JP4527496B2 - Group III nitride crystal manufacturing method - Google Patents

Description

The present invention relates to a method for producing a group III nitride crystal.

  At present, most of InGaAlN-based (group III nitride) devices used as ultraviolet, purple-blue-green light sources are formed on a sapphire or SiC substrate by MO-CVD (metal organic chemical vapor deposition) or It is produced by crystal growth using the MBE method (molecular beam crystal growth method) or the like. As a problem when sapphire or SiC is used as a substrate, there is an increase in crystal defects caused by a large difference in thermal expansion coefficient and lattice constant from the group III nitride. For this reason, it leads to the fault that a device characteristic is bad (for example, it is difficult to lengthen the lifetime of a light-emitting device), and operating power becomes large.

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

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

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

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

In the case of this prior art 1, crystal growth is possible at a relatively low temperature of 600 to 800 ° C., and the pressure in the vessel is relatively low at about 100 kg / cm ² at most, which is a practical growth condition. It is a feature. However, the problem with this method is that the crystal size obtained is small enough to be less than 1 mm.

That is, in the prior art 1, the reaction vessel is a completely closed system, and the raw material cannot be replenished from the outside. Therefore, the raw material is depleted during the crystal growth and the crystal growth stops, so that the size of the obtained crystal is as small as about 1 mm. This size is too small for practical use of the device.
Chemistry of Materials Vol. 9 (1997) 413-416

  The present invention provides a group III nitride crystal growth method, a group III nitride crystal, and a semiconductor device capable of producing a high-quality, large-sized group III nitride crystal at a lower cost than before. It is aimed.

In order to achieve the above object, the invention described in claim 1 is a group III nitride crystal manufacturing method in which a group III nitride crystal is grown from a melt in which at least an alkali metal, a group III metal raw material, and nitrogen are dissolved. , (0001) face of the group III nitride, {10-11} plane, or, in some generally covered area in a plane mixed and the (0001) plane and the {10-11} plane, (000 -1) and the group III nitride surface in contact with the melt crystals were nucleation is characterized in the nucleation is not a group III nitride crystal (000-1) growing the face as the growth face .

The invention described in claim 2 is the method for producing a group III nitride crystal according to claim 1, wherein the (0001) plane, the {10-11} plane, or the (0001) plane of the group III nitride. And the {10-11} plane are generally covered with a region made of a group III nitride crystal.

The invention described in claim 3 is the method for producing a group III nitride crystal according to claim 1, wherein the (0001) plane, the {10-11} plane, or the (0001) plane of the group III nitride. And the {10-11} plane are substantially covered with a c-axis oriented film grown on the substrate.

The invention described in claim 4 is the group III nitride crystal manufacturing method according to any one of claims 1 to 3 , wherein the mode of crystal growth is the (0001) plane of the group III nitride. Or (000-1) from a mode in which epitaxial growth (seed crystal growth) occurs in a region substantially covered with a {10-11} plane or a plane in which (0001) plane and {10-11} plane are mixed. It is characterized in that the mode is changed to a mode in which a columnar crystal whose surface becomes a growth surface grows.

The invention described in claim 5 is characterized in that, in the crystal manufacturing method according to claim 4 , the mode of crystal growth is changed by increasing the amount of nitrogen dissolved in the melt.

The invention described in claim 6 is characterized in that, in the crystal manufacturing method according to claim 5 , the amount of nitrogen dissolved in the melt is increased by increasing the pressure of nitrogen in contact with the melt at the gas-liquid interface. It is said.

The invention according to claim 7 is characterized in that, in the crystal manufacturing method according to claim 4 , the mode of crystal growth is changed by changing the amount ratio of the alkali metal and the group III metal in the melt.

The invention described in claim 8 is characterized in that, in the crystal manufacturing method according to claim 4 , the mode of crystal growth is changed by changing the temperature of the melt.

According to the first to eighth aspects of the present invention, there is provided a group III nitride crystal manufacturing method for growing a group III nitride crystal from a melt in which at least an alkali metal, a group III metal raw material, and nitrogen are dissolved. From the (0001) plane of the group nitride, or the {10-11} plane, or the region that is substantially covered with the plane in which the (0001) plane and the {10-11} plane are mixed, the (000-1) plane Group III nitride crystal having a growth plane as a growth plane, the growth in the normal direction of the (0001) plane or {10-11} plane is delayed, and the group III nitride having the (000-1) plane as the growth plane The growth of the crystal can be prioritized, and the group III nitride crystal having the (000-1) plane as the growth surface can be efficiently grown to a high quality and large size.

In particular, in the invention according to claim 2, in the method for producing a group III nitride crystal according to claim 1, the (0001) plane, the {10-11} plane, or the (0001) plane of the group III nitride. And the {10-11} plane are generally covered by the surface of the crystal made of group III nitride, and can easily be (0001) plane or {10-11] in the melt. } A region covered with a plane can be formed, so that a large group III nitride crystal having a (000-1) plane as a growth plane can be easily grown.

