JP2007290921A - Method for producing nitride single crystal, nitride single crystal, and device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for growing a nitride single crystal having good crystallinity at a faster speed. <P>SOLUTION: In the method, the nitride single crystal is grown on the surface of a seed by an ammonothermal method while controlling the pressure and temperature in an autoclave, in which the seed, a solvent containing nitrogen atom, a raw material containing a metal element of group 13 in the periodic table, and a mineralizing agent of an amount of 1.5-15 mol% of the solvent are charged, so that the solvent is in a supercritical state and/or subcritical state. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for producing a nitride single crystal by using a solvent in a supercritical state and / or a subcritical state together with a raw material and a mineralizer to grow the nitride single crystal on a seed. The present invention also relates to a nitride single crystal manufactured by the manufacturing method and a device using the nitride single crystal.

Nitride semiconductors typified by gallium nitride (GaN) are useful as materials applied to electronic devices such as light emitting diodes and laser diodes. The manufacturing method of an electronic device is currently produced by vapor phase epitaxial growth such as MOCVD (Metal-Organic Chemical Vapor Deposition) method on a substrate such as sapphire or silicon carbide.
However, in this method, GaN crystals are heteroepitaxially grown on substrates having different lattice constants and thermal expansion coefficients of GaN, so that dislocations and lattice defects are likely to occur in the obtained GaN crystals, and a quality that can be applied with a blue laser or the like is obtained. In recent years, high-quality gallium nitride massive single crystals for homoepitaxial substrates have been expected in place of the above substrates.

In the synthesis method of gallium nitride massive single crystals, raw materials and mineralizers are dissolved in a nitrogen-containing solvent typified by ammonia, the temperature and pressure are adjusted to form a supercritical state, and a temperature difference is provided in the system. Therefore, there is an ammonothermal method in which crystal growth is performed using the temperature dependence of the solute solubility in a solvent.
However, in the method using only the nitrogen-containing solvent in the ammonothermal method, the solubility of the nitride raw material is not sufficient, and the growth rate of the nitride single crystal is very small. For this reason, it is important to add a mineralizer to the solvent in order to increase the solubility of the nitride raw material. As a mineralizer for the ammonothermal method, a basic mineralizer in which the pH of the solution produced when dissolved in a nitride-containing solvent is higher than that of the original solvent, and when dissolved in a nitride-containing solvent. There are acidic mineralizers in which the pH of the resulting solution is lower than the original solvent. The difference in solvent properties when using a basic mineralizer and when using an acidic mineralizer corresponds to the difference between using a basic solution of an aqueous solvent and an acidic solution. There are significant differences in the impact on the reaction. For example, the reaction pressure suitable when a basic mineralizer is used in the ammonothermal method is relatively high (150 to 300 MPa), whereas the reaction pressure suitable when an acidic mineralizer is used is relatively low. (100-200 MPa). For this reason, it is easier to implement industrially using an acidic mineralizer. In the ammonothermal method using an acidic mineralizer, elution of inner wall components is suppressed when a noble metal typified by platinum is used for the inner wall of the autoclave. For this reason, according to the ammonothermal method using an acidic mineralizer, there is an advantage that contamination of impurities contained in the obtained nitride crystal can be suppressed. For this reason, various researches on ammonothermal methods using acidic mineralizers have been conducted. In Patent Document 1, a specific method is used to grow crystal nuclei generated in the system during the reaction (spontaneous nucleation generation method). Consideration has been made.
JP 2005-289787 A

  However, the spontaneous nucleation method specifically studied in Patent Document 1 cannot produce a large crystal and cannot control the crystal orientation. In addition, the crystal growth rate of the ammonothermal method, particularly the ammonothermal method using an acidic mineralizer, is greatly insufficient for industrially synthesizing nitride single crystals. For this reason, in order to obtain a method that can be used industrially, it is necessary to manufacture a large crystal at a high speed while controlling the crystal orientation.

