JP4719788B2 - Method for producing group 13 element nitrogen compound crystal - Google Patents

Description

  The present invention relates to a high-purity and high-quality group 13 element nitrogen compound crystal with less oxygen impurities.

  A group 13 element nitrogen compound crystal represented by GaN is used for a light emitting diode (LED) or a semiconductor laser (LD). Such a light emitting device is a crystal of a group 13 element nitrogen compound such as AlN, GaN, InN or the like composed of a group 13 element such as Al, Ga, In, or a mixed type 13 containing two or three types of group 13 elements. Group element nitrides are used. Nitride thin films for light-emitting devices are generally fabricated by heteroepitaxial growth on sapphire substrates and silicon carbide substrates, but there is a difference between the lattice constants of sapphire and silicon carbide substrates and the nitride film. Defects such as transition defects are generated in the material film, which deteriorates the characteristics of the light emitting device. If a high-quality, high-quality group 13 element nitrogen compound crystal is obtained, it can be used as a substrate, so that a thin film can be grown on the substrate without a difference in lattice constant. It can be expected that the system will be more efficient and deployed for power semiconductor applications.

  As a method for producing a bulk group 13 element nitrogen compound crystal, particularly a GaN bulk crystal, a high-temperature and high-pressure method, a HPPE (Hydride Vapor Phase Epitaxy) method, a flux method, a sublimation method, and the like have been reported. However, since it is difficult to grow a group 13 element nitrogen compound crystal mainly composed of GaN, it has not been widely used. A commercial product of a GaN substrate by the HPVE method has come out, but the price is quite high and there are problems such as a peeling method from the substrate on which GaN is grown and the warpage of the GaN substrate itself, and it has not reached a practical level. .

  A bulk crystal of GaN is obtained from a supercritical ammonia-containing solution by selective crystallization on a crystal seed described in Patent Document 1 below. Non-Patent Document 1 below reports a method of crystal growth of GaN using a supercritical ammonia-containing solution in which ammonium halide is contained in ammonia by Yuji Kagamitani et al. A method for producing a group 13 element nitrogen compound crystal using ammonia supercriticality is widely called an ammonothermal method or an thermal method.

  In order to use a bulk group 13 element nitrogen compound crystal for a semiconductor application such as an optical device, it is important to make a nitride containing no impurities. It is particularly important to eliminate oxygen impurities because group 13 elements are likely to bind to oxygen at high temperatures such as in the supercritical state. In the method using a supercritical ammonia-containing solution, oxygen impurities can be obtained from water, oxygen, oxides from autoclave containers and inner walls, additives such as group 13 elements and group 13 nitrogen compounds, alkali metal amides and ammonium halides. It is difficult to prevent contamination.

Special table 2004/533391 gazette Yuji Kagamitani, Dirk Ehrentraut, Akira Yoshikawa, Naruhiro Hoshino, Tsuguo Fukuda, `` Japanese Journal of Applied Physics '', Vol. 45, No. 5A, 2006, p. 4018-4020

  The problem to be solved by the present invention is to produce a crystal of a group 13 element nitrogen compound containing gallium as a main component from a group 13 metal containing gallium or a group 13 element nitrogen compound as a raw material in a supercritical ammonia-containing solution. In the so-called Ammonothermal method, a method for producing a high-quality, high-quality group 13 nitrogen compound crystal with less oxygen impurities is provided.

  In order to solve the above-mentioned problems, the present inventor has studied various oxygen removal additives for removing oxygen in a supercritical ammonia-containing solution, and the group consisting of titanium metal, zirconium metal, titanium alloy, and zirconium alloy at the center. And a group 13 in a supercritical ammonia solution by contacting an oxygen solution with an oxygen removal additive having a composite structure composed of a metal or alloy selected from the above and having a surface layer portion covered with a hydride of the metal or alloy It was discovered that by crystallizing elemental nitrogen compounds, high-purity and high-quality group 13 elemental nitrogen compound crystals with less oxygen can be produced, and the present invention has been completed. Specifically, the present invention is the following [1] to [3]:

  [1] A method for producing a group 13 element nitrogen compound crystal containing gallium as a main component, wherein a metal of a group 13 element containing at least gallium and / or a nitrogen compound of the metal is used as an oxygen removal additive in an ammonia atmosphere. Heat treatment in the presence to obtain crystals, wherein the oxygen scavenger additive is a metal or alloy whose core is selected from the group consisting of titanium metal, zirconium metal, titanium alloy, and zirconium alloy And having a composite structure in which the surface layer portion is covered with a hydride of the metal or alloy.

  [2] The method according to [1], wherein the group 13 element nitrogen compound containing gallium as a main component is GaN.

  [3] A group 13 element nitrogen compound crystal containing gallium as a main component, produced by the method according to [1] or [2].

  The oxygen-removing additive that can be used in the present invention is composed of a metal or an alloy whose central portion is selected from the group consisting of titanium metal, zirconium metal, titanium alloy, and zirconium alloy, and its surface layer portion is the metal. Alternatively, by having a composite structure covered with a hydride of an alloy, it has the ability to remove oxygen from oxygen-containing compounds such as oxygen in oxygen and water containing oxygen.

When such an oxygen removal additive is put into ammonia, it reacts with the oxygen component in ammonia in an ammonia atmosphere to form a metal oxide or adsorb the oxygen component, so the oxygen component in ammonia is removed by oxygen. By immobilizing on the surface of the additive, the oxygen component can be removed from the ammonia. The effect of this oxygen scavenging additive reacting with oxygen or adsorbing oxygen appears remarkably at 300 ° C. to 700 ° C. Therefore, when ammonia is used at a temperature in this range, the effect is high. Therefore, by introducing such an oxygen-bonding or oxygen-adsorbing metal into ammonia, a high-purity and high-quality group 13 element nitrogen compound crystal with less oxygen impurities can be produced.
However, when such a metal or alloy such as titanium or zirconium that binds to oxygen or adsorbs oxygen is handled in the air at the stage of charging the container, the surface of the metal or alloy is oxidized at this stage. The ability to react with oxygen in ammonia or adsorb oxygen is lost, and oxygen impurities in the obtained group 13 element nitrogen compound crystals cannot be reduced.

  Therefore, the inventor does not take oxygen into the surface even when handled in air, but under ammonia supercritical conditions, it can remove oxygen in the supercritical ammonia solution by binding to oxygen or adsorbing oxygen. As a result of examining the oxygen scavenging additive that can be formed, the central portion is composed of a metal or alloy selected from the group consisting of titanium metal, zirconium metal, titanium alloy, and zirconium alloy, and the surface layer portion of the metal or alloy An oxygen scavenging additive having a composite structure covered with hydride was found. As described above, the oxygen removal additive of the present invention has its surface layer covered with hydride, so that even if it is handled in a normal air atmosphere, oxygen remains in the center of the oxygen removal additive metal or alloy and oxide. Never make. Therefore, by adding the oxygen removing additive of the present invention into a supercritical ammonia pressure vessel for producing a group 13 element nitrogen compound crystal, the oxygen removing agent can be added to the group 13 element nitrogen without taking in oxygen at the vessel charging stage. It can be stored in a pressure vessel for producing compound crystals.

