JP2014152066A - Growth method of gallium nitride single crystal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a growth method of a gallium nitride single crystal using a novel melt which can prevent wetting-up of the melt and deterioration of a reaction vessel, and which is not intermingled into a grown GaN single crystal as an impurity.SOLUTION: In a growth method, a melt is obtained by melting a raw material comprising tin, gallium, and one or more kinds of metals selected from a group comprising alkali metals and alkaline earth metals, and the melt and a gas phase containing a nitrogen source as an indispensable are heated in the contact state, to thereby grow a gallium nitride single crystal.

Description

  The present invention relates to a method for growing a GaN single crystal.

  In recent years, in order to reduce power consumption, it is required to increase the efficiency of power devices and light emitting devices. In order to meet this requirement, the use of III-V group nitrides such as GaN, AlN, and AlGaN, which have excellent electrical characteristics, has been studied as device substrates. In particular, GaN is a material with high expectation for practical use as an electronic material.

In general, a metal nitride has a low free energy of formation, and when the metal nitride is synthesized in a gas phase, the difference in free energy of formation between the source gas and the final product becomes large. For this reason, the metal nitride fine powder can be synthesized in a large amount in a short time in the gas phase. Actually, fine powder ceramics such as boron nitride, aluminum nitride, and zinc nitride are industrially synthesized in the gas phase.
However, it is difficult to produce metal nitride single crystals with high crystallinity and large size. In order to obtain a single crystal of metal nitride having a high crystallinity and a large size, it is necessary to grow the crystal for a long time at a high temperature.

In the production of GaN single crystals, it is known that GaN single crystals can be efficiently obtained by using ammonia having high reactivity as a nitriding source. At present, as a method for growing a GaN single crystal which is close to practical use, a hydride vapor phase epitaxy method (HVPE method) can be mentioned. The HVPE method is a method of heteroepitaxially growing a GaN single crystal on a heterogeneous substrate by reacting GaCl ₃ gas chlorinated with metal Ga and ammonia (NH ₃ ) at about 1000 ° C.
However, the HVPE method has a complicated manufacturing process and requires an apparatus having a complicated configuration. Further, when growing a GaN single crystal, there is a problem that GaCl ₃ and NH ₃ react with each other to generate hydrogen chloride (HCl), which requires a hydrogen chloride gas abatement facility. Therefore, the HVPE method has a problem that the equipment cost becomes high.

  It is known that Ga is nitrided by reacting ammonia as a nitrogen source with the Ga melt. However, when the Ga melt is nitrided with ammonia, a GaN single crystal is rapidly formed on the surface of the Ga melt, and the entire surface of the Ga melt is covered with the GaN single crystal. As a result, Ga and ammonia could not be contacted, and the nitriding reaction of Ga stopped, and only a very small microcrystalline GaN single crystal was obtained.

  Also, when growing a GaN single crystal by nitriding the Ga melt with ammonia, the Ga melt wets and cannot maintain the shape of the melt, and the Ga melt flows out of the container. Therefore, it has been difficult to stably grow a GaN single crystal for a long time. Therefore, a method of growing a GaN single crystal by adding a metal other than Ga to the Ga melt and nitriding the melt is being studied.

  A method of adding Ge to the Ga melt (for example, see Non-Patent Document 1) and a method of adding Bi to the Ga melt (for example, see Non-Patent Document 2) have been studied.

  The method disclosed in Non-Patent Document 1 has a problem that Ge is easily mixed as an impurity in the grown GaN single crystal.

  In the method shown in Non-Patent Document 2, since the reactivity of Bi vapor generated when producing a GaN single crystal is high, there is a possibility that the choice of material for the reaction vessel is narrowed and the configuration of the apparatus is limited. It was. Quartz, which is a common material for reaction vessels, has the property that strength decreases when it comes into contact with Bi vapor, and therefore there is a problem that reaction vessels using quartz cannot be used.

Journal of Crystal Growth vol. 310 p738 (2008) Journal of Electrochemical Society vol. 119 p1727 (1972)

As described above, the conventional GaN single crystal growth method has a problem that the configuration of the apparatus tends to be complicated and a problem that it is difficult for the GaN single crystal to grow stably for a long time due to the wetting of the melt. . Further, when Ge or Bi is added to the Ga melt, there is a fear that it will be mixed into the grown GaN single crystal as an impurity, and there is a possibility that the vapor will deteriorate the reaction vessel.
The present invention provides a method for growing a GaN single crystal using a novel melt that solves the above-described problems.

