JP2014144890A - Production method of nitride single crystal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a production method of a nitride single crystal having an improved deposition rate, in a method for depositing a nitride single crystal after dissolving a raw material containing a nitride crystal into an ammonia solvent.SOLUTION: In a method for depositing a nitride single crystal 50 after dissolving a raw material 5 containing a nitride crystal into an ammonia solvent, the nitride single crystal 50 is deposited in the presence of an additive 13 containing at least one kind of element selected from a group comprising vanadium, zirconium, titanium, hafnium and chromium, and a halogen element.

Description

  The present invention relates to a method for producing a nitride single crystal. Specifically, the present invention relates to a method for manufacturing a nitride single crystal in which a nitride single crystal is precipitated after a raw material containing the nitride crystal is dissolved in an ammonia solvent.

  Conventionally, silicon semiconductors are used as semiconductors used for power devices and the like. In recent years, there is a growing need for lower loss, higher speed, and higher breakdown voltage in power devices. However, in the case of silicon semiconductors, it is difficult to improve characteristics in the future due to limitations on material properties. Therefore, recently, a technique using a nitride wide band gap semiconductor such as gallium nitride having excellent material properties has been proposed and attracted attention.

  As a method for producing a single crystal of gallium nitride, a vapor phase method represented by a hydride vapor phase deposition method (HVPE method) is known. In addition, liquid phase methods represented by an ammonothermal method using an ammonia solvent and a sodium flux method using a sodium melt are known.

  The ammonothermal method is a method in which ammonia, particularly supercritical ammonia, is used as a solvent, and utilizes the fact that the solubility of gallium nitride in the ammonia solvent changes with temperature changes. The ammonothermal method has a problem that it is difficult to obtain a sufficient crystal precipitation rate for industrial production because the solubility of gallium nitride in an ammonia solvent is extremely low. Therefore, in order to improve the synthesis efficiency and productivity of the nitride single crystal in the ammonothermal method, a method of adding a mineralizer for improving the solubility of gallium nitride into the reaction system is adopted. Typical mineralizers include, for example, alkali metal amides and ammonium chloride (see Non-Patent Document 1).

  In the technique using a mineralizer, a single crystal of gallium nitride can be produced by controlling the dissolution of gallium nitride in an ammonia solvent and the precipitation of gallium nitride from the ammonia solvent. The ammonothermal method uses a reversible reaction in which gallium nitride repeats dissolution and reprecipitation. For this reason, when gallium nitride molecules are adsorbed on an unfavorable site on the substrate (seed crystal substrate), the reverse reaction (that is, dissolution reaction) because the gallium nitride molecules are more unstable than when adsorbed on the preferred site. ) Easily occurs, and again the action of dissolving gallium nitride molecules in the ammonia solvent occurs. That is, even when gallium nitride molecules are adsorbed at an unfavorable site, the possibility that the gallium nitride molecules are deposited as they are and taken into the crystal is reduced, and as a result, there is an advantage that crystal defects are less likely to occur.

In addition, a method of depositing nitride crystals in a desired plane (c-plane) and a desired axial direction (m-axis direction) by an ammonothermal method has been proposed (see Patent Document 1). In Patent Document 1, in addition to controlling the temperature and / or pressure at the time of crystal precipitation, by using an acidic mineralizer using a plurality of chemical species, the solubility of the raw material in the solvent is increased and the desired plane and axial direction are increased. It has been proposed to increase the rate of crystal precipitation. For example, in an ammonium halide mineralizer (NH ₄ X), an NH ₄ Cl is mixed with an ammonium halide mineralizer (NH ₄ Br, NH ₄ I) containing Br, I which is a more reactive halogen. It is described.

Chem. Mater. (American Chemical Society); 11, 1648-1651 (1999)

JP 2008-120672 A

  However, even when the nitride single crystal is produced by the ammonothermal method with the addition of the mineralizers described in Non-Patent Document 1 and Patent Document 1, there is sufficient nitride single crystal at present. The deposition rate is not obtained. Therefore, a method that can further improve productivity is demanded.

  In view of the problems as described above, the present invention provides a method for producing a nitride single crystal having an improved precipitation rate in a method for precipitating a nitride single crystal after dissolving a raw material containing the nitride crystal in an ammonia solvent. I will provide a.

  In the method of growing a nitride single crystal after dissolving a raw material containing a nitride crystal in an ammonia solvent, the present inventor changed Gibbs free energy in a reversible reaction of dissolution and precipitation (reprecipitation) of nitride ( It has been found that a sufficient growth rate can be obtained by applying a new additive focusing on (ΔG), and the present invention has been completed.

  The method for producing a nitride single crystal according to the present invention is a method for precipitating a nitride single crystal after dissolving a raw material containing the nitride crystal in an ammonia solvent, and is made from vanadium, zirconium, titanium, hafnium, and chromium. A method for producing a nitride single crystal, comprising depositing a nitride single crystal in the presence of an additive containing at least one element selected from the group and a halogen element.

  In the method for producing a nitride single crystal, the additive may be a halide (A) of at least one element selected from the group consisting of vanadium, zirconium, titanium, hafnium, and chromium, vanadium, It may be at least one metal and halide (A) selected from the group consisting of zirconium, titanium, hafnium, and chromium, and at least one selected from the group consisting of vanadium, zirconium, titanium, hafnium, and chromium. And may be a halide (A) and an ammonium halide.

  In the above method for producing a nitride single crystal, the additive may be vanadium chloride, or vanadium metal and ammonium chloride.

  In the method for producing a nitride single crystal, the additive has a molar ratio of the number of halogen atoms to the number of atoms of at least one selected from the group consisting of vanadium, zirconium, titanium, hafnium, and chromium is 0.05. -10.

  In the above method for producing a nitride single crystal, the nitride single crystal may be precipitated at 300 to 800 ° C.

  In the above method for producing a nitride single crystal, the nitride single crystal may be precipitated by setting the pressure in the reaction vessel to a critical pressure of ammonia solvent to 150 MPa.

  In the nitride single crystal manufacturing method, the nitride single crystal may be a group 13 element nitride single crystal.

  In the nitride single crystal manufacturing method, the nitride single crystal may be a gallium nitride single crystal.

The method for producing a nitride single crystal according to the present invention is a method for producing a nitride single crystal comprising the following steps (A) to (C).
(A) A step of introducing an additive containing at least one element selected from the group consisting of vanadium, zirconium, titanium, hafnium, and chromium and a halogen element and a raw material containing a nitride crystal into a reaction vessel.
(B) A step of sealing the ammonia solvent in the reaction vessel.
(C) A step of forming a low temperature portion and a high temperature portion in the reaction vessel, reacting the raw material containing nitride crystals with the additive in an ammonia solvent, and then depositing a nitride single crystal from the low temperature portion.

  In the above method for producing a nitride single crystal, a seed crystal may be installed at a low temperature portion in the reaction vessel.

  In the method for producing a nitride single crystal, in the step (C), the low temperature portion in the reactor is 300 to 800 ° C., and the high temperature portion in the reactor is 0.5 to 100 ° C. higher than the low temperature portion. It may be temperature.