  Next, an ammonia solution and a mineralizing agent that promotes crystal growth are added to the pressure vessel for producing a group 13 element nitrogen compound crystal, and after the pressure vessel is sealed, the ammonia-containing solution temperature is set to 300 to 650 ° C. Hydrogen is removed from the hydride present in the surface layer of the additive, and the same metal or alloy as the metal or alloy constituting the central portion of the oxygen removing additive appears on the surface (surface layer portion) of the oxygen removing additive. . At this stage, the metal or alloy appearing in the surface layer is a metal or alloy such as titanium or zirconium, and can react with oxygen or adsorb oxygen to remove oxygen from the high-temperature and high-pressure ammonia-containing solution. .

  In the production of a GaN crystal by the ammonothermal method, oxygen in the GaN crystal can be reduced by reducing the oxygen component in ammonia. Since the GaN crystal with less oxygen has less oxygen impurities, the half width in the X-ray diffraction method is small, and not only the impurities in the crystal are small, but also the quality of the GaN crystal is high, and it is effective as a semiconductor substrate.

  According to the present invention, in a method for producing a group 13 element nitrogen compound crystal containing gallium as a main component by heat treatment in an ammonia atmosphere, the central portion thereof is made of any one of titanium metal, zirconium metal, titanium alloy, zirconium alloy, Producing a group 13 element nitrogen compound crystal containing gallium as a main component by bringing the surface layer portion into contact with ammonia in an oxygen removal additive having a composite structure covered with a hydride of the metal or alloy constituting the central portion. Thus, a group 13 element nitrogen compound crystal containing high-quality gallium with a low oxygen content as a main component can be provided. Moreover, since the surface layer part (surface) is covered with the hydride, the oxygen removal additive according to the present invention does not impair the oxygen removal effect even if it is handled in air, so that the handleability is good.

Examples of the group 13 element include B, Al, Ga, and In. Examples of Group 13 element nitrogen compound crystals containing gallium as a main component include crystals such as mixed crystals of Group 13 element nitrogen compounds containing BN, AlN, and InN in addition to GaN.
In this specification, the term “group 13 element nitrogen compound crystal containing gallium as a main component” refers to a group 13 element nitrogen compound crystal in which the ratio of the number of moles of GaN is 70 mol% or more and 100 mol% or less. A group 13 element nitrogen compound crystal having a mole ratio of 80 mol% to 100 mol% is preferable, and a group 13 element nitrogen compound crystal having a mole ratio of GaN of 90 mol% to 100 mol% is more preferable. In addition, these group 13 element nitrogen compound crystals contain magnesium, zinc, carbon, silicon, germanium, etc. as doping materials in a very small amount in the range of 1/10 to 1/1000000 relative to the number of Ga moles. Is contained in a crystal of a nitrogen compound of a group 13 element whose main component is.

The ammonia atmosphere refers to pure ammonia, an ammonia that is thermally decomposed to contain nitrogen and hydrogen, or an ammonia atmosphere that contains a so-called mineralizer such as alkali or acid.
The method for producing a group 13 nitrogen compound crystal containing gallium as a main component by heat treatment in an ammonia atmosphere as referred to in the present invention is a supercritical crystallization method in a high-temperature ammonia atmosphere. It is a method as described in Document 1. In this specification, “a metal of a group 13 element containing gallium and / or a nitrogen compound of the metal” is a raw material for producing a group 13 nitrogen compound crystal containing gallium as a main component, and includes gallium metal or GaN. Group 13 element metal and / or nitrogen compound containing gallium containing 50% by weight to 100% by weight of gallium, and Group 13 element metal and / or nitrogen containing gallium containing 70% to 100% by weight of GaN A compound is preferable, and a group 13 element metal and / or nitrogen compound containing gallium containing 90% by weight to 100% by weight of GaN is more preferable. BN, AlN, InN, or a mixture thereof is preferably used as the component other than gallium of the group 13 element metal and / or nitrogen compound containing gallium as the raw material. As the raw material, aluminum amide, aluminum imide, potassium amide, indium amide, indium imide, or the like is used. The nitrogen compound containing a Group 13 element containing gallium used in these raw materials is preferably high in purity, but is not required to have high crystallinity because it is dissolved in an ammonia solvent when used.

In the present invention, an acidic mineralizer, an alkaline mineralizer, or an almost neutral metal salt mineralizer can be used. Examples of the acidic mineralizer include compounds containing a halogen element, and include ammonium halides such as ammonium chloride, ammonium iodide, ammonium bromide, and ammonium fluoride. Examples of the alkaline mineralizer include mineralizers containing alkali metal elements. For _example alkali metal amides such as _{NaNH 2, KNH 2, LiNH 2} . Almost neutral metal salt mineralizers include magnesium halides such as MgCl ₂ and MgBr ₂ , calcium halides such as CaCl ₂ and BaBr ₂ , NaCl, NaBr, KCl, KBr, CsCl, CsBr, LiCl, LiBr, etc. And an alkali metal halide compound.

  The acidic mineralizer, alkaline mineralizer, or almost neutral metal salt mineralizer is used after being dissolved in an ammonia solvent and has a function of promoting dissolution of the starting nitrogen compound. The use ratio of these mineralizers is a range in which the mineralizer / ammonia molar ratio is usually 0.0001 to 0.2, and the range in which the mineralizer / ammonia molar ratio is 0.001 to 0.1. The range in which the mineralizer / ammonia molar ratio is 0.005 to 0.05 is more preferable.

  In the present invention, the temperature of the ammonia atmosphere is usually 300 ° C. to 800 ° C., preferably 400 ° C. to 700 ° C., more preferably 450 ° C. to 650 ° C. When the temperature of the ammonia atmosphere is lower than 300 ° C., the growth rate of the group 13 element nitrogen compound crystals is too slow to be suitable for production. As the temperature of the ammonia atmosphere increases from about 300 ° C. to about 700 ° C., the higher the temperature, the higher the growth rate of the group 13 element nitrogen compound crystal, which is suitable for production. However, since the temperature resistance of the autoclave (pressure vessel) is also increased, and the pressure resistance is also required due to the material of the autoclave, it is not suitable for production that the ammonia atmosphere temperature exceeds 800 ° C.

  The pressure condition in the ammonia atmosphere is usually 50 MPa to 500 MPa, preferably 90 MPa to 300 MPa, more preferably 100 MPa to 350 MPa. When the pressure is lower than 50 MPa, the growth rate of the group 13 element nitrogen compound crystal is too slow to be suitable for production. On the other hand, when the pressure exceeds 500 MPa, it is difficult to produce a large-volume autoclave (pressure vessel), which is not suitable for production.

