JP2005112718A - Method for manufacturing group 13 element nitride crystal - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method capable of simply, safely and efficiently obtaining a high quality group 13 element nitride compound, especially a bulky single crystal of gallium nitride. <P>SOLUTION: In the method for manufacturing the group 13 element nitride crystal, the bulky single crystal is obtained by performing crystal growth by heating and melting a mixture of a group 13 element nitride raw material and a metal halide. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method for producing a group 13 nitride represented by gallium nitride, and more particularly to a method for producing a high-quality group 13 nitride bulk single crystal.

Gallium nitride (GaN) is useful as a material applied to electronic devices such as light emitting diodes and laser diodes. The most common method for producing this gallium nitride crystal is a method of performing vapor phase epitaxial growth by MOCVD (Metal-Organic Chemical Vapor Deposition) on a substrate such as sapphire or silicon carbide. However, since this method uses heteroepitaxial growth in which the substrate and GaN have different lattice constants and thermal expansion coefficients, lattice defects are likely to occur in the obtained GaN, and a high-quality crystal that can be applied with a blue laser or the like is obtained. There is a problem that is difficult. Various methods for reducing lattice defects have been proposed, but problems such as complicated processes and increased costs occur.

Therefore, in recent years, there has been a strong demand for establishment of a new manufacturing technique for high-quality gallium nitride massive single crystals for homoepitaxial substrates, which can replace the above method. Various methods have been proposed for producing such a new gallium nitride crystal.
S. Porowski et al. Obtained gallium nitride crystals by reacting nitrogen and Ga under a high pressure of about 2000 MPa (see Non-Patent Document 1).

R. Dwilinski et al. Obtained gallium nitride crystals using ammonia in a supercritical state as a solvent under high pressure of 100 to 500 MPa and KNH ₂ as a mineralizer for crystallization (
Non-patent document 2).
On the other hand, H. Yamane et al. Obtained metallic gallium nitride crystals from metallic gallium and dissolved nitrogen using metallic sodium or metallic potassium as a flux (see Non-Patent Document 3).
J. Crystal Growth 178 (1997) 174-178 ACTA PHYSICA POLONICA A Vol.88 (1995) 833-836 J. Crystal Growth 218 (2000) 7-12

  However, the method of growing a nitride crystal by the above method has not been established industrially, and is only a rudimentary study. There is no clear method for obtaining large-sized high-quality single crystals, which requires a very expensive equipment for high-pressure equipment, uses highly reactive alkali metals as flux, In order to use highly dangerous ammonia as a solvent, safety must be strictly ensured, and it is therefore difficult to obtain high production efficiency.

  In view of the above problems, the present inventors can manufacture a high-quality group 13 nitride massive single crystal by a method that can be applied industrially without using a highly toxic or dangerous substance. As a result of intensive studies on the method, it has been found that according to the method of crystal growth using a metal halide as a so-called flux for a group 13 nitride raw material, a massive single crystal can be obtained efficiently, and the present invention has been achieved. . That is, the present invention resides in a method for producing a group 13 nitride crystal characterized in that a bulk single crystal is obtained by performing crystal growth by heating and melting a mixture of a group 13 nitride raw material and a metal halide.

  By the method for producing a group 13 nitride crystal of the present invention, a high-quality group 13 nitride massive single crystal can be efficiently produced by a simpler and safer method than before. According to the present invention, since a highly toxic or reactive substance is not used, safety is high and industrial implementation is easy.

Hereinafter, the present invention will be described in detail. The description of the constituent requirements described below is an example of embodiments of the present invention, and the present invention is not limited to these embodiments.
Examples of the group 13 nitride that is a production target of the present invention usually include nitrides of single metals of group 13 elements of the periodic table such as B, Al, Ga, and In (for example, GaN, AlN, InN), and alloys. Group nitrides (eg, GaInN, GaAlN) are also included. Of these, the present invention is particularly suitable for obtaining gallium nitride crystals.