  According to the method for producing a nitride single crystal of the present invention, a method for producing a nitride single crystal with improved precipitation rate can be provided.

It is the schematic which shows an example of the manufacturing apparatus which can be used for the manufacturing method of the nitride single crystal of this invention. It is the schematic which shows the other example of the manufacturing apparatus which can be used for the manufacturing method of the nitride single crystal of this invention. It is a figure which illustrates typically the Gibbs free energy change ((DELTA) G) in the manufacturing method of the nitride single crystal of this invention.

The method for producing a nitride single crystal according to the present invention is a method for precipitating a nitride single crystal after dissolving a raw material containing the nitride crystal in an ammonia solvent. In the above method, the present inventor has intensively studied in order to obtain a sufficient precipitation rate of a nitride single crystal while maintaining the reversibility of the reaction of repeating the dissolution and precipitation of nitride crystals to prevent the formation of crystal defects. Piled up. As a result, it is most effective to deposit a nitride single crystal in the presence of an additive containing at least one element selected from the group consisting of vanadium, zirconium, titanium, hafnium, and chromium, and a halogen element. I found out that there was.
The present invention will be described in detail below.

[Additive]
The additive includes at least one element selected from the group consisting of vanadium, zirconium, titanium, hafnium, and chromium, and a halogen element. Specifically, an additive comprising a halide (A) of at least one element selected from the group consisting of vanadium, zirconium, titanium, hafnium, and chromium, a group consisting of vanadium, zirconium, titanium, hafnium, and chromium An additive consisting of at least one metal selected from the group consisting of halide and (A), an additive consisting of at least one metal selected from the group consisting of vanadium, zirconium, titanium, hafnium, and chromium, or an ammonium halide, or Additives comprising halide (A) and ammonium halide can be used. More specifically, it is preferable to use an additive composed of vanadium chloride or an additive composed of vanadium metal and ammonium chloride.

The raw material containing a nitride crystal in the present invention is preferably made of a raw material containing a nitride crystal and a raw material used for precipitation of the nitride single crystal. Examples of the raw material used for the precipitation of the nitride single crystal include the raw materials used for the precipitation of the nitride single crystal by an ordinary ammonothermal method. For example, gallium and gallium nitride are particularly preferable.
As a method of dissolving a raw material containing a nitride crystal in an ammonia solvent, the raw material is halogenated to obtain a gallium halide, and then the gallium halide is nitrided to precipitate a nitride single crystal. Is preferred. In the halogenation, the nitride crystal is also halogenated to gallium halide.

For example, in the case of manufacturing a gallium nitride single crystal, a halogen element may be supplied to gallium nitride containing a nitride crystal to form a gallium halide, and the gallium halide is supplied with a nitrogen element to precipitate gallium nitride. Just do it.
According to the method for producing a nitride single crystal of the present invention, since the reaction of dissolving the raw material containing the nitride crystal and precipitating the nitride single crystal in the presence of the specific additive is a reversible reaction, it is reversible. The nitride single crystal can be precipitated at a sufficient rate while maintaining the above and preventing the generation of crystal defects. The additive in the present invention acts as a solubilizing aid for helping to dissolve the raw material containing nitride crystals and a reaction agent for helping to precipitate the nitride single crystals.

The ratio (molar ratio) of the number of halogen atoms to the number of atoms of at least one selected from the group consisting of vanadium, zirconium, titanium, hafnium, and chromium as an additive is preferably 0.05 to 10, and preferably 0.1 to 5 More preferred. In the case of the above range, the presence of the additive makes it easy to maintain the reversibility of the chemical reaction that repeats dissolution and precipitation of the nitride crystal, and the precipitation rate of the nitride single crystal is sufficiently high without depletion of the halogen element. Can be improved.
The additive is selected from the group described above, and at least selected from the group consisting of vanadium, zirconium, titanium, hafnium, and chromium while maintaining reversibility of repeating the dissolution reaction and precipitation reaction of the nitride crystal. The molar ratio of the suitable number of atoms of the halogen element to the number of one kind of atoms can be easily controlled.

The additive may be supported on a support material, for example. In that case, it is preferable that the support material is not corroded or dissolved by ammonia.
Moreover, it does not specifically limit about the shape of an additive, For example, any shape, such as a particulate form, a linear form, a block shape, plate shape, block shape, foil shape, rod shape, may be sufficient. Preferably, it may be in the form of particles, lines, or plates.

  The amount of the additive is not particularly limited as long as it is an amount sufficient to promote the precipitation of the nitride single crystal, but is usually preferably 1 to 30% by mass, and preferably 5 to 20% by mass with respect to the ammonia solvent. Is more preferable.

  As a case where a plurality of additives are combined, for example, a case where at least one metal selected from the group consisting of vanadium, zirconium, titanium, hafnium, and chromium, and a halide (A) are combined. In this case, the additive may not be mixed in advance, and may be mixed by performing a pre-combination process or a chemical process.

<Raw materials>
In the production method of the present invention, in addition to the raw material containing nitride crystals, the additive and, if necessary, seed crystals are used.

[Raw materials containing nitride crystals]
The raw material containing the nitride crystal is not particularly limited, and a raw material used for precipitation of the nitride single crystal by a normal ammonothermal method may be appropriately selected and used. The crystallinity of the nitride crystal contained in the raw material is not limited, and for example, a nitride polycrystal may be used. A raw material containing a nitride single crystal may be used, but nitride polycrystal is preferable in consideration of cost. For example, when a gallium nitride single crystal is deposited as a nitride single crystal that is a product, gallium nitride polycrystal may be used as a raw material.

[Seed crystal]
In the production method of the present invention, it is preferable to use a seed crystal. By using a seed crystal, it is possible to selectively precipitate a crystal having specific characteristics. For example, in the case of depositing a gallium nitride single crystal, if a hexagonal gallium nitride single crystal is used as the seed crystal, the hexagonal gallium nitride single crystal can be deposited on the seed crystal.

  As the seed crystal, a thin plate single crystal is usually used, but the crystal orientation of the main surface can be arbitrarily selected. In the case of a hexagonal gallium nitride single crystal, as the main surface, for example, (0001) plane, polar plane represented by (000-1) plane, (10-12) plane, (10-1-2) ) Crystallization of a gallium nitride single crystal in an arbitrary orientation by using a seed crystal having various orientations such as a semipolar plane represented by a plane and a nonpolar plane represented by a (10-10) plane. Can do. Further, the cutting direction of the seed crystal is not limited to the facet plane, and a plane shifted by an arbitrary angle from the facet plane can be selected.

<Ammonia solvent>
The ammonia solvent is not particularly limited, and an ammonia solvent used in a normal ammonothermal method may be used. For example, an ammonia solvent generated by introducing ammonia gas into a cooled reaction vessel may be used, or an ammonia solvent liquefied by cooling or pressurizing ammonia gas may be used.