  The central portion according to the present invention is composed of a metal or alloy selected from the group consisting of titanium metal, zirconium metal, titanium alloy, and zirconium alloy, and the surface layer portion is covered with a hydride of the metal or alloy. The oxygen removal additive having a composite structure has a center part (inside) covered with titanium metal and a surface layer part (surface) covered with titanium hydride, and the inside is covered with zirconium and the surface is covered with zirconium hydride. And those whose inside is a titanium alloy and whose surface is covered with a hydride of a titanium alloy, and those whose inside is a zirconium alloy and whose surface is covered with a hydride of a zirconium alloy.

  The titanium content of the titanium alloy of the oxygen removing additive, the inside of which is a titanium alloy and the surface thereof is made of a hydride of a titanium alloy, is preferably 30% by weight or more and less than 100% by weight, and the titanium content is 50% by weight or more. More preferably, the content is less than 100% by weight, and the titanium content is more preferably 70% by weight or more and less than 100% by weight. The zirconium content of the zirconium alloy of the oxygen removing additive whose inside is covered with a zirconium alloy and whose surface is covered with a hydride of the zirconium alloy is preferably 30% by weight or more and less than 100% by weight, and the zirconium content is 50%. More preferably, it is more than 100% by weight and more preferably less than 100% by weight.

  Titanium and zirconium have a large ability to bind to or adsorb oxygen and easily form a stable hydride on the surface. Even when these alloys are used, the higher the content of titanium or zirconium, the higher the oxygen content. The removal effect is great. When the content of titanium or zirconium is less than 20% by weight, the effect of removing oxygen is small. Further, even when titanium or zirconium is used as an oxygen removal additive, it is difficult to be incorporated as an impurity in the obtained group 13 element nitrogen compound crystal, so that a high-quality, high-quality group 13 element nitrogen compound crystal can be obtained.

  The central portion according to the present invention is composed of a metal or alloy selected from the group consisting of titanium metal, zirconium metal, titanium alloy, and zirconium alloy, and the surface layer portion is covered with a hydride of the metal or alloy. Although the manufacturing method of the oxygen removal additive which has a composite structure is not specifically limited, This oxygen removal additive can be produced by heat-treating titanium metal, zirconium metal, titanium alloy, and zirconium alloy in a hydrogen atmosphere. Plate or granular titanium metal, zirconium metal, titanium alloy, zirconium alloy is treated in vacuum at 500 to 900 ° C. for several hours to remove oxides present on the surface, and then in a hydrogen atmosphere, 300 to 800 The surface can be covered with a hydride of titanium or zirconium or a hydride of an alloy containing titanium or zirconium by treating at 0 ° C. for several hours. The thickness of the hydride may be such that oxidation of the internal metal can be suppressed.

  The shape of the oxygen removal additive is not particularly limited, but a granular or plate-like one is easy to use. When a granular oxygen removing additive is used, those having an average particle size of 1 μm or less are too fine and difficult to handle, so a particle size of 1 μm or more is preferable. Further, the particle diameter of the oxygen removal additive needs to be smaller than the container for producing the group 13 element nitrogen compound crystal. When a plate-like oxygen removal additive is used, those having a plate thickness of 1 μm or less are too thin and difficult to handle, and those having a plate thickness of 1 μm or more are preferable. Further, the size of the oxygen removing additive plate needs to be smaller than the container for producing the group 13 element nitrogen compound crystal.

  The thickness of the hydride of the oxygen removing additive is not particularly limited as long as it can suppress the oxidation of the internal metal as described above, but if it is in the range of 10 nm to 1 mm, the oxygen removing additive of the present invention has a thickness. It has a function. The hydride thickness of the oxygen removal additive is preferably 100 nm or more and 100 μm or less, more preferably 1 μm or more and 50 μm or less, and further preferably 1 μm or more and 20 μm or less. The thickness of the hydride of the oxygen removing additive can be determined by observing the cut surface of the oxygen removing additive with a scanning electron microscope. If the hydride thickness of the oxygen removal additive is thinner than 10 nm, the oxygen removal additive is oxidized in the air, and the effect of the oxygen removal additive is weakened. On the other hand, as the thickness of the oxygen removal additive hydride increases, the oxygen removal additive is less likely to be oxidized even if the oxygen removal additive is handled in the air. If the thickness exceeds 1 mm, the hydride is detached in a high-temperature ammonia atmosphere at 450 ° C. to 650 ° C. when producing a group 13 element nitrogen compound crystal, and the titanium or zirconium metal hardly appears on the surface. Oxygen removal addition is reduced.

  The amount of oxygen removal additive used varies depending on the size of the autoclave, the oxygen concentration on the surface of the container, the type and concentration of the mineralizer, the oxygen concentration of ammonia or the GaN raw material itself, and the like. As a result of various examinations of the amount of the oxygen removing additive used, the ratio of the oxygen removing additive to the ammonia filling amount in the autoclave such as an autoclave is preferably 0.003% by weight to 43% by weight, It was found that the content is more preferably 0.03% by weight or more and 10% by weight or less. When the amount of the oxygen removing additive is less than 0.003% by weight, the amount of the oxygen removing additive is too small and the effect of removing oxygen is small. On the other hand, the oxygen concentration in the GaN crystal decreases as the amount of the oxygen removal additive increases up to about 10% by weight. However, if it exceeds 10% by weight, the oxygen concentration in the GaN crystal increases even if more than 10% by weight is added. The effect of decreasing the concentration is small.

FIG. 1 is a schematic cross-sectional view of a production apparatus including an autoclave that can be used in the method for producing a group 13 element nitrogen compound crystal containing gallium as a main component according to the present invention.
In FIG. 1, the baffle plate 9 divides the crystal growth part 8 and the raw material part 11, and the aperture ratio is preferably 1% to 25%, more preferably 3% to 15%. The material of the baffle plate surface is preferably a metal such as platinum, gold, iridium, ruthenium, rhodium, palladium, or an alloy thereof in order to improve the erosion resistance.

  In order to produce a group 13 element nitrogen compound crystal, first, a mineralizer, an oxygen removal additive, and a raw material containing a group 13 metal element are placed in an autoclave, a baffle plate and seed are set, and an ammonia solvent is placed in the autoclave. Introduce and seal the autoclave. Before introducing ammonia into the autoclave, it is preferable to deaerate the inside of the autoclave and maintain a vacuum to remove oxygen and moisture. When introducing ammonia into the autoclave, if the autoclave is cooled below the boiling point of ammonia, the vapor pressure of ammonia is low, so that it is easy to seal the autoclave.

Production of Group 13 element nitrogen compound crystals is carried out in an autoclave. The container used in the present invention is selected from those that can withstand the high-temperature and high-pressure conditions when growing the group 13 element nitrogen compound crystal. The autoclave used in the present invention is preferably composed of a material having pressure resistance and erosion resistance. Inconel 625 (Inconel is a registered trademark of The International Nickel Company, Inc.), Rene 41 (Rene is Alvac) Metals Company registered trademark) and Udimet 520 (Udimet is a registered trademark of Special Metals, Inc.) are preferred.
In order to improve the erosion resistance of the autoclave, it is preferable to line or coat the part that contacts ammonia with a metal such as platinum, gold, iridium, ruthenium, rhodium, palladium, or an alloy thereof. In particular, an autoclave lined with platinum, iridium, or an alloy thereof is particularly preferable.
The crystal growth time in the method for producing a group 13 nitrogen compound crystal is preferably 1 day or longer, more preferably 2 days or longer.

