JP2003212696A - Method and apparatus for growing crystal of group iii nitride - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To stably grow a crystal of a group III nitride. <P>SOLUTION: When the crystal of the group III nitride 25 constituted of a group III metal and nitrogen is grown from a mixed melt 24, formed from an alkali metal and a group III metal, and a substance containing at least nitrogen in a reaction vessel 12, a part brought into contact with the mixed melt 24 of the reaction vessel 12 is constituted of a dense material. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a crystal growth method for a group III nitride used for a blue-violet light source for an optical disk, an ultraviolet light source (LD or LED), a blue-violet light source for electrophotography, a group III nitride electronic device, and the like. And a crystal growth apparatus.

[0002]

2. Description of the Related Art Conventionally, a blue LED is a red or green LED.
The brightness was smaller than that of the ED, and it was difficult to put it into practical use.
In recent years, in a group III nitride compound semiconductor represented by the general formula InAlGaN, improvement of crystal growth technology by using a low temperature AlN buffer layer or a low temperature GaN buffer layer, and a low resistance p-type semiconductor layer doped with Mg have been obtained. As a result, a high-intensity blue LED has been put into practical use,
Furthermore, a semiconductor laser that oscillates in the blue wavelength region has been realized.

Generally, when a high quality semiconductor layer is epitaxially grown on a substrate, the lattice constant and the coefficient of thermal expansion of the substrate and the semiconductor layer need to be about the same. But,
Currently, there is no substrate in the world that can satisfy these requirements for group III nitride semiconductors.

Therefore, in the group III nitride, the ELO is generally formed on a different kind of substrate whose lattice constant and thermal expansion coefficient are largely different from those of the group III nitride semiconductors such as sapphire and GaAs.
A thick film GaN is grown by using a crystal growth technique such as the above, and a semiconductor laser crystal is produced by using it as a substrate.

However, a GaN substrate crystal-grown by using a heterogeneous substrate has a very large number of crystal defects with a dislocation density of about 10 ⁷ cm ^-2 , and a practical high-power laser element or electron It cannot be said that the quality is still sufficient for manufacturing a device.

On the other hand, various research institutes have made attempts to produce a GaN bulk single crystal for producing a high quality GaN substrate, but in reality, only a few millimeters have been obtained. , It is far from practical use.

Reference “Chemistry of Materials Vol.9
(1997) p.413-416 ”(Prior Art 1) describes a GaN crystal growth method using Na as a flux. In this method, sodium azide (NaN ₃ ) as a flux and metallic Ga are used as raw materials, and a reaction vessel made of stainless steel (inner dimension of vessel; inner diameter = 7.5 mm, length = 1)
(00 mm) in a nitrogen atmosphere, and the reaction vessel is filled with 60 mm.
The GaN crystal is grown by maintaining the temperature at 0 to 800 ° C. for 24 to 100 hours. This method is characterized in that crystals can be grown at a relatively low temperature of about 600 to 800 ° C., and the pressure inside the container can be as low as about 100 kg / cm ² . A GaN crystal having a size of about 1 mm can be produced by this method.

Further, in Japanese Unexamined Patent Publication No. 2001-58900 (Prior Art 2), in order to increase the size of a group III nitride crystal, a group III metal is additionally replenished during crystal growth of the group III nitride crystal. It is shown. FIG. 3 shows the method of the prior art 2. Referring to FIG. 3, in the method of the conventional technique 2, a growth container 102 containing a flux and a group III metal supply pipe 103 are provided in a reaction container 101, and a pressure is applied to the group III metal supply pipe 103 from the outside. In addition, the group III metal 104 is additionally supplied to the growth container 102. In FIG. 3, 106 is a pressurizing device, 107 is the internal space of the reaction vessel, 108 is a gas supply pipe, 109 is a pressure control device, 110 is a lower heater, and 1 is a lower heater.
11 is a side heater.

Further, in Japanese Patent Laid-Open No. 2001-64098 (Prior Art 3), as shown in FIG.
Flux (Na) and Group III metal (Ga)
There is disclosed a method for growing a large group III nitride crystal by using a seed crystal from a mixed melt with.

Further, in Japanese Unexamined Patent Publication No. 2001-119103 (Prior Art 4), a method of crystallizing cubic III-nitride by using potassium (K) as a flux (alkali metal) is known. It is disclosed.

[0011]

As described above, by using the above-mentioned conventional crystal growth technique (prior art 2, conventional technique 3, conventional technique 4), a large hexagonal crystal or cubic crystal can be obtained.
It became possible to grow a group III nitride crystal.

[0012] However, the above-mentioned conventional technique has the following problems with respect to holding the mixed melt in the reaction vessel.

That is, in the prior art 2, niobium or nickel is used as the material for the reaction vessel holding the mixed melt, but these materials may be Na and II depending on the growth conditions.
Since the mixed melt with the Group I metal raw material gets wet, the mixed melt may travel down the wall of the reaction vessel and may crawl to the outside.