In the method of the present invention, a nitride polycrystalline powder raw material (hereinafter sometimes referred to as “polycrystalline raw material”) is usually used as the group 13 nitride crystal raw material. Hereinafter, the present invention will be described mainly with respect to a method for producing a group 13 nitride crystal using a polycrystalline raw material, but the raw material is not limited to this, and a group 13 nitride reacts during crystal growth. The present invention is also applicable to the case where (A) a group 13 elemental metal or compound and (B) nitrogen gas or nitrogen compound which can be generated. As the nitrogen compound, a state such as gas, liquid or solid can be used without any particular limitation. Examples of Group 13 element compounds of (A) are particularly preferably halogen salts, ammonium halide adducts, halometal salts, metal amides, alkali metal amides, metal imides, and the like. Acid salts and the like can also be used. Examples of nitrogen compounds in (B) are ammonia (NH ₃ ), hydrazine (NH ₂ NH ₂ ), urea, primary amines such as methylamine as organic amines, secondary amines such as dimethylamine, Tertiary amines such as trimethylamine, diamines such as ethylenediamine or melamine, N-containing cyclic compounds such as imidazole and pyridine, and cation salts of these nitrogen-containing compounds. Furthermore, it is also possible to use ammonium halide, alkali nitride, alkali amide or the like. In consideration of avoiding carbon and the like in the generated nitride crystal, it is preferable to use ammonia or hydrazine, ammonium halide, alkali nitride or alkali amide as the nitrogen compound. In view of avoidance of alkali mixing and ease of handling, it is particularly preferable to use ammonia. From the viewpoint of making the composition ratio of the obtained nitride crystal close to the theoretical stoichiometric ratio, the molar ratio of the nitrogen gas or nitrogen compound of (B) to the simple metal or compound of (A) is 0.1 or more, preferably 1 0.0 or more, more preferably 10 or more. The upper limit is 10,000 or less, preferably 1000 or less.

There are no particular restrictions on the method for producing the polycrystalline raw material, but for example, a halide as a Group 13 metal oxide, hydroxide, or more reactive metal compound in a reaction vessel in which ammonia gas is circulated. A nitride polycrystal can be obtained by reacting a compound having a covalent MN bond such as amide compound, imide compound, and galazane with ammonia. Furthermore, it is possible to use a nitride polycrystal produced by reacting a Group 13 metal with nitrogen at a high temperature and a high pressure. The nitride polycrystalline raw material as the raw material for producing the nitride crystal of the present invention is not particularly required to be a complete nitride, and depending on the conditions, the group 13 metal itself, that is, in the metal state (that is, zero valence) is used. The metal component is usually 1 ppm or more, and the upper limit is not particularly limited as long as it does not inhibit crystal growth, but it may contain up to about 20% by weight. This is because when a trace amount of oxygen is mixed in the reaction system, the metal component is expected to play a role like an oxygen trap agent that prevents the oxygen from diffusing into the flux.

  The present invention relates to the production of a group 13 element nitride crystal by a so-called flux method. Here, a metal halide is used as a flux for the nitride raw material. Usually, the flux used to produce a bulk single crystal of an inorganic compound is generally used in a molten state and has a property of dissolving an object, but the metal halide in the present invention is a nitride. The solubility of the raw material need not be particularly high. The reason for this is that, even if once dissolved, it is consumed by crystal precipitation, but if there is a sufficient amount of raw material, it is possible to grow crystals by repeating this dissolution and precipitation cycle. is there.

  The metal halide has a metal component such as lithium (Li), sodium (Na), potassium (K), rubidium (Rb), cesium (Cs) and other alkali metals, magnesium (Mg), calcium (Ca), strontium ( Sr), alkaline earth metals such as barium (Ba) and transition metals, and halogen components are fluorine (F), chlorine (Cl), bromine (Br), iodine (I), etc. The combination forms a compound. Such metal halides may be used not only in one type but also in several types. The optimum metal halide type should be selected depending on the combination with the crystal raw materials and the conditions of crystal growth. Usually, the use of alkali halides is preferred. Among alkali halides, sodium chloride and potassium chloride are preferred. The use of alkali chloride such as is preferred.

  The present invention heats and melts the mixture of the polycrystalline raw material and the metal halide as described above to carry out crystal growth to obtain a bulk single crystal. In carrying out this crystal growth reaction, an additive may be further added to the mixture of the group 13 nitride raw material and the metal halide. Such an additive is preferably a halogen atom or a compound containing an alkali metal, an alkaline earth metal, or a rare earth metal. Such a compound may be an additive and at the same time be a nitride raw material itself.

As additives, compounds containing alkali metals, alkaline earth metals, rare earth metals, sodium amide (NaNH ₂ ), potassium amide (KNH ₂ ), lithium amide (LiN
H ₂ ), alkali metal amides such as lithium diethylamide ((C ₂ H ₅ ) ₂ NLi)), alkaline earth metal amides such as Mg (NH ₂ ) ₂ , rare earth amides such as La (NH ₂ ) ₃ , Li Examples thereof include alkali metal nitrides or alkaline earth metal nitrides such as ₃ N, Mg ₃ N ₂ , Ca ₃ N ₂ , and Na ₃ N. Also, chromium nitride (CrN), niobium nitride (NbN), silicon nitride (Si ₃
N ₄ ), zinc nitride (Zn ₃ N ₂ ), salts of hydrazines such as NH ₂ NH ₃ Cl, ammonium carbonate ((NH ₄ ) ₂ CO ₃ ), ammonium carbamate (NH ₂ COONH ₄ ) It is done.