  In order to solve the above-mentioned problems, the present inventors have repeatedly studied and obtained a novel melt composed of tin, gallium, and one or more metals selected from the group consisting of alkali metals and alkaline earth metals. The inventors have found that a single crystal of gallium nitride can be used to grow, and have come up with the present invention.

[1] Obtaining a melt by melting a raw material consisting of tin, gallium, and one or more metals selected from the group consisting of alkali metals and alkaline earth metals,
Next, a GaN single crystal growth method characterized in that a gallium nitride single crystal is grown by heating the melt and a vapor phase indispensable for a nitrogen source in contact.
[2] The method for growing a gallium nitride single crystal according to [1], wherein at least one metal selected from the group consisting of the alkali metal and the alkaline earth metal is barium.
[3] The raw material is a molar amount of one or more metals selected from the group consisting of the alkali metal and the alkaline earth metal in the charged molar amount when adjusting as a raw material for the melt. The method for growing a GaN single crystal according to [1] or [2], which is 1 to 5 times the amount.
[4] The method for growing a GaN single crystal according to any one of [1] to [3], wherein the nitrogen source is ammonia.
[5] The method for growing a GaN single crystal according to any one of [1] to [4], wherein the partial pressure of ammonia in the gas phase, which essentially requires the nitrogen source, is 0.03 to 1 atm.
[6] The method for growing a GaN single crystal according to any one of [1] to [5], wherein the heating is heating to 900 to 1100 ° C.

  According to the present invention, there is provided a method for growing a GaN single crystal using a novel melt that does not cause the melt to wet, does not degrade the reaction vessel, and does not enter the grown GaN single crystal as an impurity. be able to.

FIG. 1 is a schematic diagram for explaining an example of a GaN single crystal growth apparatus used in the GaN single crystal growth method of the present invention.

  The present invention provides a melt obtained by melting a raw material consisting of tin, gallium, and one or more metals selected from the group consisting of alkali metals and alkaline earth metals, then the melt, nitrogen The present invention relates to a manufacturing method in which a gallium nitride single crystal is grown by heating in contact with a gas phase that requires a source.

(Melt)
A melt is obtained by melting a raw material consisting of tin (Sn), gallium (Ga), and one or more metals selected from the group consisting of alkali metals and alkaline earth metals.
The one or more metals selected from the group consisting of alkali metals and alkaline earth metals are preferably lithium (Li), potassium (K), sodium (Na), calcium (Ca), or barium (Ba). Earth metals are more preferred, and Ba is even more preferred. Alkaline earth metals are preferred because they have a high boiling point, are less chemically reactive than alkali metals, and are easy to handle at high temperatures. Ba is preferable because it can form a nitrogen compound to take nitrogen from ammonia and can efficiently supply nitrogen to Ga.

(Gas phase that requires a nitrogen source)
The nitrogen source is preferably ammonia. The gas phase in which the nitrogen source is essential is preferably a gas phase composed of ammonia or a gas phase composed of a mixed gas of ammonia and a diluent gas. The dilution gas may be nitrogen gas or a rare gas such as argon (Ar) gas.
In the gas phase in which a nitrogen source is essential, the growth rate of the GaN single crystal can be improved by changing the partial pressure of the gas containing the nitrogen source in the gas phase. The size of the GaN single crystal can be controlled by adjusting the partial pressure of the gas containing the nitrogen source and the time for growing the GaN single crystal. The partial pressure of the gas containing the nitrogen source in the gas phase, in which the nitrogen source is essential, that is, the partial pressure of ammonia is preferably 0.03 to 1 atm, and more preferably 0.1 to 1 atm. By setting the partial pressure of ammonia within the above range, a sufficient GaN single crystal growth rate can be obtained.

Next, a method for growing a gallium nitride (GaN) single crystal of the present invention will be described.
The melt is adjusted by melting a raw material made of Sn, Ga, and one or more metals selected from the group consisting of alkali metals and alkaline earth metals. That is, Sn, Ga, and one or more metals selected from the group consisting of alkali metals and alkaline earth metals are accommodated in the reaction vessel. For example, Sn, Ga, and one or more metals selected from the group consisting of alkali metals and alkaline earth metals are housed in a crucible, and the crucible is placed in a reaction vessel.