  Therefore, in the present invention, instead of the spontaneous nucleation method, a method (seed method) in which a seed (seed crystal) is previously present in the system and a crystal is grown on the surface (seed method) is used to improve the crystal growth rate. The idea was to manufacture large crystals while controlling the orientation. However, even if the conditions described in Patent Document 1 are applied as they are to a seed method that is largely different in principle, it has not been possible to sufficiently increase the crystal growth rate and grow a crystal with controlled orientation. For this reason, the inventors have made various changes in conditions not suggested in the patent literature, and as a result of repeating trial and error, a nitride single crystal having good crystallinity is sufficient only when specific conditions are satisfied. I found that it grows at a great speed. The present invention has been provided based on such knowledge, and specifically includes the following technical configuration.

[1] A temperature and pressure in an autoclave containing a seed, a solvent containing a nitrogen element, a raw material containing a group 13 metal element of the periodic table, and a mineralizer in an amount of 1.5 to 15 mol% of the solvent, The method includes the step of growing a nitride single crystal on the surface of the seed by an ammonothermal method while controlling the solvent to be in a supercritical state and / or a subcritical state. Method.
[2] The method for producing a nitride single crystal according to [1], wherein the nitride single crystal is a hexagonal crystal.
[3] The method for producing a nitride single crystal according to [1] or [2], wherein the temperature at which the nitride single crystal is grown is 300 to 600 ° C.
[4] The method for producing a nitride single crystal according to any one of [1] to [3], wherein a pressure at which the nitride single crystal is grown is 80 to 200 MPa.
[5] The method for producing a nitride single crystal according to any one of [1] to [4], wherein the solvent is ammonia or a derivative thereof.
[6] The method for producing a nitride single crystal according to any one of [1] to [5], wherein the source material contains gallium nitride polycrystal and / or gallium.
[7] The method for producing a nitride single crystal according to any one of [1] to [6], wherein the mineralizer is an acidic mineralizer.
[8] The method for producing a nitride single crystal according to [7], wherein the acidic mineralizer contains an ammonium salt.
[9] The method for producing a nitride single crystal according to any one of [1] to [8], wherein at least a part of the inner wall of the autoclave is made of a noble metal.
[10] The temperature and pressure in the autoclave containing a seed, a nitrogen-containing solvent, a raw material containing a group 13 metal element of the periodic table, and a mineralizer are determined in a supercritical state and / or a subcritical state. A nitride single crystal is grown on the surface of the seed by an ammonothermal method to a thickness of 50 μm or more, and the use ratio of the mineralizer to the solvent is set to an average crystal of the nitride single crystal. A method for producing a nitride single crystal, wherein the growth rate is selected within a range of 15 μm / day or more.
[11] A nitride single crystal produced by the production method according to any one of [1] to [10].
[12] A device using the nitride single crystal according to [11].

  According to the production method of the present invention, a nitride single crystal having good crystallinity can be grown greatly at a high speed. For this reason, it is possible to manufacture a relatively thick crystal in a short time.

  Hereinafter, the method for producing a nitride single crystal of the present invention will be described in detail. The description of the constituent elements described below may be made based on typical embodiments of the present invention, but the present invention is not limited to such embodiments. In the present specification, a numerical range represented by using “to” means a range including numerical values described before and after “to” as a lower limit value and an upper limit value.

(Features of the present invention)
In the production method of the present invention, the temperature and pressure in an autoclave containing a seed, a nitrogen-containing solvent, a raw material containing a group 13 metal element of the periodic table, and a mineralizer are set in a supercritical state and / or Alternatively, the method includes a step of growing a nitride single crystal on the surface of the seed by an ammonothermal method while controlling to be in a subcritical state. In this step, in the present invention, the mineralizer is used in an amount of 1.5 to 15 mol% of the solvent, or the mineralizer is used in an amount such that the average crystal growth rate of the nitride single crystal is 15 μm / day or more. It is characterized by using.

  When the amount of the mineralizer is less than 1.5 mol% of the solvent, the growth rate of the nitride single crystal is often slow or the nitride single crystal does not grow. If the mineralizer is more than 15 mol% of the solvent, nucleation cannot be sufficiently suppressed and it is often difficult to grow a single crystal on the seed surface. For this reason, in the present invention, the mineralizer is used in an amount of 1.5 to 15 mol% of the solvent. The mineralizer is preferably used in an amount of 3 to 12 mol% of the solvent, more preferably 4 to 10 mol%. In addition, the usage-amount of a mineralizer here and the usage-amount of a solvent mean the quantity of a mineralizer and a solvent in the time of lid | covering an autoclave.