According to a third aspect of the present invention, in the Group III nitride crystal manufacturing method according to the first aspect, the (0001) plane, the {10-11} plane, or the (0001) plane of the Group III nitride. And the {10-11} plane are almost covered by a c-axis oriented film grown on the substrate and has a large area by a simple film forming method such as MOCVD, MBE, HVPE, sputtering, etc. Since the c-axis alignment film can be produced by the above process, the (0001) plane or {10-11} plane can be easily cut into the melt at low cost by appropriately cutting the c-axis alignment film and putting it in the melt. A region covered with can be formed. Further, since it is possible to form a region covered with the (0001) plane or {10-11} plane over a large area, the growth of miscellaneous crystals is suppressed, and the (000-1) plane is used as the growth plane. The growth of the group III nitride crystal is given priority, and a large group III nitride crystal having the (000-1) plane as the growth surface can be grown.

According to a fourth aspect of the present invention, in the method for producing a group III nitride crystal according to any one of the first to third aspects, the mode of crystal growth is the (0001) plane of the group III nitride. Or (000-1) from a mode in which epitaxial growth (seed crystal growth) occurs in a region substantially covered with a {10-11} plane or a plane in which (0001) plane and {10-11} plane are mixed. Since the mode is changed to the mode in which the columnar crystal whose surface is the growth surface is grown, the group III is compared with the case where the crystal growth is performed in the mode in which the columnar crystal whose growth surface is the (000-1) plane from the beginning of the crystal growth. Multinuclear generation and growth of miscellaneous crystals in a region substantially covered with a (0001) plane of nitride, a {10-11} plane, or a plane in which (0001) plane and {10-11} plane are mixed. Is suppressed, and the (000-1) plane is Columnar crystals of a small number of the group III nitride as a long surface grows. Therefore, a large group III nitride columnar crystal having a (000-1) plane as a growth surface can be grown.

In the invention described in claim 5 , in the crystal manufacturing method according to claim 4 , the mode of crystal growth is changed by increasing the amount of nitrogen dissolved in the melt, so that the mode of crystal growth can be easily changed. Can do. Accordingly, generation of miscellaneous crystals can be suppressed, and a large group III nitride columnar crystal having a (000-1) plane as a growth surface can be grown.

According to a sixth aspect of the present invention, in the crystal manufacturing method according to the fifth aspect , the amount of nitrogen dissolved in the melt is increased by increasing the pressure of nitrogen in contact with the melt at the gas-liquid interface. Since the pressure can be precisely controlled, the amount of dissolved nitrogen can be controlled and increased, and the mode of crystal growth can be easily changed. Accordingly, generation of miscellaneous crystals can be suppressed, and a large group III nitride columnar crystal having a (000-1) plane as a growth surface can be grown.

Further, in the invention of claim 7, wherein, in the crystal production method according to claim 4, wherein, by varying the alkali metal and the group III ratio of the metal in the melt, since changing the mode of the crystal growth, an alkali metal or III The mode of crystal growth can be easily changed by supplying a group metal. That is, since alkali metal can supply vapor from the gas phase, the amount ratio of alkali metal in the melt can be easily increased, and the mode can be changed to a mode in which columnar crystals grow. Accordingly, generation of miscellaneous crystals can be suppressed, and a large group III nitride columnar crystal having a (000-1) plane as a growth surface can be grown.

In the invention described in claim 8 , in the crystal manufacturing method according to claim 4 , the mode of crystal growth is changed by changing the temperature of the melt, and the temperature can be controlled precisely. Therefore, it is possible to control and change the mode of crystal growth. Accordingly, generation of miscellaneous crystals can be suppressed, and a large group III nitride columnar crystal having a (000-1) plane as a growth surface can be grown.

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

(First form)
A first aspect of the present invention is a group III nitride crystal growth method for growing a group III nitride crystal from a melt in which at least an alkali metal, a group III metal raw material, and nitrogen are dissolved. The (000-1) plane is defined as the growth plane from a region that is substantially covered with the (0001) plane, or the {10-11} plane, or the plane where the (0001) plane and the {10-11} plane are mixed. It is characterized by growing group III nitride crystals.

  In the first aspect of the present invention, in a Group III nitride crystal growth method for growing a Group III nitride crystal from a melt in which at least an alkali metal, a Group III metal raw material, and nitrogen are dissolved, The (000-1) plane is defined as the growth plane from a region that is substantially covered with the (0001) plane, or the {10-11} plane, or the plane where the (0001) plane and the {10-11} plane are mixed. Since the group III nitride crystal is grown, the growth in the normal direction of the (0001) plane or the {10-11} plane is delayed and the growth of the group III nitride crystal with the (000-1) plane as the growth plane is given priority. The group III nitride crystal having the (000-1) plane as the growth plane can be efficiently grown to a high quality and large size.