<Nitride single crystal (product)>
The nitride single crystal produced by the method of the present invention is determined by the type of raw material containing the nitride crystal and the like. Note that the nitride single crystal that is the product is precipitated with higher crystallinity than the raw material containing the nitride crystal. The nitride single crystal in the present invention is preferably a nitride single crystal of a Group 13 (Group III) element. Typical group 13 elements include aluminum, gallium, indium, and the like. Among these, gallium nitride single crystals are preferable.

  Next, the effect of precipitating a nitride single crystal in the presence of a specific additive in the production method of the present invention will be described from the viewpoint of Gibbs free energy change (ΔG).

In the production method of the present invention, an example of a reaction formula for dissolving and depositing gallium nitride as a nitride crystal in the presence of an additive is represented as follows. Here, MCl ₃ is an example of an additive containing at least one element selected from the group consisting of vanadium, zirconium, titanium, hafnium, and chromium (hereinafter also referred to as M element), and a halogen element. This is an example of a halide (A) of at least one element selected from the group consisting of vanadium, zirconium, titanium, hafnium, and chromium.
GaN + MCl ₃ → GaCl ₃ + MN (dissolution reaction)
GaCl ₃ + MN → GaN + MCl ₃ (precipitation reaction (reprecipitation reaction))
In the above reaction formula, a gallium nitride single crystal is precipitated by a reaction in which dissolution and precipitation of gallium nitride are repeated. However, in order to precipitate a crystal efficiently, the precipitation reaction needs to have a sufficient reaction rate.

On the other hand, if the precipitation reaction is promoted too much, the dissolution reaction and the precipitation reaction are unlikely to proceed reversibly. For example, when a gallium nitride molecule is adsorbed on an undesired portion on a substrate (seed crystal) on which a crystal is to be deposited, the gallium nitride molecule is adsorbed on the adsorbed gallium nitride molecule before the adsorbed gallium nitride molecule is dissolved again. Accumulates one after another. As a result, there is a problem that gallium nitride molecules adsorbed on an undesired portion on the substrate are deposited as they are and taken into the crystal, and defects are generated in the gallium nitride crystal deposited on the substrate.
From such a viewpoint, in order to prevent the generation of defects, it is necessary to maintain a balance that the precipitation reaction has a sufficient reaction rate while maintaining the reversibility of the dissolution reaction and the precipitation reaction.

In order to achieve both the reversibility between the dissolution reaction and the precipitation reaction described above and the acceleration of the precipitation reaction, it is necessary to know the ease of the reaction. Therefore, the present inventor paid attention to Gibbs' free energy change (ΔG), which is an index for knowing how easy the reaction proceeds.
Here, FIG. 3 schematically shows the Gibbs free energy change (ΔG) in the dissolution reaction and the precipitation reaction. In FIG. 3, the vertical axis represents the potential. The GaN precipitation state corresponds to the reaction of GaN + MCl ₃ (a-1). The GaN dissolved state corresponds to a reaction of GaCl ₃ + MN ((b-1), (b-2), (b-3), (b-4), or (b-5)). The potential difference between the GaN precipitated state and the GaN dissolved state corresponds to the Gibbs free energy change (ΔG).

The reaction between the precipitated state and the dissolved state in FIG. 3 can be expressed as the following equation (A).
GaN + MCl ₃ (precipitation reaction) → GaCl ₃ + MN (dissolution reaction) + ΔG (A)
In the above formula (A), if ΔG is negative, it indicates that the dissolution reaction occurs spontaneously, and if ΔG is positive, it indicates that the dissolution reaction is difficult to proceed. Furthermore, the closer the ΔG is to 0 (zero), the higher the reversibility of the dissolution reaction and the precipitation reaction.

<Dissolved state (b-1)>
The dissolved state (b-1) is a state in which ΔG = 0, reversibility is high, and the precipitation reaction and the dissolution reaction proceed to the same extent.

<Dissolved state (b-2)>
The dissolved state (b-2) is ΔG> 0, and the precipitation reaction is promoted. At this time, the closer the ΔG is to 0, the higher the reversibility. Therefore, as ΔG is positive and ΔG is close to zero (that is, ΔG> 0 and ΔG≈0), the speed of the precipitation reaction is improved while maintaining the reversibility of the dissolution reaction and the precipitation reaction. be able to.

<Dissolved state (b-3)>
The dissolved state (b-3) is ΔG >> 0 and the precipitation reaction is promoted, but the reversibility is poor. Therefore, as described above, there is a high possibility that defects will occur in the precipitated crystals.

<Dissolved state (b-4)>
The dissolved state (b-4) is ΔG <0, and the dissolution reaction is accelerated. At this time, the closer the ΔG is to 0, the higher the reversibility. If ΔG is sufficiently close to 0, the speed of the precipitation reaction can be improved while maintaining the reversibility of the dissolution reaction and the precipitation reaction depending on the operating conditions such as the temperature condition, the pressure condition, and the amount of additive introduced. .

<Dissolved state (b-5)>
The dissolved state (b-5) is ΔG << 0, the dissolution reaction is accelerated, and the reversibility is poor. Therefore, it is difficult to improve the speed of the precipitation reaction.

  Gibbs free energy change of reversible reaction can be investigated by thermal equilibrium calculation. For example, thermal equilibrium calculation can be performed using calculation software such as Fact-Web programs (http://www.crct.polymtl.ca/factweb.php).

Hereinafter, an example of gallium nitride will be described. By using the above calculation software, a comparison was made between the ΔG reaction of gallium chloride generated by the halogenation reaction of gallium and hydrogen chloride and the ΔG reaction of gallium nitride generated by the nitridation reaction of ammonia and gallium. ΔG of the obtained chemical reaction can be calculated. In this case, it becomes a reversible reaction formula represented by the following formula (1).
GaN + 3HCl ← → GaCl ₃ + NH ₃ + ΔG1 (1)

Next, instead of gallium nitride, an example of an M element nitride (nitride M) will be described. ΔG2 is calculated by performing calculation in the same manner as the above gallium nitride example using the above calculation software. In this case, it becomes a reversible reaction formula represented by the following formula (2).
MN + 3HCl ← → MCl ₃ + NH ₃ + ΔG2 (2)

And the reversible reaction formula of the following (3) type | formula is guide | induced from the difference ((1) type | formula-(2)) of each reversible reaction in the said calculation. As a result, ΔG3 of the chemical reaction between gallium nitride and MCl ₃ (additive) is obtained.
GaN + MCl ₃ ← → GaCl ₃ + MN + ΔG3 (3)

  From the above formulas (1) to (3), as ΔG3 shown in formula (3) is closer to 0, the reversibility of the dissolution reaction and precipitation reaction of gallium nitride can be maintained, and the precipitation reaction has a sufficient reaction rate. Furthermore, if ΔG3 is positive, the precipitation reaction is promoted, which is preferable. Specifically, ΔG3 is preferably −80 to 80 kJ / mol, and more preferably 0 to 80 kJ / mol. The present inventor, as will be described later in the Examples section, adds vanadium (V), zirconium (Zr), titanium (Ti), hafnium (Hf), or chromium (Cr), and an additive containing a halogen element. It was found that the reversibility of the dissolution reaction and the precipitation reaction can be maintained by precipitating the nitride single crystal in the presence of, and the precipitation reaction has a sufficient reaction rate.