In another aspect of the present invention, it is preferable to use a mineralizer in an amount such that the average crystal growth rate of the nitride single crystal is 15 μm / day or more. The average crystal growth rate of the nitride single crystal is more preferably 20 μm / day or more, and further preferably 23 μm / day or more. The average crystal growth rate here means the average value of the crystal growth rate during the period (growth period) in which the nitride single crystal can be grown on the seed surface in the autoclave by the ammonothermal method. Usually, it is obtained by measuring the thickness of the grown nitride single crystal after the growth period has elapsed and dividing it by the length of the growth period (days). However, an embodiment in which the growth period is extended to lower the average crystal growth rate even though the crystal growth rate is remarkably reduced after crystal growth at a crystal growth rate of 15 μm / day or more uses the present invention. It is assumed that
The average crystal growth rate of the nitride single crystal varies depending on the raw material and the type and amount of the solvent to be put in the autoclave. The average crystal growth rate often falls within the above range.

  The nitride crystal to be manufactured in the present invention depends on the raw material used, but is mainly a crystal of a single metal nitride of a Group 13 element such as B, Al, Ga, In (for example, GaN, AlN) or An alloy nitride (eg, GaInN, GaAlN) crystal is preferable, and a gallium nitride crystal is more preferable.

(Materials used)
In the present invention, a solvent containing nitrogen element is used as the solvent. Examples of the nitrogen-containing solvent include solvents that do not impair the stability of the nitride single crystal to be grown. Specifically, ammonia, hydrazine, urea, amines (for example, methylamine) Primary amines, secondary amines such as dimethylamine, tertiary amines such as trimethylamine, diamines such as ethylenediamine), and melamine. These solvents may be used alone or in combination.

  The amount of water and oxygen contained in the solvent used in the present invention is desirably as small as possible, and the content thereof is preferably 1000 ppm or less, more preferably 10 ppm or less, and preferably 0.1 ppm or less. Further preferred. When ammonia is used as a solvent, the purity is usually 99.9% or more, preferably 99.99% or more, more preferably 99.999% or more, and particularly preferably 99.9999% or more. .

  The mineralizer used in the production method of the present invention is a compound that increases the solubility of the raw material in the solvent, and is usually a compound containing a halogen element, an alkali metal, an alkaline earth metal, or a rare earth metal. Among them, it is preferable to use a compound containing nitrogen element in the form of ammonium ion or amide so that the crystal to be grown does not contain oxygen element. In the present invention, only one type of mineralizer may be selected and used, or two or more types may be used in combination.

  In order to prevent impurities from being mixed into the nitride single crystal grown in the present invention, the mineralizer is used after being purified and dried as necessary. The purity of the mineralizer used in the present invention is usually 95% or higher, preferably 99% or higher, more preferably 99.99% or higher. It is desirable that the amount of water and oxygen contained in the mineralizer is as small as possible, and the content thereof is preferably 1000 ppm or less, more preferably 10 ppm or less, and further preferably 1.0 ppm or less. .

In the present invention, both an acidic mineralizer and a basic mineralizer can be used.
Examples of basic mineralizers include alkali metals, alkaline earth metals, compounds containing rare earth metals and nitrogen elements, specifically alkaline earth metal amides, rare earth amides, alkali metal nitrides, alkaline earth nitrides. Examples thereof include salts of metals, azide compounds and other hydrazines. Alkali metal amides are preferable, and specific examples thereof include sodium amide, potassium amide, and lithium amide.
The acidic mineralizer is a compound containing a halogen element such as ammonium halide. Specific examples include ammonium chloride, ammonium iodide, and ammonium bromide. Among them, ammonium chloride is preferable.
In the present invention, it is particularly preferable to use an acidic mineralizer. The acidic mineralizer has advantageous properties such as high solubility in a supercritical ammonia solvent, low reaction pressure, and low reactivity with noble metals such as Pt constituting the inner wall of the autoclave.