(Second form)
According to a second aspect of the present invention, there is provided the group-III nitride crystal growth method of the first aspect, wherein the group III nitride has a (0001) plane, a {10-11} plane, or a (0001) plane. The region that is substantially covered with the surface mixed with the {10-11} plane is characterized in that it is formed on the surface of the crystal made of group III nitride.

  In the second mode of the present invention, in the group III nitride crystal growth method of the first mode, the (0001) plane, the {10-11} plane, or the (0001) plane of the group III nitride The region that is substantially covered with the {10-11} plane is formed on the surface of the crystal made of group III nitride, and can easily be (0001) plane or {10-11} in the melt. Since a region covered with a surface can be formed, a large group III nitride crystal having a (000-1) plane as a growth surface can be easily grown.

(Third form)
According to a third aspect of the present invention, in the method for growing a group III nitride crystal according to the first aspect, the (0001) plane, the {10-11} plane, or the (0001) plane of the group III nitride The region that is substantially covered with the surface mixed with the {10-11} plane is a c-axis alignment film grown on the substrate.

  In the third aspect of the present invention, in the group III nitride crystal growth method of the first aspect, the (0001) plane, the {10-11} plane, or the (0001) plane of the group III nitride The region substantially covered with the {10-11} plane is a c-axis alignment film grown on the substrate, and has a large area by a simple film formation method such as MOCVD, MBE, HVPE, or sputtering. Since a c-axis alignment film can be produced, the c-axis alignment film is appropriately cut out and placed in the melt, so that it can be easily inserted into the melt at a low cost on the (0001) plane or the {10-11} plane. A covered region can be formed. Further, since it is possible to form a region covered with the (0001) plane or {10-11} plane over a large area, the growth of miscellaneous crystals is suppressed, and the (000-1) plane is used as the growth plane. The growth of the group III nitride crystal is given priority, and a large group III nitride crystal having the (000-1) plane as the growth surface can be grown.

(4th form)
According to a fourth aspect of the present invention, in the method for growing a group III nitride crystal according to any one of the first to third aspects, the (0001) plane of the group III nitride, the {10-11} plane, or , (0001) and {10-11} planes are almost covered with a region where crystal nuclei where the (000-1) plane is the growth plane are formed. It is a feature.

  In the fourth aspect of the present invention, in the group III nitride crystal growth method of any one of the first to third aspects, the (0001) plane of the group III nitride, the {10-11} plane, or In the region that is substantially covered with a plane in which the (0001) plane and the {10-11} plane are mixed, a region in which crystal nuclei whose (000-1) plane is a growth plane is formed is formed. Group III nitride crystal nuclei whose (000-1) plane is the growth plane can be easily generated, and large Group III nitride crystals having the (000-1) plane as the growth plane can be grown.

(5th form)
According to a fifth aspect of the present invention, in the group III nitride crystal growth method according to any one of the first to fourth aspects, the mode of crystal growth is changed to the (0001) plane of the group III nitride or {10 -11} plane, or (000-1) plane is a growth plane from a mode in which epitaxial growth (seed crystal growth) is performed in a region generally covered with a plane in which (0001) plane and {10-11} plane are mixed. It is characterized by changing to a mode in which the columnar crystal grows.

  In the fifth aspect of the present invention, in the group III nitride crystal growth method of any one of the first to fourth aspects, the mode of crystal growth is changed to the (0001) plane of the group III nitride or {10 -11} plane, or (000-1) plane is a growth plane from a mode in which epitaxial growth (seed crystal growth) is performed in a region generally covered with a plane in which (0001) plane and {10-11} plane are mixed. Since the columnar crystal is changed to the mode in which the columnar crystal grows, compared with the case of crystal growth in the mode in which the columnar crystal in which the (000-1) plane is the growth surface is grown from the beginning of the crystal growth, (0001 ) Surface, or {10-11} surface, or a region substantially covered with a (0001) surface mixed with a {10-11} surface, and the growth of miscellaneous crystals is suppressed. 000-1) A small number of I whose plane is the growth plane Group II nitride columnar crystals grow. Therefore, a large group III nitride columnar crystal having a (000-1) plane as a growth surface can be grown.

(Sixth form)
The sixth aspect of the present invention is characterized in that, in the crystal growth method of the fifth aspect, the mode of crystal growth is changed by increasing the amount of nitrogen dissolved in the melt.

  In the sixth aspect of the present invention, in the crystal growth method of the fifth aspect, the mode of crystal growth is changed by increasing the amount of nitrogen dissolved in the melt, so that the mode of crystal growth can be easily changed. it can. Accordingly, generation of miscellaneous crystals can be suppressed, and a large group III nitride columnar crystal having a (000-1) plane as a growth surface can be grown.

(7th form)
According to a seventh aspect of the present invention, in the crystal growth method of the sixth aspect, the amount of nitrogen dissolved in the melt is increased by increasing the pressure of nitrogen in contact with the melt at the gas-liquid interface. Yes.