On the other hand, in the prior art 3, nitrides such as BN, SiN, and TiN are used as the material of the reaction vessel, and since these materials are difficult to wet with the mixed melt,
The mixed melt rarely travels along the wall of the reaction vessel and crawls to the outside. However, since the reaction vessel made of these materials is made by sintering, it tends to be porous, and the mixed melt may permeate into the reaction vessel and exude to the outside.

In particular, leaching is more likely to occur in potassium than in sodium, and in a mixed melt of potassium and a Group III metal, the mixed melt permeates into the reaction vessel during crystal growth and oozes out to the outside. In some cases, group III nitrides were formed on the outer wall of the, or the reaction vessel cracked.

As described above, conventionally, the amount of the Group III nitride consumed is lower than the charged amount of the raw material due to the bleeding or leaching of the mixed melt. It was the cause of the decline.

The present invention solves the problem of holding a mixed melt in crystal growth of a Group III nitride from a mixed melt containing an alkali metal and a Group III metal held in a reaction vessel, and stabilizes the stability. It is possible to perform group III nitride crystal growth III
An object of the present invention is to provide a crystal growth method and a crystal growth device for a group nitride.

[0018]

In order to achieve the above-mentioned object, the invention according to claim 1 is such that a substance containing an alkali metal and a group III metal forms a mixed melt in a reaction vessel, and the mixture is formed. Crystal growth of a group III nitride composed of a group III metal and nitrogen from a melt and a substance containing at least nitrogen I
The Group II nitride crystal growth method is characterized in that Group III nitride is crystal-grown in a reaction vessel in which a portion in contact with the mixed melt is made of a dense material.

According to the second aspect of the invention, in the reaction vessel, a mixed melt of an alkali metal and a substance containing a Group III metal forms a mixed melt, and the mixed melt and a substance containing at least nitrogen In a group III nitride crystal growth apparatus for crystal-growing a group III nitride composed of a group metal and nitrogen, the reaction vessel is configured such that a portion in contact with the mixed melt is made of a dense material. It has a feature.

According to a third aspect of the invention, in the reaction vessel, a substance containing an alkali metal and a group III metal forms a mixed melt, and from the mixed melt and a substance containing at least nitrogen, III In the group III nitride crystal growth method for crystal-growing a group III nitride composed of a group metal and nitrogen, the mixed melt includes a portion in contact with the mixed melt in the reaction vessel and a contact with the mixed melt. It is characterized by the fact that it contains substances that increase the angle.

According to a fourth aspect of the invention, in the reaction vessel, a mixed melt of an alkali metal and a substance containing a Group III metal forms a mixed melt, and the mixed melt and a substance containing at least nitrogen In the Group III nitride crystal growth method of crystal-growing a Group III nitride composed of a Group metal and nitrogen, the mixed melt contains sodium (Na) and potassium (K) as alkali metals. There is.

According to a fifth aspect of the invention, in the reaction vessel, a substance containing an alkali metal and a group III metal forms a mixed melt, and from the mixture melt and a substance containing at least nitrogen, III In the group III nitride crystal growth method for crystal-growing a group III nitride composed of a group metal and nitrogen, the mixed melt contains at least potassium (K) as an alkali metal, and the reaction vessel is a mixed melt. It is characterized in that the material of the portion in contact with is tungsten (W).

According to a sixth aspect of the present invention, in the reaction vessel, a mixed melt of an alkali metal and a substance containing a Group III metal forms a mixed melt, and from the mixed melt and a substance containing at least nitrogen, III In a group III nitride crystal growth apparatus for crystal-growing a group III nitride composed of a group metal and nitrogen, the reaction vessel is characterized in that a material of a portion in contact with the mixed melt is tungsten (W). I am trying.

[0024]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below.

First Embodiment A Group III nitride crystal growth method and a crystal growth apparatus according to the first embodiment of the present invention are designed so that alkali metal and
In the case of forming a mixed melt with a substance containing a Group III metal and crystallizing a Group III nitride composed of a Group III metal and nitrogen from the mixed melt and a substance containing at least nitrogen, a mixture is formed. The portion of the reaction vessel that is in contact with the melt is made of a dense material, and the group III nitride is crystal-grown in this reaction vessel.

Here, the fact that the portion of the reaction vessel contacting the mixed melt is made of a dense material means that the mixed melt of the substance containing the alkali metal and the group III metal does not penetrate into the material of the reaction vessel. It means that the part of the reaction vessel that is in contact with the mixed melt is made of a material having

The reaction container does not have to be made of a dense material in its entirety, and the portion in contact with the mixed melt may be made of a dense material. For example, the surface of a porous material may be coated with a dense material.

The dense material that can be used in the present invention is particularly stable as long as it is stable at the crystal growth temperature and does not dissolve or react in the mixed melt to inhibit the crystal growth of the group III nitride. It is not limited. Specifically, the dense material can be selected from metals such as tungsten and various ceramics.

In the present invention, the group III metal means
It means Ga, Al, In. A substance containing nitrogen is a compound containing nitrogen gas or nitrogen such as sodium azide as a constituent element. Further, the group III nitride means a compound of a group III metal selected from gallium, aluminum and indium and nitrogen.

