JP2009051721A - Method of manufacturing gallium nitride - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing gallium nitride capable of growing a crystal at a low temperature and a low pressure. <P>SOLUTION: The method of manufacturing gallium nitride comprises growing a crystal of gallium nitride by reacting gallium oxide with lithium nitride in a liquid metal bath. The metal bath is preferably composed of gallium. The crystal growth reaction of gallium nitride is preferably carried out at a reaction temperature not lower than 700°C. Further, the molar ratio of gallium oxide to lithium nitride is preferably not greater than one quarter. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method for producing gallium nitride at low temperature and low pressure.

Gallium nitride (GaN) has been put to practical use in light emitting diodes, laser diodes, and the like because of its light emission characteristics, and is the most researched nitride.
In general, gallium nitride is mainly produced by heteroepitaxial growth in which trimethylgallium and ammonia are grown on a sapphire substrate by metal organic vapor phase epitaxy (MOVPE).

However, recently, due to the problem of lattice mismatch, a method for producing bulk gallium nitride that does not use a substrate has attracted attention. Specifically, a high-temperature and high-pressure method in which gallium and nitrogen are reacted at a high temperature of 1500 ° C. or higher and a high pressure of 10,000 atmospheres or higher, and a flux method using sodium or potassium as a flux have been proposed (see Patent Document 1).
However, since both methods use nitrogen (N ₂ ) as a nitrogen source, there is a problem that special measures such as using plasma are necessary for decomposition and excitation of nitrogen.
In order to solve such problems, the present inventors have proposed a method for producing a group III nitride such as gallium nitride by reacting with a group III oxide using lithium nitride as a nitrogen source (see Patent Document 2). ).

  However, the gallium nitride actually obtained by the above method is as small as several μm. This is presumably because the reaction between solid gallium oxide and solid lithium nitride is a solid phase reaction. That is, in the reaction between solids, the solid interface only reacts and fuses, the reaction ends, the raw material is not continuously supplied to the crystal, and the crystal growth is limited.

JP 2002-201100 A JP 2005-154193 A

  The present invention has been made in view of such conventional problems, and an object of the present invention is to provide a method for producing gallium nitride capable of crystal growth of gallium nitride at a low temperature and a low pressure.

  According to a first aspect of the present invention, there is provided a method for producing gallium nitride, characterized in that gallium nitride is crystal-grown by reacting gallium oxide and lithium nitride in a liquid metal bath (claim 1).

Next, the effects of the present invention will be described.
The inventors of the present application conducted various studies on a method for producing gallium nitride at low temperature and low pressure for the purpose of growing a high-quality gallium nitride bulk single crystal by low environmental load processing. It was considered desirable to use lithium nitride (Li ₃ N) as

Therefore, the Ga which is considered as a gallium source (gallium metal) and Ga ₂ O ₃ (gallium oxide), was examined based on thermodynamic calculations. As a result, the free energy of Gibbs reaction formation at room temperature of the reaction for obtaining gallium nitride from lithium nitride and metal gallium (Ga + Li ₃ N → GaN + 3Li) is 58.5 kJ / mol, while nitriding from lithium nitride and gallium oxide. In the reaction for obtaining gallium (Ga ₂ O ₃ + 2Li ₃ N → 2GaN + 3Li ₂ O), it was −547.6 kJ / mol. Therefore, it is assumed that the reaction with lithium nitride is likely to start by using gallium oxide as the gallium source.
However, if the lithium nitride and gallium oxide are simply reacted, the reaction becomes a solid-phase reaction between solids, so that crystal growth of gallium nitride cannot be expected.

Therefore, in the present invention, gallium oxide and lithium nitride are reacted in a liquid metal bath. Thereby, it is considered that the crystal growth of gallium nitride proceeds as follows.
That is, in the initial reaction, as described above, a reaction between gallium oxide having a low Gibbs reaction generation free energy and lithium nitride occurs, and gallium nitride serving as a nucleus is generated.

