is a cross-sectional view schematically showing a state in which the jig 8 is attached to the lid 6 and the seed crystals 4 A, 4 B, and 4 C are attached to the jig 8. The method of attaching the seed crystals 4 A, 4 B, 4 C to the jig 8 is not particularly limited, and may be mechanical attachment or adhesion.

FIG. 7 is a cross-sectional view schematically showing a state in which the lid 6 is combined with the container 1. In this example, the lid 6 is placed on the platform 9 and fixed. Container 1 is attached to shaft 10. By raising the shaft 10 as shown by the arrow A, the container 1 is lifted from the state of FIG. 6 and charged into the inner space 7 of the lid 6. During this time, axis 10 may be kept rotating as shown by arrow C. At the time of FIG. 7, the jig 8 is not immersed in the melt 3 and the liquid level H 1 of the melt 3 does not change. FIG. 8 is a cross-sectional view schematically showing a state in which the jig 8 is immersed in the melt 3A. Jig 8 is immersed in the melt by further raising axis 10 as shown by arrow A. As a result, the liquid level of the melt 3 A rises to H 2, and the seed crystals 4 A, 4 B, 4 C are immersed in the melt 3 A. In this state, nitrogen necessary for nitride single crystal growth is When the atomic pressure and time are maintained, nitride single crystals 12 A and 12 B grow on the growth surface of the seed crystals 4 A and 4 B.

Then, the shaft 10 is lowered to separate the jig 8 from the melt 3. The seed crystals 4 A, 4 B and 4 C are released from the melt together with the jig 8. As a result, the liquid level of Melt 3 drops and becomes slightly lower than the initial liquid level H 1. In this state, various crystals 4 A, 4 B and single crystals 12 A, 12 B are exposed from melt 3.

In a preferred embodiment, the jig comprises a wide width portion and a narrow width portion, and in the liquid level raising step, the wide width portion is immersed in the melt, and the narrow width portion is the gas-liquid boundary of the melt. Touch the face. 9 and 10 relate to this embodiment.

FIG. 9 is a cross-sectional view schematically showing the lid 6 to which the jig 18 is attached. A jig 18 is attached so as to protrude into the inner space 7 of the lid 6. At least the surface of jig 18 is made of a material that is non-reactive with melt 3. A wide portion 18a is formed on the tip end side of the jig 18 and a narrow portion 18b is formed on the base side thereof.

FIG. 9 is a cross-sectional view schematically showing a state in which the jig 18 is immersed in the melt 3A. Jig 18 is immersed in the melt by raising axis 10 further as shown by arrow A. At this point, the wide part 18a is totally immersed in the melt 3A, the liquid level of the melt 3A rises to H 2 and the seed crystals 4A and 4B are contained in the melt 3A. Immersed. At this time, the narrow portion 18 b contacts the gas-liquid interface of the melt, and only a part of the narrow portion is immersed in the melt. The interface 18 c enters the melt.

In this state, when the nitrogen pressure and time necessary for nitride single crystal growth are maintained, nitride single crystals 12A and 12B grow on the growth surfaces of the seed crystals 4A and 4B. Then, lower the axis 10 and separate the jig 18 from the melt 3. The level of Melt 3 drops and is slightly lower than the first level H 1. In this state, various crystals 4 A, 4 B and single crystals 12 A, 12 B are exposed from melt 3. In the present embodiment, since the entire wide width portion is immersed in the melt, the liquid level rise width (H 2 -H 1) can be increased. At the same time, since the narrow portion is in contact with the gas-liquid interface, the area of the gas-liquid interface can be increased during the single crystal growth step, and the crystal growth rate can be further improved.

In the present invention, the angle 0 between the gas-liquid interface of the melt 3 A and the growth surface of the seed crystal is set to 45 ° or more and 135 ° or less. Preferably, 0 is set to 80 ° or more and 100 ° 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 layer single crystal.

In the present invention, it is necessary that the material of the solid material constituting at least the surface of the jig does not react with flux. Therefore, this material is appropriately selected by those skilled in the art according to the type of flux used. The entire jig may be of such material, or only the surface of the jig may be of such material.