  The optimum ratio between the polycrystalline raw material and the metal halide is selected depending on the raw material, the metal halide, the kind of additive, the size of the target crystal, and the like. However, the weight percentage of polycrystalline raw material / (polycrystalline raw material + metal halide) is usually in the range of 1 to 95% by weight, preferably 2 to 50% by weight. That is, the ratio of the metal halide in the mixture of the polycrystalline raw material and the flux is usually 5 to 99% by weight, preferably 50 to 98% by weight. The amount ratio of the polycrystalline raw material to the additive is usually selected in the range of 0.01 to 10 as the metal molar ratio of additive / polycrystalline raw material.

In the present invention, a polycrystalline raw material and a metal halide as described above, and a mixture of additives, which are optional components, are filled in a reaction vessel, heated and melted for crystal growth. In this case, in order to obtain a higher quality nitride crystal, mixing of water and oxygen should be avoided as much as possible. Therefore, the oxygen atom content in each component or mixture should be usually 5% by weight or less, preferably 2% by weight or less, particularly preferably 0.5% by weight or less. When using a hygroscopic material, it should be thoroughly dried by heating and degassing before filling, and the mixing and filling of each component should be carried out promptly in an atmosphere that excludes oxygen and moisture as much as possible. It is.

For example, in a container or room filled with an inert gas, after sufficiently replacing the inside of the reaction vessel with the inert gas, after mixing each component and filling the reaction vessel, or each component separately After filling the reaction vessel, close the lid. The type of the inert gas is not particularly limited, but helium (He), nitrogen (N ₂ ), argon (Ar) and the like are preferably used. Further, a substance that functions as a scavenger that selectively absorbs oxygen and moisture (for example, a metal piece such as titanium) may be accompanied in the reaction vessel. Although it is necessary to keep the atmosphere in which oxygen and moisture are eliminated as much as possible in the reaction system, a gas containing nitrogen atoms such as ammonia may be present in addition to the inert gas.

  Here, the polycrystalline raw material is not particularly limited, but in consideration of the dissolution uniformity in the flux (metal halide), a spherical material is usually desirable. Further, it is estimated that the smaller the particle size, the larger the specific surface area and the higher the rate of dissolution in the flux, and usually the range of 1 to 20 μm is preferable. However, if the particle size is too small, it is not preferable because the particles may adhere to the seed crystal when the seed crystal is used.

  In addition, when two types of polycrystalline raw materials having different average particle diameters are used, a crystal having a high dissolution rate due to a polycrystalline raw material having a small particle diameter and a low dissolution rate having a large particle diameter are mixed in the system. Is estimated to grow by the Ostwald ripening mechanism. That is, Group 13 metal ions and the like eluted from a polycrystal having a small particle size are precipitated on a crystal having a large particle size with a slow dissolution rate, and the crystal is further enlarged. Based on this principle, in order to grow a bulk single crystal more efficiently, a method using a seed crystal described later is employed. When polycrystalline raw materials with different particle sizes are used, the supply of crystals to the crystal growth unit is prevented from being cut off due to the difference in dissolution rate described above, and as a result, a bulk single crystal called elution of seed crystals, especially when seed crystals are used. It is also possible to deter the disadvantages of training.

It is preferable to cover all or part of the inner surface of the reaction vessel for carrying out the crystal growth reaction with a surface composed of Group 4, 5, 6 or 10, 11 elements of the periodic table. Or the inner cylinder produced with the said metal can also be installed in reaction container. For example, the metals of Group 10 and Group 11 of the periodic table are nickel (Ni), palladium (Pd), platinum (Pt), and gold (Au). In this invention, the method of sealing this reaction container inner cylinder and installing in a reaction container can also be used as needed. As described above, contamination of impurities from the reaction vessel material into the generated nitride crystal can be suppressed. Moreover, BN etc. can also be used other than a metal. Furthermore, although it should not be used positively in the sense of avoiding the mixing of oxygen into the generated nitride crystal, it is not impossible to use alumina (Al ₂ O ₃ ) or quartz (SiO ₂ ).