Hereinafter, the present invention will be specifically described by way of non-limiting examples.
[Examples 1 to 6]
In order to produce the oxygen removal additive A having a titanium metal inside and a titanium hydride surface, spherical granular high-purity titanium having a particle diameter of 0.5 mm was used. This granular high-purity titanium was put in an alumina crucible, charged in a heating furnace, and subjected to vacuum heat treatment at 800 ° C. for 2 hours in order to remove the oxide layer on the titanium surface. Furthermore, the internal temperature of the heating furnace is set to 400 ° C., high-purity hydrogen is allowed to flow at atmospheric pressure, heat treatment is performed in an atmospheric pressure hydrogen atmosphere for 4 hours, and an oxygen removal additive A having a titanium metal inside and a hydride surface is added Obtained. The oxygen removal additive A was used in a constant temperature and humidity chamber with a humidity of 40% and a temperature of 20 ° C. In order to observe the internal state of the oxygen removal additive A, the oxygen removal additive A was cut and the cross section was observed with a scanning electron microscope with EPMA (Electron Probe Micro Analysis). It was found that the hydride was uniformly covered with a thickness of 3 to 5 μm.

GaN crystal growth was performed using the apparatus shown in FIG.
An autoclave 5 made of Inconel (registered trademark) 625 and having an inner diameter of 10 mm, a length of 200 mm, and a capacity of about 16 ml is used as an autoclave 5. An oxygen scavenger A was placed on the bottom of the autoclave 5 for use. The amount of oxygen removal additive A used is 0.003 g in Example 1, 0.03 g in Example 2, 0.3 g in Example 3, 1.0 g in Example 4, and in Example 5. 2.0 g was used, and 3.0 g was used in Example 6. This oxygen-removing additive A was used 10 days after production, and after being installed in the autoclave, the time in the air atmosphere was 1-2 hours. The amount of oxygen removal additive A used in each example is shown in Table 1 below as the amount of oxygen removal additive used.

Thereafter, 0.3 g of NH ₄ Cl powder having a purity of 99.99% and dried as a mineralizer was placed. Next, the raw material part 12 in which 3.5 g of a GaN polycrystal lump produced by the HVPE method is placed in a platinum net container is set on the platinum net 13, and a baffle plate is placed on the top at a position of 100 mm from the bottom. 9 was set, and a 3 mm square GaN seed produced by the HPVE method was set thereon, then the lid of the autoclave was closed and the autoclave including the lid was weighed. This GaN seed has a 3 mm square C-plane and a thickness in the c-axis direction of 50 μm.

  Once the inside of the autoclave was replaced with nitrogen gas, a vacuum deaerator was connected to the tip of the valve 4, the valves 1 and 4 were opened, and the inside of the autoclave was evacuated with vacuum. Thereafter, the autoclave 5 was cooled with a dry ice methanol solvent while the valve 4 and the valve 1 were closed and the vacuum state was maintained, and ammonia was charged into the autoclave 5 from the valve 1 side. The flow rate of ammonia was measured, and the autoclave 5 was filled with ammonia so that the ammonia amount was 65% of the volume in the autoclave in the liquid ammonia state at −33 ° C. After filling with ammonia, the valves 1 and 4 were closed, returned to room temperature, and the weight of the autoclave was measured again to confirm that the amount of filling with ammonia was appropriate.

  In order to perform GaN crystal growth by heat treatment in an ammonia atmosphere, the autoclave 5 was placed in an electric furnace 6 composed of a heater divided into two parts in the vertical direction. The temperature was raised over 8 hours so that the outer surface temperature of the lower part of the autoclave was 550 ° C. and the outer surface temperature of the upper part of the autoclave was 500 ° C., and maintained at that temperature for 96 hours to perform GaN crystal growth. The pressure in the autoclave 5 was 150 MPa. In addition, the temperature range of the outer surface temperature during holding was within ± 5 ° C. for both the external temperature at the bottom of the autoclave and the external temperature at the top. Thereafter, the autoclave was cooled down to 60 ° C. over 12 hours, and further allowed to stand at room temperature. After confirming that the temperature of the autoclave was approximately room temperature, the autoclave 5 was removed from the electric furnace 6, the valve 4 was slowly opened, and the ammonia in the autoclave 5 was discharged.

  In order to completely discharge ammonia in the autoclave, the valve 4 was once closed, high purity nitrogen was sealed from the valve 1 side at a pressure of 1 MPa, and nitrogen was discharged from the valve 4 side 10 times. Thereafter, the valve 4 was opened, the autoclave lid was opened, and GaN crystals grown on the internal GaN seeds were confirmed.

  When the GaN crystal grown on the GaN seed was confirmed by a scanning electron microscope, in all of Examples 1 to 6, a GaN crystal having a thickness of about 60 μm was grown on the C plane so as to cover the GaN seed. Furthermore, when the crystal form of GaN was confirmed by X-ray diffraction, all of Examples 1 to 6 were hexagonal, and the growth direction in the thickness direction of the GaN crystal was c-axis on the C-plane as in the seed. Oriented.

Table 1 shows the results of measuring the oxygen concentration of the GaN crystal grown on the obtained C-plane with an IMS-7f type secondary ion mass spectrometer manufactured by CAMECA. The oxygen concentration in the GaN crystal by the secondary ion mass spectrometer was quantified using a GaN standard material having a known oxygen concentration in which oxygen was implanted into a GaN substrate manufactured by a high purity HPVE method. The oxygen concentration of the GaN crystal measured by this secondary ion mass spectrometer is Cs ⁺ as the primary ion, and the primary acceleration voltage is 14.5 kV and the detection region is 30 μmφ at a depth of 1 μm in the c-axis direction from the GaN crystal surface. The measured value. The oxygen concentration of the GaN crystal by this secondary ion mass spectrometer is expressed as the number of oxygen atoms per cm ^{3 of} GaN crystal as the number of atoms / cm ³ .
As can be seen from Table 1, in Examples 1 to 6 using the oxygen removal additive A whose inside is titanium metal and the surface is made of hydride, the oxygen concentration in the GaN crystal grown on the seed is the oxygen removal additive. The oxygen concentration in the GaN crystal grown on the seed of Comparative Example 1 shown in Table 6 below is significantly lower than the oxygen concentration of 4 × 10 ¹⁹ atoms / cm ^3. By adding this oxygen scavenger, oxygen is reduced. It can be seen that a good quality GaN crystal with a small amount of GaN was obtained. The effect of this oxygen scavenger was found to be that when the ratio of the oxygen scavenging additive A to the ammonia filling amount exceeds 10% by weight, the oxygen concentration in the GaN crystal is lowered and a good quality GaN crystal is obtained.
In addition, the same result as Table 1 was obtained also when the oxygen removal additive A preserve | saved 30 days after manufacture was used.