  Next, an example of a manufacturing apparatus applicable to the manufacturing method of the present invention and an example of a manufacturing process using the manufacturing apparatus will be described.

<Manufacturing equipment>
A production apparatus applicable to the method for producing a nitride single crystal of the present invention is not particularly limited, and a production apparatus 1 including an autoclave (reaction vessel) 10 illustrated in FIG. In the manufacturing apparatus 1 shown in FIG. 1, the interior of the autoclave 10 is partitioned into an upper part 3 and a lower part 4 by a partition plate 2.

  The autoclave 10 can be sealed with the lid 6. Further, the autoclave 10 is a reaction container having a configuration in which a temperature difference is provided between the upper part 3 and the lower part 4 inside the autoclave 10 by temperature adjusting means installed outside. The temperature adjusting means includes a heater, a jacket type heat exchanger, and the like. The internal temperature of the autoclave 10 can be measured by a thermocouple (not shown). The autoclave 10 is provided with a temperature difference between the upper part 3 and the lower part 4 so that a density difference is formed in an unillustrated ammonia solvent accommodated therein, and a halide of a raw material containing nitride crystals dissolved in the ammonia solvent. Is transported from the high temperature side to the low temperature side.

  In the example shown in FIG. 1, a seed crystal 7 is provided on the upper part 3, and a single crystal nitride 50 is deposited on the seed crystal 7. That is, in order to precipitate the nitride single crystal 50 in the upper part 3, the lower part 4 is heated so that the temperature is higher than that of the upper part 3, whereby the halide of the raw material containing the nitride crystal dissolved in the ammonia solvent is reduced in the lower part. Transport from 4 to top 3. In this case, in the autoclave 10, the lower part 4 is a raw material dissolving region for dissolving the raw material 5 containing nitride crystals in ammonia, and the upper part 3 is a crystal precipitation region for precipitating the nitride single crystal. Become. Hereinafter, in the present embodiment, an example will be described in which the lower part 4 is a high-temperature part as a raw material melting area and the upper part 3 is a low-temperature part as a crystal precipitation area among the two areas partitioned by the partition plate 2.

When the nitride single crystal is manufactured using the manufacturing apparatus 1, a configuration in which the raw material 5 containing the nitride crystal and the additive 13 are introduced into the lower portion 4 in the autoclave 10 in advance can be employed.
In addition, the structure of the manufacturing apparatus applicable to the manufacturing method of this invention is not specifically limited, It is good also as a structure which arrange | positions a seed crystal in the lower part 4. FIG. In this case, in order to precipitate a nitride single crystal in the lower part 4, the upper part 3 is heated so that the temperature is higher than that of the lower part 4, whereby the halide of the raw material containing the nitride crystal dissolved in the ammonia solvent is changed to the upper part. It can be configured to be transported from 3 to the lower part 4.

  The material of the autoclave 10 is not particularly limited, but is preferably selected from materials having pressure resistance, heat resistance, and corrosion resistance that can withstand the conditions for depositing the nitride single crystal. From the viewpoint of heat resistance, the material of the autoclave 10 is austenitic stainless steel (for example, SUS310 (JIS standard)), iron-based alloy system (for example, Incoloy (registered trademark), N155, etc.), nickel-based alloy system (for example, Nimonic (registered trademark), Rene 41 (registered trademark), Inconel (registered trademark), etc.), a cobalt-based alloy system (for example, Stellite (registered trademark)), or a titanium alloy is preferable. The material of the inner wall of the autoclave 10 is austenitic stainless steel (for example, SUS316L (JIS standard)), nickel-based alloy system, noble metal (platinum, gold, iridium, etc.) from the viewpoint of corrosion resistance to the ammonia solvent and additives. Or ceramic type (synthetic quartz glass, silicon nitride, titanium nitride, etc.) is preferable. Among these, the nickel base alloy system is preferable because the material of the autoclave 10 and the inner wall of the autoclave 10 can be made of the same material. When the material of the autoclave 10 and the material of the inner wall of the autoclave 10 are changed, a combination of the above materials can be used, for example, coating such as plating or thermal spraying or lining.

The partition plate 2 may be provided to partition the upper part 3 and the lower part 4 inside the autoclave 10 as necessary. In the example shown in FIG. 1, the partition plate 2 is configured to partition an upper portion 3 that is a crystal precipitation region and a lower portion 4 that is a raw material dissolution region. Providing the partition plate 2 is preferable because a temperature difference between the upper part 3 and the lower part 4 is easily formed. The partition plate 2 is provided with a hole (not shown) so as to penetrate between the upper portion 3 and the lower portion 4. What is necessary is just to design the aperture ratio of the partition plate 2 according to the temperature difference to form in the upper part 3 and the lower part 4 inside the autoclave 10, and 5 to 80% is preferable and 20 to 70% is more preferable.
The material of the surface of the partition plate 2 is preferably the same material as the material of the inner wall of the autoclave 10.

  Furthermore, a conduit 9 is connected to the lid 6, and a gate valve 8 is provided in the path of the conduit 9. The autoclave 10 is connected to a vacuum pump 11 for sucking and reducing the pressure in the autoclave 10 through the gate valve 8 and the conduit 9 described above.

  The autoclave 10 is connected to an ammonia cylinder 12 for supplying ammonia gas into the autoclave 10 through the gate valve 8 and the conduit 9 described above. The manufacturing apparatus 1 of the present embodiment is configured so that ammonia gas can be liquefied by introducing ammonia gas into the autoclave 10 from the ammonia cylinder 12 and then cooling the autoclave 10 by a cooling means (not shown). Alternatively, in the present embodiment, a configuration in which a cooling means (not shown) is provided in the path of the conduit 9 that connects the ammonia cylinder 12 and the autoclave 10 and ammonia gas is liquefied in advance and then introduced into the autoclave 10 can be adopted.

  The gate valve 8 is configured so that the suction pressure reduction from the vacuum pump 11 can be turned on or off by opening / closing the gate valve 8 and / or the autoclave from the ammonia cylinder 12 by opening / closing the gate valve 8. 10 is configured so that the introduction of ammonia gas into the inside 10 can be turned on or off.

  In addition to the gate valve 8 and the conduit 9 described above, a pressure gauge (not shown) provided as necessary preferably uses a material having at least a surface having corrosion resistance. For example, as with the autoclave 10, austenitic stainless steel is used. It is preferable to use a corrosion-resistant material such as steel (for example, SUS316L (JIS standard)) nickel-based alloy system, noble metal (platinum, gold, iridium, etc.), or ceramic system (synthetic quartz glass, silicon nitride, titanium nitride, etc.). . The manufacturing apparatus 1 used in the manufacturing method of the present invention may have a configuration in which the gate valve 8 and the pressure gauge are omitted from the above configuration, and a plurality of the gate valve 8, the conduit 9, and the pressure gauge are arranged. It does not matter as a configuration. FIG. 1 shows an example in which the gate valve 8 is provided in a conduit 9 branched into a vacuum pump 11 and an ammonia cylinder 12.

