JP2004189590A - Group III nitride crystal, group III nitride crystal growth method, semiconductor device and system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stably grow a group III nitride crystal without forming a crystal aggregate composed of a large number of crystals and covering the surface of a mixed melt.
SOLUTION: An alkali metal and a substance containing a group III metal form a mixed melt 25 in a reaction vessel 11, and the mixed melt 25 and a substance containing at least nitrogen, and a group III metal and nitrogen are used. When growing the group III nitride 30 thus formed, the pressure of the substance containing nitrogen is increased in accordance with the temperature rise of the mixed melt 25.
[Selection diagram] Fig. 1

Description

  The present invention relates to a group III nitride crystal, a method for growing a group III nitride crystal, and a semiconductor device and system.

Currently, most of InGaAlN-based (III-nitride) devices used as violet-blue-green light sources are formed on sapphire or SiC substrates by MO-CVD (metal-organic chemical vapor deposition) or MBE. (Molecular beam crystal growth method). A problem when sapphire or SiC is used as a substrate is that crystal defects caused by a large difference in thermal expansion coefficient and lattice constant from group III nitrides are increased. In a group III nitride crystal grown on a sapphire substrate, the dislocation density is as large as about 10 ⁸ to 10 ¹⁰ cm ⁻² . This has an adverse effect on device characteristics. For example, a light emitting device has drawbacks in that it is difficult to prolong its life, decrease in luminous efficiency, and increase operating power. Therefore, practical use of a high-output light-emitting element has been hindered. Further, in the light receiving device, the dark current increases and noise increases, so that the S / N ratio decreases. In an electronic device, threading dislocations in a crystal cause abnormal diffusion of an electrode material or cause a short circuit under a high electric field.

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

  In order to solve these problems, it has been proposed to reduce the crystal defects by performing selective lateral growth of a group III nitride semiconductor film on a sapphire substrate and other measures. In this method, crystal defects can be reduced as compared with a case where a GaN film is not selectively grown in a lateral direction on a sapphire substrate. The problem remains. Furthermore, there are problems that the process becomes complicated and that the substrate is warped due to a combination of different materials such as a sapphire substrate and a GaN thin film. These have led to higher costs.

  In order to solve such a problem, a GaN substrate that is the same as a material that grows crystals on the substrate is most appropriate. Therefore, crystal growth of bulk GaN has been studied by vapor phase growth, melt growth, and the like. However, a GaN substrate having high quality and a practical size has not yet been realized.

  For example, Non-Patent Document 1 (first prior art) proposes growing a GaN bulk crystal and using it as a homoepitaxial substrate. This is a method of growing GaN from liquid Ga at a high temperature of 1400 to 1700 ° C. and a nitrogen pressure of an extremely high pressure of several tens of kbar.

  In this case, a group III nitride semiconductor film required for a device can be grown using the bulk-grown GaN substrate. Therefore, a GaN substrate can be realized without complicating the process. However, as a disadvantage in this case, there is a problem that crystal growth at a high temperature and a high pressure is required, and a reaction vessel that can withstand this becomes extremely expensive. The crystal grown by this method is a plate-like crystal having a C-plane as a main surface, and the width of the main surface is about 1 cm, but the thickness is as thin as 20 to 30 μm at the maximum, and the thickness during the device manufacturing process is small. There is a problem such as cracking.

As another technique for realizing a GaN substrate, Non-Patent Document 2 (second conventional technique) proposes a GaN crystal growth method using Na as a flux. In this method, sodium azide (NaN ₃ ) and metal Ga are used as raw materials, and the reaction vessel is sealed in a nitrogen-containing atmosphere in a stainless steel reaction vessel (inner diameter: inner diameter = 7.5 mm, length = 100 mm). The GaN crystal is grown by maintaining the temperature at 600 to 800 ° C. for 24 to 100 hours.

In the case of the second conventional technique, crystal growth can be performed at a relatively low temperature of 600 to 800 ° C., and the pressure in the container is relatively low, at most about 100 kg / cm ^2. Is a characteristic. However, a problem of this method is that the size of the obtained crystal is small to less than 1 mm.

  Until now, the inventors of the present application have been disclosed in, for example, Patent Literature 1 (Prior Art 3), Patent Literature 2 (Prior Art 4), Patent Literature 3 (Prior Art 5), and Patent Literature 4 (Prior Art 6). Have devised an invention.

  Here, Patent Literature 1 (Prior Art 3) discloses an invention for stably supplying a group V raw material. Patent Document 2 (Prior Art 4) discloses a method of growing using a seed crystal. Patent Document 3 (Prior Art 5) discloses that a group III material is supplied from a compound of a group III metal and an alkali metal to grow a group III nitride crystal. Patent Document 4 (Prior Art 6) discloses a method for growing a cubic group III nitride crystal.

  In these crystal growth methods, a nitrogen-containing substance is supplied from outside the reaction vessel to a mixed melt containing a group III metal and an alkali metal to grow a group III nitride crystal.

  Hereinafter, the invention of Patent Document 1 (Prior Art 3) will be described with reference to the drawings. FIG. 17 is a diagram showing a configuration example of a crystal growth apparatus of Patent Document 1 (Prior Art 3). Referring to FIG. 17, a mixed melt 102 of a group III metal (for example, Ga (gallium)) and a flux (for example, metal Na or a compound containing Na (such as sodium azide)) is provided in a reaction vessel 101. Is contained. Further, the reaction vessel 101 is provided with a heating device 105 which can be controlled to a temperature at which a crystal can be grown.

  A seed crystal (for example, GaN crystal) 103 is provided so as to be in contact with a gas-liquid interface 113 which is a boundary region between the gas in the reaction vessel 101 and the melt 102.

  Further, a nitrogen gas is used as a nitrogen source, and a first gas supply device 120 is provided outside the reaction vessel 101 to supply the nitrogen gas into the reaction vessel 101. Here, the first gas supply device 120 includes a first cylinder 110 for storing a gaseous nitrogen material and a first valve 111. Thereby, the nitrogen gas can be supplied from the outside of the reaction vessel 101 to the inside of the reaction vessel 101 via the nitrogen supply pipe 106 from the first cylinder 110 of the first gas supply device 120 filled with the nitrogen gas. I have.

  Further, a pressure adjusting mechanism is provided in the middle of the nitrogen supply pipe 106 to adjust the nitrogen pressure. The nitrogen gas pressure adjusting mechanism includes a pressure sensor 107 and a pressure adjusting valve 108, and pressure information measured by the pressure sensor 107 is transmitted to the pressure adjusting valve 108 via a cable 109, and the pressure adjusting valve 108 The pressure is adjusted, and the nitrogen pressure in the reaction vessel 101 is set to a desired value.

  The nitrogen gas pressure in the first cylinder 110 filled with the nitrogen gas is set to be equal to or higher than the pressure in the reaction vessel 101 generated when a group III nitride (eg, GaN) crystal grows. Is filled.

  Therefore, the nitrogen gas as the nitrogen source is supplied from the first cylinder 110, the gas pressure of the nitrogen source is adjusted by the pressure adjusting mechanism, and the nitrogen gas is supplied into the reaction vessel 101.

  Using a crystal growth apparatus having such a configuration, a group III nitride crystal (for example, a GaN crystal) is grown with the seed crystal 103 as a nucleus under conditions of a growth temperature, a nitrogen pressure, and an amount of Na at which the crystal can be grown. Using a melt 102 containing an alkali metal (eg, Na) and a group III metal (eg, Ga (gallium)) and a nitrogen gas supplied from the outside as raw materials, the size of the group III nitride crystal increases with time. To go.

  As described above, in the invention of Patent Literature 1 (Prior Art 3), when the group III metal and the alkali metal (for example, Na) are sufficiently provided, the nitrogen gas as the nitrogen raw material is supplied from the outside, whereby the continuous III gas is supplied. It is possible to grow a group III nitride crystal (GaN crystal), and to grow a group III nitride crystal (GaN crystal) to a desired size.

  Similarly, in the inventions of Patent Literature 2 (Prior Art 4), Patent Literature 3 (Prior Art 5), and Patent Literature 4 (Prior Art 6), the nitrogen raw material is supplied from the outside of the reaction vessel, and a continuous group III gas is supplied. A nitride crystal (GaN crystal) is grown.

However, in all of these inventions (prior arts 3, 4, 5, and 6), a crystal aggregate composed of a large number of crystals sometimes covers the surface of the mixed melt. For this reason, the group III metal in the mixed melt is consumed for the formation of the crystal aggregate, the raw material is depleted and the desired crystal does not become large, or the growth region near the melt surface occupies the crystal aggregate. Therefore, there is a problem that a desired crystal cannot be grown on the melt surface. Further, in the prior art 3 and the prior art 4, a large number of crystal nuclei are newly formed in the seed crystal to form a polycrystal, or the seed crystal may be covered with a crystal aggregate.
Journal of Crystal Growth, Vol. 189/190, 153-158 (1998) Chemistry of Materials Vol. 9 (1997) 413-416 JP 2001-64097 A JP 2001-64098 A JP 2001-102316 A JP 2001-119103 A

  The present invention eliminates the conventional problem that a crystal aggregate composed of a large number of crystals is formed and covers the surface of the mixed melt, whereby the group III metal in the mixed melt becomes a crystal aggregate. It is possible to grow the desired crystal in the vicinity of the melt surface by depriving the raw material of the raw material to the depletion of the raw material and the growth of the crystal aggregate near the surface of the mixed melt. It is an object of the present invention to solve the problem of disappearance and provide a method for growing a group III nitride crystal in which a group III nitride crystal can be stably grown.

  Further, in the present invention, in the growth of a group III nitride crystal using a seed crystal, a crystal nucleus is newly attached to the seed crystal and polycrystal is formed, or the seed crystal is covered with a crystal aggregate. It is an object of the present invention to provide a method for growing a group III nitride crystal which can prevent the generation of the group III crystal and grow a desired high quality group III nitride crystal from a seed crystal.

  Another object of the present invention is to provide a large, high-quality single-crystal group III nitride crystal.

  Another object of the present invention is to provide a high-performance, high-reliability semiconductor device using a high-quality group III nitride.

  Another object of the present invention is to provide a high-performance system using a high-performance, high-reliability semiconductor device using a high-quality group III nitride.

  In order to achieve the above object, the invention according to claim 1 is characterized in that, in a reaction vessel, a material containing an alkali metal and a group III metal forms a mixed melt, and the mixed melt and a material containing at least nitrogen. From the above, in a group III nitride crystal growth method for growing a group III nitride composed of a group III metal and nitrogen, the pressure of a substance containing nitrogen is increased in accordance with the temperature rise of the mixed melt. Features.

  According to a second aspect of the present invention, in the method for growing a group III nitride crystal according to the first aspect, a substance containing nitrogen is introduced into the reaction vessel from outside the reaction vessel in accordance with an increase in the temperature of the mixed melt. Then, the pressure of the substance containing nitrogen is increased.

  According to a third aspect of the present invention, in the method for growing a group III nitride crystal according to the first aspect, an inert gas and a substance containing nitrogen are supplied from outside the reaction vessel in accordance with the temperature rise of the mixed melt. It is characterized in that the pressure of a substance containing nitrogen is increased by being introduced into a reaction vessel.

  According to a fourth aspect of the present invention, in the method for growing a group III nitride crystal according to the first aspect, after introducing a nitrogen-containing substance into the reaction vessel, the reaction vessel is closed, and the mixed melt is grown. It is characterized in that a group III nitride crystal is grown by raising the temperature to a temperature.