  Next, the reaction is carried out by heating the melt and the gas phase, which essentially requires a nitrogen source, in contact. That is, by setting the reaction vessel in the furnace and heating the inside of the reaction vessel with the furnace while supplying a gas containing a nitrogen source into the reaction vessel, Sn, Ga, alkali metal and alkaline earth in the crucible One or more metals selected from the group consisting of metals are melted to form a melt, and a reaction between the melt and a gas containing a nitrogen source starts.

  The prepared molar amount of the raw material when preparing the raw material for the melt is such that the molar amount of Ga is one or more metals selected from the group consisting of alkali metals and alkaline earth metals (hereinafter referred to as metal A). 1-5 times is preferable with respect to molar amount, and 2-3 times is more preferable. Within the above range, the Ga nitriding reaction can be maintained more stably, and a large GaN single crystal can be easily grown.

The molar amount of Sn is preferably 1 to 100 times, and more preferably 3 to 10 times the molar amount of Ga. Within the above range, when growing a GaN single crystal, wetting can be more reliably suppressed, and rapid nitridation of Ga contained in the melt can be more effectively suppressed.
Here, the molar ratio of Ga to metal A and the molar ratio of Sn to Ga are not the molar ratio in the melt, but the molar ratio of the raw material for the melt (that is, the nitrogen source is essential). The molar ratio before starting the reaction with the gas phase). This is because the molar ratio of Ga to metal A and the molar ratio of Sn to Ga change as the reaction proceeds to produce a GaN single crystal.

  The reaction vessel is preferably heated to a temperature at which the GaN single crystal grows (hereinafter also referred to as a growth temperature), preferably 900 to 1100 ° C., more preferably 950 to 1050 ° C. .

  Then, the inside of the reaction vessel is held at the growth temperature, and a GaN single crystal is grown by a reaction between the melt and a gas containing a nitrogen source in a gas phase that requires a nitrogen source. The holding time of the growth temperature is preferably 1 to 10 hours, more preferably 2 to 5 hours.

  In the present embodiment, the temperature of the reaction vessel (temperature in the reaction vessel) means a temperature measured by a thermocouple installed on the reaction vessel in contact with the reaction vessel.

  The method for growing a GaN single crystal according to the present invention grows a GaN single crystal using a novel melt composed of Sn, Ga, and one or more metals selected from the group consisting of alkali metals and alkaline earth metals. Can be made.

  In the method for growing a GaN single crystal of the present invention, a melt obtained by melting a novel raw material made of Sn, Ga, and one or more metals selected from the group consisting of alkali metals and alkaline earth metals is used. Thus, a GaN single crystal can be grown without causing wetting.

  By including Sn in the melt, wetting can be suppressed. Since Sn is not easily nitrided and there is little risk of consuming nitrogen used for the growth of the GaN single crystal, the presence of Sn is less likely to affect the growth of the GaN single crystal. Sn can form a melt in a wide composition range with Ga, is not easily taken into the growing GaN single crystal, and can be suitably used as a melt material. Further, since Sn is not easily vaporized even at a high temperature close to 1000 ° C., there is little possibility of deteriorating the reaction vessel even when a reaction vessel made of quartz is used.

  In the present invention, since a melt containing Sn, Ga, and one or more metals selected from the group consisting of alkali metals and alkaline earth metals is used, Sn, Ga, and alkali are used on the melt surface. One or more metals selected from the group consisting of metals and alkaline earth metals are exposed. That is, when heated in an atmosphere containing ammonia, rapid nitridation of Ga contained in the melt can be suppressed as compared with the case where only Ga is exposed on the melt surface. Therefore, it can be prevented that the surface of the melt is covered with the GaN single crystal, and the nitriding reaction of Ga is stopped and the growth of the GaN single crystal is stopped.

Next, a manufacturing apparatus applicable to the growth method of the present invention will be described with reference to the drawings. FIG. 1 is a schematic diagram for explaining an example of a growth apparatus for a GaN single crystal.
In FIG. 1, reference numeral 1 denotes a reaction vessel. The reaction vessel 1 is installed and heated in an electric furnace when growing a GaN single crystal. FIG. 1 shows a state in which the reaction vessel 1 is installed in an electric furnace. In FIG. 1, the code | symbol 4 has shown the heater of the electric furnace.