The alkali metal is usually Na
(Sodium) and K (potassium) are used, but other alkali metals can also be used.

Another element may be melted in the mixed melt containing the alkali metal and the group III metal. For example, n-type impurities or p-type impurities may be melted and doped in the mixed melt.

According to the first embodiment, the portion of the reaction vessel which is in contact with the mixed melt is made of a dense material so that the mixed melt is held inside the reaction vessel without permeating the wall surface of the reaction vessel. It Then, at a predetermined crystal growth temperature,
Nitrogen diffused in a mixed melt in the presence of alkali metals III
Bonds with the group metal and crystallizes the group III nitride. That is, according to the first embodiment, the problem of holding the mixed melt in crystal growth of the group III nitride from the mixed melt containing the alkali metal and the group III metal held in the reaction vessel Therefore, it becomes possible to stably perform the group III nitride crystal growth.

In other words, in the first embodiment, the alkali metal and the substance containing the Group III metal form a mixed melt in the reaction vessel, and the mixed melt and the substance containing at least nitrogen. From I, composed of Group III metals and nitrogen
In the case of crystal growth of a group II nitride, a portion of the reaction vessel in contact with the melt is made of a dense material,
Since the group I nitride is crystal-grown, it has been a problem in the past.
During the crystal growth, the mixed melt of the alkali metal (particularly potassium) and the Group III metal raw material does not exude to the outside through the reaction vessel, resulting in the formation of Group III nitride on the outer wall of the reaction vessel, or Problems such as cracking of the reaction vessel are solved, and stable high-quality Group III nitride crystal growth can be performed.

Second Embodiment A method for growing a group III nitride crystal according to a second embodiment of the present invention is to prepare a mixed melt of a substance containing an alkali metal and a group III metal in a reaction vessel, I composed of a Group III metal and nitrogen from the mixed melt and a substance containing at least nitrogen
In the case of crystal growth of a Group II nitride, the mixed melt is characterized in that it contains a substance that increases the contact angle between the portion of the reaction vessel in contact with the mixed melt and the mixed melt.

Here, the fact that the contact angle between the mixed melt and the portion in contact with the mixed melt in the reaction vessel is large means that the wettability between the mixed melt and the inner wall of the reaction vessel is poor and the mixed melt is mixed in the reaction vessel. This means that the liquid is retained. Conversely, a small contact angle between the mixed melt and the portion in contact with the mixed melt in the reaction vessel means that the wettability between the mixed melt and the inner wall of the reaction vessel is good, and in this case, the mixing The melt is not retained inside the reaction container by, for example, passing through the inner wall of the reaction container and exiting to the outside.

This second embodiment is based on alkali metal and II
When the contact angle between the mixed melt of a substance containing a Group I metal and the reaction vessel is small, the contact angle is increased by mixing the substance that increases the contact angle into the mixed melt to react the mixed melt. It is intended to be held in the container. A substance that increases the contact angle is one that can achieve that effect.
There is no particular limitation as long as it does not hinder the crystal growth of the group nitride. Specifically, the substance that increases the contact angle may be a p-type or n-type dopant material or an alkali metal.

According to the crystal growth method of the second embodiment,
By mixing a substance that increases the contact angle between the mixed melt in the reaction container and the mixed melt with the mixed melt, the mixed melt travels along the wall surface of the reaction container and exits to the outside. Instead, it is retained inside the reaction vessel. Then, at a predetermined crystal growth temperature, the nitrogen diffused in the mixed melt is combined with the group III metal in the presence of the alkali metal to crystallize the group III nitride. That is, according to the second embodiment, the problem of holding the mixed melt in crystal growth of the group III nitride from the mixed melt containing the alkali metal and the group III metal held in the reaction vessel Therefore, it becomes possible to stably perform the group III nitride crystal growth.

In other words, in the second embodiment, the alkali metal and the substance containing the group III metal form a mixed melt in the reaction vessel, and the mixed melt and the substance containing at least nitrogen. From I, composed of Group III metals and nitrogen
In the case of crystal growth of a Group II nitride, the mixed melt contains a substance that increases the contact angle between the mixed melt and the portion in contact with the melt in the reaction vessel, so the reaction vessel is wet with the mixed melt. It becomes difficult to prevent the mixed melt from traveling along the wall of the reaction vessel and crawling out of the reaction vessel, and stable high-quality Group III nitride crystal growth can be performed. Further, by using the method of the second embodiment, it becomes possible to use a reaction container that could not be used because the wettability with the mixed melt was good in the past, and a reaction container more suitable for crystal growth can be provided. It is possible to make a selection, and as a result, it is possible to perform crystal growth of a higher quality group III nitride.

Third Embodiment In the third embodiment of the present invention, the alkali metal and the substance containing the group III metal form a mixed melt in the reaction vessel, and the mixed melt and at least nitrogen are contained. When crystallizing a group III nitride composed of a group III metal and nitrogen from a substance, the mixed melt is characterized by containing sodium (Na) and potassium (K) as alkali metals.