  In the seventh aspect of the present invention, in the crystal growth method of the sixth aspect, the amount of nitrogen dissolved in the melt is increased by increasing the pressure of nitrogen in contact with the melt at the gas-liquid interface. Since the pressure can be precisely controlled, the amount of dissolved nitrogen can be controlled and increased, and the mode of crystal growth can be easily changed. Accordingly, generation of miscellaneous crystals can be suppressed, and a large group III nitride columnar crystal having a (000-1) plane as a growth surface can be grown.

(8th form)
The eighth mode of the present invention is characterized in that, in the crystal growth method of the fifth mode, the mode of crystal growth is changed by changing the amount ratio of the alkali metal and the group III metal in the melt.

  In the eighth embodiment of the present invention, in the crystal growth method of the fifth embodiment, the mode of crystal growth is changed by changing the amount ratio of the alkali metal and the group III metal in the melt. The mode of crystal growth can be easily changed by supplying metal. That is, since alkali metal can supply vapor from the gas phase, the amount ratio of alkali metal in the melt can be easily increased, and the mode can be changed to a mode in which columnar crystals grow. Accordingly, generation of miscellaneous crystals can be suppressed, and a large group III nitride columnar crystal having a (000-1) plane as a growth surface can be grown.

(9th form)
The ninth aspect of the present invention is characterized in that in the crystal growth method of the fifth aspect, the mode of crystal growth is changed by changing the temperature of the melt.

  In the ninth aspect of the present invention, in the crystal growth method of the fifth aspect, the mode of crystal growth is changed by changing the temperature of the melt, and the temperature can be precisely controlled. Therefore, it is possible to control and change the mode of crystal growth. Accordingly, generation of miscellaneous crystals can be suppressed, and a large group III nitride columnar crystal having a (000-1) plane as a growth surface can be grown.

(10th form)
A tenth aspect of the present invention is a group III nitride crystal produced by the group III nitride crystal growth method of any one of the first to ninth aspects.

  In the tenth aspect of the present invention, since it is a group III nitride crystal produced by the group III nitride crystal growth method of any one of the first to ninth aspects, it is lower than the conventional group III nitride crystal. High quality (low defect) and large group III nitride crystals can be provided at low cost.

(Eleventh form)
The eleventh aspect of the present invention is a semiconductor device using the group III nitride crystal of the tenth aspect.

  In the eleventh aspect of the present invention, since the semiconductor device uses the group III nitride crystal of the tenth aspect, a semiconductor device having higher performance and longer life than the conventional one can be provided.

  Example 1 relates to the first, second, fourth, fifth, sixth, seventh, and tenth aspects of the present invention. In Example 1, Na (sodium) is used as the alkali metal. GaN was grown as a group III nitride by using metal Ga (gallium) as a group III element material and nitrogen gas as a nitrogen material.

  Here, Na and Ga were previously held in a melt holding container as a mixed melt, and nitrogen was dissolved and supplied from the gas phase into the melt during crystal growth to grow GaN crystals.

  Then, by increasing the solubility of nitrogen during the growth, the epitaxial growth (seed crystal growth) mode was changed to the mode in which columnar crystals grew, and nucleation occurred on the (0001) plane of single crystal GaN that had been scratched. A GaN columnar crystal was grown using the (000-1) plane of the GaN crystal as a growth facet.

FIG. 1 is a diagram showing the correlation among the nitrogen partial pressure P (N ₂ ), the melt temperature (T), and the growth mode. In FIG. 1, the horizontal axis represents the reciprocal of temperature (T), and the vertical axis represents the nitrogen partial pressure P (N ₂ ).

Depending on the nitrogen partial pressure P (N ₂ ) and the melt temperature (T), the growth modes are A: plate crystal growth mode, B: columnar crystal growth mode, C: epitaxial growth (seed crystal growth) mode, D: decomposition ( Dissolution).

This is considered to be a result of the amount of nitrogen dissolved in the melt necessary for crystal growth at a certain temperature depending on the nitrogen partial pressure P (N ₂ ). In the region A, the amount of dissolved nitrogen is large and the plate crystal grows, and in the region D, the amount of dissolved nitrogen is small and the crystal is decomposed (dissolved).

In Example 1, the nitrogen dissolution amount is increased by increasing the nitrogen partial pressure P (N ₂ ) from S1 to S3.

  FIG. 2 is a diagram (cross-sectional view) illustrating a configuration example of the crystal growth apparatus according to the first embodiment. The crystal growth apparatus of FIG. 2 is provided with a melt holding vessel 12 for holding a melt 24 containing an alkali metal and a group III metal in a closed reaction vessel 11 made of stainless steel and performing crystal growth. Yes.

  The melt holding container 12 can be removed from the reaction container 11. The material of the melt holding container 12 is BN (boron nitride).