  According to a fifth aspect of the present invention, there is provided the method for growing a group III nitride crystal according to the fourth aspect, wherein the partial pressure of the nitrogen-containing substance in the reaction vessel becomes a predetermined pressure at a predetermined crystal growth temperature. The method is characterized in that after introducing a substance containing nitrogen into the reaction vessel, the reaction vessel is sealed, and the temperature is raised to a predetermined crystal growth temperature to grow a group III nitride crystal.

  According to a sixth aspect of the present invention, in the method for growing a group III nitride crystal according to the first aspect, after introducing a substance containing nitrogen and an inert gas into the reaction vessel, the reaction vessel is sealed and mixed. It is characterized in that the melt is heated to a crystal growth temperature to grow a group III nitride crystal.

  According to a seventh aspect of the present invention, in the method for growing a group III nitride crystal according to the sixth aspect, the partial pressures of the nitrogen-containing substance and the inert gas in the reaction vessel are respectively adjusted at a predetermined crystal growth temperature. After introducing a substance containing nitrogen and an inert gas in a predetermined pressure amount into the reaction vessel, the reaction vessel is sealed, and the temperature is increased to a predetermined crystal growth temperature to perform group III nitride crystal growth. It is characterized by.

  According to an eighth aspect of the present invention, in the method for growing a group III nitride crystal according to any one of the first to seventh aspects, a plate-shaped group III nitride crystal is grown. And

  According to a ninth aspect of the present invention, in the method for growing a group III nitride crystal according to any one of the first to seventh aspects, a columnar group III nitride crystal is grown. .

  According to a first aspect of the present invention, in the method of growing a group III nitride according to any one of the first to seventh aspects, the group III nitride is grown as a seed crystal. I have.

  According to an eleventh aspect of the present invention, in the method for growing a group III nitride according to any one of the eighth to tenth aspects, the group III nitride is grown near the surface of the mixed melt. It is characterized by:

  According to a twelfth aspect of the present invention, there is provided a group III nitride crystal grown by the method for growing a group III nitride crystal according to the eighth, tenth or eleventh aspect, wherein the group III nitride crystal is The object is a plate-like GaN single crystal.

  According to a thirteenth aspect of the present invention, there is provided a group III nitride crystal grown by the method for growing a group III nitride according to the ninth, tenth, or eleventh aspect, wherein the group III nitride crystal is The object is characterized by being a columnar GaN single crystal.

  According to a fourteenth aspect of the present invention, there is provided a semiconductor device using the group III nitride crystal according to the twelfth or thirteenth aspect.

  According to a fifteenth aspect of the present invention, in the semiconductor device according to the fourteenth aspect, the semiconductor device is a light emitting device having a semiconductor laminated structure laminated on the group III nitride crystal according to the twelfth or thirteenth aspect. It is characterized by having.

  According to a sixteenth aspect of the present invention, in the semiconductor device according to the fourteenth aspect, the semiconductor device is a light receiving element formed using the group III nitride crystal according to the twelfth or thirteenth aspect. Features.

  According to a seventeenth aspect of the present invention, in the semiconductor device of the fourteenth aspect, the semiconductor device is an electronic device formed using the group III nitride crystal of the twelfth or thirteenth aspect. Features.

  An invention according to claim 18 is a system comprising the semiconductor device according to any one of claims 14 to 17.

  According to the invention as set forth in claims 1 to 11, in the reaction vessel, the alkali metal and the substance containing the group III metal form a mixed melt, and from the mixed melt and the substance containing at least nitrogen, In a group III nitride crystal growth method for growing a group III nitride composed of a group III metal and nitrogen, the pressure of a substance containing nitrogen is increased in accordance with the temperature rise of the mixed melt. Following the rise in the temperature of the liquid, the pressure of nitrogen in the reaction vessel increases, and the nitrogen concentration in the mixed melt increases. When such a method of introducing nitrogen into the mixed melt is performed, a large number of nuclei are generated near the surface of the mixed melt, which is a conventional problem, and a crystal aggregate composed of a large number of crystals is formed and mixed. Covering the melt surface is suppressed. For this reason, the fact that the group III metal in the mixed melt is consumed for the formation of the crystal aggregate and the raw material is depleted and the desired crystal does not become large, or that the crystal aggregate deprives the growth region near the surface of the mixed melt. Thus, the problem that a desired crystal cannot be grown in the vicinity of the melt surface can be solved, and the group III nitride crystal can be stably grown.

  In particular, according to the second aspect of the present invention, in the method for growing a group III nitride crystal according to the first aspect, a substance containing nitrogen is supplied from the outside of the reaction vessel into the reaction vessel in accordance with the temperature rise of the mixed melt. And the pressure of the substance containing nitrogen is increased, so that an accurate pressure adjustment method such as a pressure regulator can be selected, whereby the temperature can be accurately increased according to the temperature. As a result, generation of many nuclei can be eliminated, and formation of a crystal aggregate covering the surface of the mixed melt can be suppressed.

  According to a third aspect of the present invention, in the method for growing a group III nitride crystal according to the first aspect, a substance containing an inert gas and nitrogen from outside the reaction vessel in accordance with an increase in the temperature of the mixed melt. Is introduced into the reaction vessel to increase the pressure of the substance containing nitrogen, so that an inert gas is introduced into the reaction vessel in order to suppress evaporation of the alkali metal having a high vapor pressure. Also, the formation of a crystal aggregate can be suppressed. That is, it is possible to stably grow the crystal of the group III nitride while suppressing the evaporation of the alkali metal.

  According to a fourth aspect of the present invention, in the method for growing a group III nitride crystal according to the first aspect, after introducing a nitrogen-containing substance into the reaction vessel, the reaction vessel is closed, and the mixed melt is poured. The temperature is raised to the crystal growth temperature to grow the group III nitride crystal, and the pressure of the substance containing nitrogen increases with the temperature at the time of raising the temperature. Even if the pressure of the substance containing nitrogen as a raw material is not precisely controlled by a pressure regulator or the like, the pressure increase control can be easily performed only by controlling the temperature.

  According to a fifth aspect of the present invention, in the method for growing a group III nitride crystal according to the fourth aspect, the partial pressure of the nitrogen-containing substance in the reaction vessel becomes a predetermined pressure at a predetermined crystal growth temperature. After introducing the substance containing nitrogen in the reaction vessel into the reaction vessel, the reaction vessel is sealed, and the temperature is raised to a predetermined crystal growth temperature to grow the group III nitride crystal. As described above, the pressure of the substance containing nitrogen does not exceed the predetermined pressure at the crystal growth temperature. Therefore, it is not necessary to provide a mechanism for releasing pressure in the crystal growth apparatus, and the apparatus cost can be reduced. Further, since it is not necessary to perform pressure adjustment or the like after the start of temperature rise, the probability of occurrence of disturbance such as a decrease in the nitrogen concentration in the mixed melt due to a change in pressure is reduced, and crystal growth is performed under certain growth conditions. be able to.

  According to a sixth aspect of the present invention, in the method for growing a group III nitride crystal according to the first aspect, the reaction vessel is closed after introducing a nitrogen-containing substance and an inert gas into the reaction vessel. Since the mixed melt is heated to the crystal growth temperature to grow the group III nitride crystal, an inert gas is introduced into the reaction vessel to suppress evaporation of the alkali metal having a high vapor pressure, and the crystal growth is started. Also in the case of performing, formation of a crystal aggregate can be suppressed.

  According to the crystal growth method of the present invention, since the pressure of the substance containing nitrogen and the inert gas also increases with the temperature rise when the temperature is raised, the nitrogen which is the nitrogen source is removed as in the crystal growth method of the present invention. Pressure control of the pressure can be easily performed only by controlling the temperature without precisely controlling the pressure of the substance and the inert gas using a pressure regulator or the like.

  According to a seventh aspect of the present invention, in the method for growing a group III nitride crystal according to the sixth aspect, the partial pressure of the nitrogen-containing substance and the inert gas in the reaction vessel is controlled at a predetermined crystal growth temperature. After introducing a nitrogen-containing substance and an inert gas in an amount each having a predetermined pressure into the reaction vessel, the reaction vessel is sealed, and the temperature is raised to a predetermined crystal growth temperature to grow the group III nitride crystal. Therefore, the pressure of the substance containing nitrogen does not exceed a predetermined pressure at the crystal growth temperature as in the crystal growth method of the sixth aspect. Therefore, there is no need to provide a mechanism for releasing pressure in the crystal growth apparatus, and the cost can be reduced. In addition, since there is no need to perform pressure adjustment or the like after the start of the temperature increase, the probability of occurrence of disturbance such as a decrease in the nitrogen concentration in the mixed melt due to the pressure change is reduced, and crystal growth is performed under certain conditions. Can be.

  According to the eighth aspect of the present invention, in the method of growing a group III nitride crystal according to any one of the first to seventh aspects, a plate-shaped group III nitride crystal is grown. In addition, a large area group III nitride plate crystal can be stably grown without the mixed melt surface being covered with the crystal aggregate. Then, a large area substrate for crystal growth can be manufactured by using the plate-shaped group III nitride crystal grown by this method, and a device having high performance and high reliability can be manufactured. it can.

  According to the ninth aspect of the present invention, in the method for growing a group III nitride crystal according to any one of the first to seventh aspects, a columnar group III nitride crystal is grown. A large group III nitride columnar crystal can be grown stably without the melt surface being covered with the crystal aggregate. Then, a columnar group III nitride crystal grown by this method can be sliced, and a large number of crystal growth substrates can be manufactured, and a high-performance and highly reliable device can be manufactured.

  According to a tenth aspect of the present invention, in the method of growing a group III nitride according to any one of the first to seventh aspects, the group III nitride is grown as a seed crystal. In this case, a high quality desired crystal can be stably grown from the seed crystal without polycrystallizing the seed crystal or being covered with the crystal aggregate.

  According to the invention of claim 11, in the method of growing a group III nitride according to any one of claims 8 to 10, the group III nitride is crystallized in the vicinity of the surface of the mixed melt. Since it grows, a crystal aggregate composed of a large number of crystals, which is a problem in the related art, is not formed and does not cover the mixed melt surface. For this reason, the fact that the group III metal in the mixed melt is consumed for the formation of the crystal aggregate and the raw material is depleted and the desired crystal does not become large, or that the crystal aggregate deprives the growth region near the surface of the mixed melt. Thus, the problem that a desired crystal cannot be grown near the surface of the melt can be solved, and crystal growth of the group III nitride can be stably performed near the surface of the mixed melt. Further, since the nitrogen concentration is high in the vicinity of the surface of the mixed melt (gas-liquid interface), it is possible to grow a high quality crystal with few nitrogen deficiencies. In addition, since the nitrogen concentration is high near the surface of the mixed melt (gas-liquid interface), the growth rate is high, and a group III nitride crystal having a desired size can be grown in a short time.

According to a twelfth aspect of the present invention, there is provided a group III nitride crystal grown by the method for growing a group III nitride crystal according to the eighth, tenth or eleventh aspect. Since the group nitride is a plate-like GaN single crystal, a large, colorless, transparent, high-quality large-sized material having a width of 3 mm or more, a thickness of 80 μm or more, and a dislocation density of 10 ⁶ cm ⁻² or less, having a C-plane as a main surface, which has not existed conventionally. Crystals can be provided. As a result, a large-area wafer having, for example, a C-plane as a main surface can be manufactured, and a high-performance, high-reliability device can be manufactured using the wafer.