Next, when the metal bath is made of gallium, gallium nitride obtained by a liquid phase reaction between gallium and lithium nitride is supplied to the gallium nitride nucleus, and crystal growth of gallium nitride proceeds. That is, since liquid gallium exists around the nucleus, gallium is continuously supplied to lithium nitride around the nucleus, and crystal growth of gallium nitride proceeds one after another.
Thereby, a large gallium nitride crystal can be obtained.

Also, when the metal bath is made of a metal other than gallium, gallium nitride obtained by the reaction of gallium oxide and lithium nitride in the liquid phase is supplied to the gallium nitride nucleus, and the gallium nitride Crystal growth proceeds. That is, since there is a liquid metal bath around the nucleus, lithium nitride and gallium oxide in the metal bath are continuously supplied around the nucleus, and crystal growth of gallium nitride proceeds one after another.
Thereby, a large gallium nitride crystal can be obtained.

  As described above, according to the present invention, it is possible to provide a method for producing gallium nitride that allows crystal growth of gallium nitride at a low temperature and a low pressure.

  According to a second aspect of the present invention, there is provided a method for producing gallium nitride, characterized in that a metal oxide and lithium nitride are reacted in a liquid gallium bath to crystallize gallium nitride.

Next, the effects of the present invention will be described.
In the present invention, a metal oxide and lithium nitride are reacted in a liquid gallium bath. At this time, the gallium oxide produced in the liquid gallium bath reacts with lithium nitride in the liquid gallium bath, so that the crystal growth of gallium nitride proceeds as follows, as in the first aspect of the invention. it is conceivable that.

  That is, first, in a liquid gallium bath, a metal oxide and lithium nitride react to generate lithium oxide. This lithium oxide reacts with liquid gallium to produce gallium oxide. Furthermore, the gallium oxide reacts with lithium nitride to generate gallium nitride nuclei.

Next, gallium nitride obtained by a liquid phase reaction between liquid gallium and lithium nitride is supplied to the gallium nitride nucleus, and crystal growth of gallium nitride proceeds. That is, since liquid gallium exists around the nucleus, gallium is continuously supplied to lithium nitride around the nucleus, and crystal growth of gallium nitride proceeds one after another.
Thereby, a large gallium nitride crystal can be obtained.

  As described above, according to the present invention, it is possible to provide a method for producing gallium nitride that allows crystal growth of gallium nitride at a low temperature and a low pressure.

In the first invention (Invention 1), the metal bath is preferably made of gallium (Invention 2).
In this case, gallium nitride obtained by a liquid phase reaction between liquid gallium and lithium nitride is supplied to the gallium nitride (GaN) nucleus described above, and crystal growth of gallium nitride proceeds. By using gallium as the metal bath, the metal bath itself can be used mainly as a gallium source during crystal growth, and the amount of gallium oxide used as a gallium source during nucleation can be reduced. it can. As a result, the number of gallium nitride nuclei generated in the initial stage can be reduced, and accordingly, crystals centering on the respective nuclei are easily grown. As a result, a larger gallium nitride crystal can be obtained.

  In addition to gallium (Ga), the metal bath may be any metal that is liquid at the reaction temperature, that is, a metal having a melting point equal to or lower than the reaction temperature. For example, indium (In), tin (Sn), Zinc (Zn), aluminum (Al), lead (Pb), bismuth (Bi), or the like can be used. Here, as said reaction temperature, it is 700-800 degreeC, for example.

The gallium nitride crystal growth reaction is preferably performed at a reaction temperature of 700 ° C. or higher.
In this case, crystal growth of gallium nitride can be further promoted.
In addition, it is preferable that said reaction temperature is 800 degrees C or less from a viewpoint of suppression of decomposition | disassembly of a gallium nitride.