Generally, when applied to a flux containing an alkali metal or alkaline earth metal, the material of the jig is most preferably metal tantalum, but metal such as metal tan dusten, metal molybdenum, etc., alumina, alumina, It was also found that oxide ceramics such as force lucia, etc., single crystals such as sapphire, carbide ceramics such as tungsten carbide and tantalum carbide, and nitride ceramics such as aluminum nitride, titanium nitride, and zirconium nitride can also be used. Also, the surface of a solid made of another material can be coated with a material that does not react with the melt as described above. Therefore, for example, a jig in which a copper material is coated with metallic tantalum is also preferable.

From the viewpoint of the present invention, the ratio H 2 Z H 1 to the liquid level H 1 in the nitrogen dissolving process of the liquid level H 2 in the crystal growth step is preferably 2 or more, more preferably 3 or more. However, in design, H 2 Z H 1 is preferably 5 or less.

The ratio W 1 / W 2 of the width W 1 to the width W 2 of the wide part W 1 of the jig is From the viewpoint of increasing the area of the liquid interface, 2 or more is preferable, and 3 or more is more preferable. The upper limit of W 1 / W 2 is not particularly limited, but is preferably 10 or less in design.

In the single crystal growth apparatus of the present invention, an apparatus for heating the raw material mixture to generate a melt is not particularly limited. As an example of this apparatus, a hot isostatic press apparatus can be exemplified, but other atmosphere pressure type heating furnaces may be used. The flux for producing the melt is not particularly limited, but one or more metals or alloys thereof selected from the group consisting of aluminum nitride metals and alkaline earth metals are preferable. Examples of this metal include lithium, sodium, potassium, rubidium, cesium, beryllium, magnesium, calcium, strontium, and barium, with lithium, sodium and calcium being particularly preferred, with sodium being particularly preferred. Most preferred.

Further, as the substance which forms an alloy with one or more metals selected from the group consisting of the above-mentioned alkali metals and alkaline earth metals, the following metals can be exemplified.

Gallium, Aluminum, Indium, Boron, Zinc, Zinc, Tin, Tin, Anthemium, Bismuth.

For example, the following single crystals can be suitably grown by the growing method of the present invention. G a N, A l N, I nN, mixed crystals of these (A l G a I nN), BN. The heating temperature and pressure in the single crystal growth step are not particularly limited because they are selected according to the type of single crystal. The heating temperature can be set to, for example, 800-1500 ° C. Preferably it is 800-1200 degreeC, More preferably, it is 800-100 degreeC. The pressure is also not particularly limited, but the pressure is preferably IMP a or more, more preferably 2 MP a or more. The upper limit of the pressure is not particularly defined, but may be, for example, 2 0 OMP a or less, preferably 1 0 OMP a or less. The material of the growth vessel for carrying out the reaction is not particularly limited, as long as it is a material which is durable under the intended heating and pressure conditions. Such materials include refractory metals such as metal tantalum, tungsten and molybdenum, oxides such as phenolemina, sapphire and ittria, nitride ceramics such as aluminum nitride, titanium nitride, zirconium nitride and boron nitride, Examples thereof include carbides of refractory metals such as tanten carbide and tantalum carbide, and thermal decomposition products such as p-BN (pyrolytic BN) and p-GR (pyrolytic graphite).

Hereinafter, more specific single crystals and their growth procedures will be exemplified.

(Example of growing gallium nitride single crystal)

The present invention can be used to grow a gallium nitride single crystal using a flux containing at least sodium metal. Dissolve the gallium source material in this flux. As a gallium source material, a single metal of gallium, a gallium alloy, and a gallium compound can be applied, but a single metal of gallium is also preferable from the viewpoint of handling.

The flux may contain metals other than sodium, such as lithium. The ratio of the gallium source material to 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 total pressure I MP a or more and 200 MPa or less under an atmosphere of a mixed gas containing nitrogen gas. By setting the total pressure to 1 MPa or more, it is possible to grow a good quality gallium nitride single crystal in a high temperature region of 800 ° C. or more, more preferably in a high temperature region of 800 ° C. or more. Met.

In a preferred embodiment, the nitrogen partial pressure in the atmosphere during growth is set to 1 MP a or more and 200 MP a or less. By setting this nitrogen partial pressure to I MP a or higher For example, in a high temperature range of 800.degree. C. or higher, dissolution of nitrogen in the flux is promoted, and a good quality gallium nitride single crystal can be grown. From this point of view, it is further preferable to set the nitrogen partial pressure of the atmosphere to 2 MP a or more. In addition, it is preferable to set the nitrogen partial pressure to 1 O OMP a or less practically.