According to a thirteenth aspect of the present invention, there is provided a group III nitride crystal grown by the method for growing a group III nitride crystal according to the ninth, tenth, or eleventh aspect, Since the group nitride is a columnar GaN single crystal, a colorless and transparent high-quality crystal having a C axis length of 5 mm or more, a width of 1 mm or more, and a dislocation density of 10 ⁶ cm ⁻² or less, which has not existed conventionally, can be provided. Thereby, a substrate having an arbitrary main surface can be manufactured by slicing the crystal. For example, a wafer having a C-plane or an m-plane as a main surface can be manufactured, and a high-performance and highly-reliable device can be manufactured thereon.

  Further, according to the invention of claim 14, since the semiconductor device is a semiconductor device using the group III nitride crystal according to claim 12 or claim 13, the group III nitride crystal constituting the device has an adverse effect on device performance. Less defects. Therefore, a device having higher performance and higher reliability than before can be provided.

  According to a fifteenth aspect of the present invention, in the semiconductor device according to the fourteenth aspect, the semiconductor device has a semiconductor laminated structure laminated on the group III nitride crystal according to the twelfth or thirteenth aspect. Therefore, the light-emitting element has few defects and has a long life even in a high-output operation. Therefore, a highly reliable light-emitting element which can operate at a higher output than before can be provided.

  According to the sixteenth aspect of the present invention, in the semiconductor device according to the fourteenth aspect, the semiconductor device is a light receiving element formed using the group III nitride crystal according to the twelfth or thirteenth aspect. In addition, the group III nitride crystal constituting the light receiving element has few defects and a small dark current. Therefore, it is possible to provide a high-sensitivity light receiving element having a lower noise level and a higher S / N ratio than in the related art.

  According to the seventeenth aspect, in the semiconductor device according to the fourteenth aspect, the semiconductor device is an electronic device formed using the group III nitride crystal according to the twelfth or thirteenth aspect. In addition, the group III nitride crystal constituting the electronic device has few defects. Therefore, the abnormal diffusion of the electrode material and the short circuit under a high electric field are improved as compared with the related art, and a more reliable and high-performance electronic device can be provided.

According to the eighteenth aspect of the present invention, since the system includes the semiconductor device according to any one of the fourteenth to seventeenth aspects, it has higher performance and higher reliability than the conventional one. Sex system can be provided.

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

  The inventor of the present application has studied the method of introducing a substance containing nitrogen in the initial stage of crystal growth, and has completed the present invention.

(First form)
According to a first aspect of the present invention, in a reaction vessel, an alkali metal and a substance containing a group III metal form a mixed melt, and the group III metal and nitrogen In the method for growing a group III nitride crystal, the method comprises growing the pressure of a substance containing nitrogen in accordance with the temperature rise of the mixed melt.

  Note that, in the present invention, the substance containing nitrogen is a substance that is partially or entirely gaseous as a substance containing nitrogen at a crystal growth temperature. For example, it may be a gas such as nitrogen gas or ammonia gas, or a substance such as sodium azide that is solid at room temperature and decomposes into nitrogen gas and sodium at the crystal growth temperature of group III nitride. (That is, the substance containing nitrogen is a compound containing nitrogen as a constituent element, such as nitrogen gas or sodium azide). The gas of the substance containing nitrogen forms a gas-liquid interface with the mixed melt, and nitrogen is supplied into the mixed melt from the gas-liquid interface.

  In the present invention, the group III nitride means a compound of one or more kinds of group III metals selected from gallium, aluminum and indium with nitrogen.

  As the alkali metal, Na (sodium) and K (potassium) are usually used, but other alkali metals can also be used.

  Further, another element can be melted in the melt containing the alkali metal. For example, an n-type impurity or a p-type impurity may be melted and doped.

  In the present invention, raising the temperature means raising the temperature of the mixed melt. In addition, increasing the pressure means increasing the pressure of the gas.

  In the above-described prior arts 3, 4, 5, and 6, a substance containing nitrogen is supplied from the outside at a predetermined temperature at which the group III nitride crystal grows. In some cases, crystal nuclei were simultaneously generated to form a crystal aggregate covering the surface of the mixed melt.

  The inventor of the present application studied the initial stage of crystal growth, particularly the method of introducing a substance containing nitrogen, and by increasing the pressure of the substance containing nitrogen in accordance with an increase in temperature, no crystal aggregate was formed. I found that.

  That is, in the present invention, when the temperature of the mixed melt is raised to the crystal growth temperature, the pressure of the substance containing nitrogen is gradually increased in accordance with the temperature rise, so that the crystal nuclei are formed on the surface of the mixed melt. Can be suppressed from occurring, and at a predetermined crystal growth temperature, nitrogen dissolved and diffused in the mixed melt under a predetermined pressure is combined with a group III metal in the presence of an alkali metal, and III A group nitride can be crystal-grown.

  The method for causing the pressure increase of the substance containing nitrogen to follow the temperature increase is not particularly limited.

  The rate of temperature rise (in other words, the rate of pressure increase of the substance containing nitrogen) can be appropriately determined to a rate at which a crystal aggregate is not formed.

(Second form)
According to a second aspect of the present invention, there is provided the crystal growth method according to the first aspect, wherein a nitrogen-containing substance is introduced into the reaction vessel from outside the reaction vessel in accordance with the temperature rise of the mixed melt. By growing the pressure, the group III nitride crystal is grown.

  That is, in the crystal growth method according to the second embodiment of the present invention, when the temperature of the mixed melt is raised to the crystal growth temperature, the nitrogen-containing substance is converted from the outside of the reaction vessel into a gas following the temperature rise. The pressure of the nitrogen-containing substance introduced is gradually increased, and the group III nitride crystal is grown at a predetermined temperature and pressure.

  The method of increasing the pressure of the substance containing nitrogen is not particularly limited. For example, a method of gradually increasing the pressure using a pressure regulator or the like can be used.

(Third form)
According to a third aspect of the present invention, in the crystal growth method of the first aspect, an inert gas and a substance containing nitrogen are introduced into the reaction vessel from outside the reaction vessel in accordance with the temperature rise of the mixed melt. It is characterized in that a group III nitride crystal is grown by increasing the pressure of a substance containing nitrogen by being introduced.

  That is, in the crystal growth method according to the third embodiment of the present invention, when the temperature of the mixed melt is raised to the crystal growth temperature, the inert gas and the substance containing nitrogen react as a gas following the rise in temperature. The pressure of the nitrogen-containing substance and the inert gas introduced from the outside of the vessel is gradually increased to grow the group III nitride crystal at a predetermined temperature and pressure.

  Here, the inert gas is used to suppress the evaporation of the alkali metal by increasing the pressure in the reaction vessel.

  The inert gas means a gas that does not react with a group III metal, an alkali metal, or nitrogen. As the inert gas, for example, an argon gas can be used.

  Further, the inert gas may be introduced from a gas line different from the gas line of the substance containing nitrogen, or may be introduced as a mixed gas of the substance containing nitrogen and the inert gas.

(Fourth form)
According to a fourth aspect of the present invention, in the crystal growth method of the first aspect, after introducing a substance containing nitrogen into the reaction vessel, the reaction vessel is closed, and the mixed melt is heated to the crystal growth temperature. Then, a group III nitride is crystal-grown.

  In the crystal growth method according to the fourth aspect of the present invention, a substance containing nitrogen, which is a nitrogen source, is introduced into the reaction vessel at a temperature lower than the temperature at which the crystal grows, and the reaction vessel is sealed to perform predetermined crystal growth. Heat up to temperature. The gas pressure of a substance containing nitrogen in a closed reaction vessel gradually increases as the temperature increases. Along with this, the concentration of nitrogen dissolved in the mixed melt also gradually increases, and at a predetermined crystal growth temperature, nitrogen dissolved and diffused in the mixed melt is combined with a group III metal in the presence of an alkali metal, Group III nitride crystal grows.

  It is desirable that the pressure of the substance containing nitrogen at the time when the temperature reaches the crystal growth temperature is a predetermined pressure at which the crystal is grown, but may be higher. In this case, the pressure can be reduced to a predetermined pressure by opening and closing a valve or the like that separates the reaction vessel from the outside.

  Since the amount of increase in the pressure of the substance containing nitrogen is proportional to the amount of increase in the temperature, the rate of pressure increase of the gas of the substance containing nitrogen can be controlled by controlling the rate of temperature rise. The rate of temperature rise can be appropriately determined so that a crystal aggregate is not formed.

(Fifth embodiment)
According to a fifth aspect of the present invention, there is provided the crystal growth method according to the fourth aspect, wherein the nitrogen-containing substance is reacted in an amount such that a partial pressure of the nitrogen-containing substance in the reaction vessel becomes a predetermined pressure at a predetermined crystal growth temperature. After the introduction into the vessel, the reaction vessel is sealed, and the temperature is raised to a predetermined crystal growth temperature to grow a group III nitride crystal.

  That is, in the fifth embodiment, the charged amount of the nitrogen raw material is adjusted so that the pressure of the substance containing nitrogen in the gas phase in the reaction vessel becomes a predetermined pressure at which the crystal grows at the crystal growth temperature. And introduce it. Thereafter, the temperature of the reaction vessel is closed and the temperature is raised, and the crystal is grown at a predetermined crystal growth temperature and pressure.

(Sixth form)
According to a sixth aspect of the present invention, in the crystal growth method of the fifth aspect, after introducing a substance containing nitrogen and an inert gas into the reaction vessel, the reaction vessel is sealed, and the mixed melt is crystallized. It is characterized in that a group III nitride crystal is grown by raising the temperature to the growth temperature.

  Here, as described in the third embodiment of the present invention, the inert gas is used to suppress the evaporation of the alkali metal by increasing the pressure in the reaction vessel.

  The inert gas means a gas that does not react with a group III metal, an alkali metal, or nitrogen. As the inert gas, for example, an argon gas can be used.

  In the crystal growth method according to the sixth aspect of the present invention, at a temperature lower than the temperature at which crystals grow, a substance containing nitrogen as a nitrogen source and an inert gas are introduced into the reaction vessel, and the reaction vessel is sealed. The temperature is raised to a predetermined crystal growth temperature. The pressure of the nitrogen-containing substance and the inert gas in the sealed reaction vessel gradually increases as the temperature increases. Along with this, the concentration of nitrogen dissolved in the mixed melt also gradually increases, and at a predetermined crystal growth temperature, nitrogen dissolved and diffused in the mixed melt is combined with a group III metal in the presence of an alkali metal, Group III nitride crystal grows.

  The pressure of the substance containing nitrogen and the inert gas at the time when the temperature reaches the crystal growth temperature is preferably a predetermined pressure for performing the crystal growth, but may be higher. In this case, the pressure can be reduced to a predetermined pressure by opening and closing a valve or the like that separates the reaction vessel from the outside.

  Since the amount of increase in the pressure of the nitrogen-containing substance and the inert gas is proportional to the amount of increase in the temperature, it is possible to control the pressure increase rate of the nitrogen-containing substance gas by controlling the temperature increase rate. it can. The rate of temperature rise can be appropriately determined so that a crystal aggregate is not formed.

(Seventh form)
According to a seventh aspect of the present invention, there is provided the crystal growth method according to the sixth aspect, wherein the partial pressures of the nitrogen-containing substance and the inert gas in the reaction vessel each have a predetermined pressure at a predetermined crystal growth temperature. The method is characterized in that after introducing a substance containing nitrogen and an inert gas into the reaction vessel, the reaction vessel is sealed and heated to a predetermined crystal growth temperature to grow a group III nitride crystal.

  That is, in the seventh embodiment, the nitrogen source is charged so that the pressure of the substance containing nitrogen and the inert gas in the gas phase in the reaction vessel becomes a predetermined pressure at which the crystal grows at the crystal growth temperature. The amount and the pressure of the inert gas are adjusted and introduced. Thereafter, the temperature of the reaction vessel is closed and the temperature is raised, and the crystal is grown at a predetermined crystal growth temperature and pressure.