  The use ratio of the mineralizer and the raw material containing the group 13 metal element of the periodic table is within a range in which the mineralizer / group 13 metal element (molar ratio) is usually 0.0001 to 100, and GaN If it exists, the inside of the range from which a mineralizer / Ga (molar ratio) will be 0.001-20 normally is preferable. The ratio of use can be appropriately determined in consideration of the types of raw materials and mineralizers, the target crystal size, and the like.

  In the present invention, a raw material containing a group 13 metal of the periodic table is used. Preferred is a polycrystalline raw material of group 13 nitride crystal and / or gallium, and more preferred is gallium nitride and / or gallium. The polycrystalline raw material does not need to be a complete nitride, and may contain a metal component in which the group 13 element is in a metal state (zero valence) depending on conditions. For example, when the crystal is gallium nitride Is a mixture of gallium nitride and metal gallium.

  The manufacturing method of the polycrystalline raw material used as a raw material in the present invention is not particularly limited. For example, a nitride polycrystal produced by reacting a metal or an oxide or hydroxide thereof with ammonia in a reaction vessel in which ammonia gas is circulated can be used. In addition, as a metal compound raw material having higher reactivity, a compound having a covalent MN bond such as a halide, an amide compound, an imide compound, or galazan can be used. Furthermore, a nitride polycrystal produced by reacting a metal such as Ga with nitrogen at a high temperature and a high pressure can also be used.

  The amount of water and oxygen contained in the polycrystalline raw material used as the raw material in the present invention is preferably small. The oxygen content in the polycrystalline raw material is usually 1.0% by mass or less, preferably 0.1% by mass or less, and particularly preferably 0.0001% by mass or less. The ease of mixing oxygen into the polycrystalline raw material is related to the reactivity with water or the absorption capacity. The worse the crystallinity of the polycrystalline raw material, the more active groups such as NH groups exist on the surface, which may react with water and partially generate oxides or hydroxides. For this reason, it is usually preferable to use a polycrystalline material having as high crystallinity as possible. The crystallinity can be estimated by the half width of powder X-ray diffraction. The half width of the (100) diffraction line (2θ = about 32.5 ° for hexagonal gallium nitride) is usually 0.25 ° or less, preferably It is 0.20 ° or less, more preferably 0.17 ° or less.

  In the present invention, a seed is used. As the seed, it is desirable to use a single crystal of nitride grown by the manufacturing method of the present invention, but it is not always necessary to use the same nitride. However, in that case, it is a seed with a lattice constant, crystal lattice size parameter that matches or matches the desired nitride, or heteroepitaxy (ie, coincidence of the crystallographic position of some atoms). It is necessary to use seeds composed of single crystal material pieces or polycrystalline material pieces coordinated to ensure. As specific examples of seeds, for example, when growing gallium nitride (GaN), in addition to a single crystal of GaN, a single crystal of nitride such as aluminum nitride (AlN), a single crystal of zinc oxide (ZnO), silicon carbide (SiC) ) And the like.

  The seed can be determined in consideration of the solubility in the solvent and the reactivity with the mineralizer. For example, as a seed of GaN, a single crystal obtained by epitaxial growth on a dissimilar substrate such as sapphire by MOCVD method or HVPE method and then exfoliated, and obtained by crystal growth of Na, Li, Bi from metal Ga as a flux. A single crystal, a single crystal obtained by homoepitaxial growth using the LPE method, a single crystal produced based on a solution growth method including the method of the present invention, and a crystal obtained by cutting them can be used.

(Autoclave)
The production method of the present invention is carried out in an autoclave.
The autoclave used in the present invention is selected from those that can withstand the high-temperature and high-pressure conditions when growing a nitride single crystal. The autoclave used in the present invention is preferably composed of a material having pressure resistance and erosion resistance. In particular, an Ni-based alloy having excellent erosion resistance against a solvent such as ammonia, Stellite (Derolo Stellite Company It is preferable to use a Co-based alloy such as a registered trademark of Incorporated. More preferably, it is an Ni-based alloy, specifically, Inconel 625 (Inconel is a registered trademark of Huntington Alloys Canada Limited, the same shall apply hereinafter), Nimonic 90 (Nimonic is a registered trademark of Special Metals Wiggin Limited, hereinafter the same), and RENE 41. It is done.