The gas other than nitrogen in the atmosphere is not limited, but is preferably an inert gas, particularly preferably argon, helium or neon. The partial pressure of gases other than nitrogen is the value obtained by removing the partial pressure of nitrogen gas from the total pressure.

In a preferred embodiment, the growth temperature of the gallium nitride single crystal is 800 ° C. or higher, and more preferably, 850 ° C. or higher. Good quality gallium nitride single crystals can be grown even in such a high temperature region. Also, high temperature-high pressure growth may improve productivity.

The upper limit of the growth temperature of the gallium nitride single crystal is not particularly limited, but if the growth temperature is too high, the crystal is difficult to grow, so the temperature is preferably 150 ° C. or less. From this point of view, It is further preferable to set the temperature to 1 200 ° C. or less.

The material of the growth substrate for epitaxially growing the gallium nitride crystal is not limited, but sapphire, A 1 N template, G a N template, G a N free-standing substrate, silicon single crystal, Si i C single crystal, Mg O single crystal, Swinenole (Mg A1 ₂ 0 ₄ ), L i A 1 0 _{2 2} , L i G a 2, L a A 1 0 ₃ , L a G a 0 a, N d Perovskite type composite oxides such as G a O ₃ can be exemplified. The composition formula _{[Ai- y (S r _ x} B a x!) Y ] _{_{[(A 1 x _ z G a}} z) x _ u - D u ] O a (A is a rare earth element; D is , One or more elements selected from the group consisting of niobium and tantalum; y = 0. 3 to 0. 98; X = 0 to 1; z = 0 to 1; u = 0. 1 5 to 0. Beloveite-squite complex oxide of 4 9; x + z = 0.:! ~ 2) can also be used. In addition, S CAM (S c A 1 M g O ₄ ) can also be used.

(Example of growing A 1 N single crystal) The present invention is also effective in growing an A 1 N 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. That was confirmed. Example

(Example 1)

A single crystal was grown according to the method described above with reference to FIGS. Specifically, the inner diameter of the round flat bottom plate 1 was set to 160 mm, and the height was set to 120 mm. As raw materials for growth, 300 g of metal G a and 400 g of metal N a were melted and filled in a growth box, respectively. The Na was shielded from the atmosphere by first filling with Na and then filling with Ga. The melt height H 1 of the raw materials in crucible 1 was about 30 mm.

Next, on the inner periphery of the seed plate 1 on the inner surface of the seed substrate holding platform 2 A, 2 B, as the seed crystal substrate 4 A, 4 B, a 2 N diameter G a N template (G a N single on sapphire substrate Six pieces of crystal thin film (grown by 5 micron epitaxial growth) were placed vertically. At this time, the bottom of the seed crystal substrate became 35 mm high from the bottom of the crucible. Only two of the six seed substrates are shown in FIG. The jig 8 has a cylindrical shape, and the diameter in the horizontal cross section is 130 mm. After raising the temperature and pressure at 900 ° C * 4.5 MP a and holding for 24 hours, the temperature is lowered to 8 70 ° C and the jig is moved by moving the crucible upward as shown in Fig. 4 8 was infiltrated into Melt 3 A, and the liquid level was raised. The calculated liquid level H 2 at this time is 90 mm from the bottom of the pot. After holding for 96 hours in this state, as shown in FIG. 5, the crucible was moved downward and the jig 8 was pulled out of the melt to lower the liquid level to separate the seed substrate and the melt. Thereafter, it was gradually cooled to room temperature over 24 hours to recover crystals.

The grown crystals are separated from the flux and no cracks have occurred. won. About 2 mm of G.sub.a N crystals were grown on the entire surface of the six 2-inch seed substrates. The in-plane thickness variation was small, less than 10%. Also, the average thickness variation of the six sheets was as small as about 10%.

(Example 2)

Single crystals were grown in the same manner as in Example 1. However, in this example, as shown in FIGS. 6 to 8, the seed crystal substrates 4 A, 4 B, and 4 C were fixed to the surface of the jig 8. Further, the jig 8 has a hexagonal prism shape, and one side of the horizontal cross section is 70 mm and the diagonal is 140 mm. In this jig 8, six G a N templates with a diameter of 2 inches were vertically arranged as seed substrates. At this time, the bottom of the seed substrate was 5 mm above the bottom of the jig.