(Eighth form)
According to an eighth aspect of the present invention, in the method for growing a group III nitride crystal according to any one of the first to seventh aspects of the present invention, a plate-shaped group III nitride crystal is grown. And

  Here, the plate-shaped group III nitride crystal may be hexagonal or cubic.

(Ninth form)
According to a ninth aspect of the present invention, in the method for growing a group III nitride crystal according to any one of the first to seventh aspects of the present invention, a columnar group III nitride crystal is grown. And

  Here, the columnar group III nitride crystal may be hexagonal or cubic.

(Tenth form)
According to a tenth aspect of the present invention, there is provided a method for growing a group III nitride crystal according to any one of the first to seventh aspects of the present invention, wherein the group III nitride is grown as a seed crystal. Features.

(Eleventh form)
According to an eleventh aspect of the present invention, in the method for growing a group III nitride crystal according to the eighth, ninth, or tenth aspect, the group III nitride is grown near the surface of the mixed melt. And

(Twelfth form)
A twelfth aspect of the present invention is a plate-like GaN single crystal grown by the method of growing an III-nitride crystal according to the eighth, tenth, or eleventh aspect. The plate-like GaN crystal of the twelfth form is, for example, hexagonal, has a hexagonal main surface, a plane orientation of the main surface, a diagonal length of the main surface, a thickness, a dislocation density (measured by TEM), The colors shown in the following table (Table 1) can be grown.

(Thirteenth mode)
A thirteenth aspect of the present invention is a columnar GaN single crystal grown by a ninth, tenth, or eleventh group III nitride crystal growth method. The columnar GaN crystal of the thirteenth mode is, for example, hexagonal, and can grow in the following table (Table 2) with the length, width, dislocation density (measured by TEM) and color in the C-axis direction. .

(14th form)
A fourteenth aspect of the present invention is a semiconductor device using the group III nitride crystal of the twelfth or thirteenth aspect.

(15th form)
According to a fifteenth aspect of the present invention, in the semiconductor device of the fourteenth aspect, the semiconductor device is a light emitting element having a semiconductor laminated structure in which the semiconductor device is laminated on a group III nitride crystal of the twelfth or thirteenth aspect. Features.

  Here, the form of the light emitting element is not particularly limited, and any light emitting element having a semiconductor laminated structure laminated on a group III nitride crystal, such as a light emitting diode and a semiconductor laser, may be used.

(Sixteenth form)
According to a sixteenth aspect of the present invention, in the semiconductor device of the fourteenth aspect, the semiconductor device is a light receiving element formed using the group III nitride crystal of the twelfth or thirteenth aspect. .

  Here, the light receiving element is a photoconductive cell, a pn junction photodiode, a hetero junction FET type light receiving element, a hetero junction bipolar type photo transistor, etc., and is not particularly limited.

(Seventeenth form)
According to a seventeenth aspect of the present invention, in the semiconductor device of the fourteenth aspect, the semiconductor device is an electronic device formed using the group III nitride crystal of the twelfth or thirteenth aspect. .

  Here, the form of the electronic device is not particularly limited, and may be an FET or an HBT. The intended use is not particularly limited, such as a high-temperature operation device, a high-frequency device, a high-power electronic device, and the like.

(Eighteenth form)
An eighteenth aspect of the present invention is a system including the semiconductor devices of the fourteenth, fifteenth, sixteenth, and seventeenth aspects.

  The system may be, for example, a lighting device using a semiconductor device (light emitting element) of the fifteenth mode as a light source, a full-color large display device, a traffic sign, or the like, or a semiconductor device (light emitting element) of the fifteenth mode. ) May be used as a writing or reading light source, an electrophotographic apparatus using a semiconductor device (light emitting element) of the fifteenth embodiment as a writing light source, or a sixteenth embodiment. A flame sensor, a wavelength-selective detector, or the like having the semiconductor device (light-receiving element) as an optical sensor, or a mobile communication system or the like having the semiconductor device (electronic device) of the seventeenth embodiment. Is also good. In addition, there is no particular limitation as long as the system includes the semiconductor device of the fourteenth, fifteenth, sixteenth, and seventeenth modes.

  In Example 1, the GaN single crystal of the thirteenth mode was grown by the crystal growth method of the first, second, and ninth modes (that is, the outside of the reaction vessel was adjusted in accordance with the temperature rise of the mixed melt). Then, a columnar GaN single crystal was grown near the surface of the mixed melt by increasing the pressure of the nitrogen-containing substance by introducing a nitrogen-containing substance into the reaction vessel.

In the first embodiment, gallium (Ga) is used as a group III metal, sodium (Na) is used as an alkali metal, and nitrogen gas (N ₂ ) is used as a substance containing nitrogen. Let it grow.

  FIG. 1 is a diagram (cross-sectional view) illustrating a configuration example of the crystal growth apparatus used in the first embodiment. In the crystal growth apparatus of FIG. 1, a melt holding vessel 12 for holding a mixed melt 25 containing an alkali metal and a group III metal and performing crystal growth is provided in a reaction vessel 11 having a closed shape made of stainless steel. ing. This melt holding container 12 can be removed from the reaction container 11. The material of the melt holding container 12 is BN.

In addition, a gas supply pipe 14 that allows the internal space 23 of the reaction vessel 11 to be filled with nitrogen (N ₂ ) gas serving as a nitrogen source and adjusts the pressure of nitrogen (N ₂ ) in the reaction vessel 11 is provided. It is mounted through the container 11.

  The reaction vessel 11 can be detached from the crystal growing apparatus at the valve 21 and only the reaction vessel 11 can be put into a glove box for operation.

  A heater 13 is provided outside the reaction vessel 11. The temperature of the heater 13 is monitored by a temperature sensor 29, a monitor signal is sent from the temperature sensor 29 to a temperature controller 34, and the temperature of the heater 13 is controlled by the temperature controller 34. This temperature controller 34 can also control the temperature rise time and the holding time at a constant temperature. Since the temperature of the heater 13 and the temperature of the mixed melt 25 are calibrated and associated in advance, the temperature of the mixed melt 25 can be controlled by controlling the temperature of the heater 13.

  Further, an arithmetic processing unit 35 is provided to increase the pressure of the nitrogen gas following the rise in temperature. The arithmetic processing device 35 receives a signal sent from the temperature controller 34 and sends a control signal corresponding to the temperature to the pressure control device 16. Then, the pressure in the reaction vessel 11 is adjusted by the pressure control device 16.

  The pressure in the reaction vessel 11 is monitored by a pressure sensor 33, and a monitor signal from the pressure sensor 33 is sent to the pressure control device 16 to adjust the pressure inside the reaction vessel 11 to a predetermined pressure.

  A GaN crystal growth method using the crystal growth apparatus of FIG. 1 will be described.

  First, the reaction vessel 11 is separated from the crystal growing apparatus at the valve 21 and placed in a glove box in an Ar atmosphere.

  Next, Ga is put into the melt holding container 12 made of BN as a group III metal raw material, and sodium (Na) is put as an alkali metal. The ratio of Na in the mixed melt was set to Na / (Na + Ga) = 0.51.

  Next, the melt holding container 12 is set in the reaction container 11. Next, the reaction vessel 11 is sealed, the valve 21 is closed, and the inside of the reaction vessel 11 is shut off from the outside atmosphere. Next, the reaction vessel 11 is taken out of the glove box and incorporated into a crystal growth apparatus. That is, the reaction vessel 11 is installed at a predetermined position where the heater 13 is located, and is connected to the nitrogen gas supply line 14 at the valve 21.

  Next, the valves 15 and 21 are opened.

  Next, the heater 13 is energized to raise the temperature of the mixed melt 25 to the crystal growth temperature. The crystal growth temperature was 775 ° C., and the heating time from room temperature (27 ° C.) to 775 ° C. was 1 hour. That is, the heating rate is 748 ° C./hour.

  Further, the pressure of nitrogen in the reaction vessel 11 was increased by following the temperature rise of the mixed melt 25. That is, the pressure was increased from 0 MPa at room temperature (in a state where nitrogen was not put in the reaction vessel), and after 1 hour, that is, when the crystal growth temperature reached 775 ° C., the pressure was increased to 7 MPa. That is, the rate of pressure increase of the nitrogen pressure is 7 MPa / h.

  After reaching a crystal growth temperature of 775 ° C. and a nitrogen pressure of 7 MPa, the crystal growth was carried out for 320 hours. When the reaction vessel 11 is opened after completion of the crystal growth, no crystal aggregate is formed in the melt holding vessel 12 so as to cover the surface of the melt. A colorless and transparent columnar GaN single crystal 30 having a length of about 5 mm was grown.

The C-plane of the grown columnar GaN crystal was observed with a scanning electron microscope, and the length of the diagonal line was measured. Further, the dislocation density obtained by observation with a transmission electron microscope was 10 ⁶ cm ⁻² or less.

  In Example 2, the GaN single crystal of the thirteenth mode was grown by the crystal growth methods of the first, third, ninth, and eleventh modes (that is, the reaction was performed in accordance with the temperature rise of the mixed melt). An inert gas and a substance containing nitrogen were introduced into the reaction vessel from the outside of the vessel, and the pressure of the substance containing nitrogen was increased to grow a columnar GaN single crystal.

In the second embodiment, gallium (Ga) is used as the group III metal, sodium (Na) is used as the alkali metal, nitrogen gas (N ₂ ) is used as the substance containing nitrogen, and the evaporation suppressing gas of Na (inert gas) is used. Gallium nitride (GaN) is crystal-grown using Ar as a).

  FIG. 2 is a diagram (cross-sectional view) illustrating a configuration example of the crystal growth apparatus used in the second embodiment. The crystal growth apparatus shown in FIG. 2 is obtained by adding an Ar gas supply line 20 to the apparatus shown in FIG.

  That is, in the apparatus of FIG. 2, a mixed melt holding container 12 for holding a mixed melt 25 containing an alkali metal and a group III metal and performing crystal growth is provided in a closed reaction container 11 made of stainless steel. Have been. This mixed melt holding container 12 can be removed from the reaction container 11. The material of the mixed melt holding container 12 is BN.

Further, the internal space 23 of the reaction vessel 11 is filled with nitrogen (N ₂ ) gas serving as a nitrogen raw material and argon (Ar) gas for suppressing evaporation of alkali metal, and nitrogen (N ₂ ) in the reaction vessel 11 is filled. A gas supply pipe 14 that allows adjustment of the pressure and the argon (Ar) gas pressure is mounted through the reaction vessel 11.

  In the apparatus shown in FIG. 2, the gas supply pipe 14 is branched into a nitrogen supply pipe 17 and an argon supply pipe 20, and can be separated by valves 15 and 18, respectively. Further, each pressure can be adjusted by the pressure control devices 16 and 19. Thus, the pressure of the nitrogen gas can be independently adjusted while suppressing evaporation of the alkali metal, and crystal growth with high controllability becomes possible.

  A heater 13 is provided outside the reaction vessel 11. The temperature of the heater 13 is monitored by a temperature sensor 29, a monitor signal is sent from the temperature sensor 29 to a temperature controller 34, and the temperature of the heater 13 is controlled by the temperature controller 34. This temperature controller 34 can also control the temperature rise time and the holding time at a constant temperature. Since the temperature of the heater 13 and the temperature of the mixed melt 25 are calibrated and associated in advance, the temperature of the mixed melt 25 can be controlled by controlling the temperature of the heater 13.