The reaction vessel 1 is made of quartz. The reaction vessel 1 has a cylindrical shape extending in a substantially horizontal direction, and as shown in FIG. 1, one end side (right side in FIG. 1) is closed and the other end side (left side in FIG. 1) is opened. ing.
The opening of the reaction vessel 1 is sealed by a detachable flange 5. An O-ring (not shown) is preferably installed between the flange 5 and the reaction vessel 1 in order to ensure the hermeticity in the reaction vessel 1. The reaction vessel 1 is preferably provided with a heat shield plate that protects the O-ring from thermal radiation associated with the growth of the GaN single crystal.

  A crucible 3 is installed in the reaction vessel 1. The crucible 3 is made of a material that does not change the composition of the melt contained in the crucible 3 when growing the GaN single crystal. For example, a crucible made of BN is preferable. The crucible 3 is installed on a substantially horizontal support (not shown) made of quartz. The crucible 3 contains a melt composed of Sn, Ga, and one or more metals selected from the group consisting of alkali metals and alkaline earth metals.

  As shown in FIG. 1, a lining 2 is formed in the reaction vessel 1 along the inner wall excluding the vicinity of the opening. The lining 2 prevents the reaction vessel 1 made of quartz and the vapor of one or more metals selected from the group consisting of alkali metals and alkaline earth metals from reacting to reduce the strength of the reaction vessel 1. As the material of the lining 2, Ni or Pt is preferable.

  The reaction vessel 1 is provided with a source gas introduction pipe 6 for supplying a gas containing ammonia into the reaction vessel 1. As shown in FIG. 1, the source gas introduction pipe 6 is formed through the flange 5. The supply port 6a of the source gas introduction pipe 6 is disposed at a position overlapping the position where the crucible 3 is installed in a plan view. The source gas introduction pipe 6 is connected to an ammonia supply pipe (not shown) and a dilution gas supply pipe (not shown) outside the reaction vessel 1. The source gas introduction pipe 6 can supply a gas containing a nitrogen source composed of ammonia and a diluent gas such as nitrogen gas or rare gas contained as necessary from the supply port 6a at a predetermined partial pressure. In addition, a mass flow meter (not shown) is attached to the source gas introduction pipe 6, and the flow rate of the source gas supplied from the supply port 6a can be adjusted to a predetermined flow rate.

The source gas introduction pipe 6 is connected to an exhaust pipe 8 for evacuation outside the reaction vessel 1.
The reaction vessel 1 is provided with an exhaust pipe 7 that exhausts the atmospheric gas in the reaction vessel 1 through the flange 5.

Next, a method for growing a GaN single crystal using the growth apparatus shown in FIG. 1 will be described as an example of the method for growing a GaN single crystal of the present invention.
First, in the crucible 3, at least one metal selected from the group consisting of Sn and Ga, which are raw materials for the melt, and alkali metals and alkaline earth metals is accommodated. In the present embodiment, the raw material for the melt is accommodated in the crucible 3 in a glove box having a high-purity Ar atmosphere.

  Next, the crucible 3 containing the raw material for the melt is placed on a support base (not shown) in the reaction vessel 1 shown in FIG. 1, and the opening of the reaction vessel 1 is sealed by the flange 5. In the present embodiment, the crucible 3 is installed in the reaction vessel 1 and the reaction vessel 1 is sealed in a glove box having a high-purity Ar atmosphere. Next, the source gas introduction pipe 6 and the exhaust pipe 7 of the reaction vessel 1 are closed to shut off the inside of the reaction vessel 1 from the outside air.

  Thereafter, in the present embodiment, the sealed reaction vessel 1 is taken out from the glove box. Next, the gas in the reaction vessel 1 is evacuated through the evacuation exhaust pipe 8 and the source gas introduction pipe 6, and the gas in the reaction vessel 1 is evacuated through the exhaust pipe 7. Apply vacuum. Oxygen in the reaction vessel 1 is removed by exhausting the gas in the reaction vessel 1 to a vacuum.

  Next, the reaction vessel 1 is installed in an electric furnace. After that, the gas in the reaction vessel 1 is supplied to the crucible 3 installed in the reaction vessel 1 from the supply port 6 a with the valve of the raw material gas introduction pipe 6 opened, and the temperature in the reaction vessel 1 is adjusted by the heater 4 to the GaN single crystal Heat to the growth temperature. The raw material in the crucible 3 is melted by heating the reaction vessel 1 to obtain a melt, and the reaction between the melt and ammonia starts.