The molar ratio of the gallium oxide to the lithium nitride is preferably ¼ or less.
In this case, the above-described crystal growth of gallium nitride occurs effectively, and a sufficiently large gallium nitride crystal can be obtained.
On the other hand, if the amount of gallium oxide is too large, too many gallium nitride nuclei are generated in the initial stage, and there is a possibility that a gallium nitride crystal centering around each nuclei will be difficult to grow. That is, it is considered that a relatively small number of gallium nitride crystals can be formed. Further, if the amount of gallium oxide is too large, lithium nitride is consumed at an early stage, so that it is considered that subsequent crystal growth of gallium nitride may be difficult to proceed.

In the second invention (invention 5), examples of the metal oxide include an oxide of an alkali metal such as lithium oxide (Li ₂ O), an oxide of an alkaline earth metal such as magnesium oxide (MgO), Transition metal oxides such as zinc oxide (ZnO), group III metal oxides such as aluminum oxide (Al ₂ O ₃ ), and the like can be used.

In the second invention as well, the crystal growth reaction of the gallium nitride is preferably performed at a reaction temperature of 700 ° C. or higher.
In this case, crystal growth of gallium nitride can be further promoted.
In addition, it is preferable that said reaction temperature is 800 degrees C or less from a viewpoint of suppression of decomposition | disassembly of a gallium nitride.

(Example 1)
A method for producing gallium nitride according to an embodiment of the present invention will be described with reference to FIGS.
In the gallium nitride manufacturing method of this example, gallium nitride is crystal-grown by reacting gallium oxide and lithium nitride in a gallium bath.

Hereinafter, the manufacturing method of this example will be specifically described with reference to FIG.
In a nitrogen-filled glove box, 0.434 g (2.31 mmol) of gallium oxide (Ga ₂ O ₃ : Kishida chemistry: purity 99.999%) and 0.322 g of lithium nitride (Li ₃ N: Aldrich, purity unknown) ( 9.24 mmol) and weighed well. The mixture and 0.161 g (2.31 mmol) of gallium (Ga: manufactured by Nacalai Tesque: purity 99.9999%) were added to the graphite crucible 1.
That is, the molar ratio of gallium oxide, lithium nitride, and gallium was 1: 4: 1.

Next, the graphite crucible 1 was left still in the stainless steel pressure vessel 2 shown in FIG. The pressure vessel 2 was set in the electric furnace 3 and a vacuum hose was connected via a valve 42 attached to the nitrogen gas pipe 4, and the inside of the pressure vessel was reduced to 0.2 Torr (26.6 Pa) by a vacuum pump ( Arrow D).
Next, the valve 42 was closed, the valve 41 was opened, and nitrogen gas 5 (manufactured by Taiyo Nissan: purity 99.9995%) was introduced into the pressure vessel 2 and pressurized at a pressure of 0.4 MPa. Thereby, the inside of the pressure vessel 2 was made a non-oxygen atmosphere (nitrogen atmosphere) having an oxygen concentration of 0.001 vol%.

Next, the pressure vessel 2 was heated to a predetermined temperature at a heating rate of 550 ° C./hour while being pressurized with nitrogen, and held for 48 hours. At this time, the predetermined temperatures were 650 ° C., 700 ° C., 750 ° C., and 800 ° C., respectively, and the four samples were processed under four different conditions.
Thereafter, it was cooled to room temperature at a cooling rate of 60 ° C./hour. After completion of the reaction, the product 6 in the graphite crucible 1 in the pressure vessel 2 was taken out. Alcoholic 1N hydrochloric acid was added to the product 6 to dissolve by-product lithium oxide. The solution was filtered through a filter paper to obtain a solid product.

  The solid product was subjected to X-ray diffraction using RINT-Ultima manufactured by Rigaku Corporation. The obtained X-ray diffraction data was identified using a JCPDS card. As a result, as shown in FIG. 2, GaN (100), (002), and (101) diffraction peaks were obtained, confirming the formation of gallium nitride.

  The four curves in FIG. 2 show the X-ray diffraction data of the products obtained at the reaction temperatures of 650 ° C., 700 ° C., 750 ° C., and 800 ° C. in order from the bottom. In FIG. 2, ◯ represents the diffraction peak of GaN. Note that ◇ represents the diffraction peak of GaOOH, and ● represents the diffraction peak of the sample substrate.

