JP4414253B2 - Group III nitride crystal manufacturing method - Google Patents

Description

The present invention relates to crystal manufacturing how the III-nitride.

  Conventionally, as shown in, for example, Patent Document 1, a group III nitride crystal growth method for growing a group III nitride crystal by reacting a group III metal and nitrogen in a melt containing an alkali metal (that is, Flux method) is known.

  As a prior art of this flux method, Patent Document 1 discloses a method in which a nitrogen raw material is supplied from the outside of the reaction vessel 101 and the pressure is controlled as shown in FIG. 5 to continue the group III nitride crystal growth. It is shown. In FIG. 5, 102 is a melt, 103 is a seed crystal, 106 is a nitrogen supply pipe, and 113 is a gas-liquid interface.

  Patent Document 2 discloses a method of growing a group III nitride crystal by supplying a group III metal from the outside of a reaction vessel into a melt as shown in FIG. That is, in the method of Patent Document 2, nitrogen is dissolved in a mixed melt 203 of a group III metal and a flux, and a group III nitride crystal 211 is grown in the melt 203. In order to continue crystal growth, the liquid level of the mixed melt 203 of the group III metal and flux (alkali metal) held in the reaction vessel 201 and the relative height Δh of the liquid level from the outside of the reaction vessel 201 are used. Then, the Group III metal 210 is supplied to the melt 203 in the melt holding container 202, and the Group III metal consumed for crystal growth is replenished.

However, in this method, since the alkali metal having a high vapor pressure evaporates from the melt and condenses to the low temperature portion in the reaction vessel 201, the amount of alkali metal in the melt decreases. Therefore, it is difficult to carry out crystal growth while maintaining a constant ratio of the group III metal to the alkali metal, and it is difficult to produce crystals of uniform quality.
Japanese Patent Laid-Open No. 2001-64097 JP 2003-160398 A

  In the method of Patent Document 1 described above, a nitrogen raw material can be supplied from the outside of the reaction vessel, so that crystal growth can be continued and a high-quality, large-sized group III nitride crystal can be produced. However, since the group III metal consumption in the melt and evaporation of the alkali metal with high vapor pressure change due to the crystal growth of the group III nitride, the amount ratio of the group III metal to the alkali metal in the melt changes. There is a problem that it is difficult to carry out crystal growth while maintaining a constant ratio of the alkali metal to the alkali metal, and it is difficult to produce crystals of uniform quality.

  In addition, there is a problem that dark brown crystals grow at the initial stage of crystal growth.

Furthermore, a large number of crystal nuclei are generated under the condition of high nitrogen pressure under which high-quality crystals grow, and multinuclear growth occurs. For this reason, the raw material is distributed and supplied to a large number of crystals, or the growth rate becomes slow due to the fact that the crystals are densely packed and the growth region is narrowed. Cost.

  The method of Patent Document 2 makes it possible to produce a large-area group III nitride substrate crystal. However, as in Patent Document 1, a black crystal or a dark brown crystal grows at the initial stage of crystal growth. There is a problem.

  In summary, the conventional crystal growth method in which nitrogen is dissolved in a melt containing a group III metal in the presence of a flux to grow a group III nitride crystal has the following problems.

  That is, the Group III metal is consumed by crystal growth, and the Group III metal in the melt is reduced, or the amount of flux in the melt is reduced due to evaporation of the flux. The quantity ratio of metal to flux varies during crystal growth. For this reason, it is difficult to carry out crystal growth while maintaining a constant ratio of Group III metal to alkali metal, and it is difficult to produce crystals of uniform quality.

  In addition, the nucleation density is high, so that it takes a long time to enlarge the crystal due to insufficient supply of raw materials and a narrow growth region.

  Further, since dark brown crystals having poor crystallinity are grown at the initial stage of crystal growth, when crystals are grown on the seed crystal, black or dark brown crystals having poor crystal quality are grown at the interface between the seed crystal and the grown crystal.

The present invention is intended to solve the problems of these conventional Group III nitride crystal manufacturing methods and to produce a high-quality Group III nitride crystal having a practical size.

In other words, the present invention aims at providing a crystal production how possible III-nitride of controlling the flux amount ratio in the melt to a desired ratio.

More specifically, the present invention suppresses the change in the flux amount ratio in the melt due to the consumption of the group III metal and the evaporation of the flux, and always performs the crystal growth with the amount ratio of the group III metal and the flux being constant. aims at can be to provide a crystal manufacturing how uniform group III nitride crystals possible to produce a group III nitride quality.

Furthermore, the present invention aims at providing a crystal production how possible III-nitride of reducing the generation density of crystal nuclei.

In order to achieve the above object, according to the first aspect of the present invention, the melt obtained by dissolving the group III metal, the flux, and the nitrogen forms a gas-liquid interface with the atmosphere gas containing the nitrogen source gas and the flux gas. A method for producing a Group III nitride crystal in which nitrogen is dissolved in the melt from the gas-liquid interface, and Group III nitride is crystal-grown from Group III metal and nitrogen, wherein the melt contains Group III metal. Holding the melt in an unsealed melt holding container, holding the pressure adjusting flux in a region different from the melt holding container, the melt holding container holding the melt, and the melt A step of holding the pressure adjusting flux held in a region different from the holding vessel in an unsealed container, and the crystal contacting the gas-liquid interface from the region holding the pressure adjusting flux during crystal growth. Liquid preservation With the flux gas is supplied to the atmospheric gas inside the container, it comprises a step of partially is transported to the outside of the container of the melt holding vessel inside the flux gas, during crystal growth, the melt adjust either or both of the amount of flux gas exiting the supply amount of the flux gas supplied to the atmosphere gas inside the holding container and the outside of the container, the melt holding vessel interior in the atmosphere gas It is characterized by adjusting the pressure of the flux gas.