  Further, an arithmetic processing unit 35 is provided to increase the pressure following the rise in temperature. The arithmetic processing unit 35 receives a signal sent from the temperature controller 34 and sends a control signal corresponding to the temperature to the pressure controllers 16 and 19. Then, the pressures of nitrogen and Ar in the reaction vessel are adjusted by the pressure controllers 16 and 19.

  The pressure in the reaction vessel 11 is monitored by a pressure sensor 33, and a monitor signal from the pressure sensor 33 is sent to the pressure control devices 16 and 19 to adjust the pressure inside the reaction vessel 11 to a predetermined pressure.

  The reaction vessel 11 can be detached from the crystal growing apparatus at the valve 21 and only the reaction vessel 11 can be put into a glove box for operation.

  A GaN crystal growth method using the crystal growth apparatus of FIG. 2 will be described.

  First, the reaction vessel 11 is separated from the crystal growing apparatus at the valve 21 and placed in a glove box in an Ar atmosphere.

  Next, Ga as a group III metal raw material and sodium (Na) as an alkali metal are put into the mixed melt holding container 12 made of BN. The ratio of Na in the mixed melt was set to Na / (Na + Ga) = 0.51.

  Next, the mixed melt holding container 12 is set in the reaction container 11. Next, the reaction vessel 11 is sealed, the valve 21 is closed, and the inside of the reaction vessel 11 is shut off from the outside atmosphere. Next, the reaction vessel 11 is taken out of the glove box and incorporated into a crystal growth apparatus. That is, the reaction vessel 11 is installed at a predetermined position where the heater 13 is located, and connected to the gas supply line 14 for nitrogen and argon at the valve 21.

  Next, the valves 21, 15, and 18 are opened.

  Next, the heater 13 is energized to raise the temperature of the mixed melt 25 to the crystal growth temperature. The crystal growth temperature was 775 ° C., and the heating time from room temperature (27 ° C.) to 775 ° C. was 1 hour. That is, the heating rate is 748 ° C./hour.

  Further, the pressure of nitrogen and Ar in the reaction vessel 11 was increased by following the temperature rise of the mixed melt. That is, the nitrogen partial pressure and the Ar partial pressure at room temperature are each increased from 0 MPa (in a state where nitrogen and Ar are not put in the reaction vessel 11), and after one hour, that is, when the crystal growth temperature reaches 775 ° C. , And the partial pressures of nitrogen and Ar were each set to 4 MPa. That is, the rate of pressure rise of nitrogen is 4 MPa / hour.

  After reaching the crystal growth temperature of 775 ° C., the crystal was grown for 320 hours. When the reaction vessel 11 is opened after completion of the crystal growth, no crystal aggregate is formed in the melt holding vessel 12 so as to cover the melt surface, and the mixed melt holding vessel 12 near the mixed melt surface is not formed. A colorless and transparent columnar GaN single crystal 27 having a c-axis length of about 6 mm was grown on the inner wall of the substrate.

The C-plane of the grown columnar GaN crystal was observed with a scanning electron microscope, and the length of the diagonal line was measured. Further, the dislocation density obtained by observation with a transmission electron microscope was 10 ⁶ cm ⁻² or less.

  In Example 3, a GaN single crystal of the twelfth form was grown by the crystal growth methods of the first, third, eighth, and eleventh forms (that is, the reaction was performed in accordance with the temperature rise of the mixed melt). A plate-like GaN single crystal was grown by introducing an inert gas and a substance containing nitrogen into the reaction vessel from the outside of the vessel and increasing the pressure of the substance containing nitrogen.

In Example 3, gallium (Ga) was used as the group III metal, sodium (Na) was used as the alkali metal, nitrogen gas (N ₂ ) was used as the substance containing nitrogen, and argon (Ar) was used as the evaporation suppressing gas for Na. ) To grow gallium nitride (GaN). The nitrogen gas and the Ar gas were used in a 1: 1 mixed gas.

  FIG. 3 is a diagram (cross-sectional view) illustrating a configuration example of the crystal growth apparatus used in the third embodiment. In the crystal growth apparatus shown in FIG. 3, the gas supply pipe 14 functions as a supply pipe for a mixed gas of nitrogen and Ar in the apparatus shown in FIG. To clarify this, FIG. 3 shows a cylinder 37 of a mixed gas of nitrogen and Ar and a valve 36.

  A GaN crystal growth method using the crystal growth apparatus of FIG. 3 will be described.

  First, the reaction vessel 11 is separated from the crystal growing apparatus at the valve 21 and placed in a glove box in an Ar atmosphere.

  Next, Ga is put into the melt holding container 12 made of BN as a group III metal raw material, and sodium (Na) is put as an alkali metal. The ratio of Na in the mixed melt was set to Na / (Na + Ga) = 0.67.

  Next, the melt holding container 12 is set in the reaction container 11. Next, the reaction vessel 11 is sealed, the valve 21 is closed, and the inside of the reaction vessel 11 is shut off from the outside atmosphere. Next, the reaction vessel 11 is taken out of the glove box and incorporated into a crystal growth apparatus. That is, the reaction vessel 11 is installed at a predetermined position where the heater 13 is located, and the valve 21 is connected to the gas supply line 14.

  Next, the valves 15 and 21 are opened.

  Next, the heater 13 is energized to raise the temperature of the mixed melt 25 to the crystal growth temperature. The crystal growth temperature was 775 ° C., and the heating time from room temperature (27 ° C.) to 775 ° C. was 1 hour. That is, the heating rate is 748 ° C./hour.

  Further, the pressure of nitrogen and Ar in the reaction vessel 11 was increased by following the temperature rise of the mixed melt. That is, at room temperature, the pressure is increased from the partial pressure of nitrogen and Ar at 0 MPa (in a state where nitrogen and Ar are not put in the reaction vessel 11), and after one hour, that is, when the crystal growth temperature reaches 775 ° C., The total pressure was 8 MPa, that is, the partial pressures of nitrogen and Ar were each 4 MPa. That is, the pressure increase rate of nitrogen is 4 MPa / hour.

  After reaching a crystal growth temperature of 775 ° C. and a total pressure of 8 MPa (partial pressure of nitrogen was 4 MPa), the crystal was grown for 300 hours. When the reaction vessel 11 is opened after completion of the crystal growth, no crystal aggregate is formed in the mixed melt holding vessel 12 so as to cover the melt surface, and the length of the diagonal line on the melt surface is about 5 mm. And a plate-like colorless and transparent GaN single crystal 24 having a hexagonal C-plane as a main surface was grown.

A cross section parallel to the c-axis of the grown plate-like GaN crystal 24 was observed with a scanning electron microscope, and the thickness was measured. Further, the dislocation density obtained by observation with a transmission electron microscope was 10 ⁶ cm ⁻² or less.

  In Example 4, a GaN single crystal of the twelfth form was grown by the crystal growth method of the first, fourth, eighth, and eleventh forms (that is, a substance containing nitrogen was introduced into the reaction vessel). Thereafter, the reaction vessel was sealed, and the mixed melt was heated to a crystal growth temperature to grow a plate-like GaN single crystal.)

In Example 4, gallium (Ga) was used as a group III metal, sodium (Na) was used as an alkali metal, and nitrogen gas (N ₂ ) was used as a nitrogen-containing substance. Let it grow.

  FIG. 4 is a diagram (cross-sectional view) illustrating a configuration example of a crystal growth apparatus used in Example 4. The crystal growth apparatus shown in FIG. 4 includes a melt holding vessel 12 for holding a mixed melt 25 containing an alkali metal and a group III metal and performing crystal growth in a closed reaction vessel 11 made of stainless steel. ing. This melt holding container 12 can be removed from the reaction container 11. The material of the melt holding container 12 is BN.

In addition, a gas supply pipe 14 that allows the internal space 23 of the reaction vessel 11 to be filled with nitrogen (N ₂ ) gas serving as a nitrogen source and adjusts the pressure of nitrogen (N ₂ ) in the reaction vessel 11 is provided. It is mounted through the container 11. The pressure of the nitrogen gas can be adjusted by the pressure control device 16. The total pressure in the reaction vessel 11 is monitored by a pressure gauge 22.

  Further, in the apparatus shown in FIG. 4, a gas release valve 38 for releasing a gas to the outside when the pressure in the reaction vessel 11 exceeds a predetermined pressure is provided.

  A heater 13 is provided outside the reaction vessel 11. The temperature of the heater 13 is monitored by a temperature sensor 29, a monitor signal is sent from the temperature sensor 29 to a temperature controller 34, and the temperature of the heater 13 is controlled by the temperature controller 34. The temperature controller 34 can also control the temperature rising time and the holding time at a constant temperature. Since the temperature of the heater 13 and the temperature of the mixed melt 25 are calibrated and associated in advance, the temperature of the mixed melt 25 can be controlled by controlling the temperature of the heater 13.

  Further, the reaction vessel 11 can be removed from the crystal growing apparatus at the valve 21 and only the reaction vessel 11 can be put into the glove box for operation.

  A GaN crystal growth method using the crystal growth apparatus of FIG. 4 will be described.

  First, the reaction vessel 11 is separated from the crystal growing apparatus at the valve 21 and placed in a glove box in an Ar atmosphere.

  Next, Ga is put into the melt holding container 12 made of BN as a group III metal raw material, and sodium (Na) is put as an alkali metal. The ratio of Na to Ga was 2: 1, that is, Na / (Na + Ga) = 0.67.

  Next, the melt holding container 12 is set in the reaction container 11. Next, the reaction vessel 11 is sealed, the valve 21 is closed, and the inside of the reaction vessel 11 is shut off from the outside atmosphere. Next, the reaction vessel 11 is taken out of the glove box and incorporated into a crystal growth apparatus. That is, the reaction vessel 11 is installed at a predetermined position where the heater 13 is located, and is connected to the nitrogen gas supply line 14 at the valve 21.

  Next, the valves 15 and 21 are opened, and nitrogen gas is introduced into the reaction vessel 11. At this time, the nitrogen pressure was set to 3.5 MPa by the pressure controller 16.

  Next, the valve 21 is closed. Thereby, the reaction vessel 11 is sealed.

  Next, the heater 13 is energized to raise the temperature of the mixed melt 25 from room temperature (27 ° C.) to a crystal growth temperature of 775 ° C. in a heating time of 1 hour. That is, the heating rate is 748 ° C./hour.

  The pressure of nitrogen in the sealed reaction vessel 11 rose following the temperature rise, and when the crystal growth temperature reached 775 ° C., the pressure of nitrogen in the reaction vessel 11 became 4.5 MPa. That is, the rate of pressure rise of nitrogen is 1 MPa / hour. Since this pressure of 4.5 MPa exceeded a predetermined crystal growth pressure, the gas release valve was opened to release nitrogen gas, and the pressure of nitrogen was set to 4 MPa.

  After maintaining this state for 300 hours, the temperature is lowered to room temperature. When the pressure of the gas in the reaction vessel 11 is lowered and the reaction vessel 11 is opened, no crystal aggregate is formed in the melt holding vessel 12 so as to cover the melt surface. A plate-shaped, colorless and transparent GaN single crystal 24 having a hexagonal C-plane with a diagonal length of about 5 mm as a main surface was grown.

A cross section parallel to the c-axis of the grown plate-like GaN crystal 24 was observed with a scanning electron microscope, and the thickness was measured. Further, the dislocation density obtained by observation with a transmission electron microscope was 10 ⁶ cm ⁻² or less.

