JP3991823B2 - Group III nitride semiconductor crystal, method for producing the same, group III nitride semiconductor epitaxial wafer - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a group III nitride semiconductor crystal having good crystallinity used for manufacturing a light emitting diode (LED), a laser diode (LD), an electronic device, and the like, and a manufacturing method thereof. In particular, the present invention relates to a method for producing a group III nitride semiconductor crystal that can be suitably used for epitaxially growing a group III nitride semiconductor crystal having good crystallinity on a sapphire substrate.
[0002]
[Prior art]
Group III nitride semiconductors have a direct transition type band gap of energy corresponding to the visible light to ultraviolet light region, and can emit light with high efficiency, and thus are commercialized as LEDs and LDs. In addition, at the heterojunction interface between aluminum gallium nitride (AlGaN) and gallium nitride (GaN), a two-dimensional electron layer due to the piezoelectric effect that is characteristic of group III nitride semiconductors is developed. It has the potential to obtain characteristics that cannot be obtained with group III compound semiconductors.
[0003]
However, group III nitride semiconductors have a nitrogen dissociation pressure of up to 2000 atmospheres at the growth temperature of the single crystal, so that the growth of the single crystal is difficult and is used for epitaxial growth like other group III-V compound semiconductors. At present, it is difficult to use the group III nitride semiconductor single crystal substrate as the substrate. Therefore, as a substrate used for epitaxial growth, sapphire (Al ₂ O _Three ) A substrate made of a different material such as a single crystal or silicon carbide (SiC) single crystal is used.
[0004]
There is a large lattice mismatch between the substrate made of these different materials and the group III nitride semiconductor crystal epitaxially grown thereon. For example, sapphire (Al ₂ O _Three ) And gallium nitride (GaN) and 16% lattice mismatch between SiC and gallium nitride. In general, when such a large lattice mismatch exists, it is difficult to directly epitaxially grow a crystal on a substrate, and a crystal with good crystallinity cannot be obtained even if grown. Therefore, when a group III nitride semiconductor crystal is epitaxially grown on a sapphire single crystal substrate or SiC single crystal substrate by metal organic chemical vapor deposition (MOCVD), a low-temperature buffer layer composed of aluminum nitride (AlN) or AlGaN. In general, a method of first depositing a layer called III on a substrate and epitaxially growing a group III nitride semiconductor crystal on the substrate at a high temperature has been generally performed (see, for example, Patent Document 1 and Patent Document 2).
[0005]
In addition to the growth method using the low-temperature buffer layer described above, there is also a method in which an AlN layer grown in a high temperature range of about 900 ° C. to 1200 ° C. is formed on a substrate and gallium nitride is grown thereon. (For example, refer to Patent Document 3 and Non-Patent Document 1).
[0006]
Under such circumstances, the present applicant supplies a group III material on the substrate with a V / III ratio of 1000 or less (including a case where the V / III ratio is 0) to form a group III nitride semiconductor. Developed a method for producing a group III nitride semiconductor crystal having a first step and then a second step of vapor-growing a group III nitride semiconductor crystal on the substrate using a group III material and a nitrogen material. The manufacturing process of the group III nitride semiconductor epitaxial wafer was shortened, the cost was reduced, and the uniformity of the epitaxial layer within the wafer surface was improved.
[0007]
On the other hand, as a method for reducing the dislocation of a semiconductor crystal, a method is known in which irregularities are formed on a substrate surface and a semiconductor crystal is grown thereon. For example, in a group III nitride semiconductor, a stripe-shaped groove is formed on the surface of a sapphire substrate, a buffer layer made of GaN is formed on the substrate at a low temperature, and a group III nitride semiconductor crystal is epitaxially grown on the substrate at a high temperature. It has been shown that the dislocation density of the epitaxial layer can be reduced by doing so (see, for example, Patent Document 4 and Non-Patent Document 2).
[0008]
[Patent Document 1]
Japanese Patent No. 3026087
[Patent Document 2]
Japanese Patent Laid-Open No. 4-297003
[Patent Document 3]
JP-A-9-64477
[Patent Document 4]
JP 2002-164296 A
[Non-Patent Document 1]
P. Kung, et al., Applied Physics Letters, 1995, Vol. 66, p. 2958
[Non-Patent Document 2]
K. Tadatomo, et al., Japanese Journal of Applied Physics, 2001, vol. 40, p. L583-L585
[0009]
[Problems to be solved by the invention]
The present invention uses a method of growing a semiconductor crystal using a substrate whose surface is processed into an uneven shape, and can form a high-quality group III nitride semiconductor crystal on the substrate in a process with relatively little temperature change. A method for producing a group III nitride semiconductor crystal is provided. In particular, the present invention provides a method for producing a group III nitride semiconductor crystal capable of epitaxially growing a high-quality group III nitride semiconductor crystal on a sapphire substrate whose surface has been processed into an uneven shape. The present invention also provides a high-quality group III nitride semiconductor crystal produced by the above production method and a group III nitride semiconductor epitaxial wafer using the group III nitride semiconductor crystal.
[0010]
[Means for Solving the Problems]
The present invention
(1) The V / III ratio is set on a substrate whose surface has been processed into an irregular shape. 0 to 100 A first step of supplying a group III source and forming a group III nitride semiconductor, and then a second step of vapor-phase-growing a group III nitride semiconductor crystal on the substrate using the group III source and nitrogen source. The manufacturing method of the group III nitride semiconductor crystal which has these processes.
(2) The method for producing a group III nitride semiconductor crystal as described in (1) above, wherein the irregularities on the substrate surface are striped.
(3) The concave and convex widths of the concave and convex portions on the substrate surface are each 3 μm or less, and the depth of the concave and convex portions is 2/3 or less of the concave portion width. A method for producing a group III nitride semiconductor crystal.
(4) Sapphire (Al ₂ O ₃ The method for producing a group III nitride semiconductor crystal as described in (1) to (3) above, wherein
(5) The method for producing a group III nitride semiconductor crystal as described in (1) to (4) above, wherein the group III raw material supplied in the first step contains at least Al.
(6) The Group III nitride semiconductor crystal according to any one of (1) to (5) above, wherein the Group III nitride semiconductor crystal to be vapor-grown on the substrate in the second step is made of GaN. Production method.