The invention according to claim 2 is the method for producing a group III nitride crystal according to claim 1, wherein the evaporation of the flux evaporating from the surface of the pressure adjusting flux held in a region different from the melt holding container. It is characterized by adjusting the amount of flux gas supplied at a speed.

The invention described in claim 3 is characterized in that, in the method for producing a group III nitride crystal according to claim 2, the evaporation rate of the flux is adjusted by adjusting the temperature of the pressure adjusting flux .

The invention according to claim 4 is characterized in that, in the method for producing a group III nitride crystal according to claim 2, the evaporation rate of the flux is adjusted by the area in contact with the gas phase of the pressure adjusting flux surface . .

According to a fifth aspect of the present invention, in the crystal manufacturing method of the first aspect, the flux gas supply amount is adjusted, and the flux and nitrogen are passed through the gas-liquid interface from the atmospheric gas containing the nitrogen source gas in contact with the melt. It is characterized by forming a melt in which the Group III metal, flux and nitrogen are dissolved .

The invention described in claim 6 is the group III nitride crystal manufacturing method according to claim 5, characterized in that the group III nitride is crystal-grown on the seed crystal .

The invention as set forth in claim 7 is characterized in that, in the method for producing a group III nitride crystal according to any one of claims 1 to 6, the flux is an alkali metal .

The invention according to claim 8 is the method for producing a group III nitride crystal according to any one of claims 1 to 7, wherein the container is a container having a gap, and the fusion container is formed from the gap. Nitrogen source gas is supplied to the liquid holding container .

The invention according to claim 9 is the method for producing a group III nitride crystal according to any one of claims 1 to 7, wherein the container is provided in a reaction vessel, and the nitrogen source is provided in the reaction vessel. a step of filling the gas, is characterized in that the flux gas that is transported to the outside of the container and a step of condensing a liquid at the reaction vessel inside the low temperature portion.

According to the inventions of claims 1 to 9, the melt in which the group III metal, the flux, and the nitrogen are dissolved forms an air-liquid interface with the nitrogen source gas and the atmosphere gas containing the flux gas, A method for producing a group III nitride crystal in which nitrogen is dissolved in a melt from a gas-liquid interface and a group III nitride is crystal-grown from a group III metal and nitrogen, and the melt containing the group III metal is sealed. a step of holding the melt holding vessel that is not, a step of holding the fluxing pressure regulation in a different area from that of the melt holding vessel, the melt holding vessel and the melt holding vessel holding the melt A step of holding the pressure adjusting flux held in a region different from that in an unsealed container, and holding the melt in contact with the gas-liquid interface from the region holding the pressure adjusting flux during crystal growth Inside the container With the flux gas is supplied to the atmospheric gas includes a step of partially is transported to the outside of the container of the melt holding vessel inside the flux gas, during crystal growth, the melt holding vessel interior Adjusting one or both of the supply amount of the flux gas supplied into the atmosphere gas and the amount of the flux gas coming out of the container , and the flux gas in the atmosphere gas inside the melt holding vessel The pressure is adjusted, and therefore, the ratio of the flux amount in the solution can be easily controlled to allow the group III nitride crystal to grow. Also, the desired flux amount ratio can be changed during the crystal growth. In addition, by keeping the pressure of the flux gas constant, it is possible to suppress changes in the amount ratio of the flux in the solution due to consumption of the Group III metal and evaporation of the flux. , Group III nitride crystals can be grown. In this case, since the crystal growth can be performed with the growth conditions stabilized, a group III nitride crystal having few defects and uniform quality can be produced.

In particular, by adjusting one or both of the supply amount of the flux gas supplied into the atmospheric gas inside the melt holding container and the amount of the flux gas coming out of the containing container , the inside of the melt holding container Since the pressure of the flux gas in the atmospheric gas is adjusted, the flux gas pressure in the atmospheric gas can be maintained in a steady state. Therefore, the crystal growth can be performed while stabilizing the flux amount ratio in the melt, and a group III nitride crystal with few defects and uniform quality can be produced.

Hereinafter, the best mode for carrying out the present invention will be described.

(First form)
In the first embodiment of the present invention, a melt obtained by dissolving a group III metal, a flux, and nitrogen forms a gas-liquid interface with an atmosphere gas containing a nitrogen source gas and a flux gas, and nitrogen is introduced from the gas-liquid interface. Is a group III nitride crystal growth method in which a group III nitride is crystal-grown from a group III metal and nitrogen, and the flux gas in the atmospheric gas in contact with the melt at the gas-liquid interface is dissolved in the melt. By adjusting the pressure, the amount ratio of the flux in the melt is controlled to grow group III nitride crystals.

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

  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 temperature and pressure at which group III nitride grows by direct reaction between 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 control of the flux amount ratio in the melt by adjusting the pressure of the flux gas in the first embodiment of the present invention will be described below.

  The equilibrium vapor pressure P1 of the flux in the melt is determined by the melt temperature T1 and the flux ratio r1 in the melt.

  By maintaining the pressure P of the flux gas in the atmospheric gas at the equilibrium vapor pressure P1, the evaporation of the flux from the melt is apparently eliminated (that is, the amount of flow at the gas-liquid interface is balanced).