After raising the temperature and pressure at 900 ° C · 4.5 MP a and holding for 24 hours, the temperature is lowered to 8 70 ° C and the jig 8 is melted by moving the crucible upward. Infiltrated into 3 and raised the liquid level. The calculated liquid level H 2 at this time is 9 O mm from the bottom of the pot. After holding for 96 hours in this state, the crucible was moved downward and the jig was pulled out of the melt to lower the liquid level, and the seed substrate and the melt were separated. Thereafter, it was gradually cooled to room temperature over 24 hours to recover crystals.

The grown crystals were separated from the flux, and no cracks occurred. About 2 mm of G.sub.a N crystals were grown on the entire surface of the six 2-inch seed substrates. The in-plane thickness variation was small, less than 10%. In addition, the average thickness variation of the three sheets was also as small as about 10%.

(Example 3)

Single crystals were grown in the same manner as in Example 1. However, the shape of the level adjustment jig was changed as shown in Figure 9. The diameter W 1 up to 80 mm from the bottom of the level adjustment jig was 130 mm, and the diameter W 2 above that was 3 O mm.

The experiment was conducted under the same conditions as in Example 1 except that the growth time was 96 hours. Of 5 mm thick were obtained. This is because, as shown in FIG. 10, since the area of the gas-liquid interface 21 during crystal growth is improved by about 2.8 times as compared with the case of Example 1, the dissolution of nitrogen during the crystal growth It is thought that the speed is improved and the crystal growth speed is improved.

(Example 4)

In Example 1, crystal growth was performed while rotating 坩堝 1, and G A N crystals of 4 mm in thickness were obtained in the same growth time. This is thought to be because the rotation accelerates the stirring of the melt, the nitrogen supply rate on the seed substrate is improved, and the crystal growth rate is improved.

(Comparative example 1)

Single crystals were grown as shown in FIG. However, using the same crucible as in Example 1, first arrange six seed substrates vertically in the glove box, and set the liquid level to 90 mm, respectively 90 0 g of metal G a and metal N a And weighed 1 44 0 g, thawed and filled. The metal Na was isolated from the atmosphere by melt filling the metal Na first and then filling it with the metal Ga.

The crucible 1 was placed in a growth furnace, heated and pressurized to 870 ° C. * 4.5 MP a, held for 120 hours, gradually cooled over 24 hours, and the crystals were recovered. Here, no jig for liquid level adjustment was used. About 0.5 mm of G a N crystal was grown on the top of the seed substrate, but the thickness decreased toward the bottom, and G a N crystals did not grow below the center of the seed substrate. Evaluation of the recovered seed substrate revealed that the MO C VD film was not melted back below.

Although specific embodiments of the present invention have been described, the present invention is not limited to these specific embodiments and can be practiced with various changes and modifications without departing from the scope of the claims.

Claims

The scope of the claims

1. A method of growing a nitride single crystal by a flux method in a nitrogen-containing non-oxidizing atmosphere,

Nitrogen dissolving process for dissolving nitrogen in the melt in the vessel;

Then, by immersing in the melt a jig in which at least the surface is made of a material non-reactive with the melt, the liquid level of the melt is raised, and the seed crystal is immersed in the melt. Liquid level rising process; and

Single crystal growth step of growing a nitride single crystal on the seed crystal in a state where the angle between the gas-liquid interface of the melt and the growth surface of the seed crystal is 45 ° or more and 135 ° or less

And a method of growing a nitride single crystal.

2. The method according to claim 1, wherein the gas-liquid interface of the melt and the growth surface of the seed crystal are substantially perpendicular.

3. After growing the nitride single crystal, the seed crystal and the nitride single crystal are exposed outside the melt by pulling up the jig from the melt. The method described in 1 or 2.

4. The method according to any one of claims 1 to 3, characterized in that the container is rocked or pivoted in the single crystal growth step.

5. The jig includes a wide width portion and a narrow width portion, and in the liquid level raising step, the wide width portion is immersed in the melt, and the narrow width portion is formed of the melt. The air-liquid interface according to any one of claims 1 to 4, characterized in that it is in contact with the interface. Method described in

6. The method according to any one of 5 to 5, characterized in that the seed crystal is attached to the jig.