  When this gallium nitride was observed with a scanning electron microscope (SEM), as shown in FIG. 3, it was a granular crystal of several μm at a reaction temperature of 650 ° C., but as shown in FIG. 4, FIG. 5, and FIG. Above ℃, a GaN crystal grown to several tens to 100 μm size was obtained.

Thus, according to this example, gallium nitride can be crystal-grown at low temperature and low pressure. It can be seen that gallium nitride crystal growth can be promoted by setting the reaction temperature to 700 ° C. or higher. .

(Example 2)
In this example, gallium nitride was manufactured under three conditions by changing the molar ratio of gallium oxide, lithium nitride, and gallium.
That is, gallium oxide and lithium nitride were mixed in the same manner as in Example 1, and the mixture was put into the graphite crucible 1 together with gallium. Then, the molar ratio of gallium oxide, lithium nitride and gallium at that time is 0.5: 4: 1, 1: 4: 1, and 1.5: 4: 1. Prepared.
Gallium nitride was produced in the same manner as in Example 1 under these three conditions. The reaction treatment temperature was 750 ° C.

  The obtained product 6 was subjected to X-ray diffraction in the same manner as in Example 1. As a result, diffraction peaks of GaN (100), (002), and (101) were obtained as shown in FIG. The production of gallium was confirmed. In particular, a sample having a small gallium oxide molar ratio of 0.5 or 1.0 has a large (002) diffraction peak, indicating that a gallium nitride plate crystal has grown.

  The three curves in FIG. 7 show the molar ratio of gallium oxide, lithium nitride and gallium in the order from the top (0.5: 4: 1), (1: 4: 1), (1.5: 4: 1). ) Shows the X-ray diffraction data of the product obtained. In FIG. 7, ◯ represents the diffraction peak of GaN. The black circles are diffraction peaks on the sample substrate.

  When this gallium nitride was observed by SEM, when the molar ratio of gallium oxide was as small as 0.5 and 1.0, a GaN crystal exceeding 100 μm was obtained as shown in FIGS. On the other hand, when the molar ratio of gallium oxide was as high as 1.5, only a small crystal of about 10 μm was obtained as shown in FIG.

  From the above results, it can be seen that the molar ratio of gallium oxide to lithium nitride is preferably ¼ or less. That is, when the molar ratio of gallium oxide to lithium nitride is ¼ or less, gallium nitride crystal growth occurs effectively, and a sufficiently large gallium nitride crystal can be obtained. On the other hand, if the amount of gallium oxide is too large, too many gallium nitride nuclei are generated in the initial stage, and there is a possibility that a gallium nitride crystal centering on each nuclei will be difficult to grow. That is, it is considered that a relatively small number of gallium nitride crystals can be formed. Further, if the amount of gallium oxide is too large, lithium nitride is consumed at an early stage, so that it is considered that subsequent crystal growth of gallium nitride may be difficult to proceed.

(Example 3)
In this example, as shown in FIG. 11 and FIG. 12, an indium bath is used instead of the gallium bath shown in the first and second embodiments, and gallium oxide is reacted with lithium nitride in the indium bath. This is an example of crystal growth.

That is, first, 0.783 g (4.18 mmol) of gallium oxide (Kishida chemistry: purity 99.999%) and 0.582 g (16.72 mmol) of lithium nitride (made by Aldrich, purity unknown) were weighed in a nitrogen-filled glove box. And mixed well. 0.48 g (4.18 mmol) of the mixture and indium (In: manufactured by Nacalai Tesque: purity 99.9999%) were added to the graphite crucible 1.
That is, the molar ratio of gallium oxide, lithium nitride, and indium was 1: 4: 1.