[Examples 7 to 11]
In order to produce the oxygen removal additive B having a zirconium metal inside and a zirconium hydride surface, spherical granular high-purity zirconium having a particle diameter of 0.5 mm was used. This granular high-purity zirconium was put in an alumina crucible, charged in a heating furnace, and subjected to vacuum heat treatment at 800 ° C. for 2 hours in order to remove the oxide layer on the titanium surface. Furthermore, the internal temperature of the heating furnace is set to 500 ° C., high-purity hydrogen is allowed to flow at atmospheric pressure, heat treatment is performed in an atmospheric pressure hydrogen atmosphere for 8 hours, and an oxygen removing additive B having titanium metal inside and hydride on the surface is added. Obtained. Oxygen removal additive B was stored and used in a constant temperature and humidity chamber having a humidity of 40% and a temperature of 20 ° C. as in Examples 1-6. In order to observe the internal state of the oxygen removal additive B, the oxygen removal additive B was cut and the cross section was observed with a scanning electron microscope with EPMA (Electron Probe Micro Analysis). It was found that the hydride was uniformly covered with a thickness of 2 to 4 μm.

  In Examples 7 to 11, GaN crystals were produced in the same manner as in Examples 1 to 6, except that the oxygen removal additive A used in Examples 1 to 6 was replaced with the oxygen removal additive B. The amount of oxygen removal additive B used is 0.03 g in Example 7, 0.3 g in Example 8, 1.0 g in Example 9, 2.0 g in Example 10, and in Example 11. 3.0 g was used. This oxygen removal additive B was used 10 days after production, and after being installed in the autoclave, the time in the air atmosphere was 1-2 hours as in Examples 1-6. The amount of oxygen removal additive B used in each of these examples is shown in Table 2 below as the amount of oxygen removal additive used.

  When the GaN crystal grown on the GaN seed was confirmed by a scanning electron microscope, in all of Examples 7 to 11, a GaN crystal having a thickness of about 60 μm was grown on the C plane so as to cover the GaN seed. Furthermore, when the crystal form of GaN was confirmed by X-ray diffraction, all of Examples 7 to 11 were hexagonal, and the growth direction in the thickness direction of the GaN crystal was c-axis on the C-plane as in the seed. Oriented.

Table 2 shows the results of measuring the oxygen concentration of the GaN crystal grown on the obtained C-plane in the same manner as in Examples 1-6.
As can be seen from Table 2, in Examples 7 to 11 using the oxygen removal additive B having a zirconium metal inside and a zirconium hydride surface, the oxygen concentration in the GaN crystal grown on the seed was oxygen. The oxygen concentration in the GaN crystal grown on the seed of Comparative Example 1 shown in Table 6 below, which does not use the removal additive, is greatly reduced compared to 4 × 10 ¹⁹ atoms / cm ³ . It can be seen that a good quality GaN crystal with little oxygen was obtained by the addition. The effect of this oxygen scavenger was found to be that when the ratio of the oxygen scavenger additive B to the ammonia filling amount exceeds 10% by weight, the oxygen concentration in the GaN crystal is further lowered and a higher quality GaN crystal can be obtained.
In addition, the same result as Table 2 was obtained also when the oxygen removal additive B preserve | saved 30 days after manufacture was used.

[Examples 12 to 16]
In order to produce an oxygen scavenging additive C whose inner surface is an alloy of 50% titanium and 50% zirconium and whose surface is composed of a hydride of titanium and zirconium, 50% spherical high-purity titanium having a particle diameter of 0.5 mm and high-purity zirconium A 50% alloy was used. This alloy of 50% titanium and 50% zirconium is an alloy of 50 parts by weight of titanium and 50 parts by weight of zirconium. This granular high-purity alloy is placed in an alumina crucible and charged in a heating furnace, and an oxide layer on the surface of the alloy is formed. In order to remove, vacuum heat treatment was performed at 800 ° C. for 2 hours. Furthermore, the internal temperature of the heating furnace is set to 450 ° C., high-purity hydrogen is allowed to flow at atmospheric pressure, heat treatment is performed in an atmospheric hydrogen atmosphere for 8 hours, and the inside is an alloy of 50% titanium and 50% zirconium. An oxygen removal additive C made of hydride was obtained. The oxygen removal additive C was stored and used in a constant temperature and humidity chamber having a humidity of 40% and a temperature of 20 ° C. as in Examples 1-6. In order to observe the internal state of the oxygen removal additive C, the oxygen removal additive C was cut and the cross section was observed with a scanning electron microscope with EPMA (Electron Probe Micro Analysis). It was found that the surface of the hydride uniformly covered with a thickness of 3 to 5 μm.

  In Examples 12 to 16, GaN crystals were produced in the same manner as in Examples 1 to 6, except that the oxygen removal additive A used in Examples 1 to 6 was replaced with the oxygen removal additive C. The amount of oxygen removal additive C used is 0.03 g in Example 12, 0.3 g in Example 13, 1.0 g in Example 14, 2.0 g in Example 15, and in Example 16. 3.0 g was used. This oxygen removal additive C was used 10 days after production, and after being installed in the autoclave, the time in the air atmosphere was 1-2 hours as in Examples 1-6. The amount of oxygen removal additive C used in each of the examples is shown in Table 3 below as the amount of oxygen removal additive used.

  When the GaN crystal grown on the GaN seed was confirmed by a scanning electron microscope, in all of Examples 12 to 16, a GaN crystal having a thickness of about 60 μm was grown on the C plane so as to cover the GaN seed. Furthermore, when the crystal form of GaN was confirmed by X-ray diffraction, all of Examples 12 to 16 were hexagonal, and the growth direction in the thickness direction of the GaN crystal was c-axis on the C-plane as in the seed. Oriented.

Table 3 shows the results of measuring the oxygen concentration of the GaN crystal grown on the obtained C-plane by the same method as in Examples 1-6.
As can be seen from Table 3, in Examples 12 to 16 using the oxygen removal additive C having an inside alloy of 50% titanium and 50% zirconium and a hydride of titanium and zirconium on the surface, GaN grown on the seed The oxygen concentration in the crystal is greatly reduced compared to the oxygen concentration of 4 × 10 ¹⁹ atoms / cm ³ in the GaN crystal grown on the seed of Comparative Example 1 shown in Table 6 below without using an oxygen removal additive. Thus, it can be seen that a good quality GaN crystal with less oxygen was obtained by the addition of the present oxygen scavenger. The effect of this oxygen scavenger was found to be that when the ratio of the oxygen scavenging additive C to the ammonia filling amount exceeds 10% by weight, the oxygen concentration in the GaN crystal is further lowered, and a higher quality GaN crystal can be obtained.
In addition, the same result as Table 3 was obtained also when using the oxygen removal additive C preserve | saved 30 days after manufacture.