More specifically, this third embodiment is a special case of the second embodiment, where sodium
The contact angle is increased by mixing potassium with the mixed melt of the Group III metal.

Here, the amount of potassium mixed has the effect of increasing the contact angle even if it is a small amount, but the amount is not particularly limited and may be appropriately selected depending on the material of the reaction vessel used. You can Further, since the crystal system of the growing crystal can be controlled to be cubic or hexagonal depending on the ratio of sodium to potassium and the crystal growth conditions, it is possible to select a mixing ratio suitable for a desired crystal system.

In the crystal growth method of the third embodiment,
By mixing potassium and sodium as alkali metals in the mixed melt, the wetting angle with the reaction vessel increases, and the mixed melt is retained inside the reaction vessel without passing through the wall surface of the reaction vessel to the outside. To be done. Then, at a predetermined crystal growth temperature, the nitrogen diffused in the mixed melt is combined with the group III metal in the presence of the alkali metal to crystallize the group III nitride.

In other words, in the third embodiment, in the reaction vessel, the substance containing the alkali metal and the group III metal forms a mixed melt, and the mixed melt and the substance containing at least nitrogen. From I, composed of Group III metals and nitrogen
In the case of crystal growth of Group II nitride, the mixed melt contains sodium (Na) and potassium (K) as alkali metals, so a reaction vessel that could not be used in a mixed melt using only sodium as an alkali metal Can be used. That is, by mixing potassium into a mixed melt of sodium and a Group III metal, it is possible to increase the contact angle between the reaction vessel and the mixed melt, so in a mixed melt using only sodium as the alkali metal Although the mixed melt could not be held because the mixed melt crawled out of the reaction container because of good wettability with the container, by mixing potassium, the mixed melt can be held in the reaction container. Thus, according to this third embodiment,
Since it becomes possible to use a reaction vessel that could not be used in a mixed melt containing only sodium as an alkali metal, it is possible to select a reaction vessel more suitable for crystal growth. As a result, it is possible to perform higher quality group III nitride crystal growth. Also, since the Na-K alloy is a liquid even at room temperature depending on the mixing ratio, the mixed melt solidifies when cooled from the crystal growth temperature to room temperature,
A force is not applied to the group nitride crystal to give damage, and therefore a high quality group III nitride crystal can be produced.

Fourth Embodiment In the fourth embodiment of the present invention, a mixed melt of an alkali metal and a substance containing a group III metal is formed in a reaction vessel, and the mixed melt and at least nitrogen are contained. When crystallizing a Group III nitride composed of a Group III metal and nitrogen from a substance, the mixed melt contains at least potassium (K) as an alkali metal, and the reaction vessel is in contact with the mixed melt. It is characterized in that the material of the portion is tungsten (W).

The inventor of the present application has studied various materials so far, and as a result, the material of the reaction vessel for holding the mixed melt using potassium as the alkali metal and performing the crystal growth of the group III nitride is We have found that tungsten is the most suitable.

In the case of a mixed melt using sodium as an alkali metal, the wettability between the mixed melt and tungsten is good, and the mixed melt crawls out of the reaction vessel so that crystal growth cannot be performed, but sodium It has been found that by mixing potassium, the contact angle between the mixed melt and tungsten is increased, and the mixed melt is retained inside the reaction vessel.

Therefore, a feature of the fourth embodiment of the present invention is that the mixed melt contains potassium and tungsten is used as the material of the reaction vessel.

Here, potassium alone as the alkali metal may be mixed in the mixed melt, or sodium and potassium may be mixed.

When sodium and potassium are mixed, the amount ratio can be appropriately selected. That is, when crystallizing a cubic group III nitride,
The amount of potassium can be increased. Further, in the case of crystal growth of a hexagonal group III nitride, the amount of sodium can be increased.

Further, since the melting point of the sodium-potassium alloy falls below room temperature depending on the quantity ratio, the quantity ratio can be appropriately selected and kept in the liquid state even at room temperature.

In the fourth embodiment, at least a potassium (K) alkali metal is used at a predetermined crystal growth temperature.
The mixed melt with the Group III metal containing is held in a reaction vessel in which the portion in contact with the mixed melt is tungsten (W). Then, the nitrogen diffused in the mixed melt is combined with the group III metal in the presence of the alkali metal to crystallize the group III nitride.