<Procedure>
The procedure for manufacturing the nitride single crystal 50 by the manufacturing method of the present invention will be described in detail below, taking the case of using the manufacturing apparatus 1 described above as an example.

The manufacturing method of the nitride single crystal 50 of this invention can employ | adopt the method provided with the process of the following (A)-(C).
(A) A step of introducing an additive containing at least one element selected from the group consisting of vanadium, zirconium, titanium, hafnium, and chromium and a halogen element and a raw material containing a nitride crystal into a reaction vessel.
(B) A step of sealing the ammonia solvent in the reaction vessel.
(C) A step of forming a low temperature portion and a high temperature portion in the reaction vessel, reacting the raw material containing nitride crystals with the additive in an ammonia solvent, and then depositing a nitride single crystal from the low temperature portion.

  First, as shown in the step (A), an additive containing at least one element selected from the group consisting of vanadium, zirconium, titanium, hafnium, and chromium, and a halogen element, and a nitride crystal are included. Raw material 5 is introduced into the reaction vessel. Before introducing the above materials into the autoclave 10 (reaction vessel), the inside of the autoclave 10 may be degassed. Moreover, when introducing the said material into the autoclave 10, you may distribute | circulate inert gas (For example, noble gases, such as nitrogen gas and Ar, etc.).

The raw material 5 containing a nitride crystal is introduced into the autoclave 10 on the side that becomes the high temperature portion, and is introduced into the lower portion 4 in FIG.
The additive may be installed in either the high temperature part or the low temperature part of the autoclave 10 or in both. Even when the additive is placed in any region inside the autoclave 10, a sufficient precipitation rate of the nitride single crystal 50 can be obtained while maintaining a reversible reaction in which gallium nitride repeats dissolution and precipitation.
When the additive includes a halide (A) of at least one element selected from the group consisting of vanadium, zirconium, titanium, hafnium, and chromium, as shown in FIG. Should be introduced. When the additive contains at least one metal selected from the group consisting of vanadium, zirconium, titanium, hafnium, and chromium, and an ammonium halide, the metal 15 is formed in the upper part 3 and the lower part 4 as shown in FIG. And ammonium halide 14 may be introduced into the lower part 4.

If necessary, it is preferable to install a seed crystal on the low temperature part side of the reaction vessel. FIG. 1 shows an example in which a seed crystal 7 is previously installed on the upper part 3 inside the autoclave 10.
The seed crystal 7 may be installed at the same time when the raw material 5 containing the nitride crystal and the additive are introduced into the autoclave 10. The seed crystal 7 is preferably fixed to a jig made of the same metal material as that constituting the autoclave 10. Further, after the seed crystal 7 is installed, heat deaeration may be performed as necessary.

Next, as shown in the step (B), an ammonia solvent is sealed in the reaction vessel.
First, after the autoclave 10 is sealed with the lid 6, the inside of the autoclave 10 is decompressed, and the autoclave 10 is held in a decompressed state. Specifically, the vacuum pump 11 shown in FIG. 1 is operated, the interior of the autoclave 10 is sucked through the conduit 9 with the gate valve 8 opened, and the pressure is reduced to a predetermined pressure (absolute pressure of 100 Pa or less). , Hold that state.

Next, the autoclave 10 in a decompressed state is cooled to a predetermined temperature, and ammonia gas is introduced into the cooled autoclave 10 to generate an ammonia solvent (not shown) in the autoclave 10. Specifically, ammonia gas is introduced from the ammonia tank 12 shown in FIG. 1 into the autoclave 10 through the conduit 9 with the gate valve 8 opened.
Alternatively, in the present embodiment, for example, by providing a pressure increasing means or a cooling means (not shown) in the path of the conduit 9, an ammonia solvent in which ammonia gas is preliminarily pressurized or cooled is introduced into the autoclave 10. May be.
Thereafter, the autoclave 10 is sealed again by closing the gate valve 8.

  Next, as shown in the above step (C), a low temperature portion and a high temperature portion are formed in the reaction vessel, and after the raw material containing nitride crystals and the additive are reacted in an ammonia solvent, A nitride single crystal is deposited.

  The temperature inside the autoclave 10 is raised using the temperature adjusting means, and a high temperature part and a low temperature part are provided in the autoclave 10. By raising the temperature in the autoclave 10 to a predetermined temperature, the raw material 5 containing nitride crystals reacts with the halogen element, and the raw material 5 containing nitride crystals is dissolved in an ammonia solvent. As the temperature rises in the autoclave 10, a density difference is formed in the ammonia solvent by the high temperature portion and the low temperature portion provided in the autoclave 10, and the raw material 5 containing nitride crystals dissolved in the ammonia solvent is changed from the high temperature portion to the low temperature portion. To be transported to. The raw material 5 containing the nitride crystal transported to the low temperature portion is precipitated as a nitride single crystal 50 by reacting with at least one element selected from the group consisting of vanadium, zirconium, titanium, hafnium, and chromium. To do.

  In FIG. 1, since the lower part 4 is heated so as to have a temperature higher than that of the upper part 3, the raw material 5 containing nitride crystals dissolved in an ammonia solvent is transported from the lower part 4 to the upper part 3. 50 precipitates out. Further, in the example shown in FIG. 1, a nitride single crystal 50 is deposited on the seed crystal 7 installed on the upper portion 3.

  Precipitation of the nitride single crystal 50 in the autoclave 10 as described above is performed while keeping the internal ammonia solvent in a subcritical or supercritical state. Although the temperature of the ammonia solvent in the low temperature part (upper part 3 in FIG. 1) in the autoclave 10, that is, the precipitation temperature of the nitride single crystal 50 is not particularly limited, it is preferably deposited at 300 to 800 ° C. Moreover, it is preferable that the high temperature part (lower part 4 in FIG. 1) in the autoclave 10 is 0.5-100 degreeC higher than a low temperature part (upper part 3 in FIG. 1), and it is more preferable that it is 1-50 degreeC higher. By setting the above temperature range, it is possible to obtain a sufficient precipitation rate while maintaining reversibility of the repetition of the dissolution reaction and the precipitation reaction. Moreover, damage to the reaction vessel can be prevented.

  Moreover, although it does not specifically limit about the temperature increase rate until it reaches the said precipitation temperature, What is necessary is just to carry out over several hours to several days. At this time, if necessary, the temperature can be raised in multiple stages or the temperature raising speed can be changed for each temperature range.

  Note that the reaction time after reaching the precipitation temperature may also be several hours to several hundred days, although it depends on the type of nitride single crystal, the raw material, and the size and amount of the crystal. Further, during the reaction, the reaction temperature may be constant or a pattern in which the temperature is gradually raised or lowered.

  The pressure in the reaction vessel (autoclave 10) when depositing the nitride single crystal 50 is not particularly limited, but it is preferably deposited under a pressure in the range of the critical pressure of the ammonia solvent to 150 MPa. By setting it as the above-mentioned pressure range, it can prevent that an ammonia solvent evaporates and can prevent damage to a reaction container.

  In order to set the pressure in the autoclave 10 within the above range, for example, it can be adjusted to a desired pressure by controlling the amount of ammonia solvent introduced.