And operation similar to Example 1 was performed, the pressure vessel 2 was heated to 800 degreeC with the temperature increase rate of 550 degreeC / hour, pressurizing nitrogen, and was hold | maintained for 48 hours. Thereafter, it was cooled to room temperature at a cooling rate of 60 ° C./hour. After completion of the reaction, a solid product was obtained in the same manner as in Example 1.
The obtained solid product was subjected to X-ray diffraction using RINT-Ultima manufactured by Rigaku Corporation. The obtained X-ray diffraction data was identified using a JCPDS card. As a result, as shown in FIG. 11, the diffraction peaks of GaN (100), (002), and (101) were obtained, confirming the production of gallium nitride. In FIG. 11, ◯ represents the diffraction peak of GaN. The black circles are diffraction peaks on the sample substrate.
When this gallium nitride was observed with a scanning electron microscope (SEM), it was found that a GaN crystal grown to a size of several tens to 100 μm was obtained as shown in FIG.

As described above, not only a gallium bath but also a gallium nitride crystal that has grown greatly can be obtained by reacting gallium oxide and lithium nitride in an indium bath that is liquid at the reaction temperature.
Note that even if the metal bath is a metal other than gallium or indium, a crystal of gallium nitride can be grown greatly if it is a metal that is liquid at the reaction temperature.

Example 4
In this example, as shown in FIGS. 13 and 14, lithium oxide is used as an oxygen source instead of gallium oxide shown in the first to third embodiments, and lithium oxide and lithium nitride are reacted in a gallium bath to gallium nitride. This is an example of crystal growth.

First, weigh 0.0597 g (1.99 mmol) of lithium oxide (Kishida chemistry: purity 95.0%) and 1.108 g (31.8 mmol) of lithium nitride (Aldrich: purity unknown) in a nitrogen-filled glove box. Mixed. The mixture and 0.554 g (7.95 mmol) of gallium (Ga: manufactured by Nacalai Tesque: purity 99.999%) were added to the platinum crucible. That is, the molar ratio of lithium oxide, lithium nitride, and gallium was 0.25: 4: 1.
In this example, unlike Example 1, a platinum crucible was used instead of the graphite crucible 1. This is because when a graphite crucible is used, lithium oxide and the graphite crucible react to generate lithium carbide.

And operation similar to Example 1 was performed, the pressure vessel 2 was heated to 800 degreeC with the temperature increase rate of 550 degreeC / hour, pressurizing nitrogen, and was hold | maintained for 48 hours. Thereafter, it was cooled to room temperature at a cooling rate of 60 ° C./hour. After completion of the reaction, a solid product was obtained in the same manner as in Example 1.
The obtained solid product was subjected to X-ray diffraction using the same X-ray diffractometer as in Example 1. The obtained X-ray diffraction data was identified using a JCPDS card. As a result, as shown in FIG. 13, GaN (100), (002), and (101) diffraction peaks were obtained, confirming the formation of gallium nitride. In FIG. 13, ◯ represents the diffraction peak of GaN. The black circles are diffraction peaks on the sample substrate.

Observation of this gallium nitride with a scanning electron microscope (SEM) revealed that a GaN crystal grown to a size of several tens of μm or more was obtained as shown in FIG.
As described above, by using a liquid gallium bath, not only gallium oxide but also an oxide of an alkali metal such as lithium oxide can be used as an oxygen source, so that a gallium nitride crystal can be grown greatly.

(Example 5)
In this example, as shown in FIGS. 15 and 16, magnesium oxide is used as an oxygen source in place of the gallium oxide shown in the first to third embodiments, and gallium nitride is reacted by reacting lithium oxide and lithium nitride in a gallium bath. This is an example of crystal growth.
Magnesium oxide (Kishida chemistry: purity 99.0%) 0.319 g (3.46 mmol) and lithium nitride (Aldrich: purity unknown) 0.482 g (13.84 mmol) were weighed and mixed well in a nitrogen-filled glove box. . The mixture and 0.241 g (3.46 mmol) of gallium (Ga: manufactured by Nacalai Tesque: purity 99.999%) were added to the graphite crucible 1.
That is, the molar ratio of magnesium oxide, lithium nitride, and gallium was 1: 4: 1.