  The composition ratio of these alloys depends on the temperature and pressure conditions of the solvent in the system, and the reactivity with the mineralizers and their reactants contained in the system and / or the oxidizing power / reducing power, pH conditions, What is necessary is just to select suitably. In order to use these as materials constituting the inner surface of the autoclave, the autoclave itself may be manufactured using these alloys, or a thin film may be formed as an inner cylinder and installed in the autoclave. The inner surface of the material may be plated.

  In order to further improve the erosion resistance of the autoclave, the inner surface of the autoclave may be lined or coated using the superior erosion resistance of the noble metal. The material of the autoclave can be a noble metal. Examples of the noble metal include Pt, Au, Ir, Ru, Rh, Pd, Ag, and alloys containing these noble metals as main components. Among them, it is preferable to use Pt having excellent erosion resistance.

  A specific example of a crystal production apparatus including an autoclave that can be used in the production method of the present invention is shown in FIG. In the figure, 1 is a valve, 2 is a pressure gauge, 3 is an autoclave, 4 is a crystal growth region, 5 is a raw material filling region, 6 is a baffle plate, 7 is an electric furnace, 8 is a thermocouple, 9 is a raw material, 10 is a seed , 11 indicates a conduit.

  The baffle plate 6 divides the crystal growth region 4 and the raw material filling region 5, and preferably has a hole area ratio of 2 to 20%, more preferably 3 to 10%. The material of the surface of the baffle plate is preferably the same as the material of the reaction vessel. Further, in order to give more erosion resistance and to purify the crystal to be grown, the surface of the baffle plate is preferably Ni, Ta, Ti, Nb, Pd, Pt, Au, Ir, pBN, Pd, Pt, Au, Ir, and pBN are more preferable, and Pt is particularly preferable.

  As for the valve 1, the pressure gauge 2, and the conduit 11, it is preferable that at least the surface is made of an erosion resistant material. For example, it is SUS316 (JIS standard), and it is more preferable to use Inconel 625. Note that a valve, a pressure gauge, and a conduit do not necessarily have to be installed in the crystal manufacturing apparatus used when carrying out the manufacturing method of the present invention.

(Manufacturing process)
In carrying out the production method of the present invention, first, a seed, a solvent containing a nitrogen element, a raw material containing a group 13 metal element of the periodic table, and a mineralizer are put in an autoclave and sealed. At this time, the amount of the mineralizer used is 1.5 to 15 mol% of the solvent, or an amount at which the average crystal growth rate of the subsequent nitride single crystal is 15 μm / day or more. Prior to introducing these materials into the autoclave, the autoclave may be degassed. Moreover, you may distribute | circulate inert gas, such as nitrogen gas, at the time of introduction | transduction of material.

  The seeds are usually charged into the autoclave at the same time as or after the filling with the raw material containing the group 13 metal element and the mineralizer. The seed is preferably fixed to a noble metal jig similar to the noble metal constituting the inner surface of the autoclave. After loading, heat deaeration may be performed as necessary.

  In the supercritical state, the viscosity is generally low and it is more easily diffused than the liquid, but has the same solvating power as the liquid. The subcritical state means a liquid state having a density substantially equal to the critical density near the critical temperature. For example, in the raw material filling region, the raw material is melted as a supercritical state, and in the crystal growth region, the temperature is changed so that it becomes a subcritical state, and crystal growth using the difference in solubility between the supercritical state material and the subcritical state material is also performed. Is possible.

  When in the supercritical state, the reaction mixture is generally maintained at a temperature above the critical point of the solvent. When an ammonia solvent is used, the critical point is a critical temperature of 132 ° C. and a critical pressure of 11.35 MPa. However, if the filling rate with respect to the volume of the autoclave is high, the pressure far exceeds the critical pressure even at a temperature below the critical temperature. In the present invention, the “supercritical state” includes such a state exceeding the critical pressure. Since the reaction mixture is enclosed in a fixed volume autoclave, the temperature increase increases the pressure of the fluid. In general, if T> Tc (critical temperature of one solvent) and P> Pc (critical pressure of one solvent), the fluid is in a supercritical state.