  When the Group III metal is consumed as the Group III nitride grows, the flux ratio in the melt increases from r1 to r2. At this time, the equilibrium vapor pressure of the flux in the melt increases from P1 to P2. Since the pressure P of the flux gas in the atmospheric gas is maintained at P1, P <P2, and the flux evaporates from the melt. Then, the flux amount ratio in the melt decreases from r2, returns to r1, and the equilibrium vapor pressure of the flux in the melt also changes from P2 to P1.

  Therefore, the amount ratio of the flux in the melt can be kept constant by keeping the melt temperature and the pressure of the atmospheric gas constant.

  Similarly, when the melt temperature or the pressure of the flux gas in the atmosphere gas is changed, similarly, the balance between the flux gas pressure in the atmosphere gas and the vapor pressure from the flux in the melt causes a balance in the melt. The amount ratio of the flux can be controlled.

  Therefore, the amount ratio of the flux in the melt can be controlled by adjusting the temperature of the melt and the pressure of the flux gas in the atmospheric gas.

  The method of adjusting the pressure of the flux gas in the atmospheric gas is not particularly limited, and is appropriately used, such as a method by temperature control of the atmospheric gas, a method of controlling by changing the volume of the atmospheric gas, and other methods. can do.

  In the first embodiment of the present invention, the flux amount ratio in the melt can be controlled as described above, and the group III nitride crystal can be grown with the melt having a desired flux amount ratio.

  As will be described later, a seed crystal can be used to grow a crystal.

(Second form)
According to a second aspect of the present invention, in the method for producing a Group III nitride crystal according to the first aspect, a pressure adjusting flux is held in a region different from a melt containing a Group III metal. The vapor pressure of the flux and the pressure of the flux gas in the atmospheric gas contacting at the melt and gas-liquid interface are the same pressure, and the vapor pressure of the flux for pressure adjustment is controlled to contact at the melt and gas-liquid interface. It is characterized by adjusting the pressure of the flux gas in the atmospheric gas.

  In the present invention, the atmospheric gas in contact with the melt and the flux (pressure adjusting flux) held outside the melt (a region different from the melt) are spatially connected, and vapor can enter and exit. ing. A closed system is formed in which the vapor pressure in equilibrium with the flux held outside the melt and the pressure of the flux gas in the space in the reaction vessel are the same. Thereby, by raising and lowering the vapor pressure of the flux held outside the melt, the pressure of the flux gas in the atmospheric gas in contact with the melt is also raised and lowered, and the pressure of the flux gas in the atmospheric gas can be controlled. . Note that the vapor pressure of the flux can be controlled by the temperature of the flux.

  In the second embodiment of the present invention, the flux amount ratio in the melt is controlled in this way by adjusting the pressure of the flux gas in the atmospheric gas, and the group III is obtained with the melt having a desired flux amount ratio. Nitride crystal growth can be performed.

(Third form)
According to a third aspect of the present invention, in the method for producing a Group III nitride crystal according to the first aspect, a pressure adjusting flux is held in a region different from a melt containing a Group III metal, The flux gas is supplied to the atmospheric gas inside the first container that is in contact with the gas-liquid interface from the region where the pressure-adjusting flux is held and is held in the first container that is not sealed, and a part of the flux gas is In the reaction system that goes out of the first container, the group III nitride is crystal-grown, and the supply amount of the flux gas supplied into the atmospheric gas inside the first container and the outside of the first container The pressure of the flux gas in the atmospheric gas inside the first container is adjusted by adjusting either one or both of the amount of the flux gas that flows into the first container.

  In a reaction system in which the container is not completely sealed in order to supply the nitrogen raw material to the melt from the outside of the first container, the atmospheric gas comes out of the first container. In this case, since the vapor pressure of the flux gas in the atmospheric gas cannot reach the equilibrium pressure of the flux in the melt at that temperature, the flux constantly evaporates from the melt and the flux in the melt disappears. May end up.

  In the third embodiment of the present invention, in order to solve this problem, the supply amount of the flux gas supplied from the flux held outside the melt into the atmospheric gas inside the first container and the outside of the first container. The pressure of the flux in the atmospheric gas inside the first container is controlled by adjusting either one or both of the amount of the flux gas that comes out.

  The atmospheric gas in contact with the melt and the flux (pressure adjusting flux) held outside the melt are spatially connected, and vapor can enter and exit. And flux gas is supplied in atmospheric gas from the flux hold | maintained outside the melt.

  The pressure of the flux gas in the atmospheric gas can be adjusted by the difference between the supply amount of the flux gas and the flux amount that comes out of the first container. Moreover, the equilibrium state of the pressure of the flux gas in the first container is maintained by making the supply amount of the flux gas and the flux amount coming out of the first container constant.

  Since the flux amount ratio in the melt is determined by the temperature of the melt and the pressure of the flux gas, in the third embodiment of the present invention, by adjusting the pressure of the flux gas in the atmosphere gas in this way, By controlling the flux amount ratio in the melt, the group III nitride crystal can be grown with the melt having a desired flux amount ratio.

(4th form)
According to a fourth aspect of the present invention, in the method for producing a Group III nitride crystal of the third aspect, evaporation is performed from the surface of a flux (pressure adjusting flux) held in a region different from the melt containing the Group III metal. The flux gas supply rate is adjusted by the flux evaporation rate.

(5th form)
A fifth aspect of the present invention is characterized in that, in the Group III nitride crystal manufacturing method of the fourth aspect, the flux evaporation rate is adjusted by adjusting the temperature of the flux (pressure adjusting flux). Yes.

  Specifically, increasing the temperature of the flux held outside the melt increases the vapor pressure of the flux and increases the evaporation rate of the flux. As a result, the amount of flux supplied increases.