(7) In the second step, ammonia (NH ₃ The method for producing a group III nitride semiconductor crystal as described in (1) to (6) above, wherein
(8) In at least one of the first step and the second step, the vapor phase growth is performed by a metal organic chemical vapor deposition method (MOCVD method). A method for producing a group III nitride semiconductor crystal of
(9) The method for producing a group III nitride semiconductor crystal as described in (1) to (8) above, wherein the group III nitride semiconductor formed in the first step is an island-shaped crystal lump.
(10) The method for producing a group III nitride semiconductor crystal according to the above (1) to (9), wherein the group III nitride semiconductor formed in the first step is a columnar crystal.
(11) The method for producing a group III nitride semiconductor crystal according to (10), wherein the columnar crystal is attached on the substrate such that a side surface thereof is substantially perpendicular to the substrate surface.
It is.
[0011]
The present invention also provides:
(12) In the method of manufacturing a group III nitride semiconductor crystal, a first group III nitride semiconductor is manufactured on a substrate processed into an uneven shape, and a second group III nitride semiconductor crystal is manufactured thereon. A method for producing a Group III nitride semiconductor crystal, wherein the Group III nitride semiconductor is an aggregate of columnar crystals or island crystals.
(13) The method for producing a group III nitride semiconductor crystal according to (12), wherein the columnar crystal is attached on the substrate such that a side surface thereof is substantially perpendicular to the substrate surface.
It is.
[0012]
The present invention also provides:
(14) A group III nitride semiconductor crystal produced by the method described in (1) to (13) above.
It is.
[0013]
The present invention also provides:
(15) A group III nitride semiconductor epitaxial wafer in which a group III nitride semiconductor crystal layer is further formed on the group III nitride semiconductor crystal according to (14).
It is.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
In the method for producing a group III nitride semiconductor crystal according to the present invention, a V / III ratio is set on a substrate whose surface is processed to be uneven. 0 to 100 A first step of supplying a group III source and forming a group III nitride semiconductor, and then a second step of vapor-phase-growing a group III nitride semiconductor crystal on the substrate using the group III source and nitrogen source. It has the process of. By the method for producing a group III nitride semiconductor crystal having the first and second steps described above, a group III nitride semiconductor crystal having good crystallinity can be formed on the substrate.
[0015]
Compared to a conventional method for producing a group III nitride semiconductor crystal using a low-temperature buffer layer, the method of the present invention can reduce the substrate temperature, and the process is short and the power consumption is small. As a result, the manufacturing process can be shortened and the cost can be reduced. Further, since the change in the temperature of the substrate is small, the warp of the substrate can be minimized, and the uniformity of the epitaxial layer in the wafer surface is improved.
[0016]
In the present invention, glass, SiC, Si, GaAs, GaP, GaN, AlN, sapphire, or the like can be used as the substrate. Here, in the present invention, in particular, the substrate is sapphire (Al ₂ O _Three ) Is desirable. If the substrate is sapphire, there is an advantage that a high-quality substrate can be obtained at low cost. As the plane orientation of the sapphire substrate, m-plane, a-plane, c-plane, etc. can be used, among which c-plane ((0001) plane) is preferable, and the vertical axis of the substrate surface is in a specific direction from <0001> direction. It is desirable to be inclined. The substrate used in the present invention is preferably subjected to a pretreatment such as organic cleaning or etching before being used in the first step, because the surface state of the substrate can be kept constant.
[0017]
Various shapes such as a stripe shape and a hexagonal column shape can be used as the uneven shape formed on the substrate surface in the present invention. Among these, when the unevenness is formed in a stripe shape, there is an advantage that processing is easy. Further, the arrangement of the projections and depressions can be made to coincide with the surface orientation of the sapphire substrate or can be deliberately shifted. The concave and convex concave width and convex width or concave and convex depth formed on the substrate surface can be arbitrarily selected. However, in order to flatten the surface of the group III nitride semiconductor crystal grown thereon, the recess width and the protrusion width are each 3 μm or less, and the depth of the recesses is 2/3 or less of the recess width. Is desirable.
[0018]
In the present invention, the group III raw material supplied in the first step is trimethylaluminum, triethylaluminum, tertiarybutylaluminum, trimethylgallium, triethylgallium, tertiarybutylgallium, trimethylindium, triethylindium, tertiarybutylindium, cyclopenta. Dienyl indium can be used. In addition, when the Group III material contains at least Al, such as trimethylaluminum, triethylaluminum, and tertiarybutylaluminum, the nitride containing aluminum has a high decomposition temperature, so that it does not easily decompose or sublimate even at a high temperature. This is particularly preferable because it has an effect that the crystal grows easily.
[0019]
In the first step of the present invention, a Group III nitride semiconductor can be formed by supplying Group V materials such as ammonia, alkylamines, hydrazines, etc. simultaneously with the Group III materials. In this invention, V / III ratio at the time of supplying a group III raw material in a 1st process shall be 1000 or less. More preferably, it is 500 or less, More preferably, it is 100 or less. By setting the V / III ratio in this way, there is an effect that a compound semiconductor crystal having an excess of metal is easily formed on the substrate.
[0020]
In the first step of the present invention, the V / III ratio may be 0, that is, the supply amount of the group V raw material may be 0. However, in this case, ammonia (NH) is added before the second step even if the V group material to be intentionally supplied is zero. _Three ) Or the like to form a group III nitride semiconductor, or a group III nitride semiconductor is formed by nitrogen supplied from decomposition of deposits adhering to the reactor wall, top plate, susceptor, etc. It is necessary to In the latter case, it is necessary to appropriately control the composition and amount of deposits adhering to the reactor wall, top plate, susceptor, and the like. Specifically, the baking time and temperature of the reaction furnace after the growth is finished, or the operation itself is stopped. In addition, a process called thermal cleaning, which is a general technique for growth using the low temperature buffer method, adjusts time and temperature, or stops performing itself.
As an example, after the previous growth, baking was not performed, and after thermal cleaning was performed at 600 ° C. for 10 minutes, the substrate was set at 1000 ° C. as a first step, and a group III raw material metal-containing compound As a result, the group V raw material supply amount was set to 0, and crystal growth was performed as the second step. As a result, a good group III nitride semiconductor crystal could be produced.
[0021]
Another condition for obtaining a good group III nitride semiconductor crystal even when the V / III ratio in the first step is 0 is as follows. ₂ N at a temperature close to 1000 ° C ₂ There is a method of using a nitrogen (N) atom generated by slight decomposition of as a nitrogen source.