  Under supercritical conditions, a sufficient growth rate of the nitride single crystal can be obtained. The reaction time depends in particular on the reactivity of the mineralizer and the thermodynamic parameters, ie temperature and pressure values. During the synthesis or growth of the nitride single crystal, the autoclave is preferably held at a pressure of about 10 MPa to 500 MPa. The pressure is appropriately determined depending on the filling rate of the solvent volume with respect to the temperature and the volume of the autoclave. Originally, the pressure in the autoclave is uniquely determined by the temperature and filling rate, but in reality, there are raw materials, additives such as mineralizers, temperature heterogeneity in the autoclave, and the existence of dead volume. It will vary slightly.

  As for the temperature range in the autoclave, the lower limit is usually 150 ° C or higher, preferably 200 ° C or higher, particularly preferably 300 ° C or higher, and the upper limit is usually 800 ° C or lower, preferably 700 ° C or lower, particularly preferably 600 ° C or lower. It is. A preferable temperature range is 150 to 800 ° C, more preferably 200 to 700 ° C, and still more preferably 300 to 600 ° C. The lower limit of the pressure range in the autoclave is usually 20 MPa or more, preferably 30 MPa or more, more preferably 50 MPa or more, particularly preferably 80 MPa or more, and the upper limit is usually 500 MPa or less, preferably 400 MPa or less, more preferably. 300 MPa or less, particularly preferably 200 MPa or less. A preferable pressure range is 20 to 500 MPa, more preferably 50 to 300 MPa, and still more preferably 80 to 200 MPa.

  The injection ratio of the solvent into the autoclave to achieve the above autoclave temperature range and pressure range, that is, the filling rate, is the free volume of the autoclave, i.e., when a polycrystalline raw material and a seed crystal are used in the autoclave. Subtract the volume of the crystal and the structure where it will be installed from the autoclave volume, and if a baffle plate is installed, subtract the volume of the baffle plate from the volume of the autoclave and add the remaining volume of solvent. Based on the liquid density at the boiling point, it is usually 20 to 95%, preferably 40 to 90%, more preferably 50 to 85%.

  Nitride single crystal growth in the autoclave is to maintain the autoclave in a subcritical or supercritical state of a solvent such as ammonia by heating and heating the autoclave using an electric furnace with a thermocouple. Is done. The heating method and the rate of temperature increase to a predetermined reaction temperature are not particularly limited, but are usually performed over several hours to several days. If necessary, the temperature can be raised in multiple stages, or the temperature raising speed can be changed in the temperature range. It can also be heated while being partially cooled.

  The above “reaction temperature” is measured by a thermocouple provided in contact with the outer surface of the autoclave, and can be approximated to the internal temperature of the autoclave.

  The reaction time after reaching a predetermined temperature varies depending on the type of nitride single crystal, the raw material used, the type of mineralizer, and the size and amount of the crystal to be produced, but is usually several hours to several hundred days. can do. During the reaction, the reaction temperature may be constant, or the temperature may be gradually raised or lowered. After a reaction time for producing desired crystals, the temperature is lowered. The method for lowering the temperature is not particularly limited, but the heating of the heater may be stopped and the autoclave may be allowed to cool as it is installed in the furnace, or the autoclave may be removed from the electric furnace and air cooled. If necessary, quenching with a refrigerant is also preferably used.

After the temperature of the outer surface of the autoclave or the estimated temperature inside the autoclave has fallen below the predetermined temperature, the autoclave is opened. The predetermined temperature at this time is not particularly limited, and is usually −80 ° C. to 200 ° C., preferably −33 ° C. to 100 ° C. Here, a pipe may be connected to a pipe connection port of a valve attached to the autoclave, and the valve may be opened by passing through a container filled with water or the like.
Furthermore, if necessary, after removing the ammonia solvent in the autoclave sufficiently by making a vacuum or the like, it is dried and the autoclave lid is opened, etc. to produce nitride crystals and unreacted raw materials and mineralizers, etc. The additive can be removed.

