JP3656606B2 - Method for producing group III nitride semiconductor crystal - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
In the present invention, a group III nitride semiconductor with good crystallinity used for manufacturing a light emitting diode (LED), a laser diode (LD), an electronic device or the like (hereinafter, the group III nitride semiconductor is represented by InGaAlN). .) It relates to a crystal 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 these dissimilar substrates 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 a SiC single crystal substrate by metal organic chemical vapor deposition (MOCVD), Japanese Patent No. 3026087 and Japanese Patent Application Laid-Open No. 4-297703 As shown, generally, a method called a low-temperature buffer layer made of aluminum nitride (AlN) or AlGaN is first deposited on a substrate, and a group III nitride semiconductor crystal is epitaxially grown on the layer at a high temperature. Has been done.
[0005]
In addition to the growth method using the low-temperature buffer layer described above, for example, P.I. Kung, et al. , Applied Physics Letters, 66 (1995), 2958. Also disclosed is 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 on the AlN layer as disclosed in JP-A-9-64477.
[0006]
[Problems to be solved by the invention]
When sapphire is used as the substrate, the low-temperature buffer layer is generally formed as follows.
First, the sapphire substrate is heated to a high temperature of 1000 ° C. to 1200 ° C. in a MOCVD growth apparatus to remove the oxide film on the surface. Thereafter, the temperature of the growth apparatus is lowered to a temperature of about 400 to 600 ° C., the V / III ratio is set to 3000 to 10,000, and the organometallic raw material and the nitrogen source are simultaneously supplied to deposit the low temperature buffer layer. . Here, the V / III ratio refers to the number of moles of a molecule containing a group III element and the number of moles of a molecule containing a group V element flowing through a reaction furnace when a group III-V compound semiconductor crystal is grown by MOCVD. Is the ratio. For example, when growing gallium nitride using TMGa and ammonia, it is the ratio of the number of moles of TMGa circulating in the reactor to the number of moles of ammonia. Thereafter, the supply of the organometallic raw material is stopped, the temperature of the growth apparatus is raised again, and a heat treatment called crystallization of the low-temperature buffer layer is performed, and then the target group III nitride semiconductor crystal is epitaxially grown.
[0007]
At 400 ° C. to 600 ° C., which is the deposition temperature of the low temperature buffer layer, thermal decomposition of the organometallic raw material used as the raw material and the nitrogen source, particularly ammonia used as the nitrogen source is insufficient. Therefore, many defects are included in the low-temperature buffer layer as deposited at such a low temperature. In addition, in order to react the raw material at a low temperature, a polymerization reaction occurs between the organic metal alkyl group of the raw material and an undecomposed nitrogen source. It is.
[0008]
In order to eliminate these defects and impurities, a heat treatment process called crystallization of the low-temperature buffer layer is performed. In the crystallization process of the buffer layer, the low-temperature buffer layer containing many impurities and defects is heat-treated at a high temperature close to the epitaxial growth temperature of the group III nitride semiconductor crystal to remove these impurities and defects.
[0009]
As described above, in the growth method using the low-temperature buffer layer, the substrate temperature is lowered from 1200 ° C., which is the temperature for thermal cleaning, to around 500 ° C., which is the temperature for growing the buffer layer, and then annealed from around 500 ° C. It is necessary to raise it to a temperature range close to 1000 ° C. in a relatively short time. In this case, generally, a change in temperature accompanying cooling requires a long time, and a rapid increase in temperature requires a large amount of energy.
[0010]
Further, by giving such a history of various temperatures to the substrate, the substrate is warped. Further, the substrate may be cracked or cracked by warping. Further, the warpage of the substrate affects the crystal layer grown thereon, and in particular, when an LED structure is manufactured, the emission wavelength and the emission intensity are nonuniform within the substrate surface.