[0022]
In the first step of the present invention, a single gas or a mixed gas such as hydrogen, a rare gas, or nitrogen can be used as the atmospheric gas. As described above, when nitrogen is used as the atmospheric gas, the nitrogen gas may also function as a source gas.
[0023]
Moreover, the pressure of the atmosphere at the time of performing a 1st process is 1000-1x10. ^Five Pa can be used. Preferably 1x10 ^Five Pa or less, more preferably 1 × 10 ^Four Pa or less. When the pressure in the first step is low, the surface of the produced metal-rich group III nitride semiconductor layer becomes flat, and the surface of the second group III nitride semiconductor layer grown thereon is also easily flattened. There is.
[0024]
In the present invention, the temperature of the substrate when performing the first step and the temperature of the substrate when performing the second step are not particularly defined, but the temperature of the substrate when performing the first step is the following second. It is desirable that the temperature is the same as or higher than the temperature of the substrate when performing this step. When the first step is performed at a temperature equal to or higher than the temperature of the substrate when the second step is performed, the organic metal compound molecules that are the group III source gas are efficiently decomposed and crystals are formed. There is an advantage that impurities due to undecomposed alkyl groups are not mixed therein.
[0025]
The group III nitride semiconductor formed in the first step of the present invention is made to be an island-like crystal lump. That is, an island-shaped crystal having a width of about 1 nm to 500 nm and a height of about 5 nm to 100 nm. By making the group III nitride into island-like crystals, metal crystals and droplets At the interface between the substrate and the island crystal It is thought that the effect that it becomes easy to remain | survive and it functions as a layer with more metal excess is acquired. In addition, because the crystal growth rate differs between the island-like crystal and the substrate, The density of threading dislocations is reduced by the effect of selective growth, and a better crystal can be produced.
[0026]
Alternatively, the group III nitride semiconductor formed in the first step of the present invention is made to be columnar crystals. That is, a columnar crystal in which columnar particles having a width of about 0.1 nm to 100 nm and a height of about 10 nm to 500 nm are assembled. By forming the group III nitride into a columnar crystal, a large number of grain boundaries are generated in the crystal layer, so that metal crystals and droplets are likely to remain there, and the effect of functioning as a metal-excess layer can be obtained. .
[0027]
In the second step of the present invention, a group III nitride semiconductor crystal is vapor-phase grown on the substrate on which the group III nitride semiconductor is formed in the first step, using a group III material and a nitrogen material. It is preferable that the group III nitride semiconductor crystal to be grown is GaN because it is easy to form a flat GaN crystal epitaxial layer because GaN is likely to grow two-dimensionally among group III nitride semiconductors. Once a flat and good epitaxial layer is made of GaN, it becomes easy to produce semiconductor device structures using Group III nitride semiconductor crystal layers of various compositions thereon.
[0028]
In the first step, the second step, or both steps of the present invention, a metal organic chemical vapor deposition method (MOCVD method) or a vapor phase epitaxy method (VPE method) is used as the vapor phase growth method. be able to. Among these, the MOCVD method is preferable because the rate of decomposition of the group III raw material can be adjusted and the growth rate is suitable. Further, according to the MOCVD method, various element structures having good characteristics can be produced on the crystal without taking out the substrate on which the flat group III nitride semiconductor crystal is formed out of the reaction furnace. .
[0029]
The temperature of the substrate when the group III nitride semiconductor crystal is grown by MOCVD in the second step is 950 ° C. to 1200 ° C., and the atmospheric pressure is 1000 Pa to 1 × 10 6. ^Five Pa is preferable.
[0030]
The nitrogen raw material used in the second step is ammonia (NH _Three ) Is a gas and is easy to handle, and is preferred because it is widely distributed in the market and inexpensive. As the group III raw material, trimethylaluminum, triethylaluminum, tertiarybutylaluminum, trimethylgallium, triethylgallium, tertiarybutylgallium, trimethylindium, triethylindium, tertiarybutylindium, cyclopentadienylindium can be used. . Further, the V / III ratio when the group III nitride semiconductor crystal is grown in the second step is preferably 500 to 20000, and more preferably 2000 to 20000.
[0031]
In the present invention, the method for producing a group III nitride semiconductor crystal having the first and second steps described above enables high uniformity on a substrate processed into a concavo-convex shape by a power saving process in a short time. A group III nitride semiconductor crystal with good properties can be formed. Accordingly, by forming a group III nitride semiconductor crystal layer on the group III nitride semiconductor crystal, a group III nitride having a laminated structure used for manufacturing a light emitting diode, a laser diode, or an electronic device, etc. A semiconductor epitaxial wafer can be produced.
[0032]
【Example】
Hereinafter, the present invention will be specifically described based on examples.
Example 1
A method for producing a gallium nitride compound semiconductor crystal according to the present invention will be described.
In Example 1, a sapphire substrate having a (0001) surface as the surface was used. The concavo-convex shape formed on the surface of the sapphire substrate is a stripe shape in which a concave line having a width of 3 μm and a depth of 1.5 μm and a convex space having a width of 3 μm are alternately arranged in a straight line. did. The direction of the stripe was parallel to the <1-100> direction of the sapphire substrate. As a first step on the sapphire substrate on which the unevenness is formed, a gas containing a gas obtained by mixing a vapor of trimethylaluminum (TMAl) and a vapor of trimethylgallium (TMGa) at a molar ratio of 1: 2, and ammonia (NH _Three In the second step, TMGa and ammonia were circulated to grow gallium nitride, and a GaN layer made of gallium nitride crystals was formed on the sapphire substrate processed into an uneven shape. The V / III ratio under the conditions used in the first step is about 85.
[0033]
The sample including the GaN layer was produced by the following procedure using the MOCVD method.
First, before introducing a sapphire substrate whose surface is processed to be uneven, the deposits adhering to the inside of the reactor in the previous growth performed with the same apparatus are heated and nitrided in a gas containing ammonia and hydrogen. Therefore, it was made difficult to disassemble further. After waiting for the reactor to cool to room temperature, the sapphire substrate was introduced into a quartz reactor installed in the RF coil of the induction heater. The sapphire substrate was placed on a carbon susceptor for heating in a glove box substituted with nitrogen gas. After introducing the sample, the reaction furnace was purged with nitrogen gas.
After flowing nitrogen gas for 10 minutes, the induction heater was activated, and the substrate temperature was raised to 1170 ° C. over 10 minutes. While maintaining the substrate temperature at 1170 ° C., the substrate surface was left to stand for 9 minutes while flowing hydrogen gas and nitrogen gas to perform thermal cleaning of the substrate surface.
