JP2006273593A - Method for growing group iii nitride crystal, and group iii nitride crystal - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for growing a group III nitride crystal by which a colorless, transparent and high-quality crystal can be grown into a desired form without adding an additive such as Li which increases the nitrogen concentration even in an initial stage of crystal growth when conventionally a brown low-quality crystal having many defects is grown. <P>SOLUTION: A melt 46 containing a group III metal is held in a gas atmosphere 48 containing a nitrogen source gas and a flux gas, and the nitrogen and the flux are dissolved from the gas atmosphere 48 into the melt 46 containing the group III metal to grow a crystal of a group III nitride 47. The crystalline morphology of the group III nitride 47 to be grown is controlled by the pressure of the flux in the gas atmosphere 48. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a group III nitride crystal growth method and a group III nitride crystal.

  At present, most of InGaAlN-based (group III nitride) devices used as ultraviolet, purple-blue to green light sources are formed on a sapphire or SiC substrate by MO-CVD (metal organic chemical vapor deposition) or It is produced by crystal growth using the MBE method (molecular beam crystal growth method) or the like.

  As a problem when sapphire or SiC is used as a substrate, there is an increase in crystal defects caused by a large difference in thermal expansion coefficient and lattice constant from the group III nitride. For this reason, it leads to the fault that device characteristics are bad, for example, it is difficult to extend the lifetime of the light emitting device, or the operating power is increased.

  Furthermore, in the case of a sapphire substrate, since it is insulative, it is impossible to take out the electrode from the substrate side as in the conventional light emitting device, and it is necessary to take out the electrode from the nitride semiconductor surface side where the crystal has grown. . As a result, there is a problem that the device area becomes large, leading to high costs. Further, the group III nitride semiconductor device fabricated on the sapphire substrate is difficult to separate the chip by cleavage, and it is not easy to obtain the resonator end face required for the laser diode (LD) by cleavage. For this reason, at present, resonator end faces are formed by dry etching, or resonator end faces are formed in a form close to cleavage after polishing the sapphire substrate to a thickness of 100 μm or less. Also in this case, it is impossible to easily separate the resonator end face from the conventional LD and the chip in a single process, resulting in a complicated process and an increase in cost.

  In order to solve these problems, it has been proposed to reduce crystal defects by selectively growing a group III nitride semiconductor film on a sapphire substrate or by performing other devices. In this method, crystal defects can be reduced as compared with the case where a GaN film is not selectively grown in the lateral direction on the sapphire substrate, but the above-described insulation and cleavage by using the sapphire substrate. The problem remains. Furthermore, the process becomes complicated, and problems of warping of the substrate due to the combination of different materials such as a sapphire substrate and a GaN thin film arise. These have led to higher costs.

  In order to solve these problems, it is most appropriate to use a GaN substrate that is the same as the material for crystal growth on the substrate. Therefore, research on crystal growth of bulk GaN has been made by vapor phase growth, melt growth and the like. However, a high-quality and practical size GaN substrate has not yet been realized.

As one method for realizing a GaN substrate, Non-Patent Document 1 (Prior Art 1) proposes a GaN crystal growth method using Na as a flux. In the method of Prior Art 1, sodium azide (NaN ₃ ) and metal Ga are used as raw materials, and sealed in a stainless steel reaction vessel (inner vessel dimensions; inner diameter = 7.5 mm, length = 100 mm) in a nitrogen atmosphere, By holding the reaction vessel at a temperature of 600 to 800 ° C. for 24 to 100 hours, a GaN crystal is grown.

In the case of this prior art 1, crystal growth is possible at a relatively low temperature of 600 to 800 ° C., and the pressure in the vessel is relatively low at about 100 kg / cm ² at most, which is a practical growth condition. It is a feature.

In Patent Document 1 (Prior Art 2), a substrate (sapphire or the like) on which AlN or GaN is deposited, sodium azide (NaN ₃ ), and gallium metal are enclosed in a stainless steel tube and heated to about 800 ° C. A method for crystal growth of a GaN film on a substrate is disclosed. In the method of prior art 2, sodium azide is decomposed into sodium and nitrogen gas in the course of raising the temperature of the stainless tube to the crystal growth temperature (about 800 ° C.) (about 300 ° C.), and sodium and gallium are contained in the tube. And a nitrogen gas atmosphere of about 100 atm. And nitrogen melt | dissolves in a melt from a gaseous phase at a growth temperature, Ga and nitrogen react, and GaN precipitates on a substrate. In this case, a large area GaN crystal can be grown by using a large area substrate.

  Further, in Patent Document 2 (Prior Art 3), as shown in FIG. 7, a seed crystal 4 is held in a mixed melt 2 of Ga and Na under a nitrogen atmosphere of about 100 atm. A method for manufacturing a group III nitride single crystal in which GaN crystal growth is performed by locally heating is disclosed. In this method, by locally heating the seed crystal 4, growth of miscellaneous crystals on the side wall of the crucible 3 is suppressed, and only the seed crystal can be grown greatly without wasteful consumption of raw materials. .

  However, in Patent Document 1 (Prior Art 2), a Ga-Na melt and a nitrogen gas atmosphere are formed at a low temperature stage, and nitrogen is dissolved in the melt, so that the nitrogen concentration in the melt is not sufficiently high. Crystals begin to grow. For this reason, dark brown crystals with low crystal quality are grown at the early stage of growth, which adversely affects the quality of crystals grown thereon. Further, with the growth of GaN, Ga in the melt is consumed, and the amount ratio of Ga and Na in the melt changes. Since crystal quality and surface morphology vary depending on the quantity ratio of Ga and Na in the melt, it is difficult to grow a crystal having a flat surface morphology in Patent Document 1.