And operation similar to Example 1 was performed, the pressure vessel 2 was heated to 800 degreeC with the temperature increase rate of 550 degreeC / hour, pressurizing nitrogen, and was hold | maintained for 48 hours. Thereafter, it was cooled to room temperature at a cooling rate of 60 ° C./hour. After completion of the reaction, a solid product was obtained in the same manner as in Example 1.
The obtained solid product was subjected to X-ray diffraction using the same X-ray diffractometer as in Example 1. The obtained X-ray diffraction data was identified using a JCPDS card. As a result, as shown in FIG. 15, the diffraction peaks of GaN (100), (002), and (101) were obtained, confirming the formation of gallium nitride. In FIG. 15, ◯ represents the diffraction peak of GaN. The black circles are diffraction peaks on the sample substrate.

Observation of this gallium nitride with a scanning electron microscope (SEM) revealed that a GaN crystal grown to a size of several tens of μm was obtained as shown in FIG.
As described above, by using a liquid gallium bath, not only gallium oxide but also an oxide of an alkaline earth metal such as magnesium oxide can be used as an oxygen source, so that a gallium nitride crystal can be grown greatly. .

(Example 6)
In this example, as shown in FIGS. 17 and 18, zinc oxide is used as an oxygen source in place of the gallium oxide shown in the first to third embodiments, and gallium nitride is reacted by reacting zinc oxide and lithium nitride in a gallium bath. This is an example of crystal growth.
In a nitrogen-filled glove box, 0.23 g (2.83 mmol) of zinc oxide (Kishida Chemical: 99.5%) and 0.394 g (11.32 mmol) of lithium nitride (Aldrich: purity unknown) were weighed and mixed well. . The mixture and 0.197 g (2.83 mmol) of gallium (Ga: manufactured by Nacalai Tesque: purity 99.999%) were added to the graphite crucible 1.
That is, the molar ratio of zinc oxide, lithium nitride, and gallium was 1: 4: 1.

And operation similar to Example 1 was performed, the pressure vessel 2 was heated to 800 degreeC with the temperature increase rate of 550 degreeC / hour, pressurizing nitrogen, and was hold | maintained for 48 hours. Thereafter, it was cooled to room temperature at a cooling rate of 60 ° C./hour. After completion of the reaction, a solid product was obtained in the same manner as in Example 1.
The obtained solid product was subjected to X-ray diffraction using the same X-ray diffractometer as in Example 1. The obtained X-ray diffraction data was identified using a JCPDS card. As a result, GaN (100), (002), and (101) diffraction peaks were obtained as shown in FIG. 17, confirming the formation of gallium nitride. In FIG. 17, ◯ represents the diffraction peak of GaN. The black circles are diffraction peaks on the sample substrate.

Observation of the gallium nitride with a scanning electron microscope (SEM) revealed that a GaN crystal grown to a size of several tens of μm was obtained as shown in FIG.
As described above, by using a liquid gallium bath, not only gallium oxide but also a transition metal oxide such as zinc oxide can be used as an oxygen source, so that a gallium nitride crystal can be grown greatly.

(Example 7)
In this example, as shown in FIGS. 19 and 20, aluminum oxide is used as an oxygen source instead of the gallium oxide shown in the first to third embodiments, and gallium nitride is reacted by reacting aluminum oxide and lithium nitride in a gallium bath. This is an example of crystal growth.
In a nitrogen-filled glove box, 0.23 g (2.83 mmol) of aluminum oxide (Showa Denko UA-5053: purity 99.995%) and 0.394 g (11.32 mmol) of lithium nitride (made by Aldrich: purity unknown) were weighed. Mix well. The mixture and 0.197 g (2.83 mmol) of gallium (Ga: manufactured by Nacalai Tesque: purity 99.999%) were added to the graphite crucible 1.
That is, the molar ratio of zinc oxide, lithium nitride, and gallium was 1: 4: 1.