During thermal cleaning, hydrogen carrier gas was supplied to the piping of the container (bubbler) containing trimethylgallium (TMGa) and the container (bubbler) containing trimethylaluminum (TMAl) connected to the reactor. Distributed and started bubbling. The temperature of each bubbler was adjusted to be constant using a thermostatic bath for adjusting the temperature. The vapors of TMGa and TMAl generated by bubbling were circulated through the piping to the abatement apparatus together with the carrier gas until the growth process started, and were discharged out of the system through the abatement apparatus.
After completion of the thermal cleaning, the nitrogen carrier gas valve was closed and the gas supply into the reactor was hydrogen only.
[0034]
After switching the carrier gas, the temperature of the substrate was lowered to 1150 ° C. After confirming that the temperature was stabilized at 1150 ° C., the valve of the ammonia piping was opened, and distribution of ammonia into the furnace was started. Subsequently, the TMGa and TMAl piping valves were switched at the same time, and a gas containing TMGa and TMAl vapor was supplied into the reaction furnace to start the first step of depositing the group III nitride semiconductor on the sapphire substrate. The mixing ratio of TMGa and TMAl to be supplied was adjusted so that the molar ratio was 2: 1 with a flow rate controller installed in the piping to be bubbled, and the amount of ammonia was adjusted so that the V / III ratio was 85.
After the treatment for 6 minutes, the TMGa and TMAl piping valves were simultaneously switched to stop supplying gas containing TMGa and TMAl vapor into the reactor. Subsequently, the supply of ammonia was also stopped and maintained for 3 minutes.
[0035]
After annealing for 3 minutes, the valve of the ammonia gas pipe was switched, and the supply of ammonia gas into the furnace was started again. As it was, ammonia was circulated for 4 minutes. Meanwhile, the flow rate of the flow regulator of TMGa piping was adjusted. After 4 minutes, the TMGa valve was switched to start supplying TMGa together with ammonia into the furnace, and growth of GaN was started.
After the GaN layer was grown for about 3 hours, the TMGa piping valve was switched to stop supplying the raw material to the reactor and stop the growth.
After completing the growth of the GaN layer, the energization to the induction heating heater was stopped, and the temperature of the substrate was lowered to room temperature over 20 minutes. During the temperature drop, the atmosphere in the reactor was composed of ammonia, nitrogen and hydrogen in the same way as during the growth, but after confirming that the temperature of the substrate reached 300 ° C., the supply of ammonia and hydrogen was stopped. Thereafter, the substrate temperature was lowered to room temperature while flowing nitrogen gas, and the sample was taken out into the atmosphere.
[0036]
Sample obtained by forming a metal-rich group III nitride semiconductor layer having a columnar structure on a sapphire substrate whose surface is processed to be uneven by the above steps, and epitaxially growing a 6 μm-thick GaN layer undoped thereon Was made. The taken-out substrate had a slightly blackish color like metal, indicating that the group III nitride semiconductor layer formed at the interface with the substrate was of stoichiometry with excess metal. The growth surface of the GaN layer was a mirror surface.
[0037]
Next, X-ray rocking curve (XRC) measurement of the undoped GaN layer grown by the above method was performed. The measurement was performed on the (0002) plane which is a symmetric plane and the (10-12) plane which is an asymmetric plane, using a Cuβ ray X-ray generation source as a light source. In general, in the case of a gallium nitride-based compound semiconductor, the XRC spectrum half width of the (0002) plane is an index of crystal flatness (mosaicity), and the XRC spectrum half width of the (10-12) plane is the dislocation density (twist). It becomes an index.
As a result of this measurement, the undoped GaN layer produced by the method of the present invention showed a half width of 220 seconds in the (0002) plane measurement and a half width of 300 seconds in the (10-12) plane.
[0038]
The outermost surface of the GaN layer was observed using a general atomic force microscope (AFM). As a result, no growth pits were observed on the surface, and a surface with good morphology was observed.
[0039]
When the cross section of this sample was observed with a transmission electron microscope (TEM), an AlN film having many grain boundaries in the direction substantially perpendicular to the substrate surface was observed at the interface between the sapphire substrate and the gallium nitride layer. The film thickness was about 60 nm, and the distance between the grain boundaries was 5 nm to 50 nm. This layer is considered to be a layer composed of an assembly of vertically long columnar crystals. According to elemental analysis, this film contained about 20% Ga.
[0040]
(Example 2)
In Example 2, an experiment was performed using the same process as in Example 1, except that the time for growing a group III nitride semiconductor in the first process was changed to 2 minutes. Also in this case, the surface of the taken-out wafer was specular. The color was colorless and transparent.
[0041]
When the cross section of this sample was observed with a transmission electron microscope (TEM), it was confirmed that an island-shaped AlN crystal lump was present at the interface between the sapphire substrate and the gallium nitride layer. According to elemental analysis, this crystal mass contained about 15% Ga.
[0042]
The same growth as in this experimental process was performed, and the sample was taken out of the growth furnace by stopping the process before the growth of the gallium nitride layer, and the surface morphology was observed with an atomic force microscope (AFM). However, aluminum nitride crystal lumps having a rounded hexagonal shape and a trapezoidal cross section were scattered on the sapphire surface.
[0043]
(Example 3)
In Example 3, a sapphire substrate whose surface was processed to be uneven without performing baking before growth after the previous experiment was introduced into the reactor, and as a first step, trimethylaluminum (TMAl ) Was circulated and TMGa and ammonia were circulated as a second step to grow gallium nitride, and a GaN layer made of gallium nitride crystals was formed on the sapphire substrate. Although the intended V / III ratio in the first step of this embodiment is 0, a small amount of N atoms is supplied onto the substrate due to decomposition of deposits adhering to the reactor wall and top plate. ing.
[0044]
The sample including the GaN layer was produced by the following procedure using the MOCVD method.
First, the same sapphire substrate as in Example 1 was introduced into a quartz reactor installed in an RF coil of an induction heater. The sapphire substrate was placed on a carbon susceptor for heating in a glove box replaced with nitrogen gas. After introducing the sample, the reaction furnace was purged with nitrogen gas.
After flowing nitrogen gas for 10 minutes, the induction heater was activated, and the substrate temperature was raised to 600 ° C. over 10 minutes. The substrate temperature was kept at 600 ° C. and left for 9 minutes while flowing hydrogen gas.