[Examples 17 to 21]
In order to produce an oxygen scavenging additive D whose inside is an alloy of 50% titanium and 50% nickel and whose surface is made of a hydride of titanium and nickel, 50% spherical high-purity titanium having a particle diameter of 0.5 mm and high-purity nickel A 50% alloy was used. This alloy of 50% titanium and 50% nickel is an alloy of 50 parts by weight of titanium and 50 parts by weight of nickel. This granular high-purity alloy is placed in an alumina crucible, charged in a heating furnace, and an oxide layer on the surface of the alloy is formed. In order to remove, vacuum heat treatment was performed at 800 ° C. for 2 hours. Furthermore, the internal temperature of the heating furnace is set to 450 ° C., high-purity hydrogen is allowed to flow at atmospheric pressure, heat treatment is performed in an atmospheric hydrogen atmosphere for 8 hours, and the inside is an alloy of 50% titanium and 50% nickel, and the surface is made of titanium and nickel. An oxygen removal additive D made of hydride was obtained. The oxygen removal additive D was stored and used in a constant temperature and humidity chamber having a humidity of 40% and a temperature of 20 ° C. as in Examples 1-6. In order to observe the internal state of the oxygen removal additive D, the oxygen removal additive D was cut and the cross section was observed with a scanning electron microscope with EPMA (Electron Probe Micro Analysis). It was found that the surface of the hydride uniformly covered the hydride with a thickness of 1 to 3 μm.

  In Examples 17 to 21, GaN crystals were produced in the same manner as in Examples 1 to 6, except that the oxygen removal additive A used in Examples 1 to 6 was replaced with the oxygen removal additive D. The amount of oxygen removal additive D used is 0.03 g in Example 17, 0.3 g in Example 18, 1.0 g in Example 19, 2.0 g in Example 20, and in Example 21. 3.0 g was used. This oxygen-removing additive D was used 10 days after production, and after being installed in the autoclave, the time in the air atmosphere was 1-2 hours as in Examples 1-6. The amount of oxygen removal additive D used in each example is shown in Table 4 below as the amount of oxygen removal additive used.

  When the GaN crystal grown on the GaN seed was confirmed by a scanning electron microscope, in all of Examples 17 to 21, a GaN crystal having a thickness of about 60 μm was grown on the C plane so as to cover the GaN seed. Further, when the crystal form of GaN was confirmed by X-ray diffraction, all of Examples 17 to 21 were hexagonal type, and the growth direction in the thickness direction of the GaN crystal was c-axis on the C plane as in the seed. Oriented.

Table 4 shows the results of measuring the oxygen concentration of the GaN crystal grown on the obtained C-plane by the same method as in Examples 1-6.
As can be seen from Table 4, in Examples 17 to 21 using the oxygen removal additive D whose inside is an alloy of 50% titanium and 50% nickel and whose surface is made of a hydride of titanium and nickel, the GaN crystal grown on the seed And the oxygen concentration in the GaN crystal grown on the seed of Comparative Example 1 shown in Table 6 below using no oxygen removal additive is reduced compared to the oxygen concentration of 4 × 10 ¹⁹ atoms / cm ³ , It can be seen that the addition of this oxygen scavenger resulted in a good quality GaN crystal with little oxygen. The effect of this oxygen scavenger was found to be that when the ratio of the oxygen scavenging additive D to the ammonia filling amount exceeds 10% by weight, the oxygen concentration in the GaN crystal is further lowered and a higher quality GaN crystal can be obtained.
In addition, when the oxygen removal additive D stored for 30 days after production was used, the same results as in Table 4 were obtained.

[Examples 22 to 26]
In order to produce an oxygen removal additive E having an alloy of 50% zirconium and 50% nickel inside and a hydride of zirconium and nickel on the surface, 50% spherical high purity zirconium having a particle diameter of 0.5 mm and high purity nickel A 50% alloy was used. This alloy of 50% zirconium and 50% nickel is an alloy of 50 parts by weight of zirconium and 50 parts by weight of nickel. This granular high-purity alloy is placed in an alumina crucible, charged in a heating furnace, and an oxide layer on the surface of the alloy is formed. In order to remove, vacuum heat treatment was performed at 800 ° C. for 2 hours. Furthermore, the internal temperature of the heating furnace is set to 450 ° C., high-purity hydrogen is allowed to flow at atmospheric pressure, and heat treatment is performed in an atmospheric pressure hydrogen atmosphere for 8 hours. An oxygen removal additive E consisting of hydride was obtained. The oxygen removal additive E was stored and used in a constant temperature and humidity chamber having a humidity of 40% and a temperature of 20 ° C. as in Examples 1 to 6. In order to observe the internal state of the oxygen removal additive E, the oxygen removal additive E was cut and the cross section was observed with a scanning electron microscope equipped with EPMA (Electron Probe Micro Analysis). It was found that the surface of the hydride uniformly covered the hydride with a thickness of 1 to 3 μm.

  In Examples 22 to 26, GaN crystals were produced in the same manner as in Examples 1 to 6, except that the oxygen removal additive A used in Examples 1 to 6 was replaced with the oxygen removal additive E. . The amount of oxygen removal additive E used is 0.03 g in Example 22, 0.3 g in Example 23, 1.0 g in Example 24, 2.0 g in Example 25, and in Example 26. 3.0 g was used. This oxygen removal additive E was used 10 days after production, and after being installed in the autoclave, the time in the air atmosphere was 1-2 hours as in Examples 1-6. The amount of oxygen removal additive E used in each example is shown in Table 5 below as the amount of oxygen removal additive used.

When the GaN crystal grown on the GaN seed was confirmed by a scanning electron microscope, in all of Examples 22 to 26, a GaN crystal having a thickness of about 60 μm was grown on the C plane so as to cover the GaN seed. Further, when the crystal form of GaN was confirmed by X-ray diffraction, all of Examples 22 to 26 were hexagonal, and the growth direction in the thickness direction of the GaN crystal was c-axis on the C-plane as in the seed. Oriented.
Table 5 shows the results of measuring the oxygen concentration of the GaN crystal grown on the obtained C-plane by the same method as in Examples 1-6.

As can be seen from Table 5, in Examples 22 to 26 using the oxygen removal additive E whose inside is an alloy of 50% zirconium and 50% nickel and whose surface is made of a hydride of zirconium and nickel, the GaN crystal grown on the seed And the oxygen concentration in the GaN crystal grown on the seed of Comparative Example 1 shown in Table 6 below using no oxygen removal additive is reduced compared to the oxygen concentration of 4 × 10 ¹⁹ atoms / cm ³ , It can be seen that the addition of this oxygen scavenger resulted in a good quality GaN crystal with little oxygen. The effect of this oxygen scavenger was found to be that when the ratio of the oxygen scavenging additive E to the ammonia filling amount exceeds 10% by weight, the oxygen concentration in the GaN crystal is further lowered and a higher quality GaN crystal can be obtained.
In addition, the same result as Table 5 was obtained also when using the oxygen removal additive E preserve | saved 30 days after manufacture.