Thereafter, the inside of the reaction vessel 1 is maintained at the growth temperature of the GaN single crystal for a predetermined time, and the GaN single crystal is grown by heating the melt and ammonia in contact with each other.
In FIG. 1, the temperature in the reaction vessel 1 when growing the GaN single crystal is measured by a thermocouple installed on the reaction vessel 1 in contact with the reaction vessel 1.

  The inside of the reaction vessel 1 when growing the GaN single crystal is an atmosphere containing ammonia. In this embodiment, the ammonia contained in the atmosphere containing ammonia adjusts the supply amount of ammonia from an ammonia supply pipe (not shown) and the supply amount of dilution gas from a dilution gas supply pipe (not shown). Thus, a predetermined partial pressure can be obtained.

  Further, the flow rate of the gas containing ammonia supplied from the supply port 6 a when growing the GaN single crystal can be adjusted using a mass flow meter attached to the source gas introduction pipe 6.

  After holding for a predetermined time at the growth temperature of the GaN single crystal, the output from the heater 4 of the electric furnace is stopped or lowered to lower the temperature in the reaction vessel 1. And after the temperature in the reaction container 1 falls to 600 degrees C or less, the valve | bulb of the raw material gas introduction pipe | tube 6 is closed, and supply of the gas containing ammonia is stopped. By reducing the temperature in the reaction vessel 1 to 600 ° C. or lower and then stopping the supply of the gas containing ammonia, it is possible to prevent the generated GaN single crystal from being decomposed.

[Function and effect]
The reason why the method of the present invention can efficiently produce a larger GaN single crystal than the conventional method is not necessarily clear, but the present inventor thinks that the reaction proceeds by the following mechanism. That is, the melt in the present invention contains one or more metals selected from the group consisting of alkali metals and alkaline earth metals. Due to the presence of the metal, nitrogen can be effectively supplied into the melt. More specifically, in a region where at least one metal selected from the group consisting of alkali metals and alkaline earth metals is exposed on the melt surface, the metal effectively removes nitrogen from the nitrogen source and performs nitridation. Things are synthesized. The nitride stably maintains the nitriding reaction of Ga by supplying nitrogen to non-nitrided Ga in the melt. As a result, a GaN single crystal can be effectively grown. Therefore, it is estimated that larger GaN single crystals can be grown than the conventional method of nitriding Ga melt.

"Example 1"
A GaN single crystal was grown by the following method using the growth apparatus shown in FIG.
First, in a glove box having a high-purity Ar atmosphere, 1500 mg of Sn, 200 mg of Ga, and 150 mg of Ba as a raw material for melt are put into a crucible 3 made of BN having an inner diameter of 26 mm and a depth of 15 mm. Housed.
In preparing the raw material for the melt, the charged molar amount of the raw material is 2.6 times the molar amount of Ga with respect to the molar amount of Ba and the molar amount of Sn is 4. It was 4 times.

  Next, the crucible 3 containing the raw material for the melt was placed on a support base in the reaction vessel 1 having a diameter of 48 mm and a length of 330 mm, and the opening of the reaction vessel 1 was sealed with the flange 5. In addition, installation of the crucible 3 in the reaction vessel 1 and sealing of the reaction vessel 1 were performed in a glove box having a high-purity Ar atmosphere. Subsequently, the valve | bulb of the raw material gas introduction pipe | tube 6 and the exhaust pipe 7 of the reaction container 1 was closed, and the inside of the reaction container 1 was interrupted | blocked with external air.

  Thereafter, the sealed reaction vessel 1 is taken out from the inside of the glove box, the gas in the reaction vessel 1 is exhausted through the exhaust pipe 8 for evacuation and the source gas introduction pipe 6, and the reaction container is provided through the exhaust pipe 7. The gas in 1 was evacuated and evacuated to remove oxygen in the reaction vessel 1.

Next, the reaction vessel 1 was installed in an electric furnace. Thereafter, the valve of the raw material gas introduction pipe 6 is opened, and the temperature in the reaction vessel 1 is adjusted by the heater 4 while supplying ammonia (partial pressure 1 atm) to the crucible 3 installed in the reaction vessel 1 from the supply port 6a. Heated to 1000 ° C.
Thereafter, the temperature in the reaction vessel 1 was maintained at 1000 ° C. for 3 hours.