  Thus, a nitride single crystal can be produced by the production method of the present invention. In order to manufacture a nitride single crystal having a desired crystal structure, it is necessary to appropriately adjust the manufacturing conditions.

  The nitride single crystal produced by the production method of the present invention may be used as it is, or may be used after being processed. According to the manufacturing method of the present invention, a nitride single crystal having a large film thickness can be manufactured in a relatively short time. For example, a nitride single crystal having a thickness of 50 μm or more can be manufactured. The nitride single crystal produced by the production method of the present invention has good crystallinity, and can be widely used for production of various electronic devices such as light emitting diodes and laser diodes.

  The features of the present invention will be described more specifically with reference to examples and comparative examples. The materials, amounts used, ratios, processing details, processing procedures, and the like shown in the following examples can be changed as appropriate without departing from the spirit of the present invention. Therefore, the scope of the present invention should not be construed as being limited by the specific examples shown below. In the following examples and comparative examples, crystal growth was attempted using the crystal manufacturing apparatus shown in FIG.

Example 1
4.92 g of GaN polycrystal produced by the HVPE method as raw material 9 and 3.07 g of Ga in autoclave 3 (made of Inconel 625: volume of about 30 ml) with a diameter of 16 mm and a length of 160 mm lined with platinum Then, 2.50 g of NH ₄ Cl having a purity of 99.99% and sufficiently dried as a mineralizer was charged thereon.

Next, a baffle plate 6 is installed 80 mm above the bottom, and a 5-mm square GaN seed 10 having a thickness of 200 μm is installed in the crystal growth region 4 thereon, and then the lid of the autoclave 3 to which the valve 1 is mounted is quickly closed. The autoclave 3 was weighed. Next, the conduit 11 was operated through the valve 1 attached to the autoclave 3 to the vacuum pump unit, the valve 1 was opened, and the inside of the autoclave 3 was vacuum deaerated. Thereafter, while maintaining the vacuum state, the autoclave 3 was cooled with dry ice / methanol, and the valve 1 was once closed. Next, after the conduit 11 was operated so as to communicate with the NH ₃ cylinder via the valve 1, the valve 1 was opened again, and NH ₃ was continuously filled in the autoclave 3 without touching the outside air. The flow rate was controlled, and NH ₃ was filled as a liquid corresponding to 70% of the cavity of the autoclave 3 (converted with an NH ₃ concentration of −33 ° C.), and then the valve 1 was closed again. The temperature of the autoclave 3 was returned to room temperature, and the increased amount of NH ₃ filled after the outer surface was sufficiently dried was measured. The ratio of NH ₄ Cl for NH ₃ in the autoclave 3 was 5.9 mol%.

Subsequently, the autoclave 3 was accommodated in an electric furnace 7 composed of a heater divided into two parts in the vertical direction. The temperature of the lower outer surface of the autoclave 3 is increased to 550 ° C. and the temperature of the upper outer surface is increased to 500 ° C. over 6 hours while making a temperature difference. The temperature of the lower outer surface of the autoclave 3 is increased to 550 ° C. After the temperature reached 500 ° C., the temperature was further maintained for 96 hours. The pressure in the autoclave 3 was 170 MPa. Further, the temperature range during holding was controlled to ± 5 ° C. or less. Thereafter, the temperature was lowered over about 9 hours until the temperature of the lower outer surface of the autoclave 3 reached 50 ° C., and then the heating by the heater was stopped, and the mixture was naturally cooled in the electric furnace 7. After confirming that the temperature of the lower outer surface of the autoclave 3 dropped to almost room temperature, the valve 1 attached to the autoclave 3 was first opened, and NH ₃ in the autoclave ₃ was removed. Thereafter, the autoclave 3 was weighed to confirm the discharge of NH ₃ . Thereafter, the valve 1 was once closed, the conduit was operated so as to communicate with the vacuum pump, the valve 1 was opened again, and NH ₃ in the autoclave ₃ was almost completely removed.