Further, in the crystal growth apparatus of FIG. 2, it is possible to fill the internal space 23 of the reaction vessel 11 with nitrogen (N ₂ ) gas serving as a nitrogen source and adjust the nitrogen (N ₂ ) pressure in the reaction vessel 11. A gas supply pipe 14 is attached through the reaction vessel 11. Here, the pressure of the nitrogen gas can be adjusted by the pressure control device 16.

  The gas supply pipe 14 is branched by a valve 18, and Ar gas can be introduced into the internal space 23 of the reaction vessel 11. Here, the pressure of Ar gas can be adjusted by the pressure control device 19.

  The total pressure in the reaction vessel 11 is monitored by a pressure gauge 22.

  A heater 13 is installed outside the reaction vessel 11.

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

  Hereinafter, a method for growing GaN in Example 1 using the crystal growth apparatus of FIG. 2 will be described.

  First, the reaction vessel 11 is separated from the crystal growth apparatus at the valve 21 and placed in a glove box in an Ar atmosphere. Next, the GaN single crystal 26 is placed in the BN melt holding container 12. The GaN single crystal 26 is inserted with the (0001) plane facing up. Further, the (0001) plane of the GaN single crystal 26 is scratched at one place.

  Next, Ga is added to the melt holding container 12 as a group III metal raw material, and sodium (Na) is added as an alkali metal. Here, the amount of Na and Ga was such that the ratio (amount ratio) of Na in the melt 24 was Na / (Na + Ga) = 0.7.

  Next, the melt holding container 12 is placed on the melt holding container holding base 25 and installed 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 external atmosphere.

  Next, the reaction vessel 11 is taken out of the glove box and incorporated in the crystal growth apparatus. That is, the reaction vessel 11 is installed at a predetermined position with a heater 13 and connected to a nitrogen and argon gas supply line 14 at a valve 21 portion.

  Next, the valve 18 is opened, and Ar gas is put into the reaction vessel 11. At this time, the pressure was adjusted to 4 MPa by the pressure controller 19.

  Next, the heater 13 is energized with the pressure kept constant, and the temperature of the melt 24 is increased from room temperature (27 ° C.) to the crystal growth temperature in one hour. The crystal growth temperature was 800 ° C.

  Next, the valve 18 was closed, the valve 15 was opened, and nitrogen gas was introduced so that the nitrogen partial pressure was 1 MPa.

  Growth is started in a growth mode in which epitaxial growth (seed crystal growth) is performed at a growth temperature of 800 ° C. and a nitrogen pressure of 1 MPa. This condition corresponds to the condition of S1 in FIG. 1, and the crystal is grown in a growth mode in which epitaxial growth is performed. At this time, GaN crystal nuclei are formed in the scratched portion of the GaN single crystal 26 regardless of the crystal orientation of the surface of the GaN single crystal 26. GaN crystal nuclei that contact the (000-1) plane with the melt are also formed therein.

  After growing for 50 hours under these conditions, the nitrogen pressure was increased to 4 MPa over 30 hours. This condition corresponds to the condition of S3 in FIG. When the nitrogen pressure increases, the crystal growth mode becomes a columnar crystal growth mode. In this growth mode, since the growth rate in the normal direction of the (0001) plane and {10-11} plane is slow, the GaN single crystal 26 has a scratched portion than the (0001) plane growth of the GaN single crystal. GaN crystal nuclei in contact with the melt on the (000-1) plane in which nuclei are generated preferentially grow to form columnar crystals of GaN. Crystal growth was continued for another 200 hours.

  After crystal growth is completed, a colorless and transparent c-axis with the (000-1) plane and the {10-10} plane grown in the [000-1] direction from the scratched portion of the GaN single crystal 26 as growth facet planes Columnar GaN 27 with a length in the direction extending to 5 mm or more was growing.

  Example 2 relates to the first, third, fourth, fifth, eighth, and tenth aspects of the present invention. In Example 2, Na (sodium) is used as the alkali metal, and the group III is used. GaN was crystal-grown as a group III nitride using metal Ga (gallium) as the elemental raw material and nitrogen gas as the nitrogen raw material.

  Here, Na and Ga were previously held in a melt holding container as a mixed melt, and nitrogen was dissolved and supplied from the gas phase into the melt during crystal growth to grow GaN crystals.

  Then, by increasing the Na amount ratio in the melt during the growth (by supplying Na vapor), the epitaxial growth (seed crystal growth) mode is changed to the mode in which columnar crystals grow and exposed to the GaN template substrate. A GaN columnar crystal was grown using the (000-1) plane of the GaN crystal nucleated on the sapphire that had been allowed to grow as a growth facet.

  The crystal growth method of Example 2 will be described below.

  FIG. 3 is a diagram (sectional view) illustrating a configuration example of the crystal growth apparatus according to the second embodiment.

  In the second embodiment, the same apparatus as in the first embodiment is used. However, in the second embodiment, as shown in FIG. Is different from the first embodiment in that Na 31 held in the Na holding container 30 is evaporated and Na is supplied into the melt holding container 12 by vapor.