In the meantime, hydrogen carrier gas was circulated through the piping of the vessel (bubbler) containing trimethylgallium (TMGa), which is the raw material connected to the reactor, and the vessel (bubbler) containing trimethylaluminum (TMAl). Started. The temperature of each bubbler was adjusted to be constant using a thermostatic bath for adjusting the temperature. The vapors of TMGa and TMAl generated by bubbling were circulated through the piping to the abatement apparatus together with the carrier gas until the growth process started, and were discharged out of the system through the abatement apparatus.
Thereafter, the nitrogen carrier gas valve was closed and supply of hydrogen gas into the reaction furnace was started.
[0045]
After switching the carrier gas, the temperature of the substrate was raised to 1150 ° C. After confirming that the temperature was stabilized at 1150 ° C., the valve of TMAl piping was switched, and a gas containing TMAl vapor was supplied into the reactor. At this time, it is considered that a small amount of N was supplied to the substrate simultaneously with TMAl due to decomposition of the deposits adhering to the wall of the reactor and the top plate.
After the treatment for 9 minutes, the TMAl piping valves were simultaneously switched to stop the supply of the gas containing TMAl vapor into the reaction furnace, and held there for 3 minutes.
[0046]
After annealing for 3 minutes, the ammonia gas piping valve was switched and the supply of ammonia gas into the furnace was started.
As it was, ammonia was circulated for 4 minutes. Meanwhile, the flow rate of the flow regulator of TMGa piping was adjusted. After 4 minutes, the TMGa valve was switched to start supplying TMGa together with ammonia into the furnace, and growth of GaN was started.
After the GaN layer was grown for about 3 hours, the TMGa piping valve was switched to stop supplying the raw material to the reactor and stop the growth.
After completing the growth of the GaN layer, the energization to the induction heating heater was stopped, and the temperature of the substrate was lowered to room temperature over 20 minutes. During the temperature drop, the atmosphere in the reactor was composed of ammonia, nitrogen and hydrogen in the same way as during the growth, but after confirming that the temperature of the substrate reached 300 ° C., the supply of ammonia and hydrogen was stopped. Thereafter, the substrate temperature was lowered to room temperature while flowing nitrogen gas, and the sample was taken out into the atmosphere.
[0047]
Through the above steps, a metal-rich group III nitride semiconductor layer having a columnar structure was formed on the sapphire substrate in the first step, and an undoped GaN layer having a thickness of 6 μm was formed thereon. . The substrate taken out has a slightly blackish color like metal as in Example 1, and the group III nitride semiconductor formed at the interface with the substrate is of stoichiometry with excess metal. Was showing. The growth surface was a mirror surface.
[0048]
Next, XRC measurement of the undoped GaN layer grown by the above method was performed. The measurement was performed on the (0002) plane which is a symmetric plane and the (10-12) plane which is an asymmetric plane, using a Cuβ ray X-ray generation source as a light source. As a result of the measurement, the undoped GaN layer produced by the method of the present invention showed a half-value width of 260 seconds in the (0002) plane measurement and a half-value width of 300 seconds in the (10-12) plane.
[0049]
The outermost surface of the GaN layer was observed using a general atomic force microscope (AFM). As a result, no growth pits were observed on the surface, and a surface with good morphology was observed.
[0050]
When the cross section of this sample was observed with a transmission electron microscope (TEM), an AlN film having many grain boundaries in the direction substantially perpendicular to the substrate surface was observed at the interface between the sapphire substrate and the gallium nitride layer. The film thickness was about 20 nm, and the distance between the grain boundaries was 10 nm to 50 nm. This layer is considered to be a layer composed of an assembly of vertically long columnar crystals. According to elemental analysis, this film contained about 5% Ga.
[0051]
(Example 4)
In this example 4, as in the first example, on the sapphire substrate whose surface is processed to be uneven, as a first step, the vapor ratio of trimethylaluminum (TMAl) and trimethylindium (TMIn) is set to a molar ratio. A gas containing a gas mixed at a ratio of 2: 1 is circulated using nitrogen as a carrier gas, and then, as a second step, TMGa and ammonia are circulated to grow gallium nitride. From the gallium nitride crystal on the sapphire substrate, A GaN layer was produced. In the first step, it is considered that the nitrogen gas as the carrier gas is slightly decomposed to supply a small amount of nitrogen atoms.
[0052]
The sample including the GaN layer was produced by the following procedure using the MOCVD method.
First, before introducing the sapphire substrate processed into a concavo-convex shape, the adhering matter adhering to the inside of the reaction furnace in the previous growth performed in the same apparatus is heated and nitrided in a gas containing ammonia and hydrogen, I tried not to disassemble. After waiting for the reactor to cool to room temperature, the sapphire substrate was introduced into a quartz reactor installed in the RF coil of the induction heater. The sapphire substrate was placed on a carbon susceptor for heating in a glove box substituted with nitrogen gas. After introducing the sample, the reaction furnace was purged with nitrogen gas.
After flowing nitrogen gas for 10 minutes, the induction heater was activated, and the substrate temperature was raised to 1170 ° C. over 10 minutes. While maintaining the substrate temperature at 1170 ° C., the substrate surface was left to stand for 9 minutes while flowing hydrogen gas to perform thermal cleaning of the substrate surface.
While performing thermal cleaning, a vessel (bubbler) containing trimethylgallium (TMGa) and a vessel containing trimethylaluminum (TMAl) and a trimethylindium (TMIn) material connected to the reactor Hydrogen carrier gas was circulated through the piping of the container (bubbler) contained, and bubbling was started. The temperature of each bubbler was adjusted to be constant using a thermostatic bath for adjusting the temperature. The vapors of TMGa, TMAl, and TMIn generated by bubbling were circulated through the piping to the detoxifying device together with the carrier gas until the growth process started, and were discharged out of the system through the detoxifying device.
After completion of the thermal cleaning, the hydrogen carrier gas valve was closed, and instead, the nitrogen gas supply valve was opened, and the gas supply into the reaction furnace was nitrogen.
[0053]
After switching the carrier gas, the temperature of the substrate was lowered to 1150 ° C. After confirming that the temperature was stabilized at 1150 ° C., the TMIn and TMAl piping valves were switched simultaneously, and a gas containing TMIn and TMAl vapor was supplied into the reactor, and as a first step on the sapphire substrate A process for depositing a group III nitride semiconductor was started. The mixing ratio of TMIn and TMAl to be supplied was adjusted to a molar ratio of 1: 2 with a flow controller installed in the piping to be bubbled.