  Thereafter, the lid of the autoclave 3 was opened and the inside was confirmed. As a result, a GaN crystal having a thickness of 110 μm was grown on the surface of the seed 10, and the crystal growth rate was 27.5 μm / day. When the GaN crystal grown on the seed surface was taken out and the crystal plane state was observed with an SEM (scanning electron microscope), no acicular crystals or agglomerates were found. Further, as a result of X-ray diffraction measurement, the crystal type was hexagonal type, which was C-axis oriented in the same direction as the seed, and it was confirmed that the crystallinity was very good.

(Example 2, Example 3, and Comparative Examples 1-3)
Growth of GaN crystals was attempted in the same manner as in Example 1 except that the production conditions of Example 1 and the amounts of raw materials and solvent used were changed as shown in Table 1. As a result, in Example 2, Example 3, and Comparative Example 3, GaN crystals grew on the seed surface, but in Comparative Examples 1 and 2, no GaN crystal grew on the seed surface.
When the GaN crystal grown on the seed surface was taken out and observed by SEM, needle-like crystals and agglomerates were not found in Example 2 and Example 3, but spontaneous nuclei were found on the seed surface in Comparative Example 3. A large number of microcrystals were generated due to the occurrence and were not single crystals. Furthermore, as a result of X-ray diffraction measurement of the crystals obtained in Example 2 and Example 3, the crystal type is hexagonal type, and the C-axis orientation is the same as the seed, and the crystallinity is very good. It was confirmed that there was.

  In Example 1 and Example 3, the crystal growth rate was faster than that in Example 2. This is considered to be because the mineralizer concentration is in a more preferable range.

  According to the production method of the present invention, a nitride single crystal having good crystallinity can be grown at a high rate. Since a relatively thick crystal can be manufactured in a short time, the present invention is expected to be widely used for manufacturing various electronic devices such as a light emitting diode and a laser diode.

It is a schematic sectional drawing of the crystal manufacturing apparatus used by the Example and the comparative example.

Explanation of symbols

1 Valve 2 Pressure gauge 3 Autoclave 4 Crystal growth area 5 Raw material filling area 6 Baffle plate 7 Electric furnace 8 Thermocouple 9 Raw material 10 Seed 11 Conduit

Claims (12)

  The temperature and pressure in the autoclave containing a seed, a nitrogen-containing solvent, a raw material containing a group 13 metal element of the periodic table, and a mineralizer in an amount of 1.5 to 15 mol% of the solvent are determined by the solvent. A method for producing a nitride single crystal, comprising the step of growing a nitride single crystal on the surface of the seed by an ammonothermal method while controlling to be in a supercritical state and / or a subcritical state.   The method for producing a nitride single crystal according to claim 1, wherein the nitride single crystal is a hexagonal crystal.   3. The method for producing a nitride single crystal according to claim 1, wherein a temperature at which the nitride single crystal is grown is 300 to 600 ° C. 3.   The method for producing a nitride single crystal according to any one of claims 1 to 3, wherein a pressure when growing the nitride single crystal is 80 to 200 MPa.   The method for producing a nitride single crystal according to any one of claims 1 to 4, wherein the solvent is ammonia or a derivative thereof.   The method for producing a nitride single crystal according to any one of claims 1 to 5, wherein the raw material contains gallium nitride polycrystal and / or gallium.   The method for producing a nitride single crystal according to any one of claims 1 to 6, wherein the mineralizer is an acidic mineralizer.   The method for producing a nitride single crystal according to claim 7, wherein the acidic mineralizer contains an ammonium salt.   The method for producing a nitride single crystal according to any one of claims 1 to 8, wherein at least a part of an inner wall of the autoclave is made of a noble metal.   The temperature and pressure in the autoclave containing the seed, the nitrogen-containing solvent, the raw material containing the group 13 metal element of the periodic table, and the mineralizer are set so that the solvent becomes a supercritical state and / or a subcritical state. And controlling the amount of the mineralizer to be used with respect to the solvent by the average crystal growth rate of the nitride single crystal. A method for producing a nitride single crystal, which is selected within a range of 15 μm / day or more.   The nitride single crystal manufactured by the manufacturing method as described in any one of Claims 1-10.   A device using the nitride single crystal according to claim 11.

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