  In the production method of the present invention, a sufficient precipitation rate can be obtained while maintaining reversibility by adopting the above-described method using the additive. For example, the deposition rate is preferably 20 to 5000 μm / day, more preferably 100 to 2000 μm / day, and even more preferably 200 to 1500 μm / day. The precipitation rate described here is a value obtained by dividing the total size precipitated on both surfaces of a plate-like seed crystal cut out on an arbitrary crystal plane by the number of days of precipitation. Productivity can be improved by being able to achieve the said precipitation rate.

  After passing the reaction time for depositing the desired crystals, the temperature of the autoclave 10 is lowered. The temperature lowering method at this time is also not particularly limited. For example, the autoclave 10 may be allowed to cool after stopping energization to a heating means such as an electric furnace (not shown), or as necessary. The autoclave 10 may be rapidly cooled using a refrigerant.

  Then, after the temperature of the outer surface of the autoclave 10 or the estimated internal temperature becomes equal to or lower than a predetermined temperature, for example, 200 ° C. or lower, the lid 6 is removed from the autoclave 10. At this time, one end side of another pipe may be connected to the gate valve 8 connected to the autoclave 10, and the gate valve 8 may be opened with the other side of the pipe connected to the water in the container. Alternatively, if necessary, the internal ammonia solvent is sufficiently removed by reducing the pressure in the autoclave 10 again to a vacuum state, and then the interior is dried, then the lid 6 is opened, and the nitridation generated in the autoclave 10 is performed. The single crystal 50, unreacted raw materials, additives and the like may be taken out.

  The nitride single crystal 50 can be manufactured by the above steps (A) to (C). In addition, a nitride single crystal having a desired crystal structure can be manufactured by appropriately adjusting the manufacturing conditions.

  For other nitride single crystal deposition conditions and procedures, reference can be made to the column of manufacturing conditions described in JP 2007-238347 A, JP 2010-222152 A, and the like.

[Function and effect]
In the method for producing a nitride single crystal according to the present invention, in the method of depositing a nitride single crystal after dissolving a raw material containing the nitride crystal in an ammonia solvent, Gibbs free energy change (ΔG Gallium nitride by precipitating a nitride single crystal in the presence of an additive containing at least one element selected from the group consisting of vanadium, zirconium, titanium, hafnium, and chromium, and a halogen element It is possible to obtain a sufficient precipitation rate of a nitride single crystal while maintaining reversibility of repeating dissolution and reprecipitation, more specifically, maintaining reversibility of a halogenation reaction and a nitridation reaction. Thereby, defects in the nitride single crystal can be reduced, the precipitation rate can be sufficiently improved, and the nitride single crystal can be produced with high productivity.

  In addition, although it does not specifically limit as a diameter of the nitride single crystal (ingot) obtained with the manufacturing method of this invention, since it is a method with which a comparatively large diameter can be obtained, for example, the maximum diameter is Nitride single crystals of 50 to 400 mm or more are also possible.

  Hereinafter, the present invention will be described in more detail by way of examples. However, the present invention is not limited to these examples.

In the method of precipitating a nitride single crystal after dissolving a raw material containing a nitride crystal in an ammonia solvent, the present inventor, in addition to the examination from the viewpoint of reversibility of the reaction of repeatedly dissolving and precipitating the nitride, From the viewpoint of the precipitation rate of nitrides, the inventors have intensively studied about elements having a suitable ΔG. As a result, after screening a reaction system that can maintain reversibility, by carrying out the obtained reaction system in an actual test, V, Zr, Ti, Hf, and Cr have a high deposition rate, Above all, it was found that V has a sufficiently high deposition rate.
As a result, by using an additive containing vanadium as the M element, it is possible to produce a nitride single crystal at a sufficient precipitation rate while maintaining the reversibility of repeated reactions of dissolution and precipitation of nitride crystals. It was revealed that. Details will be described below.

<Selection of halogen elements>
In this example, a chlorine element was selected as the halogen element.

<Selection of M element>
In this example, when a gallium nitride single crystal was produced, ΔG generated by the reaction between each metal element and gallium nitride was determined for the case where the metal element shown in Table 1 below was used as the M element. Specifically, ΔG was determined for Zr, V, Ta, Ti, Nb, Mo, Hf, La, Cr, Mn, Ca, Li, and Zn. Also for NH ₄ , ΔG was determined in the same manner as the above metal element.

In this example, the Gibbs free energy change (ΔG) of the reversible reaction was calculated using the above-described Reaction-web of Fact-Web programs.
First, it was investigated what kind of compound gallium is stable in the system. Gallium may be GaN as a nitride and GaCl and GaCl ₃ as chlorides. In order to investigate which of two types of chlorides, GaCl and GaCl ₂ , is stable, the Gibbs free energy change was calculated in the reaction represented by the chemical reaction formula of the following formula (4).
GaCl + 2HCl ← → GaCl ₃ + H ₂ + ΔG4 (4)

First, using the above-described Reaction-web, each compound is set to the default phase, the min temperature is set to 500K, the max temperature is set to 1000K, and the temperature range is set to 50K, and ΔG4 in the above equation (4) is calculated. did. It was confirmed that ΔG4 was negatively large under the temperature condition set this time, that is, it was confirmed that GaCl ₃ was easily formed. As for nitride, only GaN is known, so the above calculation was not performed.
From the above results, the reversible reaction of gallium was expressed by the following equation (5).
GaN + 3HCl ← → GaCl ₃ + NH ₃ + ΔG5 (5)
For this reaction, the Gibbs free energy change (ΔG5) was calculated in the same manner as ΔG4.

Next, in this example, the above calculation was performed for each metal element by the same calculation method as described above.
In the case of vanadium, there may be VN as the nitride and VCl ₂ , VCl ₃ , and VCl ₄ as the chloride. Therefore, the Gibbs free energy change was calculated for the following formulas (6) and (7) as in the case of gallium.
VCl ₂ + HCl ← → VCl ₃ + 1 / 2H ₂ + ΔG6 (6)
VCl ₂ + 2HCl ← → VCl ₄ + H ₂ + ΔG7 (7)
Under the temperature conditions set this time, it was confirmed that both ΔG6 and ΔG7 were positively large, that is, VCl ₂ was easily formed.
From the above results, the reversible reaction of vanadium was expressed by the following formula (8).
VN + 2HCl + 1 / 2H ₂ ← → VCl ₂ + NH ₃ + ΔG8 (8)
The Gibbs free energy change (ΔG8) was also calculated for this reaction.

Next, using the calculation results of the above formulas (5) and (8), the dissolution and precipitation reactions of gallium nitride were directly evaluated by subtracting the reactions represented by the respective reaction formulas. In the case of gallium and vanadium which are the above examples, the above formula (5) is applied to the reversible reaction of gallium, the above formula (8) is applied to the reversible reaction of vanadium, and the above formula (5) The equation (8) was subtracted, and the following equation (9) and the value of ΔG9 were calculated. More specifically, ΔG9 was obtained by calculating the difference between ΔG5 and ΔG8 (ΔG9 = ΔG5-ΔG8).
GaN + VCl ₂ + HCl ← → VN + GaCl ₃ + 1 / 2H ₂ + ΔG9 (9)

  ΔG9 in this example is ΔG3 in the above embodiment. Therefore, in order to maintain reversibility in each reaction formula, ΔG9 in the formula (9) needs to be as close to 0 as possible.