  Thereafter, the output from the heater 4 of the electric furnace was decreased to lower the temperature in the reaction vessel 1 to 600 ° C. or less, and then the valve of the raw material gas introduction pipe 6 was closed to stop the supply of ammonia. The GaN single crystal growth step is completed through the above steps.

The inside of the crucible 3 was observed, and it was confirmed that no melt wet-up occurred. Here, “wetting up of the melt” means that the melt obtained by melting the raw material rises against the gravity on the side wall surface of the container containing the raw material. That is, the melt rises along the side wall surface in the crucible 3 from the bottom surface of the crucible 3 toward the upper edge.
In the embodiment, the crucible 3 having an inner diameter of 26 mm and a depth of 15 mm is visually observed, and when the melt flows out of the crucible 3, it is determined that there is wetting up, and the melt flows out of the crucible 3. When it did not flow out, it was judged that there was no wetting.

In the crucible 3, there was a massive alloy in which gray crystals were densely grown on the surface. Using energy dispersive X-ray spectroscopy (EDX), the composition of crystals grown on the surface of the massive alloy was analyzed. In addition, crystals grown on the surface of the massive alloy were confirmed by X-ray diffraction (XRD). From the results of EDX and XRD, it was confirmed that the GaN single crystal was grown and that Sn and Ba were not mixed in the grown GaN single crystal.
When a crystal (GaN single crystal) grown on the surface of the massive alloy was observed using a scanning electron microscope (SEM), it was a crystal having a side of 1 to 5 μm and a height of 50 μm.

"Examples 2 and 3"
In Examples 2 and 3, the partial pressure of ammonia was controlled by supplying a mixed gas of ammonia and nitrogen and controlling the flow ratio of ammonia and nitrogen in the mixed gas. That is, in Example 2, the partial pressure of ammonia in the GaN single crystal growth step was set to 0.1 atm, and the partial pressure of nitrogen was set to 0.9 atm. In Example 3, the partial pressure of ammonia was 0.03 atm, and the nitrogen partial pressure was 0.97 atm. A GaN single crystal growth step was performed in the same manner as in Example 1 except for the partial pressure of ammonia.

After the GaN single crystal growth step in Examples 2 and 3, the inside of each crucible 3 was observed. As a result, also in Examples 2 and 3, it was confirmed from the above-described determination criteria that no melt wetting occurred.
Also in Examples 2 and 3, the crucible 3 had a massive alloy in which gray crystals were densely grown on the surface. As a result of analyzing the crystal grown on the surface of the bulk alloy using EDX and XRD, it was confirmed that the GaN single crystal was grown and that Sn and Ba were not mixed in the grown GaN single crystal.
Observation of the GaN single crystal using SEM revealed that Example 2 was a crystal having a size of about 1 μm and a layer thickness of about 10 μm. Example 3 was a crystal having a size of 1 μm or less.

(Results of Examples 1 to 3)
Table 1 below shows the raw materials for the melts of Examples 1 to 3 (referred to as melt raw materials in Table 1), the partial pressure of ammonia, the presence or absence of GaN single crystal growth, the presence or absence of melt wetting, and the reaction. The result of presence or absence of deterioration of a container is shown.

"Comparative Example 1"
A GaN single crystal was grown in the same manner as in Example 1 except that only 270 mg of Ga was contained in the crucible 3 as a raw material for the melt, and then a GaN single crystal growth step in the same manner as in Example 1. Ended.
In Comparative Example 1, the inside of the crucible 3 after the growth step of the GaN single crystal was observed. As a result, in Comparative Example 1, it was confirmed that the melt wets up from the above-described determination criteria. Most of the melt overcame the side wall surface of the crucible 3 and flowed out of the crucible 3.
In Comparative Example 1, in the crucible 3, a small amount of a massive alloy having gray crystallites grown on the surface remained. As a result of analyzing the microcrystals grown on the surface of the massive alloy using EDX and XRD, it was a GaN single crystal.