  Patent Document 2 (Prior Art 3) discloses a method of suppressing a large number of natural nucleus growth on the inner wall of the crucible 3 by locally heating the seed crystal 4. Since the penetration of nitrogen from the gas phase depends on the temperature and the area of the gas-liquid interface, when the high temperature region is small by local heating as in Patent Document 2, the amount of nitrogen penetration is small, so Many crystals can grow. Therefore, as in Patent Document 1, dark brown crystals with low crystal quality may grow at the initial growth stage.

  The inventor of the present application has so far made an invention relating to the suppression of low-quality crystals at the initial stage of growth, which is a problem of Patent Document 1 (Prior Art 2) and Patent Document 2 (Prior Art 3).

That is, in Patent Document 3 (Prior Art 4), by adding Li to a mixed melt of Ga and Na, the solubility of nitrogen in the mixed melt is increased, so that it is transparent and high even at the initial stage of crystal growth. Quality GaN crystals are grown.
Chemistry of Materials Vol. 9 (1997) 413-416 JP 2000-327495 A JP 2002-68896 A JP 2004-307322 A

  In Patent Document 3 described above, an additive such as Li is added, but a transparent and high-quality crystal can be grown from the initial stage of crystal growth without adding an additive such as Li. It would be desirable if a method could be established that could grow a large amount of the desired shape.

  The present invention is a colorless, transparent, high-quality crystal without adding an additive that increases the nitrogen concentration such as Li, even in the early stage of crystal growth, where many brown defects and low-quality crystals have been grown. It is an object of the present invention to provide a group III nitride crystal growth method and a group III nitride crystal that can grow a crystal in a desired shape.

  In order to achieve the above object, the invention according to claim 1 is characterized in that a melt containing a group III metal is held in a gas atmosphere containing a nitrogen source gas and a flux gas, and the melt containing the group III metal is added to the melt. Nitrogen and flux are dissolved from the gas atmosphere to grow group III nitride crystals. At this time, the crystal form of the group III nitride to be grown is controlled by the pressure of the flux in the gas atmosphere. It is a feature.

  The invention according to claim 2 is the method of growing a group III nitride crystal according to claim 1, wherein the melt containing the group III metal is preliminarily provided with a smaller amount of flux than the amount of crystal growth. It is characterized by being included.

  The invention described in claim 3 is characterized in that in the group III nitride crystal growth method according to claim 1 or claim 2, the group III nitride is crystal-grown on a seed crystal.

  According to a fourth aspect of the present invention, there is provided a group III nitride crystal growth method according to the first or second aspect of the present invention. 3. The group III nitride crystal growth method according to claim 1 or 2, wherein the group nitride is crystal-grown with the growth direction being substantially the same direction, and then the plurality of group III nitride crystals are used as seed crystals. It is characterized by crystal growth of group III nitride.

  The invention described in claim 5 uses the group III nitride crystal growth method described in claim 1 or claim 2 to bring the melt-gas interface between the melt and the gas atmosphere to the melt side. A group III nitride crystal aggregate comprising a grown crystal and a crystal grown on the gas phase side is formed, and then the crystal constituting the group III nitride crystal is used as a seed crystal. The group III nitride crystal growth method according to claim 2, wherein the group III nitride crystal is grown.

  The invention according to claim 6 is the method of growing a group III nitride crystal according to claim 5, wherein the crystal growth direction of the crystal growing on the gas phase side of the group III nitride crystal aggregate is the melt direction. It is characterized by adjusting the amount.

  A seventh aspect of the present invention is a group III nitride crystal produced by the group III nitride crystal growth method according to any one of the first to sixth aspects.

  According to invention of Claim 1 thru | or 6, the melt containing a group III metal is hold | maintained in the gas atmosphere containing nitrogen source gas and flux gas, and the gas atmosphere is contained in the melt containing the said group III metal. Nitrogen and flux are dissolved from the crystal to grow group III nitride, and at this time, the crystal form of the group III nitride to be grown is controlled by the pressure of the flux in the gas atmosphere. Even in the early stage of crystal growth where many brown defects and low-quality crystals were grown, colorless transparent high-quality crystals were formed in the desired shape (form) without adding an additive such as Li. ) Crystal growth.

  That is, in the group III nitride crystal growth method according to claim 1, since the flux is dissolved from the gas phase into the melt containing the group III metal, the flux concentration at the gas-liquid interface is high, and therefore the dissolution rate of nitrogen is high. fast. For this reason, conventionally, brown and low-quality crystals have grown in the early stage of growth due to lack of nitrogen. However, the method of the present invention can grow colorless and transparent high-quality crystals even in the early stage of growth. At the gas-liquid interface of the melt, flux enters and exits so that the flux pressure in the gas atmosphere and the vapor pressure of the flux in the melt are balanced, so the flux pressure in the gas atmosphere must be controlled. The amount ratio of the flux in the melt can be controlled. The growing crystal shape (crystal form) changes depending on the amount ratio of the group III metal and the flux in the melt, so that the desired shape (form) can be obtained by adjusting the pressure of the flux in the atmospheric gas. The group III nitride can be crystal-grown. Since the pressure of the flux can be precisely controlled by temperature control or the like, the crystal shape (crystal form) can be easily controlled.

  Further, in the Group III nitride crystal growth method according to Claim 2, in the Group III nitride production method according to Claim 1, the amount of crystal growth is smaller in the melt containing the Group III metal. Since the amount of flux is included in advance, it is possible to shorten the time during which the flux is dissolved in the melt from the gas phase and the flux amount ratio in the melt increases to the amount at which crystal growth occurs. Therefore, crystals can be produced in a shorter time than when a melt containing no flux is used.