  Here, as the numerical value of ΔG9 based on the calculation result is larger on the positive side (ΔG >> 0), the reaction proceeds to the left side in the above equation (9), that is, the direction in which gallium nitride is easily formed (precipitation reaction). . Further, the larger the numerical value of ΔG9 is on the negative side (ΔG << 0), the more the reaction proceeds to the right side in the above formula (9), that is, the direction in which gallium chloride is easily formed (dissolution reaction).

Similar to the above example of vanadium, the calculation results for calculating the Gibbs free energy change (hereinafter referred to as ΔG _r ) generated by the reaction between the metal element and gallium are shown in Table 1 below.

  Furthermore, the present inventor, in the “deposition rate confirmation test” to be described later, the absolute value of ΔGr when the metal element chloride that can maintain the reversibility of each of the above reaction formulas uses the metal element shown in Table 1. The value was found to be 80 kJ / mol or less. That is, it was found from these calculation results that Zr, V, Ti, Hf, and Cr can be M elements.

<Deposition rate confirmation test (1)>
Next, using a production apparatus 1 including an autoclave 10 as shown in FIG. 1, a confirmation test of a crystal deposition rate for producing a nitride single crystal using the above elements as additives was performed.

(Experimental Examples 1-4)
[manufacturing device]
In Experimental Examples 1 to 4, as shown in the schematic diagram of FIG. 1, the interior includes an autoclave 10 that is partitioned by a partition plate 2 into an upper part 3 and a lower part 4. In addition to a vacuum pump 11 and an ammonia tank 12, an electric furnace A manufacturing apparatus 1 shown in FIG. 1 is used, which is provided with a temperature adjusting means (not shown) and further provided with safety equipment (not shown). Further, as shown in FIG. 1, the additive 13 was introduced into the lower part 4.

[Procedure and Evaluation]
In an autoclave (inner diameter φ10 mm, length 230 mm, volume 18 cm ³ ) 10, 0.012 mol of polycrystalline GaN as a raw material 5 containing nitride crystals, VCl ₃ (Experiment 1), NH ₄ Cl (additive 13) Experimental Example 2), LiCl (Experimental Example 3), and CaCl ₂ (Experimental Example 4) were introduced so that each chlorine atom was 0.012 mol.
After the inside of the autoclave was sealed, the vacuum pump 11 was used to deaerate from the gate valve 8 and the inside was evacuated.
Next, the autoclave 10 is cooled from the outside with a dry ice-ethanol refrigerant, and the inside of the autoclave 10 is sufficiently cooled. Then, 7.5 g of ammonia gas is liquefied and the gate valve 8 is closed to close the autoclave 10. Was kept sealed.

Next, the autoclave 10 was set at 300 ° C. for the upper part, 520 ° C. for the middle part, and 550 ° C. for the lower part with an electric furnace divided into three parts along the longitudinal direction of the autoclave 10 for 1.5 hours. The temperature was raised from room temperature to the predetermined temperature. At this time, regarding the temperatures at the upper, middle and lower positions of the autoclave 10, the position of the lid at the top of the autoclave 10 (upper part), the waist (middle part) of the autoclave 10 at the substantially center position in the longitudinal direction, the autoclave 10 Each was measured and confirmed by attaching a thermocouple to the position of the bottom surface.
After the temperature inside the autoclave 10 became constant at the predetermined temperature, the temperature was kept constant for 4.5 hours to dissolve the polycrystalline GaN. After 4.5 hours passed in this state, the autoclave 10 was cooled again, the internal ammonia solvent was removed, and then the solid in the autoclave 10 was dissolved and dispersed using pure water and recovered.
Next, a precipitate of the gallium nitride single crystal was recovered from the recovered solid, and the recovered gallium nitride single crystal was washed with water and dried.

  Using a scanning electron microscope, the deposition length of the precipitate collected from the autoclave 10 was measured. The deposition rate (μm / hr) per unit time was calculated by dividing the deposition length by the holding time (4.5 hours) after the temperature inside the autoclave 10 became constant. Table 2 below shows the results.

In Experimental Example 1 using VCl ₃ as an additive used in the production method of the present invention, the nitride single crystal deposition rate was 56 μm / hr. On the other hand, in Experimental Example 2 using NH ₄ Cl as an additive, the precipitation rate of the nitride single crystal was 44 μm / hr. Therefore, it was confirmed that the precipitation rate of crystals was improved by using VCl ₃ which is a halide of vanadium as an additive.

In addition, GaN single crystal precipitates were recovered from the recovered solid, and polycrystalline GaN was recovered. The recovered polycrystalline GaN was washed with water and dried, and then the weight was measured to determine the amount of polycrystalline GaN consumed by the dissolution / reprecipitation reaction.
And from the consumption amount of the measured polycrystalline GaN, the dissolution amount with respect to the chlorine atom of the consumed polycrystalline GaN was computed by the following formula.
Here, the dissolution reaction rate r _{1 at which} polycrystalline GaN dissolves exists in the reaction rate constant (k ₁ ), the molar concentration of polycrystalline GaN in the reactor (= [polycrystalline GaN]), and in the reactor. It is expressed as the product of the molar concentration of chlorine ([chlorine]).
r ₁ = k ₁ [polycrystalline GaN] [chlorine content]
In addition, the deposition reaction rate r ₂ at which GaCl ₃ reacts to deposit GaN is present in the reaction rate constant (k ₂ ), the molar concentration of GaCl ₃ in the reactor (= [GaCl ₃ ]), and in the reactor. Expressed as the product of the molar concentration of nitrogen ([nitrogen]).
r ₂ = k ₂ [GaCl ₃ ] [nitrogen content]

In the above relational expression, the higher the ratio (= k ₂ / k ₁ ) of k ₂ (precipitation reaction rate constant) to k ₁ (dissolution reaction rate constant), the higher the reversibility and the higher the precipitation reaction rate. Show. In the above relational expression, r ₁ = r ₂ in a state where the reversible reaction proceeds in a steady manner (steady state), and therefore the following formula was calculated from the above formulas.
{K ₁ [polycrystalline GaN] [chlorine content] = k ₂ [GaCl ₃ ] [nitrogen content]} ← → {k ₂ / k ₁ = [polycrystalline GaN] [chlorine content] / [GaCl ₃ ] [nitrogen content] ]}