  In Example 5, the GaN single crystal of the twelfth form was grown by the crystal growth methods of the first, fifth, eighth, and eleventh forms (that is, the partial pressure of the nitrogen-containing substance in the reaction vessel). After introducing a substance containing nitrogen at a predetermined pressure at a predetermined crystal growth temperature into the reaction vessel, the reaction vessel is sealed, and the temperature is increased to a predetermined crystal growth temperature to grow a group III nitride crystal. The crystal growth of plate-like GaN was performed by performing the above.

In Example 5, gallium (Ga) was used as a group III metal, sodium (Na) was used as an alkali metal, and nitrogen gas (N ₂ ) was used as a substance containing nitrogen to form gallium nitride (GaN). Let it grow.

  FIG. 5 is a diagram (cross-sectional view) illustrating a configuration example of a crystal growth apparatus used in Example 5. The crystal growth apparatus shown in FIG. 5 includes a melt holding vessel 12 for holding a mixed melt 25 containing an alkali metal and a group III metal and growing a crystal in a closed reaction vessel 11 made of stainless steel. ing. This melt holding container 12 can be removed from the reaction container 11. The material of the melt holding container 12 is BN.

In addition, a gas supply pipe 14 that allows the internal space 23 of the reaction vessel 11 to be filled with nitrogen (N ₂ ) gas serving as a nitrogen source and adjusts the pressure of nitrogen (N ₂ ) in the reaction vessel 11 is provided. It is mounted through the container 11. The pressure of the nitrogen gas can be adjusted by the pressure control device 16. The total pressure in the reaction vessel 11 is monitored by a pressure gauge 22.

  A heater 13 is provided outside the reaction vessel 11. The temperature of the heater 13 is monitored by a temperature sensor 29, a monitor signal is sent from the temperature sensor 29 to a temperature controller 34, and the temperature of the heater 13 is controlled by the temperature controller 34. The temperature controller 34 of this device can control the heating time and the holding time at a constant temperature. Since the temperature of the heater 13 and the temperature of the mixed melt 25 are calibrated and associated in advance, the temperature of the mixed melt 25 can be controlled by controlling the temperature of the heater 13.

  Further, the reaction vessel 11 can be removed from the crystal growing apparatus at the valve 21 and only the reaction vessel 11 can be put into the glove box for operation.

  A GaN crystal growth method using the crystal growth apparatus of FIG. 5 will be described.

  First, the reaction vessel 11 is separated from the crystal growing apparatus at the valve 21 and placed in a glove box in an Ar atmosphere.

  Next, Ga is put into the melt holding container 12 made of BN as a group III metal raw material, and sodium (Na) is put as an alkali metal. The ratio of Na to Ga was 2: 1, that is, Na / (Na + Ga) = 0.67.

  Next, the melt holding container 12 is set in the reaction container 11. Next, the reaction vessel 11 is sealed, the valve 21 is closed, and the inside of the reaction vessel is shut off from the outside atmosphere. Next, the reaction vessel 11 is taken out of the glove box and incorporated into a crystal growth apparatus. That is, the reaction vessel 11 is installed at a predetermined position where the heater 13 is located, and is connected to the nitrogen gas supply line 14 at the valve 21.

  Next, the valves 15 and 21 are opened, and nitrogen gas is introduced into the reaction vessel 11. At this time, the nitrogen pressure was adjusted to 3.3 MPa by the pressure controller 16. This pressure of 3.3 MPa is a pressure at which the total pressure in the reaction vessel 11 becomes 4 MPa when the temperature is raised from room temperature to the crystal growth temperature of 775 ° C. in the apparatus of FIG.

  Next, the valve 21 is closed. Thereby, the reaction vessel 11 is sealed.

  Next, the heater 13 is energized to raise the temperature of the mixed melt 25 from room temperature (27 ° C.) to a crystal growth temperature of 775 ° C. in a heating time of 1 hour. That is, the heating rate is 748 ° C./hour.

  The pressure of nitrogen in the closed reaction vessel 11 rose following the temperature rise, and when the crystal growth temperature reached 775 ° C., the pressure of nitrogen in the reaction vessel 11 became 4 MPa. That is, the pressure of nitrogen was changed from 3.3 MPa (room temperature 27 ° C.) to 4 MPa (775 ° C.). The pressure increase rate is 0.7 MPa / hour.

  After maintaining this state for 300 hours, the temperature is lowered to room temperature. When the pressure of the gas in the reaction vessel 11 is reduced and the reaction vessel 11 is opened, no crystal aggregate is formed in the melt holding vessel 12 so as to cover the melt surface. A plate-shaped, colorless and transparent GaN single crystal 24 having a hexagonal C-plane with a diagonal length of about 5 mm as a main surface was grown.

A cross section parallel to the c-axis of the grown plate-like GaN crystal 24 was observed with a scanning electron microscope, and the thickness was measured. Further, the dislocation density obtained by observation with a transmission electron microscope was 10 ⁶ cm ⁻² or less.

  In Example 6, a GaN single crystal of the twelfth form was grown by the crystal growth methods of the first, sixth, eighth, and eleventh forms (that is, a substance containing nitrogen and an inert gas contained in the reaction vessel). After the introduction of the gas, the reaction vessel was sealed, and the mixed melt was heated to a crystal growth temperature to grow a group III nitride crystal, thereby growing a plate-like GaN crystal).

In the sixth embodiment, gallium (Ga) is used as a group III metal, sodium (Na) is used as an alkali metal, nitrogen gas (N ₂ ) is used as a nitrogen-containing substance, and a Na evaporation suppressing gas (an inert gas) is used. Gallium nitride (GaN) is crystal-grown using Ar as a).

  FIG. 6 is a diagram (cross-sectional view) illustrating a configuration example of a crystal growth apparatus used in Example 6. The crystal growth apparatus shown in FIG. 6 is obtained by adding an Ar gas supply line 20 to the apparatus shown in FIG.

  A GaN crystal growth method using the crystal growth apparatus of FIG. 6 will be described.

  First, the reaction vessel 11 is separated from the crystal growing apparatus at the valve 21 and placed in a glove box in an Ar atmosphere.

  Next, Ga is put into the melt holding container 12 made of BN as a group III metal raw material, and sodium (Na) is put as an alkali metal. The ratio of Na to Ga was 2: 1, that is, Na / (Na + Ga) = 0.67.

  Next, the melt holding container 12 is set in the reaction container 11. Next, the reaction vessel 11 is closed, the valves 15, 18, and 21 are closed, and the inside of the reaction vessel 11 is shut off from the outside atmosphere. Next, the reaction vessel 11 is taken out of the glove box and incorporated into a crystal growth apparatus. That is, the reaction vessel 11 is installed at a predetermined position where the heater 13 is located, and connected to the gas supply line 14 for nitrogen and argon at the valve 21.

  Next, the valves 15 and 21 are opened, and nitrogen gas is introduced into the reaction vessel. At this time, the nitrogen pressure was set to 3.5 MPa by the pressure controller 16.

  Next, the valve 15 is closed.

  Next, the valve 18 is opened, and Ar gas is introduced into the reaction vessel 11. At this time, the pressure was set to 7 MPa by the pressure control device 19. That is, the partial pressure of Ar in the reaction vessel 11 is 3.5 MPa.

  Next, the valve 18 and the valve 21 are closed. That is, the reaction vessel 11 is sealed.

  Next, the heater 13 is energized to raise the temperature of the mixed melt 25 from room temperature (27 ° C.) to a crystal growth temperature of 775 ° C. in a heating time of 1 hour. That is, the heating rate is 748 ° C./hour.

  Following the temperature rise, the pressure in the closed reaction vessel 11 increased, and when the crystal growth temperature reached 775 ° C., the total pressure in the reaction vessel 11 became 9 MPa. That is, the partial pressures of nitrogen and Ar became 4.5 MPa, respectively. That is, the rate of pressure rise of nitrogen is 1 MPa / hour.

  Since this pressure exceeded a predetermined crystal growth pressure, the gas release valve 38 was opened to release gas, and the total pressure was set to 8 MPa. That is, the partial pressures of nitrogen and Ar were each set to 4 MPa.

  After maintaining this state for 300 hours, the temperature is lowered to room temperature. When the pressure of the gas in the reaction vessel 11 is reduced and the reaction vessel 11 is opened, no crystal aggregate is formed in the melt holding vessel 12 so as to cover the melt surface. A plate-shaped, colorless and transparent GaN single crystal 24 having a hexagonal C-plane with a diagonal length of about 5 mm as a main surface was grown.

A cross section parallel to the c-axis of the grown plate-like GaN crystal 24 was observed with a scanning electron microscope, and the thickness was measured. Further, the dislocation density obtained by observation with a transmission electron microscope was 10 ⁶ cm ⁻² or less.

  In the seventh embodiment, the GaN single crystal of the thirteenth mode is grown by the crystal growth methods of the first, seventh, and ninth modes (that is, the amount of the nitrogen-containing substance and the inert gas in the reaction vessel is increased). At a predetermined crystal growth temperature, a substance containing nitrogen and an inert gas are introduced into the reaction vessel in an amount that becomes a predetermined pressure, and then the reaction vessel is closed, and the temperature is raised to a predetermined crystal growth temperature. The columnar GaN crystal was grown by performing group III nitride crystal growth.

In Example 7, gallium (Ga) was used as the group III metal, sodium (Na) was used as the alkali metal, nitrogen gas (N ₂ ) was used as the substance containing nitrogen, and Ar was used as the evaporation suppressing gas for Na. Then, gallium nitride (GaN) is crystal-grown.

  FIG. 7 is a diagram (cross-sectional view) illustrating a configuration example of a crystal growth apparatus used in Example 7. The crystal growth apparatus shown in FIG. 7 is obtained by adding an Ar gas supply line 20 to the apparatus shown in FIG.

  A GaN crystal growth method using the crystal growth apparatus of FIG. 7 will be described.

  First, the reaction vessel 11 is separated from the crystal growing apparatus at the valve 21 and placed in a glove box in an Ar atmosphere.

  Next, Ga is put into the melt holding container 12 made of BN as a group III metal raw material, and sodium (Na) is put as an alkali metal. The ratio of Na in the mixed melt 25 was set to Na / (Na + Ga) = 0.51.

  Next, the melt holding container 12 is set in the reaction container 11. Next, the reaction vessel 11 is sealed, the valve 21 is closed, and the inside of the reaction vessel 11 is shut off from the outside atmosphere. Next, the reaction vessel 11 is taken out of the glove box and incorporated into a crystal growth apparatus. That is, the reaction vessel 11 is installed at a predetermined position where the heater 13 is located, and connected to the gas supply line 14 for nitrogen and argon at the valve 21.

  Next, the valves 15 and 21 are opened, and nitrogen gas is introduced into the reaction vessel 11. At this time, the nitrogen pressure was adjusted to 3.3 MPa by the pressure controller 16. This pressure of 3.3 MPa is a pressure at which the total pressure in the reaction vessel 11 becomes 4 MPa when the temperature is raised to the crystal growth temperature (775 ° C.) in the apparatus of FIG.

  Next, the valve 15 is closed.

  Next, the valve 18 is opened, and Ar gas is introduced into the reaction vessel 11. At this time, the pressure was adjusted to 6.6 MPa by the pressure controller 19. That is, the partial pressure of Ar in the reaction vessel 11 is 3.3 MPa. This pressure (6.6 MPa) is a pressure at which the total pressure in the reaction vessel 11 becomes 8 MPa when the temperature is raised to the crystal growth temperature (775 ° C.) in the apparatus of FIG. That is, the pressure is such that the partial pressures of nitrogen and Ar are each 4 MPa.

  Next, the valve 18 and the valve 21 are closed. Thereby, the reaction vessel 11 is sealed.