  Further, in the method for growing a group III nitride crystal according to claim 3, the method for growing a group III nitride crystal according to claim 1 or 2, wherein the group III nitride is grown on a seed crystal. And since the low quality crystal | crystallization does not grow in the growth initial stage like the past, the crystal | crystallization of the quality equivalent to or more than a seed crystal can be grown.

  Further, in the group III nitride crystal growth method of claim 4, the melt bottom portion of the substrate on which the melt is held is obtained by using the group III nitride crystal growth method of claim 1 or claim 2. 3. The group III nitride according to claim 1 or 2, wherein a plurality of group III nitrides are grown in the contact region in a substantially same growth direction, and then the plurality of group III nitride crystals are used as seed crystals. Since the group III nitride crystal is grown by the crystal growth method of the product, a large group III nitride crystal with good crystal quality can be grown.

  In the Group III nitride crystal growth method according to claim 5, the gas-liquid interface between the melt and the gas atmosphere is generally set using the Group III nitride crystal growth method according to claim 1 or claim 2. Form a group III nitride crystal aggregate consisting of a crystal grown on the melt side and a crystal grown on the gas phase side at the boundary, and then seed the crystals constituting the group III nitride crystal aggregate. Since the group III nitride crystal is grown as the crystal by the group III nitride crystal growth method according to claim 1 or claim 2, a high-quality and large group III nitride crystal can be grown. That is, in the invention described in claim 5, the crystal grown on the gas phase side of the group III nitride crystal aggregate can be used as the seed crystal. Since the gas-liquid interface is curved, the crystals grown on the gas phase side grow in different directions. Therefore, even if the crystal growth is continued, the mutual growth is hardly inhibited and the crystal grows greatly. Therefore, in the crystal growth method according to the fifth aspect, a high-quality and large-sized group III nitride crystal can be grown.

  Further, in the group III nitride crystal growth method according to claim 6, in the group III nitride crystal growth method according to claim 5, the crystal grown on the gas phase side of the group III nitride crystal aggregate is obtained. Since the growth direction is adjusted by the amount of the melt, the crystal growth direction can be easily adjusted.

According to the invention described in claim 7, since it is a group III nitride crystal produced by the group III nitride crystal growth method according to any one of claims 1 to 6, A small number of high-quality group III nitride crystals can be provided.

  Hereinafter, the best mode for carrying out the present invention will be described with reference to the drawings.

(First form)
In the first aspect of the present invention, a melt containing a group III metal is held in a gas atmosphere containing a nitrogen source gas and a flux gas, and nitrogen and flux are supplied from the gas atmosphere to the melt containing the group III metal. The group III nitride is crystallized by dissolution, and at this time, the crystal form of the group III nitride to be grown is controlled by the pressure of the flux in the gas atmosphere.

  In the first embodiment of the present invention, a melt containing a group III metal is held in a gas atmosphere containing a nitrogen source gas and a flux gas, and nitrogen and flux are supplied from the gas atmosphere to the melt containing the group III metal. It is made to melt and crystallize the group III nitride. At this time, the crystal form of the group III nitride to be grown is controlled by the pressure of the flux in the gas atmosphere. Even in the early stage of crystal growth where low-quality crystals were growing, colorless and high-quality crystals were grown in the desired shape (form) without adding an additive such as Li that increases the nitrogen concentration. be able to.

  That is, in the Group III nitride crystal growth method of the first embodiment, the flux dissolves from the gas phase into the melt containing the Group III metal, so the flux concentration at the gas-liquid interface is high, and therefore the dissolution rate of nitrogen. Is fast. For this reason, conventionally, brown and low-quality crystals have grown in the early stage of growth due to lack of nitrogen. However, the method of the present invention can grow colorless and transparent high-quality crystals even in the early stage of growth. At the gas-liquid interface of the melt, flux enters and exits so that the flux pressure in the gas atmosphere and the vapor pressure of the flux in the melt are balanced, so the flux pressure in the gas atmosphere must be controlled. The amount ratio of the flux in the melt can be controlled. The growing crystal shape (crystal form) changes depending on the amount ratio of the group III metal and the flux in the melt, so that the desired shape (form) can be obtained by adjusting the pressure of the flux in the atmospheric gas. The group III nitride can be crystal-grown. Since the pressure of the flux can be precisely controlled by temperature control or the like, the crystal shape (crystal form) can be easily controlled.

(Second form)
According to a second aspect of the present invention, in the Group III nitride crystal growth method of the first aspect, the melt containing the Group III metal contains in advance a smaller amount of flux than the amount at which crystal growth occurs. It is characterized by keeping it.

  In the second aspect of the present invention, in the method for producing a Group III nitride of the first aspect, the melt containing the Group III metal contains in advance a smaller amount of flux than the amount at which crystal growth occurs. Therefore, the time during which the flux dissolves from the gas phase into the melt and the flux amount ratio in the melt increases to the amount at which crystal growth occurs can be shortened. Therefore, crystals can be produced in a shorter time than when a melt containing no flux is used.

(Third form)
A third aspect of the present invention is characterized in that the group III nitride crystal is grown on a seed crystal in the group III nitride crystal growth method of the first or second aspect.

  In the third aspect of the present invention, in the group III nitride crystal growth method of the first or second aspect, the group III nitride is crystal-grown on the seed crystal. Therefore, a crystal having a quality equal to or higher than that of the seed crystal can be grown.