After the treatment for 6 minutes, the TMIn and TMAl piping valves were simultaneously switched to stop the supply of the gas containing the vapors of TMIn and TMAl into the reaction furnace, and held there for 3 minutes.
[0054]
After annealing for 3 minutes, the ammonia gas piping valve was switched and the supply of ammonia gas into the furnace was started.
As it was, ammonia was circulated for 4 minutes. Meanwhile, the flow rate of the flow regulator of TMGa piping was adjusted. After 4 minutes, the TMGa valve was switched to start supplying TMGa together with ammonia into the furnace, and growth of GaN was started.
After the GaN layer was grown for about 1 hour, the TMGa piping valve was switched, the supply of the raw material to the reactor was terminated, and the growth was stopped.
After completing the growth of the GaN layer, the energization to the induction heating heater was stopped, and the temperature of the substrate was lowered to room temperature over 20 minutes. During the temperature drop, the atmosphere in the reactor was composed of ammonia, nitrogen and hydrogen in the same way as during the growth, but after confirming that the temperature of the substrate reached 300 ° C., the supply of ammonia and hydrogen was stopped. Thereafter, the substrate temperature was lowered to room temperature while flowing nitrogen gas, and the sample was taken out into the atmosphere.
[0055]
A sample in which a metal-rich group III nitride semiconductor layer having a columnar structure is formed on a sapphire substrate whose surface is processed to be uneven by the above steps, and an undoped GaN layer having a thickness of 6 μm is formed thereon. Was made. The substrate taken out was colorless and transparent. The growth surface was a mirror surface.
[0056]
Next, XRC measurement of the undoped GaN layer grown by the above method was performed. The measurement was performed on the (0002) plane which is a symmetric plane and the (10-12) plane which is an asymmetric plane, using a Cuβ ray X-ray generation source as a light source.
As a result of this measurement, the undoped GaN layer produced by the method of the present invention showed a half width of 350 seconds in the (0002) plane measurement and a half width of 400 seconds in the (10-12) plane.
[0057]
The outermost surface of the GaN layer was observed using a general atomic force microscope (AFM). As a result, no growth pits were observed on the surface, and a surface with good morphology was observed.
[0058]
When the cross section of this sample was observed with a transmission electron microscope (TEM), an AlInN film having many grain boundaries in the direction substantially perpendicular to the substrate surface was observed at the interface between the sapphire substrate and the gallium nitride layer. The film thickness was about 10 nm, and the distance between the grain boundaries was 5 nm to 50 nm. This layer is considered to be a layer composed of an assembly of vertically long columnar crystals.
[0059]
(Example 5)
In Example 5, a method for producing a gallium nitride compound semiconductor light emitting device using the method for producing a group III nitride semiconductor crystal of the present invention will be described.
In this example 5, a flat low Si-doped GaN crystal is produced using the same conditions as in example 3, and a group III nitride semiconductor crystal layer is further formed thereon, and finally the semiconductor light emission shown in FIG. An epitaxial wafer having an epitaxial layer structure for an element was produced. In the epitaxial wafer shown in FIG. 1, a metal-excess AlN layer 8 having a columnar structure is formed on a sapphire substrate 9 having a c-plane by the same growth method as described in Example 3, and then in order from the substrate side. 1 × 10 ¹⁷ cm ^-3 2 μm low Si-doped GaN layer 7 having an electron concentration of 1 × 10 ¹⁹ cm ^-3 1.8 μm high Si-doped GaN layer 6 having an electron concentration of 1 × 10 ¹⁷ cm ^-3 100-inch InGaN cladding layer 5 having an electron concentration of 6 GaN barrier layers 3 starting from the GaN barrier layer 3 and ending on the GaN barrier layer 3 and having a layer thickness of 70 と and 5 layers of non-doped Multi-quantum well structure 20 and 30 ノ ン non-doped Al formed by alternately laminating InGaN well layers 4 _0.2 Ga _0.8 N diffusion prevention layer 2, 8 × 10 ¹⁷ cm ^-3 A 0.15 μm Mg-doped GaN layer 1 having a positive hole concentration is stacked.
[0060]
Fabrication of an epitaxial wafer having an epitaxial layer structure for the above-described semiconductor light emitting device was performed by the following procedure using MOCVD.
The same procedure as described in Example 3 was used until the AlN layer 8 having a columnar structure was formed on the sapphire substrate 9.
After forming the AlN layer 8 having a columnar structure on the sapphire substrate, the flow rate of the flow rate regulator of the TMGa pipe was adjusted while continuing the circulation of ammonia. Si ₂ H ₆ Started distribution to the pipe. Until the growth of the low Si-doped GaN layer begins, Si ₂ H ₆ Was circulated through the piping to the abatement device together with the carrier gas, and discharged out of the system through the abatement device. Then TMGa and Si ₂ H ₆ TMGa and Si by switching the valve ₂ H ₆ Then, the growth of the low-Si-doped GaN layer 7 was started, and the low-Si-doped GaN layer 7 was grown for about 2 hours and 30 minutes. SiH _Four The amount to be distributed is examined in advance, and the electron concentration of the low Si-doped GaN layer 7 is 1 × 10. ¹⁷ cm ^-3 It adjusted so that it might become.
In this way, a low Si-doped GaN layer 7 having a thickness of 5 μm was formed.
[0061]
Further, a high Si doped n-type GaN layer 6 was grown on the low Si doped GaN layer 7. After the growth of the low Si-doped GaN layer 7, TMGa and Si are grown for 1 minute. ₂ H ₆ The supply to the furnace was stopped. Meanwhile, Si ₂ H ₆ The distribution volume of was changed. The amount to be circulated has been examined in advance, and the electron concentration of the highly Si-doped GaN layer 6 is 1 × 10 6. ¹⁹ cm ^-3 It adjusted so that it might become. Ammonia continued to be fed into the furnace at the same flow rate.
After stopping for 1 minute, TMGa and Si ₂ H ₆ The supply was resumed and the growth continued for 1 hour. By this operation, a highly Si-doped GaN layer 6 having a thickness of 1.8 μm was formed.
[0062]
After growing the highly Si-doped GaN layer 6, TMGa and Si ₂ H ₆ The supply of these raw materials into the furnace was stopped by switching the valve. While the ammonia was circulated as it was, the valve was switched to switch the carrier gas from hydrogen to nitrogen. Thereafter, the temperature of the substrate was lowered from 1160 ° C. to 820 ° C.