As a growth method, the temperature difference (Gradient Transport) method used in the flux method, the slow cooling (Slow Cooling) method, the temperature cycle (Temperature Cycling) method, the crucible accelerated rotation (Accelerated Crucible-Rotation Technique: ACRT) method, For example, a top-seeded solution growth (TSSG) method, a solvent transfer method, or a solvent transfer floating zone (TSFZ) method, which is a modification thereof, can be used. A combination of these methods can also be used.

Polycrystalline raw materials, metal halides and the like are usually mixed in a powder state and then packed so as to fit in the lower part of the reactor. Since these powders are reduced in volume when heated and melted, they may be charged after being pressed and compressed in advance.
In addition, by preparing a seed crystal in the upper part of the reactor, the generation of a single crystal can be promoted and a larger single crystal can be obtained. The seed crystal is usually charged after filling a polycrystalline raw material, a metal halide, or the like. As the seed crystal, it is desirable to use a single crystal of the target nitride, but it is not always necessary to use the same nitride as the target. In some cases, a single crystal other than the nitride may be used. However, in that case, it is consistent with the desired nitride, has a suitable lattice constant, crystal lattice size parameters, or is coordinated to ensure heteroepitaxy (ie, match the crystallographic position of some atoms). It is necessary to be composed of a single crystal material piece or a polycrystalline material piece. For example, in the case of gallium nitride (GaN), in addition to a single crystal of GaN, a single crystal of zinc oxide (ZnO), a single crystal of silicon carbide (SiC), lithium gallate (LiGaO ₂ ), zirconium diboride (ZrB 2) The single crystal etc. are mentioned.

  As a seed crystal of GaN, a crystal grown epitaxially on a dissimilar substrate such as sapphire by MOCVD method or HVPE method, a single crystal obtained by peeling the dissimilar substrate after epitaxial growth, and flux of metal Na, metal K, or Bi from metal Ga Single crystals obtained by crystal growth and homo / heteroepitaxially grown single crystals obtained by using the LPE method, or single crystals prepared based on the solution growth method including the method of the present invention, and their cut crystals, etc. Is used.

In the case of using a seed crystal, a temperature difference method, a slow cooling method, a top seed (TSSG) method, a solvent transfer floating zone (TSFZ) method, or the like can be employed as a growth method. The material for the wire rod, rod, pipe, etc. for holding the seed crystal is preferably that of a periodic table 4, 5, 6 or 10, 11 element, for example, nickel (Ni), tantalum (Ta), titanium (Ti). , Palladium (Pd), platinum (Pt), gold (Au), and niobium (Nb). In some cases, BN other than metal can be used. Furthermore, although it should not be used positively in the sense of avoiding the mixing of oxygen into the generated nitride crystal, it is not impossible to use alumina (Al ₂ O ₃ ) or quartz (SiO ₂ ). In the case of the temperature difference method, it is divided into two overlapping zones, that is, a lower raw material filling portion and an upper growing portion separated by a baffle plate, and a temperature gradient ΔT between these two zones is usually 10 to 100. Keep it at ℃. And a seed crystal is hold | maintained at the upper growth part with a metal wire or a metal rod. In this case, the seed crystal is preferably rotated.

  As a baffle plate that is divided into a raw material filling portion filled with a raw material made of a polycrystalline raw material and a crystal growth portion where a seed crystal is arranged, one having an opening ratio of about 2 to 5% is preferable. The material is preferably nickel (Ni), tantalum (Ta), titanium (Ti), palladium (Pd), platinum (Pt), gold (Au), niobium (Nb), or the like. In order to increase the melting rate of the raw material, a stirring plate made of the same material as the baffle plate can be provided under the baffle plate. By controlling the aperture ratio of the baffle plate, it becomes easy to appropriately control the degree of supersaturation in the crystal growth portion under the solution growth conditions. In some cases, a polycrystalline raw material can be additionally supplied onto the baffle plate. Thus, by further interposing a polycrystalline raw material on the baffle plate, that is, between the raw material filling part and the seed crystal arranging part, the transition speed of the crystal growing part to the supersaturated state can be increased, and the seed crystal It is possible to prevent various disadvantages in elution.

  In the present invention, in order to appropriately control the degree of supersaturation as described above, it is preferable to set the ratio of the crystal growth part volume to the raw material filling part volume within a range of 1 to 5 times. If the degree of supersaturation usually exceeds 1.5, the rate of precipitation on the seed crystal is too high, so that the consistency inside the grown crystal is deteriorated and defects are introduced, which is not preferable. In addition, since the amount deposited on the inner wall of the growth vessel increases, it is not preferable that the precipitate grows in contact with the GaN single crystal and hinders the growth of the single crystal.