  On the contrary, by lowering the temperature, the vapor pressure of the flux is lowered, and the evaporation rate of the flux is reduced. As a result, the amount of flux supplied is reduced.

  In the fifth embodiment of the present invention, the supply amount of the flux is adjusted in this way, and the pressure of the flux gas in the atmospheric gas is adjusted. By adjusting the pressure of the flux gas in the atmosphere gas, the flux amount ratio in the melt can be controlled, and the group III nitride crystal can be grown with the melt having a desired flux amount ratio.

(Sixth form)
The sixth aspect of the present invention is characterized in that, in the crystal manufacturing method of the fourth aspect, the flux evaporation rate is adjusted by the area in contact with the gas phase on the surface of the flux (pressure adjusting flux).

  Specifically, increasing the area of the flux held outside the melt in contact with the gas phase increases the flux evaporation rate. As a result, the amount of flux supplied increases.

  Conversely, by reducing the area of the flux in contact with the gas phase, the flux evaporation rate is reduced. As a result, the amount of flux supplied is reduced.

  In the sixth embodiment of the present invention, the supply amount of the flux is adjusted in this way, and the pressure of the flux gas in the atmospheric gas is adjusted. By adjusting the pressure of the flux gas in the atmosphere gas, the flux amount ratio in the melt can be controlled, and the group III nitride crystal can be grown with the melt having a desired flux amount ratio.

(7th form)
According to a seventh aspect of the present invention, in the method for producing a Group III nitride crystal according to any one of the third to sixth aspects, the melt includes a Group III metal that does not effectively contain a flux, Flux and nitrogen are dissolved through a gas-liquid interface under a predetermined flux gas pressure from an atmosphere gas containing nitrogen source gas in contact with the group III nitride in a melt in which the group III metal, flux and nitrogen are dissolved. It is characterized by crystal growth.

  Here, “effectively no flux” means that the number of crystal nuclei is not generated or is not generated even when a substance to be flux is included in the melt. If the amount is small enough that the crystal growth rate is low and the subsequent crystal growth does not cause problems such as multinuclear growth or dark brown crystal growth, it means that the flux is not included.

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

  In the seventh embodiment of the present invention, when the flux is dissolved from the atmosphere gas side containing the nitrogen source gas in contact with the melt into the melt that does not contain the flux effectively and contains the group III metal, Dissolves in the melt and reacts with the group III metal in the melt to grow group III nitride.

  As in the conventional method, when nitrogen is first dissolved in a melt containing a flux and a Group III metal and crystal growth is started, multinucleation occurs, dark brown crystals grow at the initial stage of growth, and the growth rate is slow.

On the other hand, in the crystal manufacturing method according to the seventh aspect of the present invention, the generation of nuclei is small, the growth rate is high, and dark brown crystals do not grow even in the initial stage of growth. If no impurity is intentionally added, a transparent crystal grows.

  This is because when the flux dissolves at the gas-liquid interface, nitrogen uptake occurs simultaneously, and the amount of nitrogen taken up at the gas-liquid interface increases compared to the case where the flux previously contained in the melt takes up nitrogen. It is guessed that there is.

  In the seventh aspect of the present invention, at the initial stage of crystal growth, the flux dissolves from the atmospheric gas into the melt, and the flux amount ratio in the melt increases. Along with this, the vapor pressure of the flux evaporating from the melt also increases. When this vapor pressure is balanced with the pressure of the flux gas in the atmospheric gas, the flux ratio in the melt becomes constant. When the group III metal is consumed, the amount of group III metal decreases, and the flux amount ratio increases, the flux evaporates and the flux amount ratio is kept constant.

  As a result, in the initial stage of growth, the generation of multinuclear crystals and dark brown crystals are suppressed, and a small number of high-quality crystals grow, and then stable and high-quality crystals are grown under the growth conditions of a predetermined flux ratio. Crystal growth takes place.

(8th form)
The eighth aspect of the present invention is characterized in that, in the Group III nitride crystal manufacturing method of the seventh aspect, a Group III nitride crystal is grown on a seed crystal.

  The seed crystal is preferably a group III nitride crystal, but may be a crystal other than the group III nitride as long as crystal growth is possible. Moreover, the shape is not specifically limited, Arbitrary shapes may be sufficient.

(9th form)
According to a ninth aspect of the present invention, in the crystal manufacturing method according to any one of the first to eighth aspects, the flux is an alkali metal.

  Here, Na (sodium), K (potassium), and Li (lithium) are usually used as the flux, but other alkali metals can also be used.

Example 1 is an example corresponding to the first, second, and ninth aspects of the present invention.

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

  Here, Ga and Na are previously held in a melt holding container as a melt, and nitrogen is supplied by dissolving nitrogen gas generated by decomposition of sodium azide from the gas phase into the melt during crystal growth. By adjusting the Na pressure in the atmospheric gas with the vapor pressure of Na in the Na holding vessel provided outside the reaction vessel, the amount ratio of Na in the melt is kept constant, and the GaN in the melt holding vessel Crystal was grown.

FIG. 1 is a diagram illustrating a configuration example of a crystal manufacturing apparatus used in the first embodiment.

The crystal manufacturing apparatus of FIG. 1 is provided with a melt holding container 26 for holding a melt 28 containing a group III metal and a flux in a closed reaction vessel 23 made of stainless steel and performing crystal growth. Yes.

  In addition, a flux container 24 that stores a flux for adjusting the vapor pressure of the flux in the reaction container 23 is connected to the reaction container 23 by a pipe 27. As a result, the reaction vessel 23, the flux storage vessel 24, and the inside of the pipe 27 have the same pressure (same pressure).