(4th form)
According to a fourth aspect of the present invention, there is provided a plurality of group III nitrides in a region where the melt bottom of the substrate holding the melt is in contact with the group III nitride crystal growth method of the first or second mode. The crystal is grown with the growth directions being substantially the same, and then the group III nitride crystal is grown by the group III nitride crystal growth method of the first or second form using the plurality of group III nitride crystals as seed crystals. It is characterized by crystal growth of objects.

  In the fourth aspect of the present invention, using the group III nitride crystal growth method of the first or second aspect, a plurality of group III nitrides are formed in the region where the melt bottom of the substrate holding the melt is in contact. The crystal is grown with the growth directions being substantially the same, and then the group III nitride crystal is grown by the group III nitride crystal growth method of the first or second form using the plurality of group III nitride crystals as seed crystals. Since a crystal is grown, a large group III nitride crystal with good crystal quality can be grown.

(5th form)
In the fifth embodiment of the present invention, the group III nitride crystal growth method of the first or second embodiment is used to grow on the melt side with the gas-liquid interface between the melt and the gas atmosphere as a general boundary. Forming a group III nitride crystal aggregate composed of the crystal and a crystal grown on the gas phase side, and then using the crystal constituting the group III nitride crystal as a seed crystal, The group III nitride crystal growth method is characterized in that the group III nitride crystal is grown.

  In the fifth embodiment of the present invention, the group III nitride crystal growth method of the first or second embodiment is used to grow on the melt side with the gas-liquid interface between the melt and the gas atmosphere as a general boundary. Forming a group III nitride crystal aggregate composed of the crystal and a crystal grown on the gas phase side, and then using the crystal constituting the group III nitride crystal as a seed crystal, Since the group III nitride crystal is grown by the method of growing a group III nitride crystal in the form, a large group III nitride crystal of high quality can be grown. That is, in the fifth embodiment, a crystal grown on the gas phase side of the group III nitride crystal aggregate can be used as a seed crystal. Since the gas-liquid interface is curved, the crystals grown on the gas phase side grow in different directions. Therefore, even if the crystal growth is continued, the mutual growth is hardly inhibited and the crystal grows greatly. Therefore, in the fifth aspect of the crystal growth method, a high-quality and large-sized group III nitride crystal can be grown.

(Sixth form)
According to a sixth aspect of the present invention, in the Group III nitride crystal growth method of the fifth aspect, the growth direction of the crystal growing on the gas phase side of the group III nitride crystal aggregate is the amount of the melt. It is characterized by adjusting with.

  According to a sixth aspect of the present invention, in the Group III nitride crystal growth method of the fifth aspect, the growth direction of the crystal growing on the gas phase side of the group III nitride crystal aggregate is the amount of the melt. Therefore, the crystal growth direction can be easily adjusted.

(7th form)
A seventh aspect of the present invention is a group III nitride crystal produced by the group III nitride crystal growth method of any one of the first to sixth aspects.

  In the seventh aspect of the present invention, since the group III nitride crystal is manufactured by the group III nitride crystal growth method of any one of the first to sixth aspects, the high-quality group III nitride with few defects Physical crystals can be provided.

  Next, examples of the present invention will be described.

  Example 1 corresponds to the first mode.

  In Example 1, Na (sodium) was used as a flux, metal Ga (gallium) was used as a Group III metal material, nitrogen gas was used as a nitrogen material, and GaN was crystal-grown as a Group III nitride.

  Crystal growth was performed by putting Ga in a melt holding container and holding it in a gas atmosphere composed of nitrogen and sodium vapor, and dissolving nitrogen and sodium in the melt from the gas atmosphere.

  Sodium is held and heated in a flux holding container provided outside the melt holding container, and supplied as a gas to the melt in the melt holding container. The sodium pressure was controlled by controlling the sodium heating temperature. Sodium was dissolved until the vapor pressure of sodium in the melt reached equilibrium with the pressure of sodium in the gas atmosphere, and then crystal growth was allowed to proceed with the sodium ratio in the melt kept constant. In Example 1, the sodium amount ratio in the melt was maintained at 45%, and columnar crystals could be grown. Further, by maintaining the sodium amount ratio in the melt at 70%, plate crystals could be grown.

  FIG. 1 is a diagram showing a crystal growth apparatus used in the first embodiment.

  In the apparatus of FIG. 1, a container 41 is provided in a closed reaction vessel 31 made of stainless steel. A flux holding container 44 that holds the flux 45 is accommodated in the lower part of the accommodating container 41, and a melt holding container 43 is accommodated in the upper part. A melt 46 containing a group III metal is held in the melt holding container 43.

  The container 41 is covered with a lid 42. There is a slight gap between the container 41 and the lid 42, and nitrogen gas is supplied into the container 41 through this gap. The storage container 41 can be removed from the reaction container 31. The material of the storage container 41, the melt holding container 43, and the flux holding container 44 is BN.

In addition, a gas supply pipe 34 that fills the reaction vessel 31 with nitrogen (N ₂ ) gas, which is a nitrogen raw material, and adjusts the nitrogen (N ₂ ) pressure in the reaction vessel 31 connects the reaction vessel 31. Installed through.

  The pressure of the nitrogen gas can be adjusted by the pressure control device 36. The total pressure in the reaction vessel 31 is monitored with a pressure gauge 39.

  A heater 32 and a heater 33 for heating the upper and lower portions of the reaction vessel 31 are installed outside the reaction vessel 31.

The heaters 32 and 33 can control the temperature of the melt 46 or the flux 45.

  The GaN growth method in Example 1 using the crystal growth apparatus of FIG. 1 will be specifically described below.