Here, “supersaturation” refers to a state in which the amount of dissolution has increased more than the saturated state. Further, the “supersaturation degree” refers to the ratio between the dissolved amount in the supersaturated state and the dissolved amount in the saturated state. In the solution growth method, the amount of nitride dissolved in the crystal growth portion that is supersaturated due to the transport of nitride by thermal convection from the raw material filling portion is compared to the amount of nitride dissolution in the saturation state of the crystal growth portion. Say ratio. The degree of supersaturation as described above can be controlled by appropriately changing and selecting the density of polycrystalline nitride, the baffle plate opening ratio, the temperature difference between the raw material filling portion and the crystal growth portion, and the like.

In the slow cooling method, a polycrystalline raw material and a flux are put in a reaction vessel such as a crucible, melted, a seed crystal is attached to the tip of a metal wire or a metal rod, and the seed crystal is inserted so that it is located immediately below the liquid surface, and the seed crystal is rotated and inverted However, the reaction vessel temperature is lowered. At this time, it is preferable to rotate the seed crystal at a critical rotational speed or higher so that the diffusion process in the flux melt does not become a rate-determining step. The critical rotation speed here is the minimum rotation speed at which the crystal growth speed becomes independent of the rotation speed.
In the top seed method, a polycrystalline raw material and a flux are filled in a lower part of a reaction vessel such as a crucible and melted, and a seed crystal is put in the center of the melt surface and gradually pulled up. When the seed crystal is attached to a metal pipe, it is suitable for a heat escape route. The temperature difference between the flux melt and the center of the surface where the seed crystals are present is usually 10 to 100 ° C. Also in this case, the seed crystal can be rotated.

  In the solvent transfer floating zone (TSFZ) method, a polycrystalline raw material and a flux are formed in advance into a rod shape and set in a growth apparatus, and a seed crystal is placed at the bottom. A part of the raw material rod is heated so as to be in a molten state, and the heating zone is moved upward. In this method, since the solution layer is held in the air by surface tension, it is not necessary to use a container such as a crucible, and there is no fear of mixing impurities from the container.

  The crystal growth reaction as described above is performed by heating and raising the temperature in the reaction vessel using an electric furnace or the like. In the TSFZ method, infrared heating or high-frequency induction heating is also used. The method for heating the reaction vessel and the rate of temperature increase to a predetermined reaction temperature are not particularly limited, but it is usually carried out over several hours to several days. If necessary, it is also preferable to perform multi-stage temperature rise or change the temperature rise speed in the temperature range. Further, the reaction vessel can be partially heated with a temperature difference, or partially heated while being cooled.

  The reaction temperature here is measured by a thermocouple provided so as to be in contact with the outer surface of the reaction vessel, and is not strictly an actual temperature inside the reaction vessel. The temperature gradient inside the reaction vessel varies depending on the shape of the reaction vessel, the shape of the furnace in which it is stored, and the heating and thermal insulation conditions represented by the positional relationship, but some of the temperature gradient was opened inward from the outer surface of the reaction vessel for thermocouples. The temperature inside the reaction vessel is estimated by extrapolating or extrapolating the temperature gradient toward the inside of the reaction vessel using a hole that does not penetrate to the cavity inside the reaction vessel. Similarly, the temperature in the vertical direction of the reaction vessel also varies depending on the shape of the reaction vessel, the shape of the furnace in which it is stored, and the heating and heat retention conditions represented by the positional relationship. Therefore, it is desirable to measure the temperature at several points above and below the outer surface of the reaction vessel and to control the temperature after estimating the temperature inside the reaction vessel at each position. Depending on the shape and temperature of the reaction vessel, even when the temperature of the outer surface of the reaction vessel is the same up and down, or even when the upper part is several tens of degrees Celsius higher, the temperature inside the reaction container may be lower by several tens of degrees Celsius. In addition, as described above, in order to promote dissolution and precipitation of crystals, when a temperature gradient is provided in advance during the reaction, the temperature at several points on the outer surface of the reaction vessel is measured, and a heater divided into multiple stages is used. It is also effective to perform temperature control mainly divided in the vertical direction of the reaction vessel.