"Comparative Example 2"
Example 1 except that 1000 mg of Ga and 158 mg of Bi were housed in the crucible 3 as the raw material for the melt, the partial pressure of ammonia was 0.1 atm, and the partial pressure of nitrogen was 0.9 atm. Similarly, a GaN single crystal growth step was performed. The inside of the crucible 3 was observed, and it was confirmed from the above criteria that the melt did not rise.
In the crucible 3, there was a massive alloy in which gray crystals were densely grown on the surface. As a result of analyzing the crystal grown on the surface of the massive alloy using EDX and XRD, the growth of the GaN single crystal was confirmed.
However, when the reaction vessel 1 after the completion of the growth process of the GaN single crystal was visually observed, the quartz constituting the reaction vessel 1 was devitrified and the reaction vessel was deteriorated.

“Comparative Example 3”
A GaN single crystal growth step was performed in the same manner as in Example 1 except that only 3000 mg of Sn and 270 mg of Ga were contained in the crucible 3 as raw materials for the melt. The inside of the crucible 3 was observed, and it was confirmed from the above criteria that the melt did not rise.
There was only a massive alloy in the crucible 3. The bulk alloy was analyzed using EDX and XRD, but the GaN single crystal was not grown and only the Sn—Ga alloy was present.

“Comparative Example 4”
A GaN single crystal growth step was performed in the same manner as in Example 1 except that only 150 mg of Ba and 270 mg of Ga were contained in the crucible 3 as raw materials for the melt. The inside of the crucible 3 was observed, and it was confirmed from the above criteria that the melt did not rise.
There was only a massive alloy in the crucible 3. The bulk alloy was analyzed using EDX and XRD, but the GaN single crystal was not grown and there was only a Ba-Ga alloy.

(Results of Comparative Examples 1 to 4)
Table 1 above shows the results of the raw materials for the melts of Comparative Examples 1 to 4, the partial pressure of ammonia, the presence or absence of GaN single crystal growth, the presence or absence of melt wetting, and the presence or absence of deterioration of the reaction vessel.

(Comparison between Examples 1 to 3 and Comparative Examples 1 to 4)
When a melt composed only of Ga is used, wetting occurs. When a melt composed of Ga and Bi is used, the reaction vessel deteriorates. When a melt composed only of Sn and Ga is used, and when Ga and Ba are used. It was confirmed that the GaN single crystal did not grow when the melt consisting only of was used. That is, a melt obtained by melting a raw material composed of Sn, Ba, and Ga is heated in contact with a gas phase that requires a nitrogen source, so that wetting does not occur and Sn or Ba is mixed as an impurity. Thus, it was confirmed that a GaN single crystal can be grown without deteriorating the reaction vessel.

  Moreover, according to Examples 1 to 3, it was confirmed that the larger the partial pressure of the gas containing the nitrogen source, the larger the GaN single crystal grows.

  According to the present invention, a GaN single crystal can be grown by heating a novel melt composed of Sn, Ba, and Ga in contact with a gas phase that requires a nitrogen source. According to the present invention, it is possible to grow a GaN single crystal while preventing the melt from getting wet and without deteriorating the reaction vessel and using a simple apparatus while suppressing the introduction of impurities.

  1 reaction vessel, 2 lining, 3 crucible, 4 heater, 5 flange, 6 source gas introduction pipe, 6a supply port, 7 exhaust pipe, 8 exhaust pipe for vacuuming.

Claims (6)

Melting a raw material consisting of tin, gallium, and one or more metals selected from the group consisting of alkali metals and alkaline earth metals to obtain a melt;
Next, the gallium nitride single crystal is grown by heating the melt and a gas phase indispensable for a nitrogen source in contact with each other.   The method for growing a gallium nitride single crystal according to claim 1, wherein the one or more metals selected from the group consisting of the alkali metal and the alkaline earth metal are barium.   In the charged molar amount when the raw material is prepared as a raw material for the melt, the molar amount of the gallium is relative to the molar amount of one or more metals selected from the group consisting of the alkali metal and the alkaline earth metal. The method for growing a gallium nitride single crystal according to claim 1 or 2, wherein the growth rate is 1 to 5 times.   The method for growing a gallium nitride single crystal according to any one of claims 1 to 3, wherein the nitrogen source is ammonia.   The method for growing a gallium nitride single crystal according to any one of claims 1 to 4, wherein a partial pressure of ammonia in a gas phase essentially including the nitrogen source is 0.03 to 1 atm.   The method for growing a gallium nitride single crystal according to any one of claims 1 to 5, wherein the heating is heating to 900 to 1100 ° C.

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