  First, 0.75 g of metal Ga as a group III metal raw material is put into the melt holding container 43, and 2 g of Na (sodium) 25 is put into the flux holding container 44. Next, the melt holding container 43 and the flux holding container 24 are stored in the receiving container 21 and the lid 22 is put on.

  Next, the storage container 41 is stored in the reaction container 31.

  Then, nitrogen gas is introduced from the nitrogen introduction pipe 37. That is, the valves 35 and 38 are opened, nitrogen gas is introduced into the reaction vessel 31, and the nitrogen pressure in the reaction vessel 31 is set to 5 MPa by the pressure controller 36. Nitrogen gas is also introduced into the storage container 41 through a slight gap between the storage container 41 and the lid 42.

  Next, the heater 32 is energized to raise the temperature of the Ga melt 46 from room temperature (27 ° C.) to the crystal growth temperature in 1 hour. The crystal growth temperature was 800 ° C.

  Next, the heater 33 is energized, and the Na in the flux holding container 44 is heated to a predetermined temperature. In this example, the temperature was raised to 750 ° C.

  Na evaporates from the flux holding container 44 and is supplied to the gas atmosphere 48 on the Ga melt 46 in the melt holding container 43. Then, Na dissolves from the gas atmosphere 48 in the Ga melt 46 to form a Ga—Na mixed melt.

  On the other hand, a part of the Na vapor in the storage container 41 is transported to the outside of the storage container 41 through a slight gap between the storage container 41 and the lid 42, and is condensed as a liquid in the low temperature part in the reaction container 31.

  Since the amount of Na coming out of the container 41 and the amount of Na evaporated from the flux holding container 44 are kept constant, the pressure of Na in the gas atmosphere 48 is kept constant.

  Therefore, until the Na pressure in the gas atmosphere 48 and the vapor pressure of Na in the melt 46 reach equilibrium, Na dissolves in the melt 46 from the gas atmosphere 48 and the Na amount ratio in the melt 46 increases. .

  When the pressure of Na in the gas atmosphere 48 and the vapor pressure of Na in the melt 46 reach equilibrium, the amount ratio of Na in the melt 46 becomes constant. Even if the crystal growth proceeds, Ga in the melt 46 is consumed, and the Ga amount decreases, the equilibrium relationship of Na vapor at the gas-liquid interface is maintained, so the amount ratio of Na in the melt 46 is constant. The crystal growth is continued.

  After the temperature increase, the temperature and nitrogen pressure were kept constant, and crystal growth continued for 200 hours. After 200 hours, the temperature is lowered to room temperature.

  When the reaction vessel 31 was opened after the temperature was lowered, brown crystals did not grow on the inner surface of the melt holding vessel 43, and colorless and transparent columnar crystals 47 had grown.

  FIG. 2 shows changes in the Na amount ratio in the melt 46 during crystal growth and the yield (precipitation rate) of the GaN crystal under the growth conditions of Example 1.

  After the temperature increase, the Na amount ratio gradually increased and became constant at 45%. By controlling the Na pressure while keeping the Na temperature constant, the Na amount ratio was maintained at 45% under the conditions of Example 1, and columnar crystals could be grown.

  In Example 1, columnar crystals were grown by setting the Na temperature in the flux holding container 44 to 750 ° C., but the Na pressure in the gas atmosphere 48 was set to 790 ° C. By increasing the ratio, the Na amount ratio in the melt is maintained at 70%, and plate crystals can be grown.

  Example 2 corresponds to the second mode.

  In Example 2, the melt containing the group III metal was preliminarily included with an amount of flux smaller than the amount of crystal growth, and the crystal growth was performed.

  Example 2 is the same as Example 1 except that the flux is previously contained in the melt containing the Group III metal.

  That is, Na (sodium) was used as a flux, metal Ga (gallium) was used as a group III metal material, nitrogen gas was used as a nitrogen material, and GaN was crystal-grown as a group III nitride.

  In Example 2, the raw material was charged in advance with the Na amount ratio of the melt 46 being 25% (Note that the Na content ratio of the melt 46 was previously set to 25% in FIG. The ratio of Na is 0% up to 25% and almost no crystal growth up to 35%), and GaN is grown for 175 hours under the same crystal growth conditions as in Example 1. It was. The grown GaN crystal was colorless and transparent as in Example 1, and the size was similar. In Example 2, the time required to grow a crystal having the same size as in Example 1 was shortened.

  Example 3 corresponds to the third mode.

  In Example 3, a seed crystal is used, and in the same manner as in Example 2, a melt containing a Group III metal is preliminarily included with an amount of flux smaller than the amount at which crystal growth occurs, and crystal growth is performed. It was.

  FIGS. 3A and 3B are diagrams for explaining the crystal growth method of the third embodiment. Since the crystal growth apparatus is the same as that of the first embodiment shown in FIG. 1, only the melt holding container 43 portion is shown in FIG. In Example 3, a colorless and transparent GaN columnar crystal was used as the seed crystal 49.

  Hereinafter, a method for growing GaN in Example 3 using the crystal growth apparatus of FIG. 1 will be described in detail.

  First, as shown in FIG. 3A, a GaN columnar crystal 49 is placed in a melt holding container 43 as a seed crystal. Next, 1.5 g of metal Ga and 0.17 g of Na are added so that the Na amount ratio of the melt 46 is 25%. Next, 3 g of Na (sodium) 45 is put into the flux holding container 44. Next, the melt holding container 43 and the flux holding container 44 are stored in the receiving container 41 and the lid 42 is put on.

  Next, the storage container 41 is stored in the reaction container 31.