While waiting for the temperature change in the furnace, Si ₂ H ₆ The supply amount of was changed. The amount to be circulated is examined in advance, and the electron concentration of the Si-doped InGaN cladding layer 5 is 1 × 10 6. ¹⁷ cm ^-3 It adjusted so that it might become. Ammonia continued to be fed into the furnace at the same flow rate.
In addition, distribution of carrier gas to a bubbler of trimethylindium (TMIn) and triethylgallium (TEGa) has been started in advance. Si ₂ H ₆ The gas and TMIn and TEGa vapors generated by bubbling were circulated through the piping to the abatement device together with the carrier gas until the cladding layer growth process started, and were discharged out of the system through the abatement device.
After that, waiting for the state in the furnace to stabilize, TMIn, TEGa and Si ₂ H ₆ These valves were switched at the same time to start supplying these raw materials into the furnace. Supply was continued for about 10 minutes, and a Si-doped InGaN cladding layer 5 having a thickness of 100 mm was formed on the highly Si-doped GaN layer 6.
Then TMIn, TEGa and Si ₂ H ₆ The supply of these raw materials was stopped.
[0063]
Next, a multiple quantum well structure 20 composed of a barrier layer 3 made of GaN and a well layer 4 made of InGaN was produced. In manufacturing the multiple quantum well structure 20, the GaN barrier layer 3 was first formed on the Si-doped InGaN cladding layer 5, and the InGaN well layer 4 was formed on the GaN barrier layer. After repeating this structure five times, the sixth GaN barrier layer 3 was formed on the fifth InGaN well layer 4 and both sides of the multiple quantum well structure 20 were constituted by the GaN barrier layers 3.
That is, after the growth of the Si-doped InGaN cladding layer 5 is completed, the supply of the group III material is stopped for 30 seconds, and the substrate temperature, the pressure in the furnace, the flow rate and type of the carrier gas are kept as they are, and the TEGa valve The TEGa was supplied into the furnace. Ammonia continued to be fed into the furnace at the same flow rate. After supplying TEGa for 7 minutes, the valve was switched again to stop the TEGa supply and the growth of the GaN barrier layer 3 was completed. Thereby, the GaN barrier layer 3 having a thickness of 70 mm was formed.
[0064]
During the growth of the GaN barrier layer 3, the flow rate of TMIn flowing through the piping to the exclusion equipment is adjusted to be twice the molar flow rate compared to the growth of the cladding layer. Oita.
After stopping the growth of the GaN barrier layer 3, the supply of the group III raw material is stopped for 30 seconds, and the TEGa and TMIn valves are switched while the substrate temperature, the pressure in the furnace, the flow rate and type of the carrier gas remain unchanged. TEGa and TMIn were supplied into the furnace. Ammonia continued to be fed into the furnace at the same flow rate. After supplying TEGa and TMIn for 2 minutes, the valve was switched again to stop the supply of TEGa and TMIn, and the growth of the InGaN well layer 4 was completed. As a result, an InGaN well layer 4 having a thickness of 20 mm was formed.
[0065]
After the growth of the InGaN well layer 4 is finished, the supply of the group III raw material is stopped for 30 seconds, and then the substrate temperature, the pressure in the furnace, the flow rate and type of the carrier gas are maintained, and the TEGa is supplied into the furnace. The GaN barrier layer 3 was grown again.
Such a procedure was repeated five times to produce five GaN barrier layers 3 and five InGaN well layers 4. Further, the GaN barrier layer 3 was formed on the last InGaN well layer 4.
[0066]
On the multiple quantum well structure 20 ending with this GaN barrier layer 3, non-doped Al _0.2 Ga _0.8 N diffusion prevention layer 2 was produced.
Distribution of carrier gas to a bubbler of trimethylaluminum (TMAl) was started in advance. The TMAl vapor generated by bubbling was circulated to the piping to the detoxifying apparatus together with the carrier gas until the growth process of the diffusion preventing layer 2 started, and was discharged out of the system through the detoxifying apparatus.
[0067]
Waiting for the pressure in the furnace to stabilize, the valves for TEGa and TMAl were switched, and the supply of these raw materials into the furnace was started. Then, after growing for about 3 minutes, the supply of TEGa and TMAl is stopped, and non-doped Al _0.2 Ga _0.8 The growth of the N diffusion preventing layer 2 was stopped. Thereby, non-doped Al having a thickness of 30 mm. _0.2 Ga _0.8 N diffusion prevention layer 2 was formed.
[0068]
This non-doped Al _0.2 Ga _0.8 An Mg-doped GaN layer 1 was stacked on the N diffusion prevention layer 2.
Stop supply of TEGa and TMAl, and undoped Al _0.2 Ga _0.8 After the growth of the N diffusion preventing layer 2 was completed, the temperature of the substrate was raised to 1060 ° C. over 2 minutes. Furthermore, the carrier gas was changed to hydrogen.
In addition, biscyclopentadienyl magnesium (Cp ₂ Distribution of carrier gas to the Mg) bubbler was started. Cp generated by bubbling ₂ Until the growth process of the Mg-doped GaN layer 1 was started, the Mg vapor was circulated to the piping to the abatement apparatus together with the carrier gas, and was discharged out of the system through the abatement apparatus.
[0069]
Change the temperature and pressure and wait for the pressure in the furnace to stabilize, then TMGa and Cp ₂ The supply of these raw materials into the furnace was started by switching the Mg valve. Cp ₂ The amount of Mg to be distributed has been examined in advance, and the hole concentration of the Mg-doped GaN layer 1 is 8 × 10. ¹⁷ cm ^-3 It adjusted so that it might become. After that, after growing for about 6 minutes, TMGa and Cp ₂ The supply of Mg was stopped, and the growth of the Mg-doped GaN layer 1 was stopped. As a result, an Mg-doped GaN layer 1 having a thickness of 0.15 μm was formed.
[0070]
After the growth of the Mg-doped GaN layer 1 was completed, energization of the induction heater was stopped, and the temperature of the substrate was lowered to room temperature over 20 minutes. During the temperature drop from the growth temperature to 300 ° C., the carrier gas in the reactor is composed only of nitrogen and has a capacity of 1% NH. _Three Distributed. Then, when it was confirmed that the substrate temperature reached 300 ° C., NH _Three Was stopped, and the atmosphere gas was only nitrogen. After confirming that the substrate temperature was lowered to room temperature, the wafer was taken out into the atmosphere.