  A flux holding container 25 is accommodated in the flux container 24, and the flux 30 is held therein.

  The melt holding container 26 and the flux holding container 25 can be detached from the reaction container 23 and the flux storage container 24, respectively. The material of the melt holding container 26 and the flux holding container 25 is BN.

  A heater 21 and a heater 22 are installed outside the reaction vessel 23 and the flux container 24, respectively.

  A temperature sensor 34 and a temperature sensor 32 are installed in the reaction vessel 23 and the flux container 24 as temperature measuring units, respectively, and monitor signals corresponding to the respective temperatures are respectively sent to the temperature controller 35 and the temperature controller. 33 to be sent. Then, the temperature controller 35 and the temperature controller 33 adjust the input power to the heater 21 and the heater 22 in accordance with the respective monitor signals, and thereby the temperature of the temperature sensor 34 and the temperature sensor 32 of the temperature sensor 32 is adjusted. Are controlled independently.

  The temperature of the temperature measuring unit is associated with the temperature of the melt or flux, and the temperature of the melt or flux can be controlled by controlling the temperature of the temperature measuring unit.

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

  First, in the melt holding container 26, metal Ga is added as a group III metal source, Na is added as a flux, and sodium azide is added as a nitrogen source. Sodium azide was added in such an amount that it decomposes and the pressure of nitrogen gas reaches 8 MPa at the crystal growth temperature.

  The flux holding container 25 contained metal Na30 as a flux.

  Next, the heater 22 is energized, the temperature of the metal Na30 is increased, and the temperature is maintained at a predetermined Na vapor pressure. At this time, the Na vapor pressure in the reaction vessel 23, the flux holding vessel 25, and the pipe 27 is the same pressure.

  Next, the heater 21 is energized to raise the temperature of the melt 28 from room temperature (27 ° C.) to the crystal growth temperature in 1 hour. The crystal growth temperature was 775 ° C.

  During the temperature rise, the sodium azide in the melt holding container 26 is decomposed to generate nitrogen gas, and the pressure of the nitrogen gas in the reaction container 23, the flux holding container 25, and the pipe 27 becomes 8 MPa at 775 ° C.

  The temperature of the melt 28 in the melt holding vessel 26 and the temperature of the sodium 30 in the flux holding vessel 25 are kept constant at a predetermined temperature, and the sodium vapor pressure in the reaction vessel 23, the flux holding vessel 25, and the pipe 27 is kept constant. Thus, the crystal grows continuously for 400 hours.

  After 400 hours, the temperature is lowered to room temperature.

  After the temperature is lowered, when the reaction vessel 23 is opened, dark brown microcrystals grow on the inner surface of the melt holding vessel 26 and a large number of columnar colorless and transparent GaN 31 having a length of 5 mm or more in the c-axis direction grows. Was.

Example 2 is an example corresponding to the first, third, fourth, fifth, seventh, and ninth modes.

  In Example 2, GaN was crystal-grown using Na (sodium) as a flux, metal Ga (gallium) as a Group III element material, and nitrogen gas as a nitrogen material.

  Here, Ga and Na are previously held in a melt holding container as a mixed melt, and nitrogen is dissolved and supplied from the gas phase into the melt during crystal growth. Further, Na is supplied to the melt as a gas from a flux holding container provided outside the melt holding container. Then, the amount ratio of Na in the melt is made constant by adjusting the pressure of Na in the atmospheric gas in contact with the mixed melt by the amount of Na supplied by evaporation from the flux holding container provided outside the reaction vessel. Then, GaN was crystal-grown in the melt holding container.

FIG. 2 is a diagram illustrating a configuration example of a crystal manufacturing apparatus used in the second embodiment.

  In the apparatus of FIG. 2, a container 43 is provided as a first container in a reaction container 41 made of stainless steel. A flux holding container 46 that holds the flux 48 is accommodated in the lower part of the accommodating container 43, and a melt holding container 45 is accommodated in the upper part thereof. A melt 47 containing a group III metal is held in the melt holding container 45.

  The container 43 is covered with a lid 44. There is a slight gap between the container 43 and the lid 44, and nitrogen gas is supplied through this gap. The storage container 43 can be removed from the reaction container 41. The material of the storage container 43, the melt holding container 45, and the flux holding container 46 is BN.

In addition, the gas supply pipe 14 that allows the reaction vessel 41 to be filled with nitrogen (N ₂ ) gas, which is a nitrogen raw material, and adjusts the nitrogen (N ₂ ) pressure in the reaction vessel 41, connects the reaction vessel 41. Installed through.

  The pressure of the nitrogen gas can be adjusted by the pressure control device 16. The total pressure in the reaction vessel 41 is monitored by the pressure gauge 19.

  Further, a heater 53 and a heater 54 for heating the upper and lower portions of the reaction vessel 41 are installed outside the reaction vessel 41, respectively.

  A temperature sensor 55 and a temperature sensor 52 are installed at a height at which the melt 47 and the flux 48 containing the group III metal in the reaction vessel 41 are held, and monitor signals corresponding to the respective temperatures are temperature controlled. 56 and a temperature controller 57. Then, the temperature controller 56 and the temperature controller 57 adjust the input power to the heater 53 and the heater 54 in accordance with the respective monitor signals, whereby the temperature of the temperature sensor 55 and the temperature measuring unit of the temperature sensor 54 is adjusted. Are controlled independently.