  Then, nitrogen gas is introduced from the nitrogen introduction pipe 37. That is, the valves 35 and 38 are opened, nitrogen gas is introduced into the reaction vessel 31, and the nitrogen pressure in the reaction vessel 31 is set to 5 MPa by the pressure controller 36. Nitrogen gas is also introduced into the storage container 41 through a slight gap between the storage container 41 and the lid 42.

  Next, the heater 32 is energized to raise the temperature of the Ga—Na mixed melt 46 from room temperature (27 ° C.) to the crystal growth temperature in 1 hour. The crystal growth temperature was 800 ° C.

  Next, the heater 33 is energized, and the Na in the flux holding container 44 is heated to a predetermined temperature. In Example 3, the temperature was raised to 750 ° C.

  Na evaporates from the flux holding container 44 and is supplied to the gas atmosphere 48 on the Ga—Na mixed melt 46 in the melt holding container 43. Then, until the Na pressure in the gas atmosphere and the vapor pressure of Na in the melt 46 reach equilibrium, Na dissolves from the gas atmosphere 48 into the melt 46, and the Na amount ratio in the melt 46 increases. When the pressure of Na in the gas atmosphere 48 and the vapor pressure of Na in the melt 46 reach equilibrium, the amount ratio of Na in the melt 46 becomes constant. Even if the crystal growth proceeds, Ga in the melt 46 is consumed, and the Ga amount decreases, the equilibrium relationship of Na vapor at the gas-liquid interface is maintained, so the amount ratio of Na in the melt 46 is constant. The crystal growth is continued. In Example 3, the Na amount ratio increases to 45%, and is thereafter maintained at this value, and crystal growth continues.

  After the temperature increase, the temperature and nitrogen pressure were kept constant, and crystal growth was continued for 350 hours. After 350 hours, the temperature is lowered to room temperature. When the reaction vessel 31 was opened after the temperature was lowered, as shown in FIG. 3 (b), no brown crystal grew on the seed crystal 49, and the columnar crystal 50 grew colorless and transparent.

  Example 4 corresponds to the fourth mode.

  In Example 4, Na (sodium) was used as a flux, metal Ga (gallium) was used as a group III metal material, nitrogen gas was used as a nitrogen material, and GaN was crystal-grown as a group III nitride.

  First, a plurality of colorless and transparent high-quality GaN columnar crystals are grown on the bottom of the melt holding container 43 by the same method as in Example 2, and then the same crystal as in Example 3 is used as a seed crystal. Made growth. That is, in Example 4, the crystal growth process is performed twice.

  4A to 4E are diagrams for explaining the crystal growth method of Example 4. FIG. Since the crystal growth apparatus is the same as that of the first embodiment shown in FIG. 1, only the melt holding container 43 portion is shown in FIGS. 4 (a) to 4 (e).

  Hereinafter, a GaN growth method in Example 4 using the crystal growth apparatus of FIG. 1 will be described in detail.

  First, as shown in FIG. 4A, 0.75 g of metal Ga and 0.08 g of Na are put in the melt holding container 43 so that the Na amount ratio of the melt 46 is 25%. Next, 2 g of sodium 25 is placed in the flux holding container 44. Next, the melt holding container 43 and the flux holding container 44 are stored in the receiving container 41 and the lid 42 is put on.

  Next, the storage container 41 is stored in the reaction container 31. Then, nitrogen gas is introduced from the nitrogen introduction pipe 37. That is, the valves 35 and 38 are opened, nitrogen gas is introduced into the reaction vessel 31, and the nitrogen pressure in the reaction vessel 31 is set to 5 MPa by the pressure controller 36. Nitrogen gas is also introduced into the storage container 41 through a slight gap between the storage container 41 and the lid 42.

  Next, the heater 32 is energized to raise the temperature of the Ga—Na mixed melt 46 from room temperature (27 ° C.) to the crystal growth temperature in 1 hour. The crystal growth temperature was 800 ° C.

  Next, the heater 33 is energized, and the Na in the flux holding container 44 is heated to a predetermined temperature. In Example 4, the temperature was raised to 750 ° C.

  Na evaporates from the flux holding container 44 and is supplied to the gas atmosphere 48 on the Ga—Na mixed melt 46 in the melt holding container 43. Then, until the Na pressure in the gas atmosphere 48 and the vapor pressure of Na in the melt 46 reach equilibrium, Na dissolves from the atmosphere gas 48 into the melt 46, and the Na amount ratio in the melt 46 increases. Then it becomes constant. In Example 4, the Na amount ratio increases to 45%, and is thereafter maintained at this value, and crystal growth continues. FIG. 4B shows the state at this time.

  After the temperature increase, the temperature and nitrogen pressure were kept constant, and crystal growth was continued for 175 hours. As a result, as shown in FIG. 4 (c), a plurality of GaN columnar crystals 51 are directed to the gas-liquid interface side at the bottom (base) of the melt holding container 43 with which the melt 46 is in contact. Crystal growth. The c-plane in contact with the melt 46 was an N-polar surface. The grown crystal 51 was colorless and transparent.

  Next, as shown in FIG. 4 (d), the plurality of grown GaN columnar crystals 51 are taken out and accommodated in another melt holding container 43. Next, 1.5 g of metal Ga and 0.17 g of Na are placed in the melt holding container 43 so that the Na amount ratio of the melt 46 is 25%. Next, 3 g of Na (sodium) 45 is put into the flux holding container 44. Next, the melt holding container 43 and the flux holding container 44 are stored in the storage container 41, the lid 42 is put on, and the storage container 41 is stored in the reaction container 31.