[0071]
By the procedure as described above, an epitaxial wafer having an epitaxial layer structure for a semiconductor light emitting device was produced. Here, the Mg-doped GaN layer 1 showed p-type without annealing for activating p-type carriers.
[0072]
Next, a light-emitting diode, which is a kind of semiconductor light-emitting element, was manufactured using an epitaxial wafer in which an epitaxial layer structure was stacked on the sapphire substrate. FIG. 2 shows a plan view of the electrode structure of the semiconductor light emitting device manufactured in Example 5. FIG.
About the produced wafer, it consists only of the p electrode bonding pad 12 with the structure which laminated | stacked titanium, aluminum, and gold in order from the surface side on the surface 14 of the Mg dope GaN layer 1 by well-known photolithography, and Au joined to it. A translucent p-electrode 13 was formed to produce a p-side electrode.
Further, dry etching is performed on the wafer to expose a portion 11 where the n-side electrode of the highly Si-doped GaN layer 6 is formed, and an n-electrode 10 composed of four layers of Ni, Al, Ti, and Au is produced in the exposed portion. did. Through these operations, an electrode having a shape as shown in FIG. 2 was produced on the wafer.
[0073]
For the wafer on which the p-side and n-side electrodes were formed in this way, the back surface of the sapphire substrate was ground and polished to form a mirror-like surface. Thereafter, the wafer was cut into 350 μm square chips and placed on a TO-18 stem so that the electrodes were on top, and gold wires were connected to the electrodes to form bare chip light emitting diodes.
When a forward current was passed between the p-side and n-side electrodes of the bare chip light-emitting diode produced as described above, the forward voltage at a current of 20 mA was 3.5V. Moreover, when light emission was observed through the translucent electrode of the p side, the light emission wavelength was 400 nm and the light emission output showed 4.5 mW. Such characteristics of the light-emitting diode were obtained with no variation for light-emitting diodes manufactured from almost the entire surface of the manufactured wafer.
[0074]
【The invention's effect】
When the method for producing a group III nitride semiconductor crystal of the present invention is used, since the temperature rises and falls, the time required for the process is short and the power consumption is small. As a result, the manufacturing process can be shortened and the cost can be reduced. Further, since the change in temperature is small, the warpage of the substrate can be minimized, and the uniformity of the epitaxial layer in the wafer plane is improved. Furthermore, by using a substrate whose surface has been processed into a concavo-convex shape, a low dislocation of the group III nitride semiconductor crystal can be realized.
As a result, when a semiconductor light emitting device using a gallium nitride compound semiconductor is manufactured by using the method for manufacturing a group III nitride semiconductor crystal of the present invention, a light emitting diode having high brightness and substantially uniform characteristics in a wafer surface is obtained. Can be produced.
[0075]
In addition, according to the method described in the present invention, a crystal having a low columnarity and a low dislocation density and a device structure formed thereon having good device characteristics as compared with a conventional method using AlN grown at a high temperature. Can be produced.
[Brief description of the drawings]
FIG. 1 is a schematic view showing a cross section of an epitaxial wafer for a semiconductor light emitting device according to Example 5 of the present invention.
FIG. 2 is a plan view showing an electrode structure of a semiconductor light emitting device according to Example 5 of the invention.
[Explanation of symbols]
1 Mg-doped GaN layer
2 Al _0.2 Ga _0.8 N diffusion prevention layer
3 GaN barrier layer
4 InGaN well layers
5 InGaN cladding layer
6 High Si-doped GaN layer
7 Low Si-doped GaN layer
8 AlN layer
9 Sapphire substrate
10 n electrode
11 Portion for forming the n-side electrode of the highly Si-doped GaN layer
12 p-electrode bonding pad
13 Translucent p-electrode
14 Surface of Mg-doped GaN layer
20 Multiple quantum well structure

Claims (12)

A first step of supplying a group III source material with a V / III ratio of 0 or more and 100 or less and forming a group III nitride semiconductor on a substrate whose surface has been processed into an uneven shape, and then a group III source material and a nitrogen source And a second step of vapor-phase-growing a group III nitride semiconductor crystal on the substrate, wherein the group III nitride semiconductor formed in the first step has a width of 1 nm to 500 nm and a height of 5 nm to 100 nm. A method for producing a group III nitride semiconductor crystal, wherein A first step of supplying a group III source material with a V / III ratio of 0 or more and 100 or less and forming a group III nitride semiconductor on a substrate whose surface has been processed into an uneven shape, and then a group III source material and a nitrogen source And a second step of vapor-phase-growing a group III nitride semiconductor crystal on the substrate, wherein the group III nitride semiconductor formed in the first step has a width of 0.1 nm to 100 nm and a height of 10 nm. A method for producing a group III nitride semiconductor crystal, which is a columnar crystal of ˜500 nm. The method for producing a group III nitride semiconductor crystal according to claim 1 or 2, wherein the irregularities on the substrate surface are striped. The recess width and the projection width of the unevenness of the substrate surface and 3μm or less, respectively, III according to any one of claims 1 to 3, characterized in that the depth of the irregularities and less than 2/3 of the recess width A method for producing a group nitride semiconductor crystal. The method for producing a group III nitride semiconductor crystal according to any one of claims 1 to 4, wherein the use of sapphire (Al 2 _{O 3)} as the substrate. It said first group III material supplied in step, method for producing a group III nitride semiconductor crystal according to any one of claims 1 to 5, characterized in that it comprises at least Al. The group III nitride semiconductor crystal according to any one of claims 1 to 6 , wherein the group III nitride semiconductor crystal to be vapor-phase grown on the substrate in the second step is made of GaN. Method. Wherein in a second step, the manufacturing method of a group III nitride semiconductor crystal according to any one of claims 1 to 7, characterized in that ammonia (NH ₃₎ as a nitrogen source. In at least one of the first step or the second step, vapor deposition metal organic chemical vapor deposition method according to one of claims 1 to 8, characterized in that in (MOCVD method) A method for producing a group III nitride semiconductor crystal. 3. The method for producing a group III nitride semiconductor crystal according to claim 2, wherein the columnar crystal is attached on the substrate such that a side surface thereof is substantially perpendicular to the substrate surface. A group III nitride semiconductor crystal produced by the method according to any one of claims 1 to 10. A group III nitride semiconductor epitaxial wafer in which a group III nitride semiconductor crystal layer is further formed on the group III nitride semiconductor crystal according to claim 11.

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