[Comparative Example 1]
Comparative Example 1 is an example in which no oxygen removal additive is used. In Comparative Example 1, a GaN crystal was produced in the same manner as in Examples 1 to 6 except that no oxygen removal additive was used.
When the GaN crystal grown on the GaN seed was confirmed by a scanning electron microscope, a GaN crystal having a thickness of about 60 μm was grown on the C plane so as to cover the GaN seed. Further, when the crystal form of GaN was confirmed by X-ray diffraction, it was a hexagonal type, and the growth direction in the thickness direction of the GaN crystal was oriented on the c-axis on the C-plane like the seed.
Table 6 below shows the results of measuring the oxygen concentration of the GaN crystal grown on the obtained C-plane by the same method as in Examples 1-6.

As shown in Table 6, the oxygen concentration of 4 × 10 ¹⁹ atoms / cm ³ in the GaN crystal grown on the seed of Comparative Example 1 is higher than that of any of Examples 1 to 26. The purity was not high.

[Comparative Examples 2 and 3]
Comparative Examples 2 and 3 are comparative examples in the case of using an oxygen removal additive K made of titanium metal whose surface is not a hydride. As the oxygen removal additive K, a spherical granular high-purity titanium having a particle diameter of 0.5 mm similar to that in Examples 1 to 6 was used after being stored and filled with nitrogen.
In Comparative Examples 2 and 3, a GaN crystal was produced in the same manner as in Examples 1 to 6, except that the oxygen removal additive A used in Examples 1 to 6 was replaced with the oxygen removal additive K. . The amount of oxygen removal additive K used was 1.0 g in Comparative Example 2 and 3.0 g in Comparative Example 3. This oxygen removal additive K was used after being released from nitrogen filling immediately before use, and after being installed in the autoclave, the time in the air atmosphere was 1-2 hours as in Examples 1-6. The amount of oxygen removal additive K used in each example is shown in Table 6 as the amount of oxygen removal additive used.

When the GaN crystal grown on the GaN seed was confirmed by a scanning electron microscope, in both Comparative Examples 2 and 3, a GaN crystal having a thickness of about 60 μm was grown on the C plane so as to cover the GaN seed. Further, when the crystal form of GaN was confirmed by X-ray diffraction, both Comparative Examples 2 and 3 were hexagonal, and the growth direction in the thickness direction of the GaN crystal was c-axis on the C-plane as in the seed. Oriented.
Table 6 shows the results of measuring the oxygen concentration of the GaN crystal grown on the obtained C-plane by the same method as in Examples 1-6.
As shown in Table 6, the oxygen concentration in the GaN crystals grown on the seeds of Comparative Examples 2 and 3 was higher than that in any of Examples 1 to 26, and the purity of GaN was not high.

[Comparative Examples 4 and 5]
Comparative Examples 4 and 5 are comparative examples in the case of using an oxygen removal additive L made of zirconium metal whose surface is not a hydride. As the oxygen removal additive L, spherical granular high-purity zirconium having a particle diameter of 0.5 mm as in Examples 7 to 11 was used after storage and nitrogen-sealed.
In Comparative Examples 4 and 5, GaN crystals were produced in the same manner as in Examples 1 to 6, except that the oxygen removal additive A used in Examples 1 to 6 was replaced with the oxygen removal additive L. The amount of oxygen removal additive L used was 1.0 g in Comparative Example 4 and 3.0 g in Comparative Example 5. This oxygen removal additive L was used by being released from nitrogen filling immediately before use, and after being installed in the autoclave, the time in the air atmosphere was 1-2 hours as in Examples 1-6. The amount of oxygen removal additive L used in each of these examples is shown in Table 6 as the amount of oxygen removal additive used.

When the GaN crystal grown on the GaN seed was confirmed with a scanning electron microscope, in both Comparative Examples 4 and 5, a GaN crystal having a thickness of about 60 μm was grown on the C plane so as to cover the GaN seed. Furthermore, when the crystal form of GaN was confirmed by X-ray diffraction, both Comparative Examples 4 and 5 were hexagonal, and the growth direction in the thickness direction of the GaN crystal was c-axis on the C-plane as in the seed. Oriented.
Table 6 shows the results of measuring the oxygen concentration of the GaN crystal grown on the obtained C-plane by the same method as in Examples 1-6.
Comparative Examples 4 and 5 As shown in Table 6, the oxygen concentration in the GaN crystals grown on the seeds was higher than those in Examples 1 to 26, and the purity of GaN was not high.

[Comparative Examples 6 and 7]
Comparative Examples 6 and 7 are comparative examples in the case of using an oxygen removal additive M made of an alloy of 50% titanium and 50% zirconium whose surfaces are not hydride. As the oxygen removal additive M, a spherical alloy of 50% high-purity titanium and 50% high-purity zirconium having a particle diameter of 0.5 mm, which is the same as in Examples 12 to 16, was used after storage and nitrogen-sealed. It was.
In Comparative Examples 6 and 7, GaN crystals were produced in the same manner as in Examples 1 to 6, except that the oxygen removal additive A used in Examples 1 to 6 was replaced with the oxygen removal additive M. The amount of oxygen removal additive M used was 1.0 g in Comparative Example 6 and 3.0 g in Comparative Example 7. This oxygen removal additive M was used after being released from nitrogen filling immediately before use, and after being installed in the autoclave, the time in the air atmosphere was 1-2 hours as in Examples 1-6. The amount of oxygen removal additive M used in each of these examples is shown in Table 6 as the amount of oxygen removal additive used.

When the GaN crystal grown on the GaN seed was confirmed with a scanning electron microscope, in both Comparative Examples 6 and 7, a GaN crystal having a thickness of about 60 μm was grown on the C plane so as to cover the GaN seed. Furthermore, when the crystal form of GaN was confirmed by X-ray diffraction, both Comparative Examples 6 and 7 were hexagonal, and the growth direction in the thickness direction of the GaN crystal was c-axis on the C-plane as in the seed. Oriented.
Table 6 shows the results of measuring the oxygen concentration of the GaN crystal grown on the obtained C-plane by the same method as in Examples 1-6.
As shown in Table 6, the oxygen concentration in the GaN crystals grown on the seeds of Comparative Examples 6 and 7 was higher than that in any of Examples 1 to 26, and the purity of GaN was not high.