  Thereafter, crystal growth is performed for 350 hours by the same method. That is, the crystal growth was continued for 350 hours at a growth temperature of 800 ° C. and a nitrogen pressure of 5 MPa, with the Na amount ratio in the melt being 45%. When the reaction vessel 31 is opened after the completion of crystal growth, as shown in FIG. 4E, brown crystals are not grown, and a plurality of seed crystals 51 are grown into large columnar crystals 52 while being colorless and transparent. It was.

  In the fourth embodiment, the base body on which the melt 46 is held is the bottom of the melt holding container 43, but a BN plate or a substrate such as sapphire may be used.

  Example 5 corresponds to the fifth and sixth embodiments.

  In Example 5, Na (sodium) was used as a flux, metal Ga (gallium) was used as a Group III metal material, nitrogen gas was used as a nitrogen material, and GaN was crystal-grown as a Group III nitride.

  First, in the same manner as in Example 2, an aggregate of GaN columnar crystals composed of a crystal grown on the melt side and a crystal grown on the gas phase side with the gas-liquid interface between the melt and the gas atmosphere as a general boundary. Thereafter, the crystal grown in the vapor phase side was used as a seed crystal, and crystal growth was performed in the same manner as in Example 3.

  First, a method of forming an aggregate of GaN columnar crystals composed of a crystal grown on the melt side and a crystal grown on the gas phase side with the gas-liquid interface between the melt and the gas atmosphere as a boundary will be described.

  FIGS. 5A, 5B, and 5C show a cross section of the melt 46 after the growth in the case where GaN is grown by changing the amount of Ga melt in the crystal growth method of the first embodiment. FIG. As growth conditions, the temperature of the melt 46 was 720 ° C., the temperature of the flux Na was 690 ° C., the nitrogen pressure was 5 MPa, and the growth time was 200 hours. Moreover, the melt 46 at the time of preparation is only Ga.

  The amount of Ga is 0.15 g in FIG. 5 (a), 0.45 g in FIG. 5 (b), and 0.75 g in FIG. 5 (c).

  As shown in FIGS. 5A, 5B, and 5C, GaN columnar crystals grow on the melt side and the gas phase side with the gas-liquid interface between the melt 46 and the gas atmosphere as a boundary. did. These crystals were transparent. Further, the crystal 54 grown on the gas phase side is larger than the crystal 53 grown on the melt side.

  When the Ga content is 0.15 g, the melt becomes ball-shaped, and as shown in FIG. 5A, the crystals 54 grown on the gas phase side grow radially and some crystals grow upward. When the Ga amount is 0.45 g and 0.75 g, the bottom of the melt spreads as shown in FIGS. 5B and 5C, and the number of crystals 53 that grow on the melt side increases. The crystal 53 that grows on the melt side grows upward. Many of the crystals 54 growing on the gas phase side are found on the side surface of the melt, and there are almost no crystals growing upward. Further, as the amount of Ga increases, the crystal becomes smaller as a whole.

In Example 5, crystal growth is performed using a large crystal 54 grown on the gas phase side as a seed crystal.
For this purpose, it is desirable that the growth direction of each crystal is radial because it does not inhibit the growth of each other. Therefore, in this Example 5, GaN crystal growth was performed using an aggregate of GaN columnar crystals (as shown in FIG. 5A) formed by performing crystal growth with a Ga amount of 0.15 g as a seed crystal. Was done. That is, in Example 5, the crystal growth process is performed twice.

  6 (a) to 6 (e) are diagrams for explaining the crystal manufacturing method of the fifth embodiment. A crystal manufacturing method of Example 5 will be described with reference to FIGS.

  Since the crystal growth apparatus is the same as that of the first embodiment shown in FIG. 1, only the portion of the melt holding container 43 is shown in FIGS. 6 (a) to 6 (e).

  Hereinafter, a GaN growth method in Example 5 using the crystal growth apparatus of FIG. 1 will be described.

  First, as shown in FIG. 6A, 0.15 g of metal Ga is put in the melt holding container 43. Next, 2 g of sodium 45 is placed in the flux holding container 44. Next, the melt holding container 43 and the flux holding container 44 are stored in the receiving container 41 and the lid 42 is put on.

  Next, the storage container 41 is stored in the reaction container 31.

  Then, nitrogen gas is introduced from the nitrogen introduction pipe 37. That is, the valves 35 and 38 are opened, nitrogen gas is introduced into the reaction vessel 31, and the nitrogen pressure in the reaction vessel 31 is set to 5 MPa by the pressure controller 36. Nitrogen gas is also introduced into the storage container 41 through a slight gap between the storage container 41 and the lid 42.

  Next, the heater 32 is energized to raise the temperature of the Ga melt 46 from room temperature (27 ° C.) to the crystal growth temperature in 1 hour. The crystal growth temperature was 720 ° C.

  Next, the heater 33 is energized, and the Na in the flux holding container 44 is heated to a predetermined temperature. In Example 5, the temperature was raised to 690 ° C.

  Na evaporates from the flux holding container 44 and is supplied to the atmospheric gas 48 on the Ga melt 46 in the melt holding container 43. Then, until the pressure of Na in the atmospheric gas and the vapor pressure of Na in the melt 46 reach equilibrium, Na is dissolved in the melt 46 from the atmospheric gas 48, and the Na amount ratio in the melt 46 is increased. It becomes constant. In the present Example 5, the Na amount ratio increases to 45%, and thereafter maintained at this value, crystal growth continues. FIG. 6B shows the state at this time.