According to this fourth embodiment, the alkali metal and the substance containing the group III metal form a mixed melt in the reaction vessel, and the mixture melt and the substance containing at least nitrogen When a group III nitride composed of a group metal and nitrogen is crystal-grown, even if the mixed melt contains at least potassium (K) as an alkali metal, the reaction vessel has a portion in contact with the melt. Since it is tungsten (W), it can hold a mixed melt containing potassium.
That is, even if only potassium is used as an alkali metal, tungsten does not bleed out to the outside through the reaction vessel, which was a problem in the past, because the mixed melt of potassium and the group III metal raw material was grown during crystal growth. . As a result, it is possible to solve the problem that the group III nitride is generated on the outer wall of the reaction container or the reaction container is cracked. Further, since the contact angle between the mixed melt and tungsten is large and the mixed melt does not wet with tungsten, the mixed melt is held in the reaction vessel, and stable and high quality Group III nitride crystal growth is performed. be able to. On the other hand, when only sodium is used as the alkali metal, the mixed melt is wet with tungsten and is difficult to hold in the reaction vessel, but when potassium is mixed, the contact angle between the mixed melt and tungsten is It grows in size and the mixed melt does not wet the tungsten. As a result, the mixed melt is held in the reaction vessel, and stable high-quality Group III nitride crystal growth can be performed. Further, since tungsten can be highly purified, impurities are hardly mixed into the crystal and high quality group III nitride can be crystal-grown.

Fifth Embodiment A fifth embodiment of the present invention comprises a reaction vessel holding a mixed melt containing an alkali metal and a Group III metal, and the mixed melt and at least nitrogen are held in the reaction vessel. From substances containing
In a group III nitride crystal growth apparatus for crystal growing a group III nitride composed of a group III metal and nitrogen, the reaction vessel is characterized in that the portion in contact with the mixed melt is tungsten (W). .

Here, the form of the crystal growth apparatus is not particularly limited, as long as it has a reaction vessel for holding a mixed melt containing an alkali metal and a Group III metal.
Either device may be used. That is, it may be an apparatus for growing crystals in the mixed melt, an apparatus for pulling crystals from the mixed melt, or any other form.

In the crystal growth using the crystal growth apparatus of the fifth embodiment, a mixed melt containing an alkali metal and a group III metal is placed in a reaction vessel in which the portion in contact with the mixed melt is tungsten (W). , Is maintained at a predetermined crystal growth temperature. Then, the nitrogen diffused in the mixed melt held in the reaction vessel is combined with the group III metal in the presence of the alkali metal, and the group III nitride is crystal-grown.

The crystal growth apparatus of the fifth embodiment is provided with a reaction vessel for holding a mixed melt containing an alkali metal and a Group III metal, and the mixed melt and a substance containing at least nitrogen are used to Composed of group metals and nitrogen III
When crystallizing a group nitride, since the portion of the reaction vessel that is in contact with the mixed melt is tungsten (W), the mixed melt containing potassium can be held in the reaction vessel. As a result, it is possible to stably perform high-quality Group III nitride crystal growth.

Next, a concrete apparatus configuration example of the present invention will be described.

FIG. 1 is a diagram showing a first structural example of a crystal growth apparatus according to the present invention. In the crystal growth apparatus of FIG. 1, a reaction vessel 12 for holding a mixed melt 24 containing an alkali metal and a group III metal and performing crystal growth is provided in a closed pressure vessel 11 made of stainless steel. .

In the internal space 23 of the pressure resistant container 11,
A nitrogen (N ₂ ) gas as a nitrogen raw material and an argon (Ar) gas for suppressing evaporation of an alkali metal are filled, and the nitrogen (N ₂ ) pressure and the argon (A) in the pressure vessel 11 are filled.
r) Gas supply pipe 1 that makes it possible to control the gas pressure
4 is attached through the pressure resistant container 11.

The gas supply pipe 14 is branched into a nitrogen supply pipe 17 and an argon supply pipe 20, which can be separated by valves 15 and 18, respectively. Also,
The respective pressures can be adjusted by the pressure control devices 16 and 19.

Further, a pressure gauge 22 for monitoring the total pressure inside the pressure resistant container 11 is installed. The reason for mixing argon as an inert gas is to control the pressure of nitrogen gas independently while suppressing the evaporation of alkali metal. This enables crystal growth with high controllability. Further, the reaction container 12 can be removed from the pressure resistant container 11.

In FIG. 1, the material of the reaction vessel 12 is tungsten. Further, a heater 13 is installed outside the pressure resistant container 11. The heater 13 can be controlled to any temperature.

The pressure-resistant container 11 can be detached from the crystal growth apparatus at the valve 21, and only the pressure-resistant container 11 can be put in the glove box for work.

Below, G using the crystal growth apparatus of FIG.
The crystal growth method of aN is demonstrated. First, the pressure resistant container 11 is separated from the crystal growth apparatus at the valve 21 and placed in a glove box in an Ar atmosphere.

Next, the reaction container 12 made of tungsten
Ga is added as a group III metal raw material, and potassium (K) is added as an alkali metal. Next, the reaction container 12 is installed in the pressure resistant container 11. Then, the pressure vessel 11 is closed, the valve 21 is closed, and the inside of the reaction vessel 12 is shut off from the external atmosphere. Since a series of operations is performed in a glove box in a high-purity Ar gas atmosphere, the pressure vessel 11 is filled with Ar gas. Next, the pressure resistant container 11 is taken out from the glove box and incorporated in the crystal growth apparatus.
That is, the pressure vessel 11 is installed at a predetermined position where the heater 13 is located, and is connected to the nitrogen and argon gas supply line 14 at the valve 21. Then, the heater 13 is energized to raise the temperature of the reaction vessel 12 to the crystal growth temperature. The crystal growth temperature was 675 ° C.