  Next, the heater 13 is energized to raise the temperature of the mixed melt 25 from room temperature (27 ° C.) to a crystal growth temperature of 775 ° C. in a heating time of 1 hour. That is, the heating rate is 748 ° C./hour.

  The pressure in the closed reaction vessel 11 rose following the temperature rise, and when the crystal growth temperature reached 775 ° C., the total pressure in the reaction vessel 11 became 8 MPa. That is, the partial pressures of nitrogen and Ar became 4 MPa, respectively. The pressure rise rate of nitrogen is 0.7 MPa / hour.

  After maintaining this state for 300 hours, the temperature is lowered to room temperature. When the reaction vessel 11 is opened after completion of the crystal growth, no crystal aggregate is formed in the melt holding vessel 12 so as to cover the melt surface, and the c-axis length is located at the bottom of the mixed melt holding vessel. A colorless and transparent columnar GaN single crystal 30 having a size of about 5 mm was grown.

The C-plane of the grown columnar GaN crystal was observed with a scanning electron microscope, and the length of the diagonal line was measured. Further, the dislocation density obtained by observation with a transmission electron microscope was 10 ⁶ cm ⁻² or less.

  In Example 8, a GaN single crystal of the thirteenth mode was grown by the crystal growth methods of the first, seventh, tenth, and eleventh modes (that is, a substance containing nitrogen in a reaction vessel and an inert gas). At a predetermined crystal growth temperature, a gas containing nitrogen and an inert gas are introduced into the reaction vessel at a predetermined pressure, and then the reaction vessel is closed, and the reaction vessel is closed at a predetermined crystal growth temperature. A columnar GaN single crystal was grown by raising the temperature to grow a group III nitride on the seed crystal.)

In Example 8, gallium (Ga) was used as the group III metal, sodium (Na) was used as the alkali metal, nitrogen gas (N ₂ ) was used as the substance containing nitrogen, and Ar was used as the evaporation suppressing gas for Na. Then, gallium nitride (GaN) is crystal-grown.

  FIG. 8 is a diagram (cross-sectional view) illustrating a configuration example of a crystal growth apparatus used in Example 8. The crystal growth apparatus shown in FIG. 8 is obtained by adding an Ar gas supply line 20 to the apparatus shown in FIG.

  A GaN crystal growth method using the crystal growth apparatus of FIG. 8 will be described.

  First, the reaction vessel 11 is separated from the crystal growing apparatus at the valve 21 and placed in a glove box in an Ar atmosphere.

  Next, Ga as a group III metal raw material and sodium (Na) as an alkali metal are put into the mixed melt holding container 12 made of BN. The ratio of Na in the mixed melt 25 was set to Na / (Na + Ga) = 0.51.

  Next, the seed crystal 31 is suspended from the upper part of the mixed melt holding container 12, and a part thereof is immersed in the mixed melt 25.

  Next, the mixed melt holding container 12 is set in the reaction container 11. Next, the reaction vessel 11 is sealed, the valve 21 is closed, and the inside of the reaction vessel 11 is shut off from the outside atmosphere. Next, the reaction vessel 11 is taken out of the glove box and incorporated into a crystal growth apparatus. That is, the reaction vessel 11 is installed at a predetermined position where the heater 13 is located, and connected to the gas supply line 14 for nitrogen and argon at the valve 21.

  Next, the valves 15 and 21 are opened, and nitrogen gas is introduced into the reaction vessel 11. At this time, the nitrogen pressure was adjusted to 3.3 MPa by the pressure controller 16. The pressure of 3.3 MPa is a pressure at which the total pressure in the reaction vessel 11 becomes 4 MPa when the temperature is increased from room temperature (27 ° C.) to reach the crystal growth temperature of 775 ° C. in the apparatus of FIG.

  Next, the valve 15 is closed.

  Next, the valve 18 is opened, and Ar gas is introduced into the reaction vessel 11. At this time, the pressure was adjusted to 6.6 MPa by the pressure controller 19. That is, the partial pressure of Ar in the reaction vessel 11 is 3.3 MPa. This pressure (6.6 MPa) is a pressure at which the total pressure in the reaction vessel 11 becomes 8 MPa when the temperature is raised from room temperature (27 ° C.) to reach the crystal growth temperature of 775 ° C. in the apparatus of FIG. . That is, the pressure is such that the partial pressures of nitrogen and Ar are each 4 MPa.

  Next, the valve 18 and the valve 21 are closed. Thereby, the reaction vessel 11 is sealed.

  Next, the heater 13 is energized to raise the temperature of the mixed melt 25 from room temperature (27 ° C.) to a crystal growth temperature of 775 ° C. in a heating time of 1 hour. That is, the heating rate is 748 ° C./hour.

  The pressure in the closed reaction vessel 11 rose following the temperature rise, and when the crystal growth temperature reached 775 ° C., the total pressure in the reaction vessel 11 became 8 MPa. That is, the partial pressures of nitrogen and Ar became 4 MPa, respectively. The pressure rise rate of nitrogen is 0.7 MPa / hour.

  After maintaining this state for 320 hours, the temperature is lowered to room temperature. When the reaction vessel 11 is opened after the pressure of the gas in the reaction vessel 11 is reduced, no crystal aggregate is formed in the melt holding vessel 12 so as to cover the melt surface, and the seed crystal 31 As a result, a colorless and transparent columnar GaN single crystal 32 with a c-axis length of about 8 mm was grown.

  Example 9 is a semiconductor laser which is an example of the semiconductor device (light emitting element) of the fifteenth embodiment.

  9 and 10 show a semiconductor laser according to the ninth embodiment. FIG. 9 is a perspective view of the semiconductor laser according to the ninth embodiment, and FIG. 10 is a cross-sectional view taken along a plane perpendicular to the light emitting direction.

  The semiconductor laser of the ninth embodiment is manufactured with a group III nitride semiconductor multilayer structure stacked on an n-type GaN substrate 50 formed of a GaN crystal of the twelfth embodiment.

That is, in FIGS. 9 and 10, the semiconductor laser laminated structure 400 has an n-type GaN layer 40, an n-type Al _0.2 Ga _0.8 N clad layer 41 on a 250 μm-thick n-type GaN substrate 50. n-type GaN light guide layer 42, In _0.05 Ga _0.95 N / In _0.15 Ga _0.85 N quantum well active layer 43, p-type GaN light guide layer 44, p-type Al _0.2 Ga _{0. 8} N cladding layer 45, a p-type GaN cap layer 46 are sequentially stacked, are produced are grown by MOCVD.

Then, the laminated structure 400 is etched leaving a stripe shape from the p-type GaN cap layer 46 to the middle of the p-type Al _0.2 Ga _0.8 N clad layer 45, and the current constriction ridge waveguide structure 51 is manufactured. I have. This current constriction ridge waveguide structure is formed along the <1-100> direction of the GaN substrate.

An insulating film 47 made of SiO ₂ is formed on the surface of the laminated structure. An opening is formed in the insulating film 47 on the ridge 51. A p-side ohmic electrode 48 is formed on the surface of the p-type GaN cap layer 46 exposed at the opening.

  An n-side ohmic electrode 49 is formed on the back surface of the n-type GaN substrate 50. The n-side ohmic electrode 49 was formed by depositing Ti / Al, and the p-side ohmic electrode 48 was formed by depositing Ni / Au.

  Optical resonator surfaces 401 and 402 are formed perpendicular to the ridge 51 and the active layer 43. The optical resonator surfaces 401 and 402 are formed by cleaving the (1-100) plane of the GaN substrate perpendicular to the current confinement ridge waveguide structure 51 along the <1-100> direction.

  The n-side ohmic electrode 49 and the optical resonator surfaces 401 and 402 were formed after polishing the back surface of the n-type GaN substrate 50 to 80 μm.

  In the semiconductor laser of the ninth embodiment, by injecting current into the p-side ohmic electrode 48 and the n-side ohmic electrode 49, carriers are injected into the active layer, and light emission and light amplification occur. , 402 emit laser beams 411, 412.

  The semiconductor laser according to the ninth embodiment is manufactured by crystal-growing a laser structure on a substrate different from a group III nitride such as a conventional sapphire substrate, or a GaN substrate manufactured by vapor phase growth or other methods. Compared to those fabricated above, the laser structure laminated on the substrate has lower crystal defects and higher crystal quality, and thus has a longer life even under high-power operation.

  Further, since the semiconductor laser of the ninth embodiment is manufactured using a GaN substrate that is sufficiently thick to perform the manufacturing process, the semiconductor laser does not break during the manufacturing process as in the first related art. , And a good yield was obtained.

  Embodiment 10 is an embodiment of a sixteenth semiconductor device (light receiving element). FIG. 11 is a diagram illustrating a light receiving element according to a tenth embodiment.

  The light receiving element of Example 10 is manufactured with a group III nitride semiconductor multilayer structure stacked on an n-type GaN substrate 60 manufactured by slicing a columnar crystal of the thirteenth embodiment.

  Here, the thickness of the GaN substrate 60 is 300 μm.

  The structure of the light receiving element of the tenth embodiment is such that an n-type GaN layer 61 and an insulating GaN layer 62 are laminated on an n-type GaN substrate 60, and a transparent Schottky electrode 63 made of Ni / Au is formed thereon. MIS type light receiving element.

  An ohmic electrode 64 made of Ti / Al is formed on the back surface of the n-type GaN substrate 60, and an electrode 65 made of Au is formed on a part of the upper part of the transparent Schottky electrode 63.

  In the light receiving element of the tenth embodiment, when light (ultraviolet light) 601 is incident from the transparent Schottky electrode 63 side, carriers are generated and a photocurrent is extracted from the electrode.

  The light-receiving element of Example 10 was manufactured by crystal-growing a light-receiving element structure on a substrate different from a group III nitride such as a conventional sapphire substrate, or a GaN formed by vapor phase growth or other methods. Compared with those fabricated on the substrate, the light receiving element structure laminated on the substrate had low crystal defects and high crystal quality, so that the dark current was small and the S / N ratio was high.

  Further, since the light receiving element of Example 10 is manufactured using a GaN substrate that is sufficiently thick to perform the manufacturing process, the substrate is not broken during the manufacturing process as in the first related art. , And a good yield was obtained.

  Example 11 is an example of a semiconductor device (electronic device) according to the seventeenth embodiment. FIG. 12 is a cross-sectional view of the semiconductor device (electronic device) according to the eleventh embodiment. The electronic device of Example 11 is a high electron mobility transistor (HEMT).

  The high electron mobility transistor (HEMT) of Example 11 is manufactured with a group III nitride semiconductor multilayer structure stacked on a GaN substrate 70 formed of a GaN crystal of the twelfth embodiment.

  Here, the thickness of the GaN substrate 70 is 300 μm.

  The structure of the high electron mobility transistor (HEMT) is a recess gate HEMT including an insulating GaN layer 71, an n-type AlGaN layer 72, and an n-type GaN layer 73 stacked on a GaN substrate 70.

  The gate portion of the n-type GaN layer 73 is etched down to the n-type AlGaN layer 72, and a gate electrode 76 made of Ni / Au is formed on the n-type AlGaN layer 72. A drain electrode 75 and a source electrode 74 made of Ti / Al are formed on the n-type GaN layers 73 on both sides of the gate.

  The high electron mobility transistor (HEMT) of the eleventh embodiment is manufactured by crystal-growing a high electron mobility transistor (HEMT) structure on a substrate different from a group III nitride such as a conventional sapphire substrate, Compared to those fabricated on a GaN substrate fabricated by phase growth or other methods, the high electron mobility transistor (HEMT) structure stacked on the substrate has lower crystal defects and higher crystal quality, The abnormal diffusion and short circuit of the electrode due to the above were suppressed, the withstand voltage was high, and good frequency characteristics were exhibited.