  After the temperature increase, the temperature and nitrogen pressure were kept constant, and crystal growth continued for 200 hours. After 200 hours, as shown in FIG. 6 (c), GaN composed of a crystal 53 grown on the melt side and a crystal 54 grown on the gas phase side with the gas-liquid interface between the melt 46 and the gas atmosphere as a boundary. An aggregate of columnar crystals was formed. The c-plane of the crystal 54 grown on the gas phase side was an N-polar plane. The grown crystal was colorless and transparent.

  Next, as shown in FIG. 6 (d), the grown aggregate of GaN columnar crystals is taken out and stored in another melt holding container 43. Next, 1.5 g of metal Ga and 0.17 g of Na are placed in the melt holding container 43 so that the Na amount ratio of the melt 46 is 25%. Next, 3 g of sodium 45 is placed in the flux holding container 44. Next, the melt holding container 43 and the flux holding container 44 are stored in the storage container 41, the lid 42 is put on, and the storage container 41 is stored in the reaction container 31.

  Thereafter, crystal growth is performed for 350 hours by the same method. That is, crystal growth is continued for 350 hours at a growth temperature of 800 ° C. and a nitrogen pressure of 5 MPa with an Na content ratio in the melt of 45%.

  When the reaction vessel 31 is opened after the completion of crystal growth, as shown in FIG. 6E, brown crystals have not grown, and the seed crystals 54 grown on the gas phase side remain colorless and transparent, and are large columnar crystals 55. Was growing up.

  In the present invention, the group III nitride is a compound of one or more kinds of group III metals selected from Ga (gallium), Al (aluminum), In (indium), and B (boron) and nitrogen. Means.

  The raw material of the group III metal is not particularly limited, and a group III metal, a group III nitride, a substance containing a group III element as a constituent element, and other appropriate materials can be used.

  The nitrogen raw material is a substance containing nitrogen as a constituent element and is a substance capable of supplying nitrogen into the melt from the gas phase. Nitrogen gas or other nitrogen compound gas can be used. Further, nitrogen gas generated by decomposition of the nitrogen compound can also be used.

  The flux means a substance that causes group III nitride to grow at a temperature lower and lower than the pressure and temperature at which group III nitride grows by direct reaction between the group III metal and nitrogen. As the flux, alkali metals such as Na (sodium), K (potassium), and Li (lithium) are usually used, but other alkali metals, alkaline earth metals, or a plurality of types of alkali metals and alkaline earths are used. It is also possible to use a mixture of metals. Moreover, substances other than alkali metals and alkaline earth metals may be used.

  In addition to the group III metal, the melt may contain impurities for controlling electrical conduction.

The present invention can be used for an optical disk light source, an ultraviolet light source (LD, LED), a white LED light source, an electrophotographic light source, a group III nitride electronic device, a light receiving device, and the like.

1 is a diagram showing a crystal growth apparatus used in Example 1. FIG. It is a figure which shows the growth time change of the quantity ratio of Na and the yield of GaN. 6 is a diagram for explaining a crystal growth method of Example 3. FIG. 6 is a diagram for explaining a crystal growth method of Example 4. FIG. It is a figure which shows the cross section of the melt 46 after completion | finish of growth at the time of changing the quantity of Ga melt and growing GaN with the crystal growth method of Example 1. FIG. 10 is a diagram for explaining a crystal growth method of Example 5. FIG. It is a figure which shows the structural example of the conventional crystal growth apparatus.

Explanation of symbols

31 Reaction Vessel 32 Upper Heater 33 Lower Heater 34 Gas Supply Pipe 35, 38 Valve 36 Pressure Control Device 37 Nitrogen Introduction Pipe 39 Pressure Gauge 40 Storage Container Support Base 41 Storage Container 42 Lid 43 Melt Holding Container 44 Flux Holding Container 45 Flux ( sodium)
46 Melt containing Group III metal 47, 51 Grown crystal 48 Internal space 49 Seed crystal 50, 52, 55 Crystal grown on seed crystal 53 Crystal grown on melt side 54 Crystal grown on gas phase side

Claims (7)

A melt containing a group III metal is held in a gas atmosphere containing a nitrogen source gas and a flux gas, and the nitrogen and flux are dissolved from the gas atmosphere in the melt containing the group III metal to obtain a group III nitride. A method of growing a group III nitride crystal, characterized in that the crystal form of the group III nitride to be grown is controlled by the pressure of a flux in a gas atmosphere. 2. The method for growing a group III nitride crystal according to claim 1, wherein the melt containing the group III metal contains in advance a smaller amount of flux than the amount of crystal growth. Group nitride crystal growth method. 3. The group III nitride crystal growth method according to claim 1, wherein the group III nitride crystal is grown on a seed crystal. The method for growing a group III nitride according to claim 1 or 2, wherein a plurality of group III nitrides are grown in substantially the same direction in a region where the melt bottom of the substrate holding the melt is in contact. And then growing the group III nitride by the group III nitride crystal growth method according to claim 1 or 2 using the plurality of group III nitride crystals as seed crystals. A method for growing a group III nitride crystal. Using the group III nitride crystal growth method according to claim 1 or claim 2, the crystal grown on the melt side and the gas phase side are grown with the gas-liquid interface between the melt and the gas atmosphere as a general boundary. A group III nitride crystal aggregate comprising the crystal is formed, and then the crystal constituting the group III nitride crystal aggregate is used as a seed crystal. A method for growing a group III nitride crystal, wherein the group III nitride crystal is grown by a crystal growth method. 6. The method for growing a group III nitride crystal according to claim 5, wherein the growth direction of the crystal growing on the gas phase side of the group III nitride crystal aggregate is adjusted by the amount of the melt. Group nitride crystal growth method. A group III nitride crystal produced by the group III nitride crystal growth method according to any one of claims 1 to 6.

Images