Here, [polycrystalline GaN], [GaCl ₃ ], [chlorine], and [nitrogen] in a steady state cannot be observed directly, but can be approximately calculated by the following method.
[Polycrystalline GaN]: Corresponds to the remaining amount of polycrystalline GaN recovered after the experiment. Polycrystalline GaN was added under conditions sufficient to remain in this reaction, and was treated as a constant A approximately.
[GaCl ₃ ]: Corresponds to the amount of consumed polycrystalline GaN. It can be calculated by obtaining the difference between the introduced amount of polycrystalline GaN and the remaining amount of polycrystalline GaN.
[Chlorine]: Corresponds to the amount of chlorine remaining without being consumed. It can be calculated by determining the difference between the amount of introduced chlorine and the amount of three times the amount of consumed polycrystalline GaN.
[Nitrogen]: Indicates the amount of introduced nitrogen source. The nitrogen source in this example corresponds to ammonia used as a solvent. Ammonia was in large excess in this reaction and was treated as a constant B approximately.
By the above method, the amount of consumed polycrystalline GaN is X, and the amount of introduced chlorine is Y, whereby k ₂ / k ₁ can be estimated by the following formula.
k ₂ / k ₁ = {A × (Y−3 × X)} / (X × B)
= (A / B) × {(Y / X) -3}

  In order to precipitate a GaN single crystal (nitride single crystal) with a sufficient precipitation rate, it is necessary to maintain a high precipitation reaction while maintaining reversibility. From the above formula, Y / X, that is, (the amount of introduced chlorine) / (the amount of consumed polycrystalline GaN), the polycrystalline GaN with respect to the amount of chlorine (halogen element) (raw material including nitride crystals) It is important to find a reaction that can keep the amount consumed by high.

  In Experimental Examples 1 to 4, the results of calculating the amount of dissolved polycrystalline GaN with respect to the amount of chlorine are shown in Table 2 above.

In Experimental Example 1 using VCl ₃ , it was confirmed that the amount of consumed polycrystalline GaN was higher than in Experimental Examples 2 to 4. Therefore, it was confirmed that the precipitation reaction was promoted while maintaining reversibility by using VCl ₃ which is a halide of vanadium as an additive.

<Deposition rate confirmation test (2)>
(Experimental Examples 5-9)
[manufacturing device]
In Experimental Examples 5 to 9, the interior is provided with an autoclave 10 that is partitioned into an upper part 3 and a lower part 4 by a partition plate 2, and in addition to a vacuum pump 11 and an ammonia tank 12, temperature adjusting means (not shown) including an electric furnace is provided. The manufacturing apparatus 1 shown in FIG. 2 which is provided and further provided with safety equipment (not shown) was used. Further, as shown in FIG. 2, metal 15 and ammonium chloride (ammonium halide 14) were introduced.

[Procedure and Evaluation]
Tests were conducted in the same manner as in Experimental Examples 1 to 4 except that 12 mmol of NH ₄ Cl (ammonium chloride) and a metal shown in Table 3 below were introduced as additives.
The results of the deposition rate (μm / hr) per unit time in Experimental Examples 5 to 9 and the results of calculating the amount of dissolved polycrystalline GaN with respect to chlorine atoms are shown in Table 3 below.

In Experimental Example 5 using V, it was confirmed that the crystal precipitation rate was improved as compared with Experimental Example 2 using only NH ₄ Cl in Table 2 above. Further, it was confirmed that the example using V (Experimental Example 5), Cr (Experimental Example 6), and Zr (Experimental Example 7) kept the dissolved amount of polycrystalline GaN high. Similarly, for Ti and Hf, it was confirmed that the deposition rate was improved and the amount of dissolved polycrystalline GaN was kept high.

  According to the present invention, a nitride single crystal is formed by an ammonothermal method using an additive containing at least one metal selected from the group consisting of vanadium, zirconium, titanium, hafnium, and chromium, and a halogen element. By precipitating, a sufficient precipitation rate of the nitride single crystal can be obtained while stably maintaining a reversible reaction that repeats dissolution and reprecipitation of gallium nitride. Thereby, defects in the nitride single crystal can be reduced and the precipitation rate can be sufficiently improved, so that a nitride single crystal having excellent crystallinity can be produced with high productivity. By applying the nitride single crystal obtained by such a manufacturing method to, for example, a power device or the like, low loss, high speed, and high breakdown voltage can be realized.

1 ... Manufacturing device (nitride single crystal manufacturing device),
2 ... Partition plate,
3 ... Upper part (autoclave, reaction vessel),
4 ... Lower part (autoclave, reaction vessel),
5 ... Raw material containing nitride crystal,
6 ... lid,
7 ... Seed crystal,
8 ... Gate valve,
9 ... Conduit,
10 ... autoclave (reaction vessel),
11 ... vacuum pump,
12 ... Ammonia tank,
13 ... Additives,
14 ... Additive (halide),
15 ... Additive (metal),
50 ... Nitride single crystal,

Claims (11)

A method for precipitating a nitride single crystal after dissolving a raw material containing a nitride crystal in an ammonia solvent,
A nitride characterized by depositing a nitride single crystal in the presence of an additive containing at least one element selected from the group consisting of vanadium, zirconium, titanium, hafnium, and chromium, and a halogen element A method for producing a single crystal.   The additive is a halide (A) of at least one element selected from the group consisting of vanadium, zirconium, titanium, hafnium, and chromium, and is selected from the group consisting of vanadium, zirconium, titanium, hafnium, and chromium At least one metal and halide (A), at least one metal selected from the group consisting of vanadium, zirconium, titanium, hafnium, and chromium, or ammonium halide, or halide (A) and The method for producing a nitride single crystal according to claim 1, which is ammonium halide.   The method for producing a nitride single crystal according to claim 1 or 2, wherein the additive is vanadium chloride, or vanadium metal and ammonium chloride.   The molar ratio of the number of halogen atoms to the number of atoms of at least one selected from the group consisting of vanadium, zirconium, titanium, hafnium, and chromium of the additive is 0.05 to 10. A method for producing a nitride single crystal according to claim 1.   The method for producing a nitride single crystal according to any one of claims 1 to 4, wherein the nitride single crystal is precipitated at 300 to 800 ° C.   The method for producing a nitride single crystal according to any one of claims 1 to 5, wherein the nitride single crystal is precipitated by setting the pressure in the reaction vessel to a critical pressure of ammonia solvent to 150 MPa.   The method for producing a nitride single crystal according to claim 1, wherein the nitride single crystal is a single crystal of a group 13 element nitride.   The method for producing a nitride single crystal according to claim 1, wherein the nitride single crystal is a gallium nitride single crystal. The manufacturing method of the nitride single crystal characterized by including the process of the following (A)-(C).
(A) A step of introducing an additive containing at least one element selected from the group consisting of vanadium, zirconium, titanium, hafnium, and chromium and a halogen element and a raw material containing a nitride crystal into a reaction vessel.
(B) A step of sealing the ammonia solvent in the reaction vessel.
(C) A step of forming a low temperature portion and a high temperature portion in the reaction vessel, reacting the raw material containing nitride crystals with the additive in an ammonia solvent, and then depositing a nitride single crystal from the low temperature portion.   The method for producing a nitride single crystal according to claim 9, wherein a seed crystal is installed in a low temperature part in the reaction vessel.   In the step (C), the low temperature part in the reactor is 300 to 800 ° C, and the high temperature part in the reactor is a temperature higher by 0.5 to 100 ° C than the low temperature part. The manufacturing method of the nitride single crystal of description.

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