  As the temperature rises, the solubility of the nitride raw material increases, but as described above, in the present invention, it is important to dissolve even a small amount of the nitride in the flux, and the solubility value is not necessarily large. Therefore, it is desirable that the temperature in the reaction vessel is not less than the melting temperature of the flux at the lower limit, preferably not less than + 5 ° C. of the melting temperature, particularly preferably not less than the melting temperature + 10 ° C.

Whether or not crystal growth is promoted by the application of pressure depends on whether the system shrinks due to dissolution or crystallization because the equilibrium shifts in a direction in which the system shrinks more in response to an external change such as an increase in pressure. . Assuming that the molar volume of the crystal is VC and the volume change (partial molar volume) of the solvent when 1 mol of the crystal is dissolved is VS, the volume change ΔV in the dissolution process is
ΔV = VS−VC
This value is determined according to whether the value is positive or negative. If the value is positive, crystal growth is caused by pressurization. In the method for producing a nitride crystal of the present invention, since the form of dissolution in the molten flux is not clear, the value of VS is unknown, but crystal growth may be promoted by pressurization. Therefore, it is desirable to keep the pressure in the reaction vessel at an upper limit of usually 500 MPa or less, preferably 400 MPa or less, particularly preferably 200 MPa or less.

The pressure can be applied by pressurizing and filling an inert gas in the pressure vessel. In this case, the type of inert gas is not particularly limited, but helium (He), nitrogen (N ₂
), Argon (Ar) or the like is preferably used. Moreover, when using a metal inner cylinder as a reaction container, the inner cylinder can be sealed and pressurized using gas or liquid from the outside. In this case, since the inner cylinder is sealed, the type of gas or liquid used for pressurization is not particularly limited, but water or the like is preferably used.

  The reaction time after reaching the predetermined temperature and pressure is usually several hours to several hundred days, although it varies depending on the type of nitride crystal, the raw material used, the flux, and the size and amount of the crystal to be obtained. During the reaction, the reaction temperature may be constant or may be gradually raised or lowered. After a reaction time to produce the desired crystals, the temperature is lowered. The method of lowering the temperature is not particularly limited, but the heating of the heater may be stopped and the reactor may be allowed to cool with the reactor installed in the furnace, or the reactor may be removed from the furnace and air cooled. For example, it can be rapidly cooled using a refrigerant.

  In addition, in order to prevent partial precipitation of crystals and certain additives when the temperature drops, the reaction vessel is partially cooled with a temperature difference, or partially cooled with slight heating. You can also. After the temperature of the outer surface of the reaction vessel or the estimated temperature inside the reaction vessel is lower than the predetermined temperature, return the pressure to normal pressure, open the reaction vessel, and use a solvent that dissolves the flux but does not dissolve the nitride crystals. The formed solid is obtained by dissolving the solidified flux. As such a solvent, water, warm water, acid or the like is preferably used.

The size of the bulk single crystal obtained by the method of the present invention as described above is not particularly limited in its range, but usually when the crystal is approximated to a cylindrical shape, the diameter is 20 μm or more, The length is in a range of 50 μm or more, and the crystal shape is not particularly limited.
In the above, the production mainly using the nitride polycrystalline material has been described. However, when a bulk nitride crystal is obtained using a material other than the nitride polycrystalline material, nitride synthesis and nitriding are performed. Since it is necessary to simultaneously dissolve and precipitate the product in the flux, stricter reaction condition control is required. When one of the raw materials is gaseous at room temperature, the mass raw material is fed into the reaction vessel filled with the flux and the other solid or liquid raw material at room temperature in order to control the group 13 nitride formation reaction. It is also preferable to distribute the flow while controlling the flow rate using a method such as the above. Moreover, when it is desired to obtain a larger lump crystal, a multistage production method is preferably employed. The reaction divided into multiple stages may be carried out as it is without removing the flux or the like in the same reactor, or may be carried out by replacing with the same or another flux or additive.

Hereinafter, the present invention will be described in more detail by way of examples. However, the present invention is not limited to the following examples unless it exceeds the gist (Example 1).

  The polycrystalline gallium nitride reagent (manufactured by Mitsuwa Chemical) was pulverized in an agate mortar in a nitrogen atmosphere glove box. An SEM photograph of the pulverized material is shown in FIG. It was an irregular particle having a particle size of about 2 to 3 μm. The same applies to the flux (A) in which CsCl (manufactured by Kanto Chemical), KCl (manufactured by Kishida Chemical), and NaCl (manufactured by Junsei Chemical) are mixed at a molar ratio of CsCl: KCl: NaCl = 45.2: 24.4: 30.4. Were crushed in a glove box. The melting temperature of the flux (A) is 480 ° C. according to Phase Diagrams for Ceramists (The American Ceramic Society, 1966). 0.07 g of pulverized gallium nitride and 0.63 g of pulverized flux (A) were pulverized and mixed in an agate mortar and filled in a gold pipe having an outer diameter of 5 mm, an inner diameter of 4.7 mm, and a length of 65 mm. After firmly attaching, was taken out from the glove box and the upper part was also welded and completely enclosed. The sealed gold pipe was put in a pressure vessel having an internal volume of 6 ml, capped, and an appropriate amount of water was added through a valve. Then, the valve was closed and the pressure vessel was heated in an electric furnace.