Then, the valves 21 and 18 are opened,
Ar gas is introduced from the Ar gas supply pipe 20, the pressure is adjusted by the pressure control device 19, and the total pressure in the pressure vessel 11 is adjusted to 3MP.
Then, the valve 18 is closed. Next, nitrogen gas is introduced from the nitrogen gas supply pipe 17, the pressure is adjusted by the pressure control device 16, the valve 15 is opened, and the total pressure in the pressure vessel 11 is adjusted to 5M.
Set to Pa. That is, the partial pressure of nitrogen in the internal space 23 of the pressure vessel 11 is 2 MPa. After maintaining this state for 200 hours, the temperature is lowered to room temperature.

After reducing the pressure of the gas in the pressure vessel 11,
When the pressure vessel 11 was opened, part of the potassium used as the alkali metal was evaporated and transported to the low temperature part, and adhered to the pedestal 26 portion at the bottom of the reaction vessel 12, but the mixed melt 24 was made of tungsten. It did not seep out of the reaction vessel 12, and most of the mixed melt 24 remained in the reaction vessel 12.

Then, in the reaction vessel 12, 100 μm
A large number of colorless and transparent cubic GaN single crystals 25 having front and rear sizes were grown.

When a reaction vessel made of BN which is sintered and molded is used as the reaction vessel 12, the holding capacity of the mixed melt is poor.
Although not produced as N, almost all of the Ga charged as the raw material was produced as GaN when the reaction vessel made of tungsten was used.

FIG. 2 is a diagram showing a second configuration example of the crystal growth apparatus according to the present invention.

In the crystal growth apparatus shown in FIG. 2, a pressure vessel 31 made of stainless steel and having a closed shape is provided with a reaction vessel 34 for holding a mixed melt containing an alkali metal and a group III metal for crystal growth. ing.

In the internal space 48 of the pressure resistant container 31,
A nitrogen (N ₂ ) gas as a nitrogen source and an argon (Ar) gas for suppressing evaporation of an alkali metal are filled, and the nitrogen (N ₂ ) pressure and the argon (A) in the pressure vessel 31 are filled.
r) A gas supply pipe 50 for allowing control of the gas pressure is attached to penetrate the pressure resistant container 31. The gas supply pipe 50 includes a nitrogen supply pipe 37 and an argon supply pipe 4.
It is branched into 0 and can be separated by valves 35 and 38, respectively. Further, the respective pressures can be adjusted by the pressure control devices 36 and 39.

Further, a pressure gauge 42 for monitoring the total pressure inside the pressure resistant container 31 is installed. Further, the reaction container 34 can be removed from the pressure resistant container 31.

In FIG. 2, the material of the reaction vessel 34 is tungsten. Further, on the outside of the reaction container 34, a pressure resistant container 31 due to scattering of alkali metal or raw material vapor
A cover 32 is covered to prevent contamination inside. In the example of FIG. 2, a stainless cover is used as the cover 32.

Here, a gap 43 is slightly opened between the cover 32 and the pressure resistant container 31. Nitrogen and argon gases enter the cover 32 through the gap 43 between the cover 32 and the pressure-resistant container 31, and the nitrogen and argon gas pressure is applied to the mixed melt 44 of the flux and the group III metal.

A heater 33 is provided outside the cover 32.
Is installed. The heater 33 can be controlled to any temperature. The heater 33 can be removed.

The pressure-resistant container 31 can be detached from the crystal growth apparatus at the valve 41, and only the pressure-resistant container 31 can be put in the glove box for work.

Below, Ga using this crystal growth apparatus was used.
A method of growing N will be described. First, the pressure resistant container 31 is separated from the crystal growth apparatus at the valve 41 and placed in a glove box in an Ar atmosphere.

Then, the reaction container 34 made of tungsten is used.
Ga is added as a group III metal source, and sodium (Na) and potassium (K) are added as alkali metals. The molar ratio of sodium and potassium was 10: 1. Sodium and potassium are solids at room temperature, but when they are mixed, they become liquid even at room temperature.

Next, the reaction container 34 is placed in the pressure resistant container 31. Next, the reaction container 34 is covered with a stainless cover 32, and the heater 33 is installed at a predetermined position.
Next, the pressure-resistant container 31 is closed, the valve 41 is closed, and the inside of the pressure-resistant container 31 is shut off from the external atmosphere.

Since a series of operations are performed in a glove box in a high-purity Ar gas atmosphere, the inside of the pressure resistant container 31 is A
It is filled with r gas. Next, the pressure resistant container 31 is taken out of the glove box and incorporated in the crystal growth apparatus. That is, the pressure vessel 31 is connected to the nitrogen and argon gas supply line 50 at the valve 41.

Next, the heater 33 is energized to raise the temperature of the reaction vessel 34 to the crystal growth temperature. Crystal growth temperature is 80
It was set to 0 ° C. Next, the valves 41 and 38 are opened, Ar gas is introduced from the Ar gas supply pipe 40, the pressure is adjusted by the pressure control device 39, the total pressure in the pressure vessel 31 is set to 5 MPa, and the valve 38 is closed.