[Comparative Examples 8 and 9]
Comparative Examples 8 and 9 are comparative examples in the case of using an oxygen removal additive N composed of an oxygen removal additive consisting of an alloy containing 20% titanium and 80% nickel inside and a hydride of titanium and nickel on the surface. . In order to produce an oxygen removal additive N consisting of an alloy containing 20% titanium and 70% nickel and a hydride of titanium and nickel on the inside, 20% spherical high-purity titanium with a particle size of 0.5 mm and high-purity nickel An 80% alloy was used. This alloy of 20% titanium and 80% nickel is an alloy of 20 parts by weight titanium and 80 parts by weight nickel. This granular high-purity alloy is put in an alumina crucible and charged in a heating furnace, and an oxide layer on the surface of the alloy is formed. In order to remove, vacuum heat treatment was performed at 800 ° C. for 2 hours. Furthermore, the internal temperature of the heating furnace is set to 450 ° C., high-purity hydrogen is allowed to flow at atmospheric pressure, heat treatment is performed in an atmospheric hydrogen atmosphere for 8 hours, and the inside is an alloy of 20% titanium and 80% nickel, and the surface is made of titanium and nickel. An oxygen removal additive N consisting of hydride was obtained. The oxygen removal additive N was used in a constant temperature and humidity chamber having a humidity of 40% and a temperature of 20 ° C. as in Examples 1 to 6. In order to observe the internal state of the oxygen removal additive N, the oxygen removal additive N was cut and the cross section was observed with a scanning electron microscope with EPMA (Electron Probe Micro Analysis). It was found that the hydride covered the surface with a thickness of 1 to 2 μm.

  Comparative Examples 8 and 9 produced GaN crystals in the same manner as in Examples 1 to 6, except that oxygen removal additive A used in Examples 1 to 6 was replaced with oxygen removal additive N. The amount of oxygen removal additive N used was 1.0 g in Comparative Example 8 and 3.0 g in Comparative Example 9. After the oxygen removing additive N was placed in the autoclave, the time in the air atmosphere was 1-2 hours as in Examples 1-6. The amount of oxygen removal additive N used in each of these examples is shown in Table 6 as the amount of oxygen removal additive used.

When the GaN crystal grown on the GaN seed was confirmed by a scanning electron microscope, in both Comparative Examples 8 and 9, a GaN crystal having a thickness of about 60 μm was grown on the C plane so as to cover the GaN seed. Furthermore, when the crystal form of GaN was confirmed by X-ray diffraction, both Comparative Examples 8 and 9 were hexagonal, and the growth direction in the thickness direction of the GaN crystal was c-axis on the C-plane as in the seed. Oriented.
Table 6 shows the results of measuring the oxygen concentration of the GaN crystal grown on the obtained C-plane by the same method as in Examples 1-6.
As shown in Table 6, the oxygen concentration in the GaN crystals grown on the seeds of Comparative Examples 8 and 9 was higher than that in any of Examples 1 to 26, and the purity of GaN was not high.

[Comparative Examples 10 and 11]
Comparative Examples 10 and 11 are comparative examples in the case of using an oxygen removal additive O composed of an oxygen removal additive composed of an alloy containing 20% zirconium and 80% nickel inside and a hydride of zirconium and nickel on the surface. . In order to produce an oxygen scavenging additive O whose inside is an alloy of 20% zirconium and 70% nickel and whose surface is composed of a hydride of zirconium and nickel, 20% spherical high purity zirconium having a particle diameter of 0.5 mm and high purity nickel An 80% alloy was used. This alloy of 20% zirconium and 80% nickel is an alloy of 20 parts by weight zirconium and 80 parts by weight nickel. This granular high-purity alloy is placed in an alumina crucible and charged in a heating furnace, and an oxide layer on the surface of the alloy is formed. In order to remove, vacuum heat treatment was performed at 800 ° C. for 2 hours. Furthermore, the internal temperature of the heating furnace is set to 450 ° C., high-purity hydrogen is allowed to flow at atmospheric pressure, heat treatment is performed for 8 hours in an atmospheric hydrogen atmosphere, an alloy containing 20% zirconium and 80% nickel inside, and the surface is made of titanium and nickel. An oxygen removal additive O consisting of hydride was obtained. The oxygen removal additive O was stored and used in a constant temperature and humidity chamber having a humidity of 40% and a temperature of 20 ° C. as in Examples 1-6. In order to observe the internal state of the oxygen removal additive O, the oxygen removal additive O was cut and the cross section was observed with a scanning electron microscope with EPMA (Electron Probe Micro Analysis). It was found that the hydride covered the surface with a thickness of 1 to 2 μm.

  In Comparative Examples 10 and 11, a GaN crystal was produced in the same manner as in Examples 1 to 6, except that the oxygen removal additive A used in Examples 1 to 6 was replaced with the oxygen removal additive O. . The amount of oxygen removal additive O used was 1.0 g in Comparative Example 10 and 3.0 g in Comparative Example 11. After the oxygen removing additive O was placed in the autoclave, the time in the air atmosphere was 1-2 hours as in Examples 1-6. The amount of oxygen removal additive O used in each example is shown in Table 6 as the amount of oxygen removal additive used.

When the GaN crystal grown on the GaN seed was confirmed with a scanning electron microscope, in Comparative Examples 10 and 11, a GaN crystal having a thickness of about 60 μm was grown on the C plane so as to cover the GaN seed. Further, when the crystal form of GaN was confirmed by X-ray diffraction, both Comparative Examples 10 and 11 were hexagonal, and the growth direction in the thickness direction of the GaN crystal was c-axis on the C-plane as in the seed. Oriented.
Table 6 shows the results of measuring the oxygen concentration of the GaN crystal grown on the obtained C-plane by the same method as in Examples 1-6.
As shown in Table 6, the oxygen concentration in the GaN crystal grown on the seed of the comparative example was higher than that in any of Examples 1 to 26, and the purity of GaN was not high.

  In the present invention, in a production method in a so-called ammonothermal method in which a group 13 nitrogen compound crystal is obtained by heat treatment in an ammonia atmosphere, the inside is a metal and / or alloy and the surface is a hydride of the metal and / or alloy. By producing the group 13 element nitrogen compound crystal by contacting the covered oxygen removal additive with ammonia, a high-quality group 13 element nitrogen compound crystal having a low oxygen content can be provided. In addition, the oxygen removing additive according to the present invention is an easy-to-handle oxygen removing additive because the surface is covered with hydride and the oxygen removing effect is not impaired even when handled in air. A group 13 element nitrogen compound crystal such as a high-quality high-quality GaN crystal with few oxygen impurities can be obtained, is industrially useful, and has extremely high industrial applicability.

The schematic sectional drawing of the group 13 element nitrogen compound crystal manufacturing apparatus of this invention.

Explanation of symbols

1 Valve 1
2 Piping 3 Pressure gauge 4 Valve 4
5 Autoclave 6 Electric furnace 7 Seed 8 Crystal growth part 9 Baffle plate 10 Thermocouple 11 Raw material part 12 Raw material 13 Platinum wire mesh 14 Oxygen removal additive

Claims (2)

  A method for producing a Group 13 element nitrogen compound crystal containing gallium as a main component, wherein a Group 13 element metal containing at least gallium and / or a nitrogen compound of the metal is added in an ammonia atmosphere in the presence of an oxygen removal additive. Heat treatment to obtain crystals, wherein the oxygen scavenging additive is composed of a metal or alloy whose central portion is selected from the group consisting of titanium metal, zirconium metal, titanium alloy, and zirconium alloy. And the said manufacturing method which has the composite structure where the surface layer part was covered with the hydride of this metal or alloy.   The method according to claim 1, wherein the nitrogen compound of a group 13 element containing gallium as a main component is GaN.

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