  The temperature of the temperature measuring unit is associated with the temperature of the melt or flux, and the temperature of the melt 47 or the flux 48 can be controlled by controlling the temperature of the temperature measuring unit.

The GaN growth method in Example 2 using the crystal manufacturing apparatus of FIG. 2 will be described below.

  First, in the melt holding container 45, metal Ga is put as a group III metal raw material, and Na is put as alkali metal.

  Then, nitrogen gas is introduced from the nitrogen introduction pipe 17. That is, the valves 15 and 18 are opened, nitrogen gas is introduced into the reaction vessel 41, and the nitrogen pressure in the reaction vessel 41 is set to 8 MPa by the pressure control device 16. Nitrogen gas is also introduced into the storage container 43 through a slight gap between the storage container 43 and the lid 44.

  Next, the heater 53 is energized, and the mixed melt 47 is heated from room temperature (27 ° C.) to the crystal growth temperature in one hour. The crystal growth temperature was 775 ° C.

  Next, the heater 54 is energized to heat Na in the flux holding container 46 to a predetermined temperature.

  Na evaporates from the flux holding container 46 and is supplied to the atmospheric gas 51 on the mixed melt 47 in the melt holding container 45.

  On the other hand, a part of the Na vapor in the storage container 43 is transported to the outside of the storage container 43 through a slight gap between the storage container 43 and the lid 44 and condenses as a liquid in the low temperature part in the reaction container 41.

  Since the amount of Na coming out of the storage container 43 and the evaporation amount of Na evaporating from the flux holding container 46 are kept constant, the vapor pressure of Na in the atmospheric gas 51 is kept constant. Therefore, the amount ratio of Na in the mixed melt 47 becomes an amount ratio that balances with the vapor pressure of Na in the atmospheric gas 51 and becomes constant during crystal growth.

  The temperature and nitrogen pressure are kept constant, and crystal growth continues for 100 hours.

After 100 hours, the temperature is lowered to room temperature.

  When the reaction vessel 41 is opened after the temperature is lowered, dark brown microcrystals grow on the inner surface of the melt holding vessel 45 and a large number of columnar colorless and transparent GaN 50 having a length of 5 mm or more in the c-axis direction grows. Was.

Example 3 is an example corresponding to the first, third, fourth, fifth, sixth, seventh, and ninth aspects of the present invention.

  In Example 3, GaN was crystal-grown using Na (sodium) as a flux, metal Ga (gallium) as a group III element material, and nitrogen gas as a nitrogen material.

  Here, Ga is previously held as a melt in a melt holding container serving as a first container, nitrogen is dissolved and supplied from the gas phase into the melt during crystal growth, and Na is external to the melt holding container. The GaN was crystal-grown in the melt holding container by evaporating from the flux holding container provided in the gas and supplying it as a gas to the melt inside the melt holding container.

  Then, the pressure of Na in the atmospheric gas is adjusted by the supply amount of Na evaporated and supplied from the flux holding container provided outside the reaction vessel, so that the amount ratio of Na in the melt is kept constant and the melt is held. GaN crystal was grown in the container.

FIG. 3 is a diagram illustrating a configuration example of a crystal manufacturing apparatus used in the third embodiment.

The crystal manufacturing apparatus of FIG. 3 holds a melt 75 containing a group III metal in a closed reaction vessel 61 made of stainless steel, and a melt holding vessel 63 (first vessel) for crystal growth. Is provided.

  The melt holding container 63 is covered with a lid 64. There is a slight gap between the melt holding container 63 and the lid 64, and nitrogen gas is supplied through this gap.

  In addition, a flux storage container 69 that stores a flux for adjusting the vapor pressure of the flux in the reaction container 61 is connected to the reaction container 61 by a flux supply pipe 68. The flux supply pipe 68 is installed so as to penetrate the reaction container 61 and the lid 64 of the melt holding container 63, and can supply the flux directly to the internal space 76 of the melt holding container 63.

  A flux holding container 70 is accommodated in the flux container 69, and a flux 74 is held therein.

  In order to increase the evaporation amount of the flux 74, the flux holding container 70 is configured such that the area of the gas-liquid interface where the flux 74 and the gas phase are in contact with each other is widened.

  The melt holding container 63 and the flux holding container 64 can be detached from the reaction container 61 and the flux storage container 69, respectively. The material of the melt holding container 63 and the flux holding container 70 is BN.

  A heater 65 and a heater 71 are installed outside the reaction container 61 and the flux container 69, respectively.

  A temperature sensor 66 and a temperature sensor 72 are installed in the reaction container 61 and the flux container 69, respectively, so that monitor signals corresponding to the respective temperatures are sent to the temperature controller 67 and the temperature controller 73, respectively. It has become. Then, the temperature controller 67 and the temperature controller 73 adjust the input power to the heater 65 and the heater 71, respectively, corresponding to the respective monitor signals, and thereby the temperature measuring units of the temperature sensor 66 and the temperature sensor 72 are adjusted. The temperature is controlled independently.

  The temperature of the temperature measurement unit is associated with the temperature of the melt or flux, and the temperature of the melt 75 or the flux 74 can be controlled by controlling the temperature of the temperature measurement unit.

In addition, a gas supply pipe 14 that fills the reaction vessel 61 with nitrogen (N ₂ ) gas, which is a nitrogen raw material, and adjusts the nitrogen (N ₂ ) pressure in the reaction vessel 61, connects the reaction vessel 61. Installed through.

  The pressure of the nitrogen gas can be adjusted by the pressure control device 16. The total pressure in the reaction vessel 61 is monitored by a pressure gauge 19.