Then, nitrogen gas is introduced from the nitrogen gas supply pipe 37, the pressure is adjusted by the pressure control device 36, and the valve 35 is adjusted.
Is opened, and the total pressure in the pressure resistant container 31 is set to 10 MPa. That is, the partial pressure of nitrogen in the pressure vessel 31 is 5 MPa. After maintaining this state for 200 hours, the temperature is lowered to room temperature.

After reducing the pressure of the gas in the pressure resistant container 31,
When the pressure vessel 31 was opened, part of the sodium and potassium used as alkali metals was evaporated and transported to the low temperature part, and adhered to the pedestal portion 47 at the bottom of the reaction vessel 34, but the mixed melt 44 was made of tungsten. Most of the mixed melt 44 remained in the reaction container 34 without getting wet to the reaction container 34 and crawling out.

Then, in the reaction vessel 34, a hexagonal GaN plate single crystal 45 having a size of about 10 mm and 2 mm
A columnar hexagonal GaN 46 having a size of about 3 was crystal-grown.

[0086]

As described above, according to the first and second aspects of the invention, the substance containing the alkali metal and the group III metal forms a mixed melt in the reaction vessel, In a case where a group III nitride composed of a group III metal and nitrogen is crystal-grown from a mixed melt and a substance containing at least nitrogen, a portion in contact with the mixed melt is made of a dense material in a reaction vessel Since the group III nitride is crystal-grown, the mixed melt of the alkali metal (particularly potassium) and the group III metal raw material does not seep out through the reaction vessel during crystal growth, which has been a problem in the past. As a result, problems such as generation of group III nitride on the outer wall of the reaction vessel or cracking of the reaction vessel are solved, and stable high-quality group III nitride crystal growth can be performed.

Further, according to the invention of claim 3, in the reaction vessel, the substance containing the alkali metal and the group III metal forms a mixed melt, and the mixed melt and the substance containing at least nitrogen are formed. A group III nitride crystal growth method in which a group III nitride composed of a group III metal and nitrogen is grown, and the mixed melt includes a portion in contact with the mixed melt in the reaction vessel and a mixed melt. Since it contains a substance that increases the contact angle of the reaction vessel, it becomes difficult for the mixed melt to get wet in the reaction vessel, and the mixed melt does not travel along the wall of the reaction vessel and crawl out of the reaction vessel. High quality III-nitride crystal growth can be performed. Further, by using the crystal growth method of the present invention according to claim 3, it becomes possible to use a reaction vessel which could not be used because of its good wettability with the mixed melt, and a reaction more suitable for crystal growth can be used. A container can be selected, and as a result, higher quality III-nitride crystal growth can be performed.

Further, according to the invention of claim 4, in the reaction vessel, the substance containing the alkali metal and the group III metal forms a mixed melt, and the mixed melt and the substance containing at least nitrogen are formed. In the Group III nitride crystal growth method of growing a Group III nitride composed of a Group III metal and nitrogen, the mixed melt is sodium (N
Since it contains a) and potassium (K), it becomes possible to use a reaction vessel that could not be used in a mixed melt using only sodium as an alkali metal. Ie sodium and II
By mixing potassium into a mixed melt with a Group I metal, the contact angle between the reaction vessel and the mixed melt can be increased. However, the mixed melt could not be held because the mixed melt crawled out of the reaction container, but by mixing potassium, the mixed melt can be held in the reaction container. Therefore,
By using the crystal growth method of the invention according to claim 4, it becomes possible to use a reaction vessel that could not be used in a mixed melt containing only sodium as an alkali metal, and a reaction vessel more suitable for crystal growth can be selected. can do. As a result, it is possible to perform higher quality group III nitride crystal growth. Further, since the Na-K alloy is a liquid even at room temperature depending on the mixing ratio, the mixed melt is solidified when cooled from the crystal growth temperature to room temperature, and a force is applied to the group III nitride crystal to cause damage. Therefore, a high-quality group III nitride crystal can be produced.

According to the invention of claim 5, the alkali metal and the substance containing the group III metal form a mixed melt in the reaction vessel, and the mixed melt and the substance containing at least nitrogen are mixed. In the method for growing a group III nitride crystal in which a group III nitride composed of a group III metal and nitrogen is grown, even when the mixed melt contains at least potassium (K) as an alkali metal, the reaction vessel is Since the portion in contact with the melt is tungsten (W), the mixed melt containing potassium can be held. That is, even if only potassium is used as an alkali metal for tungsten, the conventional problem is that the mixed melt of potassium and the group III metal raw material does not exude to the outside through the reaction vessel during crystal growth. . As a result, II is formed on the outer wall of the reaction vessel.
Problems such as the formation of group I nitrides or the cracking of the reaction vessel can be solved. Further, since the contact angle between the mixed melt and tungsten is large and the mixed melt does not wet with tungsten, the mixed melt is held in the reaction vessel, and stable and high quality Group III nitride crystal growth is performed. be able to. On the other hand, when only sodium is used as the alkali metal, the mixed melt gets wet with tungsten,
Although it is difficult to keep it in the reaction vessel, when potassium is mixed, the contact angle between the mixed melt and tungsten becomes large, and the mixed melt does not get wet with tungsten. As a result, the mixed melt is held in the reaction vessel, and stable high-quality Group III nitride crystal growth can be performed. Further, since tungsten can be highly purified, impurities are hardly mixed into the crystal and high quality group III nitride can be crystal-grown.