  The temperature was increased at 3 ° C./min until the temperature of the upper part of the gold pipe mounted in the pressure vessel reached 490 ° C. At that time, water was purged by opening and closing the valve so that the pressure was 84 MPa. Thereafter, the inside of the pressure vessel was held at 490 ° C. and 84 MPa for 12 hours. Next, the temperature was lowered to room temperature at 1 ° C./min. The gold pipe was taken out and the contents were put into 50 ml of pure water to dissolve the flux, and then the supernatant was discarded to obtain a precipitate. After repeating this operation two more times, 50 ml of acetone was added, the supernatant was discarded, and the precipitate was collected and air-dried.

A scanning electron microscope (SEM) photograph of the precipitate is shown in FIG. 2, and a powder X-ray diffraction diagram (XRD) is shown in FIG. A hexagonal columnar crystal having a diameter of 30 μm and a length of 150 μm was observed by SEM. In XRD, no impurity phase other than hexagonal gallium nitride (h-GaN) was observed.
(Example 2)

The operation was performed in the same manner as in Example 1 except that the holding time after the temperature of the upper part of the gold pipe reached 490 ° C. was 84 hours. An SEM photograph of the obtained precipitate is shown in FIG. From the SEM, a prism-shaped crystal having a diameter of 40 μm and a length of 150 μm was observed. It was h-GaN when the powder X-ray diffraction of the obtained deposit was measured.
(Example 3)

The operation was performed in the same manner as in Example 1 except that the pressure was 152 MPa at 490 ° C. SEM observation of the resulting precipitate revealed hexagonal columnar crystals having a diameter of 50 μm and a length of 130 μm. It was h-GaN when the powder X-ray diffraction of the deposit was measured.
Example 4

The operation was performed in the same manner as in Example 1 except that a gold pipe was filled with a polycrystalline raw material and a flux and the pressure was set to 90 MPa in an argon atmosphere glove box. SEM observation of the obtained precipitate revealed hexagonal columnar crystals having a diameter of 60 μm and a length of 200 μm. It was h-GaN when the powder X-ray diffraction of the deposit was measured.
(Example 5)

A flux (B) in which CsCl (manufactured by Kanto Chemical) and NaCl (manufactured by Junsei Chemical) were mixed at a molar ratio of CsCl: NaCl = 65: 35 was used as the flux. The melting temperature of the flux (B) is 493 ° C. according to Phase Diagrams for Ceramists (The American Ceramic Society, 1966). The operation was performed in the same manner as in Example 1 except that the flux (A) was changed to the flux (B) and the temperature was 510 ° C. and the pressure was 96 MPa. SEM observation of the obtained precipitate revealed hexagonal columnar crystals having a diameter of 60 μm and a length of 200 μm. It was h-GaN when the powder X-ray diffraction of the deposit was measured.
(Example 6)

As the flux, a flux (C) in which CsBr (manufactured by Kanto Chemical) and NaBr (manufactured by Kishida Chemical) were mixed at a molar ratio of CsBr: NaBr = 60: 40 was used. The melting temperature of the flux (C) is 460 ° C. according to Phase Diagrams for Ceramists (The American Ceramic Society, 1966). Flux (A) is replaced with flux (C) and the temperature is 47
The operation was performed in the same manner as in Example 1 except that the temperature was 0 ° C. and the pressure was 84 MPa. SEM observation of the resulting precipitate revealed hexagonal columnar crystals having a diameter of 40 μm and a length of 140 μm. It was h-GaN when the powder X-ray diffraction of the deposit was measured.
(Example 7)