Below, the growth method of GaN in Example 3 using the crystal manufacturing apparatus of FIG. 3 is demonstrated.

  First, metal Ga is put into the melt holding container 63 as a group III metal raw material.

  Then, nitrogen gas is introduced from the nitrogen introduction pipe 17. That is, the valves 15 and 18 are opened, nitrogen gas is introduced into the reaction vessel 61, and the nitrogen pressure in the reaction vessel 61 is set to 8 MPa by the pressure control device 16. Nitrogen gas is also introduced into the melt holding container 63 (first container) through a slight gap between the melt holding container 63 and the lid 64.

  Next, the heater 65 is energized, and the melt 75 is heated from room temperature (27 ° C.) to the crystal growth temperature in one hour. The crystal growth temperature was 775 ° C.

  Next, the heater 71 is energized to heat the Na 74 in the flux holding container 70 to a predetermined temperature.

  Na 74 evaporates from the flux holding container 70, is introduced into the internal space 76 in the melt holding container 63 through the flux supply pipe 68, and enters the melt 75 from the atmospheric gas 76 on the Ga melt 75 through the gas-liquid interface. Dissolve in Along with this, nitrogen is also taken into the melt 75, and GaN crystal growth is started.

  On the other hand, a part of the Na vapor in the melt holding vessel 63 is transported to the outside of the melt holding vessel 63 through a slight gap between the melt holding vessel 63 and the lid 64, and the low temperature portion in the reaction vessel 61 is transferred. Condensed as a liquid.

  Since the amount of Na coming out of the melt holding vessel 63 and the supply amount of Na supplied from the flux holding vessel 70 are kept constant, the vapor pressure of Na in the atmospheric gas 76 is kept constant. For this reason, the amount ratio of Na in the melt 75 increases in the initial stage of growth, but thereafter, the amount ratio becomes balanced with the vapor pressure of Na in the atmospheric gas 76 and becomes constant during crystal growth.

  The temperature and nitrogen pressure are kept constant, and crystal growth continues for 100 hours.

  After 100 hours, the temperature is lowered to room temperature.

  When the reaction vessel 61 is opened after the temperature is lowered, dark brown microcrystals are not grown in the melt holding vessel 63, and the number of columnar colorless and transparent GaN 77 having a length in the c-axis direction extending to 6 mm or more is increased. I was growing up.

Example 4 is an example corresponding to the first, third, fourth, fifth, eighth, and ninth aspects of the present invention.

  In Example 4, Na (sodium) is used as a flux, metal Ga (gallium) is used as a Group III element material, nitrogen gas is used as a nitrogen material, and a GaN plate crystal is used as a seed crystal. GaN was grown as a crystal.

  Here, Ga is held in advance in the melt holding container as a melt, nitrogen is dissolved and supplied from the gas phase into the melt during crystal growth, and Na is a flux holding container provided outside the melt holding container. The GaN was crystal-grown on the seed crystal GaN in the melt holding container.

  Then, the pressure of Na in the atmospheric gas is adjusted by the supply amount of Na evaporated and supplied from the flux holding container provided outside the reaction vessel, so that the amount ratio of Na in the melt is kept constant and the melt is held. GaN crystal was grown in the container.

FIG. 4 is a diagram illustrating a configuration example of a crystal manufacturing apparatus used in the fourth embodiment.

  The apparatus of FIG. 4 is similar to the apparatus of FIG.

Below, the growth method of GaN in Example 4 using the crystal manufacturing apparatus of FIG. 4 is demonstrated.

  First, a GaN plate crystal 49 is placed as a seed crystal in the melt holding container 45, and metal Ga is placed as a group III metal raw material.

  Then, nitrogen gas is introduced from the nitrogen introduction pipe 17. That is, the valves 15 and 18 are opened, nitrogen gas is introduced into the reaction vessel 61, and the nitrogen pressure in the reaction vessel 61 is set to 8 MPa by the pressure control device 16. Nitrogen gas is also introduced into the storage container 43 through a slight gap between the storage container 43 and the lid 44.

  Next, the heater 53 is energized to raise the temperature of the melt 60 from room temperature (27 ° C.) to the crystal growth temperature in one hour. The crystal growth temperature was 775 ° C.

  Next, the heater 54 is energized to heat the Na 48 in the flux holding container 46 to a predetermined temperature.

  Na 48 evaporates from the flux holding container 46 and dissolves in the melt 60 from the atmosphere gas 51 on the Ga melt 60 in the melt holding container 45 through the gas-liquid interface. Along with this, nitrogen is also taken into the melt 60, and crystal growth of GaN is started.

  On the other hand, a part of the Na vapor in the storage container 43 is transported to the outside of the storage container 43 through a slight gap between the storage container 43 and the lid 44 and condenses as a liquid in the low temperature part in the reaction container 41.

  Since the amount of Na coming out of the storage container 43 and the evaporation amount of Na evaporating from the flux holding container 46 are kept constant, the vapor pressure of Na in the atmospheric gas 51 is kept constant. For this reason, the amount ratio of Na in the melt 60 increases in the initial stage of growth, but thereafter, the amount ratio becomes balanced with the vapor pressure of Na in the atmospheric gas 51 and becomes constant during crystal growth.

  The temperature and nitrogen pressure are kept constant, and crystal growth continues for 100 hours.

  After 100 hours, the temperature is lowered to room temperature.

  When the reaction vessel 41 was opened after the temperature was lowered, colorless and transparent GaN 59 was grown on the GaN seed crystal 49 in the melt holding vessel 45. Further, no dark brown crystal grew at the interface portion between the seed crystal 49 and the grown GaN crystal 59.