And operation similar to Example 1 was performed, the pressure vessel 2 was heated to 800 degreeC with the temperature increase rate of 550 degreeC / hour, pressurizing nitrogen, and was hold | maintained for 48 hours. Thereafter, it was cooled to room temperature at a cooling rate of 60 ° C./hour. After completion of the reaction, a solid product was obtained in the same manner as in Example 1.
The obtained solid product was subjected to X-ray diffraction using the same X-ray diffractometer as in Example 1. The obtained X-ray diffraction data was identified using a JCPDS card. As a result, as shown in FIG. 19, GaN (100), (002), and (101) diffraction peaks were obtained, confirming the formation of gallium nitride. Further, since a diffraction pattern of unreacted aluminum oxide was observed, the reaction between aluminum oxide and lithium nitride is considered to be slower than that of gallium oxide. In FIG. 19, ◯ represents the diffraction peak of GaN, and ◎ represents the diffraction peak of Al ₂ O ₃ . The black circles are diffraction peaks on the sample substrate.

Observation of this gallium nitride with a scanning electron microscope (SEM) revealed that a GaN crystal grown to a size of several tens of μm was obtained as shown in FIG.
As described above, by using a liquid gallium bath, not only gallium oxide but also a group III metal oxide such as aluminum oxide can be used as an oxygen source, so that a gallium nitride crystal can be grown greatly.

FIG. 3 is an explanatory diagram of a method for producing gallium nitride in Example 1. The diagram showing the X-ray diffraction data of the product in Example 1. The SEM photograph of the product (GaN) in the case of the reaction temperature of 650 degreeC in Example 1. FIG. The SEM photograph of the product (GaN) in case the reaction temperature in Example 1 is 700 degreeC. The SEM photograph of the product (GaN) in case the reaction temperature in Example 1 is 750 degreeC. The SEM photograph of the product (GaN) in case the reaction temperature in Example 1 is 800 degreeC. The diagram showing the X-ray diffraction data of the product in Example 2. The SEM photograph of the product (GaN) in case the molar ratio of gallium oxide, lithium nitride, and gallium in Example 2 is 0.5: 4: 1. The SEM photograph of the product (GaN) in the case where the molar ratio of gallium oxide, lithium nitride and gallium in Example 2 is 1: 4: 1. The SEM photograph of the product (GaN) when the molar ratio of gallium oxide, lithium nitride, and gallium in Example 2 is 1.5: 4: 1. The diagram showing the X-ray diffraction data of the product in Example 3. The SEM photograph of the product (GaN) in Example 3. The diagram showing the X-ray diffraction data of the product in Example 4. The SEM photograph of the product (GaN) in Example 4. The diagram showing the X-ray diffraction data of the product in Example 5. The SEM photograph of the product (GaN) in Example 5. The diagram showing the X-ray diffraction data of the product in Example 6. The SEM photograph of the product (GaN) in Example 6. The diagram showing the X-ray diffraction data of the product in Example 7. The SEM photograph of the product (GaN) in Example 7.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Graphite crucible 2 Pressure vessel 3 Electric furnace 4 Nitrogen gas piping 5 Nitrogen gas 6 Product

Claims (6)

  A method for producing gallium nitride, characterized in that gallium nitride is crystal-grown by reacting gallium oxide and lithium nitride in a liquid metal bath.   2. The method for producing gallium nitride according to claim 1, wherein the metal bath is made of gallium.   3. The method for producing gallium nitride according to claim 1, wherein the crystal growth reaction of gallium nitride is performed at a reaction temperature of 700 ° C. or higher.   4. The method for producing gallium nitride according to claim 1, wherein the molar ratio of the gallium oxide to the lithium nitride is ¼ or less.   A method for producing gallium nitride, characterized in that a metal oxide and lithium nitride are reacted in a liquid gallium bath to crystallize gallium nitride.   6. The method for producing gallium nitride according to claim 5, wherein the crystal growth reaction of gallium nitride is performed at a reaction temperature of 700 ° C. or higher.