  In Example 2, a template substrate 28 in which a GaN thin film (c-axis alignment film) is epitaxially grown on a c-plane sapphire substrate by MOCVD is placed at the bottom of the melt holding container 12. The template substrate 28 is placed with the (0001) face of the GaN thin film facing up. The template substrate 28 is previously provided with a portion where the sapphire substrate is exposed by etching a part of the epitaxially grown GaN thin film.

  In Example 2, the initial amount ratio of Na in the melt 24 was set to 0.4, the growth temperature was set to 800 ° C., the partial pressures of nitrogen gas and Ar gas were set to 4 MPa, and growth was started. Steam was supplied from the phase to increase the Na amount ratio of the melt 24 during growth.

  When the amount ratio of Na in the melt 24 is 0.4, the epitaxial growth mode is set, so that GaN is epitaxially grown on the GaN thin film of the template substrate 28. At this time, GaN crystal nuclei are formed in the exposed portion of the sapphire substrate regardless of the crystal orientation of the GaN thin film of the template substrate 28. GaN crystal nuclei that contact the (000-1) plane with the melt are also formed therein.

  When Na is supplied with vapor and the Na amount ratio in the melt 24 increases, the crystal growth mode becomes a columnar crystal growth mode. In this growth mode, the growth rate in the normal direction of the (0001) plane and the {10-11} plane is slow, so that the sapphire substrate is exposed at a portion where the sapphire substrate is exposed rather than the (0001) plane growth of the GaN thin film of the template substrate 28. GaN crystal nuclei in contact with the melt on the generated (000-1) plane preferentially grow to form columnar crystals of GaN. In this state, crystal growth was continued for 300 hours.

  After crystal growth is completed, the transparent substrate is colorless and transparent, with the (000-1) plane and the {10-10} plane grown in the [000-1] direction from the exposed portion of the sapphire substrate by etching of the template substrate 28 as growth facet planes. Columnar GaN 29 having a length of 5 mm or more in the c-axis direction was growing.

  Example 3 relates to the first, second, fourth, fifth, ninth, and tenth aspects of the present invention. In Example 3, Na (sodium) is used as the alkali metal, and the group III is used. GaN was crystal-grown as a group III nitride using metal Ga (gallium) as the elemental raw material and nitrogen gas as the nitrogen raw material.

  Here, Na and Ga were previously held in a melt holding container as a mixed melt, and nitrogen was dissolved and supplied from the gas phase into the melt during crystal growth to grow GaN crystals.

  Then, by reducing the melt temperature during the growth, the mode is changed from the epitaxial growth (seed crystal growth) mode to the mode in which the columnar crystal grows, and the GaN single crystal placed on the template substrate with the (0001) plane of GaN facing up is changed. A GaN columnar crystal is grown using the (000-1) plane of the crystal as a growth facet.

As described above, FIG. 1 is a diagram showing the correlation between the nitrogen partial pressure P (N ₂ ), the melt temperature (T), and the growth mode. In the third embodiment, the melt temperature is changed from S1 to S2. By lowering, the growth mode is changed from the mode of epitaxial growth to the mode of growing columnar crystals.

  The crystal growth method of Example 3 will be described below.

  FIG. 4 is a diagram (sectional view) illustrating a configuration example of the crystal growth apparatus according to the third embodiment. In Example 3, the same crystal growth apparatus as in Example 1 is used.

  In Example 3, a template substrate 28 obtained by epitaxially growing a GaN thin film on a c-plane sapphire substrate by MOCVD is placed at the bottom of the melt holding container 12. Here, the template substrate 28 is placed with the (0001) plane of GaN facing up.

  A GaN single crystal 32 is installed on the template substrate 28. Here, the GaN single crystal 32 is placed with the (000-1) face up.

  In Example 3, the amount ratio of Na in the melt 24 was 0.7, the nitrogen pressure was 3 MPa, the growth was started from 875 ° C., and the temperature was lowered to 800 ° C. after 50 hours. Crystal growth was continued for 300 hours.

  When the nitrogen pressure is 3 MPa and the temperature is 875 ° C., the temperature grows epitaxially (seed crystal growth), but when the temperature is lowered to 800 ° C., the growth mode changes and the columnar crystal whose (000-1) plane becomes the growth facet plane Enter growth mode. The GaN single crystal 32 begins to grow as a columnar crystal. In this growth mode, since the growth rate in the normal direction of the (0001) plane and the {10-11} plane is slow, the GaN columnar crystal 32 (33) grows preferentially over the growth of the template substrate.

  After the completion of crystal growth, the GaN single crystal 32 was grown into a columnar GaN 33 having a colorless and transparent length in the c-axis direction extended to 5 mm or more.

  Example 4 relates to the first, second, fourth, fifth, ninth, and tenth aspects of the present invention. In Example 4, Na (sodium) is used as the alkali metal, and the group III is used. GaN was crystal-grown as a group III nitride using metal Ga (gallium) as the elemental raw material and nitrogen gas as the nitrogen raw material.