  Since the high electron mobility transistor (HEMT) of Example 11 is manufactured using a GaN substrate that is sufficiently thick to perform the manufacturing process, the substrate is broken during the manufacturing process as in the first related art. It was possible to manufacture with a good yield without any mess.

  Example 12 is an example of the system according to the eighteenth mode. That is, Example 12 is a lighting device including the semiconductor device (light emitting element) of the fifteenth embodiment.

  FIG. 13 is a schematic diagram of a lighting device according to a twelfth embodiment. FIG. 14 is a circuit diagram of the lighting apparatus according to the twelfth embodiment. FIG. 15 is a cross-sectional view of a white LED module which is a light source of the illumination device of the twelfth embodiment. FIG. 16 is a sectional view of an ultraviolet light emitting LED which is a light source of a white LED module.

  In the lighting device according to the twelfth embodiment, two white LED modules 902, a current limiting resistor 96, a DC power supply 97, and a switch 98 are connected in series, and the white LED module 902 emits light when the switch 98 is turned on and off. It is made to let.

  Here, the white LED module 902 has a structure in which a YAG-based phosphor 91 is applied to an ultraviolet light emitting LED 90. Then, when a predetermined voltage is applied between the electrode terminals 94 and 95, the ultraviolet light-emitting LED 90 emits light, and the ultraviolet light excites the YAG-based phosphor 91 to extract white light 901.

  Here, the ultraviolet light emitting LED 90 is manufactured with a group III nitride semiconductor multilayer structure stacked on an n-type GaN substrate 80 manufactured by slicing a columnar crystal of the thirteenth embodiment.

  The thickness of the GaN substrate 80 is 300 μm.

The structure of the ultraviolet light emitting LED 90 is such that an n-type GaN layer 81, an n-type Al _0.1 Ga _0.9 N layer 82, an active layer 83 having an InGaN / GaN multiple quantum well structure, a p-type An Al _0.1 Ga _0.9 N layer 84 and a p-type GaN layer 85 are stacked, and a transparent ohmic electrode 86 made of Ni / Au is formed thereon. On the transparent ohmic electrode 86, an electrode 87 for wire bonding made of Ni / Au is formed. On the back surface of the n-type GaN substrate 80, an ohmic electrode 88 made of Ti / Al is formed.

  In this ultraviolet light emitting LED 90, carriers are injected into the active layer by injecting a current into the p-side electrode 87 and the n-side ohmic electrode 88, light is emitted, and ultraviolet light 801 is extracted outside the LED.

  The LED of the twelfth embodiment is manufactured by crystal growth of the LED structure on a substrate different from a group III nitride such as a conventional sapphire substrate, or by a GaN substrate manufactured by vapor phase growth or other methods. Compared to those fabricated above, the LED structure stacked on the substrate has low crystal defects and high crystal quality, so that the luminous efficiency is high and high output operation is performed.

  Further, since the LED of Example 12 is manufactured using a GaN substrate that is sufficiently thick to perform the manufacturing process, the substrate does not break during the manufacturing process as in the first related art. It was manufactured with good yield.

Therefore, the lighting fixture of Example 12 was manufactured by crystal-growing an LED structure on a substrate different from a group III nitride such as a conventional sapphire substrate, or by vapor phase growth, or by other methods. It is brighter and consumes less power than white LED lighting fixtures using ultraviolet LEDs fabricated on a GaN substrate.

FIG. 3 is a diagram (cross-sectional view) illustrating a configuration example of a crystal growth apparatus used in Example 1. FIG. 9 is a diagram (cross-sectional view) illustrating a configuration example of a crystal growth apparatus used in Example 2. FIG. 14 is a diagram (cross-sectional view) illustrating a configuration example of a crystal growth apparatus used in a third embodiment. FIG. 14 is a diagram (cross-sectional view) illustrating a configuration example of a crystal growth apparatus used in Example 4. FIG. 14 is a diagram (cross-sectional view) illustrating a configuration example of a crystal growth apparatus used in Example 5. FIG. 14 is a diagram (cross-sectional view) illustrating a configuration example of a crystal growth apparatus used in Example 6. FIG. 14 is a diagram (cross-sectional view) illustrating a configuration example of a crystal growth apparatus used in Example 7. FIG. 14 is a diagram (cross-sectional view) illustrating a configuration example of a crystal growth apparatus used in Example 8. FIG. 19 is a perspective view of a semiconductor laser according to a ninth embodiment. FIG. 21 is a cross-sectional view taken along a plane perpendicular to the light emission direction of the semiconductor laser of Example 9; FIG. 21 is a sectional view of a light receiving element according to a tenth embodiment. FIG. 21 is a sectional view of an electronic device according to an eleventh embodiment. FIG. 19 is a schematic diagram of a lighting device according to a twelfth embodiment. FIG. 18 is a circuit diagram of a lighting device according to a twelfth embodiment. FIG. 21 is a cross-sectional view of a white LED module that is a light source of the lighting device according to Example 12; FIG. 21 is a cross-sectional view of an ultraviolet light emitting LED which is a light source of a white LED module according to Example 12. FIG. 11 is a diagram (cross-sectional view) illustrating a configuration example of a conventional crystal growth apparatus.

Explanation of reference numerals

11, 101 Reaction vessel 12 Mixed melt holding vessel 13, 28 Heater 14 Gas supply pipe 15, 18, 21, 34, 35 Valve 16, 19 Pressure control device 17 Nitrogen supply pipe 20 Argon supply pipe 22 Pressure gauge 23 Reaction vessel Internal space 24 GaN plate crystal 25 Mixed melt 26 Pedestal 29 Temperature sensor 27, 30, 32 GaN columnar crystal 31 Seed crystal 33 Pressure sensor 34 Temperature controller 35 Pressure controller 36 Valve 37 Gas cylinder 38 Pressure release valve 40 n -Type GaN layer 41 n-type Al _0.2 Ga _0.8 N cladding layer 42 n-type GaN light guide layer 43 In _0.05 Ga _0.95 N / In _0.15 Ga _0.85 N quantum well active layer 44 p -Type GaN optical guide layer 45 p-type Al _0.2 Ga _0.8 N cladding layer 46 p-type GaN cap layer 47 Insulating film 48 p-side ohmic electrode 49 n-side ohmic electrode 50 n-type GaN substrate 51 current confinement ridge waveguide structure 60 n-type GaN substrate 61 n-type GaN layer 62 insulating GaN layer 63 transparent Schottky electrode 64 ohmic electrode 65 electrode 70 GaN substrate 71 insulating GaN layer 72 n-type AlGaN layer 73 n-type GaN layer 74 source electrode 75 drain electrode 76 gate electrode 80 n-type GaN substrate 81 n-type GaN layer 82 n-type Al _0.1 Ga _0.9 N layer 83 Active layer having InGaN / GaN multiple quantum well structure 84 p-type Al _0.1 Ga _0.9 N layer 85 p-type GaN layer 86 transparent ohmic electrode 87 electrode 88 n-side ohmic electrode 90 ultraviolet light emitting LED
91 YAG-based phosphor 92 Gold wire 93 Lens 94, 95 Electrode terminal 96 Current limiting resistor 97 DC power supply 98 Switch 102 Mixed melt 103 Seed crystal (for example, GaN crystal)
Reference Signs List 105 heating device 106 nitrogen supply pipe 113 gas-liquid interface 107 pressure sensor 108 pressure regulating valve 109 cable 110 first cylinder 111 first valve 120 first gas supply device 400 laminated structure 401, 402 optical resonator surface 411, 412 Laser light 601 Light (ultraviolet light)
801 UV light 901 White light 902 White LED module

Claims (18)

In a reaction vessel, a substance containing an alkali metal and a group III metal forms a mixed melt, and a group III nitride composed of a group III metal and nitrogen from the mixed melt and a substance containing at least nitrogen. A method for growing a group III nitride crystal, comprising: increasing the pressure of a substance containing nitrogen in accordance with an increase in the temperature of a mixed melt. 2. The method for growing a group III nitride crystal according to claim 1, wherein a nitrogen-containing substance is introduced into the reaction vessel from outside the reaction vessel to increase the pressure of the nitrogen-containing substance in accordance with the temperature rise of the mixed melt. A method for growing a group III nitride crystal, comprising: 2. The method for growing a group III nitride crystal according to claim 1, wherein an inert gas and a substance containing nitrogen are introduced into the reaction vessel from outside the reaction vessel in accordance with an increase in the temperature of the mixed melt to contain nitrogen. A method for growing a group III nitride crystal, comprising increasing the pressure of a substance. The method for growing a group III nitride crystal according to claim 1, wherein after introducing a substance containing nitrogen into the reaction vessel, the reaction vessel is sealed, and the mixed melt is heated to a crystal growth temperature. A method for growing a group III nitride crystal, comprising: growing a group III nitride. 5. The method for growing a group III nitride crystal according to claim 4, wherein a nitrogen-containing substance is introduced into the reaction vessel in such an amount that a partial pressure of the nitrogen-containing substance in the reaction vessel becomes a predetermined pressure at a predetermined crystal growth temperature. A method for growing a group III nitride crystal, comprising: sealing the reaction vessel, raising the temperature to a predetermined crystal growth temperature, and growing the group III nitride crystal. 2. The method for growing a group III nitride crystal according to claim 1, wherein after introducing the nitrogen-containing substance and the inert gas into the reaction vessel, the reaction vessel is closed, and the mixed melt is heated to a crystal growth temperature. A method for growing a group III nitride crystal, comprising: growing a group III nitride crystal. 7. The method for growing a group III nitride crystal according to claim 6, wherein the partial pressures of the nitrogen-containing substance and the inert gas in the reaction vessel each include nitrogen in an amount that becomes a predetermined pressure at a predetermined crystal growth temperature. After introducing a substance and an inert gas into the reaction vessel, the reaction vessel is sealed, and a group III nitride crystal is grown by raising the temperature to a predetermined crystal growth temperature to grow a group III nitride crystal. Growth method. The method for growing a group III nitride crystal according to any one of claims 1 to 7, wherein a plate-shaped group III nitride crystal is grown. . 8. The method for growing a group III nitride crystal according to claim 1, wherein a columnar group III nitride crystal is grown. 9. The method for growing a group III nitride crystal according to any one of claims 1 to 7, wherein the group III nitride is grown as a seed crystal. The method for growing a group III nitride according to any one of claims 8 to 10, wherein the group III nitride is grown near the surface of the mixed melt. Crystal growth method. A group III nitride crystal grown by the method for growing a group III nitride crystal according to claim 8, claim 10, or claim 11, wherein the group III nitride is a plate-like GaN single crystal. A group III nitride crystal, characterized in that: 12. A group III nitride crystal grown by the method for growing a group III nitride crystal according to claim 9, wherein the group III nitride is a columnar GaN single crystal. A group III nitride crystal characterized by the following. A semiconductor device using the group III nitride crystal according to claim 12. 15. The semiconductor device according to claim 14, wherein the semiconductor device is a light-emitting element having a semiconductor laminated structure laminated on the group III nitride crystal according to claim 12 or 13. 15. The semiconductor device according to claim 14, wherein the semiconductor device is a light receiving element formed using the group III nitride crystal according to claim 12 or 13. 15. The semiconductor device according to claim 14, wherein the semiconductor device is an electronic device formed using the group III nitride crystal according to claim 12 or 13. A system comprising the semiconductor device according to any one of claims 14 to 17.

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