According to the invention of claim 6, there is provided a reaction vessel for holding a mixed melt containing an alkali metal and a group III metal, and the group III is selected from the mixed melt and a substance containing at least nitrogen. In a group III nitride crystal growth apparatus for crystal growing a group III nitride composed of metal and nitrogen,
Since the reaction vessel is made of tungsten (W) at the portion in contact with the mixed melt, the mixed melt containing potassium can be held in the reaction vessel. As a result, it is possible to stably perform high-quality Group III nitride crystal growth.

[Brief description of drawings]

FIG. 1 is a diagram showing a first configuration example of a crystal growth apparatus according to the present invention.

FIG. 2 is a diagram showing a second configuration example of the crystal growth apparatus according to the present invention.

FIG. 3 is a diagram showing a configuration example of a crystal growth apparatus shown in Related Art 2.

FIG. 4 is a diagram showing a configuration example of a crystal growth apparatus shown in Related Art 3.

[Explanation of symbols]

11,31 Pressure vessel 12,34 Reaction vessel 13,33 heater 14,50 gas supply pipe 15, 18, 21, 35, 38, 41 valves 16, 19, 36, 39 Pressure control device 17,37 Nitrogen supply pipe 20,40 Argon supply pipe 22,42 pressure gauge 23,48 Internal space of pressure vessel 24,44 mixed melt 25 Cubic GaN Single Crystal 26,47 pedestal 32 covers 43 Gap 45 Plate-shaped single crystal of hexagonal GaN 46 columnar hexagonal GaN

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Masahiko Shimada             3-29-5 Kaigamori, Aoba-ku, Sendai City, Miyagi Prefecture (72) Inventor Hisanori Yamane             1-12-4 Tsurugaya, Miyagino-ku, Sendai City, Miyagi Prefecture (72) Inventor Takashi Araki             31-10-105 Matsugaoka, Taihaku-ku, Sendai City, Miyagi Prefecture F term (reference) 4G077 AA02 BE15 CB01 CB06 EA02                       EA04 EA06 EG02 HA02 HA12

Claims (6)

[Claims] 1. A reaction vessel, in which a substance containing an alkali metal and a group III metal forms a mixed melt, and the mixture melt and a substance containing at least nitrogen are used to form a group III metal and nitrogen. In the method for crystal growth of a group III nitride for crystallizing a group III nitride according to claim 1, characterized in that the group III nitride is crystal-grown in a reaction vessel in which a portion in contact with the mixed melt is made of a dense material. Method for growing group III nitride crystal. 2. A reaction vessel, wherein an alkali metal and a substance containing a group III metal form a mixed melt, and the mixed melt and a substance containing at least nitrogen are used to form a group III metal and nitrogen. In a group III nitride crystal growth apparatus for crystal-growing a group III nitride according to claim 1, the reaction vessel is characterized in that a portion in contact with the mixed melt is made of a dense material. Crystal growth equipment. 3. A reaction vessel, wherein an alkali metal and a substance containing a group III metal form a mixed melt, and the mixture melt and the substance containing at least nitrogen are composed of a group III metal and nitrogen. In the group III nitride crystal growth method for crystal-growing a group III nitride according to claim 1, the mixed melt contains a substance that increases the contact angle between the portion of the reaction vessel in contact with the mixed melt and the mixed melt. And a method for growing a group III nitride crystal. 4. A reaction vessel, wherein an alkali metal and a substance containing a group III metal form a mixed melt, and the mixture melt and the substance containing at least nitrogen are composed of a group III metal and nitrogen. A group III nitride crystal growth method for growing a group III nitride crystal according to claim 1, wherein the mixed melt contains sodium (Na) and potassium (K) as alkali metals. Method. 5. A reaction vessel, wherein an alkali metal and a substance containing a group III metal form a mixed melt, and the mixture melt and the substance containing at least nitrogen are composed of a group III metal and nitrogen. In the method for growing a group III nitride crystal for crystallizing a group III nitride according to claim 1, the mixed melt contains at least potassium (K) as an alkali metal, and the reaction vessel is made of tungsten ( W) A method for growing a group III nitride crystal. 6. A reaction vessel, in which a substance containing an alkali metal and a group III metal forms a mixed melt, and the mixture melt and a substance containing at least nitrogen are used to form a group III metal and nitrogen. In a group III nitride crystal growth apparatus for crystallizing a group III nitride according to claim 3, the material of a portion of the reaction vessel in contact with the mixed melt is tungsten (W). Growth equipment.