  Here, Na and Ga are previously held in a melt holding container as a mixed melt, nitrogen is dissolved and supplied from the gas phase into the melt during crystal growth, and a GaN thin film is epitaxially grown on the template substrate. Crystal was grown.

  Then, by raising the template substrate in the melt during the GaN crystal growth, the mode was changed from the epitaxial growth (seed crystal growth) mode to the column crystal growth mode, and the GaN columnar crystal was grown.

  The crystal growth method of Example 4 will be described below.

  FIG. 5 is a diagram (sectional view) illustrating a configuration example of the crystal growth apparatus according to the fourth embodiment. In Example 4, the same crystal growth apparatus as in Example 1 is used.

  In Example 4, a template substrate 28 obtained by epitaxially growing a GaN thin film by MOCVD on a c-plane sapphire substrate is placed at the bottom of the melt holding container 12. Here, the template substrate 28 is placed with the (0001) plane of GaN facing up. The template substrate 28 can be moved up and down in the melt 24 by moving the substrate moving jig 35 up and down.

  In Example 4, the amount ratio of Na in the melt 24 is 0.7, the growth temperature is 800 ° C., the nitrogen pressure is 4 MPa, the template substrate 28 is placed on the bottom of the melt holding container 12, and GaN Start crystal growth. At the bottom of the melt holding container 12, the supply of nitrogen is small, and GaN grows epitaxially (seed crystal growth). After 50 hours, the template substrate 28 moves to the upper part of the melt 24. When the template substrate 28 is moved upward, the supply of nitrogen increases, so that new crystal nuclei are generated and GaN crystal growth continues in a mode in which columnar crystals grow. In this growth mode, since the growth rate in the normal direction of the (0001) plane and the {10-11} plane is slow, the GaN columnar crystals 34 grow preferentially over the growth of the template substrate 28.

  Crystal growth was continued for 300 hours. After crystal growth is completed, the length in the colorless and transparent c-axis direction, with the (000-1) plane and the {10-10} plane grown from a part of the template substrate 28 in the [000-1] direction as growth facet planes. Columnar GaN 34 having a length of 5 mm or more was growing.

  Example 5 is an example (semiconductor laser) of the semiconductor device according to the eleventh aspect of the present invention.

  FIG. 6 is a perspective view of the semiconductor laser of Example 5. FIG. 7 is a sectional view taken along a plane perpendicular to the light emitting direction of the semiconductor laser of FIG.

  The semiconductor laser of Example 5 is manufactured with a group III nitride semiconductor multilayer structure laminated on an n-type GaN substrate 50 formed of the GaN crystal of the tenth form.

That is, referring to FIGS. 6 and 7, a semiconductor laser stacked structure 400 includes an n-type GaN layer 40 and an n-type Al _0.2 Ga _0.8 N clad layer on an n-type GaN substrate 50 having a thickness of 250 μm. 41, 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 It has a structure in which a _0.8 N clad layer 45 and a p-type GaN cap layer 46 are sequentially laminated, and is produced by crystal growth by MOCVD.

The stacked structure 400 is etched leaving the p-type GaN cap layer 46 to the middle of the p-type Al _0.2 Ga _0.8 N cladding layer 45 in a stripe shape, and the current confined ridge waveguide structure 51 is produced. ing. The current confinement ridge waveguide structure 51 is formed along the [10-10] direction of the GaN substrate.

In addition, an insulating film 47 made of SiO ₂ is formed on the surface of the laminated structure 400. An opening is formed in the insulating film 47 on the ridge 51, and a p-side ohmic electrode 48 is formed on the surface of the p-type GaN cap layer 46 exposed through 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 can be formed by depositing Ti / Al, and the p-side ohmic electrode 48 can be 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 (10-10) plane perpendicular to the current confinement ridge waveguide structure 51 along the [10-10] direction of the GaN substrate.

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

  In the semiconductor lasers of FIGS. 6 and 7, carriers are injected into the active layer 43 by injecting current into the p-side ohmic electrode 48 and the n-side ohmic electrode 49, causing light emission and light amplification, and optical resonance. Laser light 411 and 412 are emitted from the vessel surfaces 401 and 402.

  The semiconductor laser of Example 5 was manufactured by crystal growth of a laser structure on a substrate different from Group III nitride, such as a conventional sapphire substrate, or was manufactured by vapor phase growth or other methods. Compared to those produced on a GaN substrate, the laser structure laminated on the substrate has low crystal defects and high crystal quality, and thus has a long life even under high output operation.

  In Examples 1 to 4 described above, Group III nitride is obtained by using Na (sodium) as an alkali metal, using metal Ga (gallium) as a Group III element material, and using nitrogen gas as a nitrogen source. Although GaN is grown as a crystal, the present invention is not limited to these.

  That is, in the present invention, the group III nitride means a compound of one or more kinds of group III metals and nitrogen selected from gallium, aluminum, indium, and boron, and is limited to GaN. is not.