  On the other hand, when crystal growth was performed using Na-Ga mixed melt as in the conventional method without supplying Na from the outside of the melt, dark brown crystals grew on the seed crystal 49.

  As in Example 4, when the crystal was grown by dissolving Na as a gas in the Ga melt, a dark brown crystal did not grow and a transparent crystal grew.

  The present invention can be used for a blue-violet light source for optical disks, an ultraviolet light source (LD, LED), a blue-violet light source for electrophotography, a group III nitride electronic device, and the like.

1 is a diagram illustrating a configuration example of a crystal manufacturing apparatus used in Example 1. FIG. 6 is a diagram illustrating a configuration example of a crystal manufacturing apparatus used in Example 2. FIG. 6 is a diagram illustrating a configuration example of a crystal manufacturing apparatus used in Example 3. FIG. It is a figure which shows the structural example of the crystal manufacturing apparatus used for Example 4. FIG. It is a figure which shows the structural example of the conventional crystal growth apparatus. It is a figure which shows the structural example of the conventional crystal growth apparatus.

Explanation of symbols

23, 41, 61 Reaction vessel 26, 45, 63 Melt holding vessel 21, 22, 53, 54, 75, 71 Heater 14 Gas supply pipe 15, 18 Valve 16 Pressure control device 17 Nitrogen introduction pipe 19 Pressure gauge 32, 34 , 52, 55, 66, 72 Temperature sensor 33, 35, 56, 57, 67, 73 Temperature controller 60, 75 Melt containing group III metal 29 Internal space 44, 64 Lid 42, 62 Container support 49 GaN plate Seed crystals 24, 69 Flux container 25, 46, 70 Flux container 27 Pipe 28 Melt 30, 48, 74 flux 31 containing group III metal and flux Columnar GaN
43 Container 47 Melt 50 GaN growth crystal 51 Atmospheric gas 58 Internal space 59 of reaction vessel Crystal 68 grown on GaN plate seed crystal 68 Flux supply pipe 75 Ga melt 76 Internal space 77 of melt holding vessel Grown crystal 101 Reaction vessel 102 Melt 103 Seed crystal 105 Heating device 106 Nitrogen supply pipe 107 Pressure sensor 108 Pressure adjustment valve 109 Cable 110 First cylinder 111 First valve 113 Gas-liquid interface 201 Reaction vessel 202 Mixed melt holding vessel 203 Mixing melt Liquid 204 Nitrogen supply pipe 205 Pressure adjustment mechanism 206 First heating device 207 Ga supply pipe 208 Space 209 in reaction vessel 209 Ga vessel 210 Ga
211 Group III nitride (GaN) crystal 212 Height adjustment unit 213 Post 214 Second heating device 215 Ga supply tube tip 216 Pressure adjustment tube

Claims (9)

The melt in which the group III metal, flux, and nitrogen are dissolved forms a gas-liquid interface with the nitrogen source gas and the atmospheric gas containing the flux gas, and nitrogen is dissolved in the melt from the gas-liquid interface, and III A method for producing a group III nitride crystal comprising growing a group III nitride from a group metal and nitrogen,
Holding the melt containing a Group III metal in a non-sealed melt holding container;
Holding the pressure adjusting flux in a region different from the melt holding container;
Holding the pressure adjusting flux held in a region different from the melt holding container and the melt holding container holding the melt in an unsealed storage container;
During crystal growth, the flux gas is supplied from the region where the pressure adjusting flux is held into the atmospheric gas inside the melt holding container that is in contact with the gas-liquid interface, and one of the flux gases inside the melt holding container. A portion is transported to the outside of the container,
During the crystal growth, by adjusting either or both of the amount of flux gas exiting outside the supply amount and the container flux gas supplied to the atmosphere gas inside the melt holding vessel, the melt holding A method for producing a group III nitride crystal, comprising adjusting a pressure of a flux gas in an atmospheric gas inside a container . 2. The method for producing a group III nitride crystal according to claim 1, wherein the supply amount of the flux gas is adjusted by the evaporation rate of the flux evaporating from the surface of the pressure adjusting flux held in a region different from the melt holding container. A method for producing a group III nitride crystal, comprising:   3. The method for producing a group III nitride crystal according to claim 2, wherein the evaporation rate of the flux is adjusted by adjusting the temperature of the pressure adjusting flux.   3. The method for producing a group III nitride crystal according to claim 2, wherein the evaporation rate of the flux is adjusted according to the area of the pressure adjusting flux surface in contact with the gas phase.   The method for producing a crystal according to claim 1, wherein the supply amount of the flux gas is adjusted, and the flux and nitrogen are dissolved through the gas-liquid interface from the atmosphere gas containing the nitrogen source gas in contact with the melt, and the group III metal and the flux A method for producing a group III nitride crystal, comprising forming a melt in which nitrogen is dissolved.   6. The method for producing a group III nitride crystal according to claim 5, wherein group III nitride is grown on the seed crystal.   The method for producing a group III nitride crystal according to any one of claims 1 to 6, wherein the flux is an alkali metal. The Group III nitride crystal manufacturing method according to any one of Claims 1 to 7, wherein the container is a container having a gap, and a nitrogen source gas is supplied from the gap to the melt holding container . A method for producing a group III nitride crystal, comprising: 8. The method for producing a group III nitride crystal according to claim 1, wherein the container is provided in a reaction container, and the reaction container is filled with a nitrogen source gas; and the container And a step of condensing the flux gas transported to the outside as a liquid in a low temperature portion inside the reaction vessel.

Images