A flux (D) in which CsI (manufactured by Kanto Chemical) and KI (manufactured by Nacalai Tesque) were mixed at a molar ratio of CsI: KI = 60: 40 was used as the flux. The melting temperature of the flux (D) is 536 ° C. according to Phase Diagrams for Ceramists (The American Ceramic Society, 1966). The operation was performed in the same manner as in Example 1 except that the flux (A) was changed to the flux (D), the temperature was 550 ° C., and the pressure was 81 MPa. SEM observation of the resulting precipitate revealed a prism type having a diameter of 30 μm and a length of 70 μm, and a hexagonal plate crystal having a diameter of 20 μm and a thickness of 5 μm. It was h-GaN when the powder X-ray diffraction of the deposit was measured.
(Example 8)

The flux (E) mixed at a molar ratio of LiCl: KCl: CsCl = 51: 20: 29 previously vacuum dried was pulverized in a glove box in an argon atmosphere. The melting temperature of this flux (E) is ACerS-NIST Phase Equilibria Diagrams CD-ROM Database Version
According to 3.0, it is 263 ° C. 1.05 g of pulverized flux (E) and 0.32 g of metal gallium (Sumitomo Chemical Co., Ltd.) were placed in an alumina crucible (SSA-S) in a glove box and placed in the center of a quartz tube having an inner diameter of 30 mm and a length of 70 mm. . While flowing high-purity nitrogen at a flow rate of 100 sccm, the temperature was increased at 10 ° C./min until the temperature of the alumina crucible portion mounted in the quartz tube reached 850 ° C. After that, NH ₃ (5N) 250 sccm, high purity nitrogen 100 sc
A mixed gas of cm was supplied and held at 850 ° C. for 3 hours. After the temperature was lowered to room temperature at about 5 ° C./min, the alumina crucible was taken out, the contents were put into 50 ml of pure water to dissolve the flux, and the supernatant was discarded to obtain a precipitate. Next, a precipitate was added to 35% hydrochloric acid to dissolve unreacted metal, and then the supernatant was discarded to recover insoluble components. Furthermore, the insoluble component was put into 50 ml of pure water, and the supernatant was discarded to obtain a precipitate. After this washing operation with pure water was repeated twice, 50 ml of acetone was added, the supernatant was discarded, and the precipitate was collected and dried in vacuum at room temperature. SEM observation of the resulting precipitate revealed hexagonal columnar crystals having a diameter of 30 μm and a length of 60 μm. When the powder X-ray diffraction of the precipitate was measured, it was h-GaN, and no impurity phase other than h-GaN was observed.
From the results of the above examples, it can be seen that nitride crystals can be grown by the method of the present invention of the examples by using metal halide as the flux.

  Although the present invention has been described with reference to the most practical and preferred embodiments at the present time, the invention is not limited to the embodiments disclosed herein. The method of manufacturing a group 13 nitride crystal with such a change can also be appropriately changed without departing from the gist or the idea of the invention that can be read from the claims and the entire specification. Must be understood as encompassed by.

It is a scanning electron microscope (SEM) photograph of a polycrystalline raw material. 2 is a SEM photograph of a precipitate obtained in Example 1. 2 is a powder X-ray diffraction pattern of a precipitate obtained in Example 1. FIG. 2 is a SEM photograph of a precipitate obtained in Example 2.

Claims (10)

A method for producing a group 13 nitride crystal, wherein a mixture of a group 13 nitride raw material and a metal halide is heated and melted to perform crystal growth to obtain a bulk single crystal. The method for producing a group 13 nitride crystal according to claim 1, wherein crystal growth is performed in an atmosphere of an inert gas and / or a gas containing nitrogen atoms. 3. The method for producing a group 13 nitride crystal according to claim 1, wherein a group 13 element metal element or compound and nitrogen gas or a nitrogen compound are used as the group 13 nitride raw material. The method for producing a group 13 nitride crystal according to claim 1 or 2, wherein a polycrystalline powder of a group 13 nitrogen compound is used as the group 13 nitride raw material. 5. The method for producing a bulk crystal of a group 13 element nitride nitride according to claim 4, wherein the group 13 nitrogen compound polycrystalline powder contains a group 13 element metal. The method for producing a group 13 nitride crystal according to any one of claims 1 to 5, wherein the pressure is maintained under a pressure of 500 MPa or less during heating and melting. The method for producing a group 13 nitride crystal according to any one of claims 1 to 6, wherein the ratio of the metal halide in the mixture is 5 to 99% by weight. The method for producing a group 13 nitride crystal according to any one of claims 1 to 7, wherein the amount of oxygen atoms contained in the mixture is 5% by weight or less. 9. The method for producing a group 13 nitride crystal according to claim 1, wherein the metal halide is an alkali halide. The method for producing a group 13 nitride crystal according to any one of claims 1 to 9, wherein the group 13 elemental nitride is gallium nitride.

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