  In addition, Na (sodium) or K (potassium) is usually used as the alkali metal, but Li (lithium), other alkali metals, or a mixture of a plurality of types of alkali metals can also be used. .

  In addition, the Group III metal raw material is not particularly limited, and a Group III metal, a Group III nitride, a substance containing a Group III element as a constituent element, and the like can be used as appropriate.

  Further, the raw material of nitrogen is not particularly limited, and a substance containing nitrogen as a constituent element can be used.

  Group III nitrides or other nitrogen compounds may be dissolved in the melt, or may be dissolved in the melt from the gas phase as nitrogen gas or other nitrogen compound gas.

  Further, in the crystal growth method of the sixth aspect, the method for increasing the amount of dissolved nitrogen in the melt is not limited to the method for increasing the nitrogen partial pressure in Example 1, and other methods are also used. can do. For example, the amount of nitrogen dissolved in the melt can be increased by adding impurities, and the mode of crystal growth can be easily changed.

  In the present invention, the semiconductor device is not limited to the semiconductor laser of Example 5, and can be configured as a light emitting diode, a light receiving device, an electronic device, or any other semiconductor device.

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

It is a figure showing the correlation of nitrogen partial pressure, melt temperature, and growth mode. 1 is a diagram (sectional view) showing a configuration example of a crystal growth apparatus according to Example 1. FIG. FIG. 6 is a diagram (cross-sectional view) showing a configuration example of a crystal growth apparatus according to Example 2. FIG. 6 is a diagram (cross-sectional view) illustrating a configuration example of a crystal growth apparatus according to a third embodiment. FIG. 10 is a diagram (cross-sectional view) showing a configuration example of a crystal growth apparatus according to Example 4. 10 is a perspective view of a semiconductor laser according to Example 5. FIG. It is sectional drawing in a surface perpendicular | vertical to the light emission direction of the semiconductor laser of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 Reaction container 12 Melt holding container 13 Heater 14 Gas supply pipe 15, 18, 21 Valve 16, 19 Pressure regulator 17 Nitrogen supply pipe 20 Argon supply pipe 22 Pressure gauge 23 Internal space 24 Melt 25 Melt holding container holding stand 26, 32 GaN single crystal 27, 29, 33, 34 GaN columnar crystal 28 Template substrate 30 Na holding container 31 Na
35 substrate moving jig 40 n-type GaN layer 41 n-type Al _0.2 Ga _0.8 N clad 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 light 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 400 Laminated structure 401, 402 Optical resonator surface 411, 412 Laser light

Claims (8)

In a Group III nitride crystal manufacturing method of growing a Group III nitride crystal from a melt in which at least an alkali metal, a Group III metal raw material, and nitrogen are dissolved, the (0001) plane of the Group III nitride , {10-11} plane, or, (0001) plane and the {10-11} plane and is generally part of the area covered by a plane mixed, the group III nitride crystal in contact with the melt of (000-1) plane by nucleation, crystal manufacturing method of a group III nitride, characterized in that for the nucleation is not a group III nitride crystal (000-1) plane as the growth plane growth. 2. The method for producing a group III nitride crystal according to claim 1, wherein the (0001) plane, or the {10-11} plane, or the (0001) plane and the {10-11} plane of the group III nitride are mixed. A method for producing a group III nitride crystal, characterized in that the region substantially covered by the surface is formed on the surface of the group III nitride crystal. 2. The method for producing a group III nitride crystal according to claim 1, wherein the (0001) plane, or the {10-11} plane, or the (0001) plane and the {10-11} plane of the group III nitride are mixed. A method for producing a group III nitride crystal, wherein the region substantially covered with the surface is a c-axis oriented film grown on a substrate. The method for producing a group III nitride crystal according to any one of claims 1 to 3 , wherein the mode of crystal growth is a (0001) plane of a group III nitride or a {10-11} plane. Alternatively, a columnar crystal having a (000-1) plane as a growth plane grows from a mode of epitaxial growth (seed crystal growth) in a region that is substantially covered with a plane in which the (0001) plane and the {10-11} plane are mixed. A method for producing a crystal of a group III nitride, characterized in that the mode is changed to a mode. In the crystal production method according to claim 4, wherein, by increasing the nitrogen solubility of the melt, crystal manufacturing method of a group III nitride, wherein changing the mode of the crystal growth. In the crystal production method according to claim 5, wherein, by increasing the pressure of the nitrogen in contact with the melt and air-liquid interface, the method of crystal manufacturing III-nitride, characterized in that to increase the nitrogen solubility of the melt . In the crystal production method according to claim 4, wherein, by varying the amount ratio of the alkali metal and the group III metal in the melt, the crystal production method of a group III nitride, wherein changing the mode of the crystal growth. In the crystal production method according to claim 4, wherein, by varying the temperature of the melt, crystal manufacturing method of a group III nitride, wherein changing the mode of the crystal growth.

Images