[0011]
In contrast to such a growth method using a low-temperature buffer layer, a method is also disclosed in which AlN grown in a high temperature range of about 900 ° C. to 1200 ° C. is formed on a substrate and gallium nitride is grown thereon. (E.g., P. Kung, et al., Applied Physics Letters, 66 (1995), 2958. Such). This prior example describes that this method makes it possible to produce a very good crystal of 30 arcsec with a (0002) plane X-ray rocking curve. However, according to a place where we have tried this method, it has been found that the gallium nitride crystal film produced by this method is a crystal having a very high columnarity and includes many grain boundaries in the crystal. Such a crystal has a high density of threading dislocations generated from the substrate toward the surface. For this reason, the characteristic which may produce element structures, such as a light emitting element and an electronic device, is not acquired.
[0012]
Similarly, a growth method using an AlN layer produced at a high temperature is described in JP-A-9-64477. In this document, it is desirable that the group III nitride semiconductor crystal to be produced is a single crystal having good crystallinity. Although we have repeated experiments, the growth method using a good single crystal AlN film as described in this document is similar to the method described in the above-mentioned document, and the device structure is fabricated to be good. It was not possible to grow crystals that would give the properties. This is because, when a single crystal layer having good crystallinity is used as a buffer layer, when a group III nitride semiconductor is grown thereon, migration of atoms attached at the initial stage of growth is not performed well, and two-dimensional growth is difficult. I think because.
[0013]
As described above, since a group III nitride semiconductor crystal having sufficient crystallinity for manufacturing the device cannot be obtained, a method for growing a group III nitride semiconductor crystal using an AlN buffer layer grown at a high temperature is currently available. Not very common.
[0014]
The present invention replaces the method using a low-temperature buffer layer that needs to set a large number of temperature regions and the method using a high-temperature AlN layer having a problem with the quality of a crystal to be produced, and a process with relatively little temperature change. And a method for producing a group III nitride semiconductor crystal capable of forming a high-quality group III nitride semiconductor crystal. 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. The present invention is also a high-quality group III nitride semiconductor crystal manufactured by the above-described method for manufacturing a group III nitride semiconductor crystal, and a group III nitride semiconductor epitaxial wafer using the group III nitride semiconductor crystal. .
[0015]
[Means for Solving the Problems]
The present invention
(1) A Group III material is supplied on a heated substrate with a V / III ratio of 1000 or less (including a case where the V / III ratio is 0), and a Group III nitride semiconductor (hereinafter, Group III nitride semiconductor is A first step of forming a group III nitride semiconductor crystal on the substrate using a group III source and a nitrogen source. A method for producing a Group III nitride semiconductor crystal.
(2) Sapphire (Al ₂ O _Three The method for producing a group III nitride semiconductor crystal according to (1), wherein
(3) The method for producing a group III nitride semiconductor crystal according to the above (1) or (2), wherein the group III raw material supplied in the first step contains at least Al.
(4) The group III nitride semiconductor crystal according to any one of (1) to (3) 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.
(5) In at least one of the first step and the second step, 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
(6) In the second step, ammonia (NH _Three The method for producing a group III nitride semiconductor crystal as described in any one of (1) to (5) above, wherein
(7) The method for producing a group III nitride semiconductor crystal according to the above (1) to (6), wherein the group III nitride semiconductor formed in the first step is an island-like crystal lump.
(8) The method for producing a group III nitride semiconductor crystal as described in (1) to (7) above, wherein the group III nitride semiconductor formed in the first step is a columnar crystal.
(9) The method for producing a group III nitride semiconductor crystal according to (8), wherein the columnar crystal is attached on the substrate such that a side surface thereof is substantially perpendicular to the substrate surface.
It is.
[0016]
The present invention also provides:
(10) In a Group III nitride semiconductor crystal manufacturing method in which a first Group III nitride semiconductor is fabricated on a heated substrate and a second Group III nitride semiconductor crystal is fabricated thereon, A method for producing a group III nitride semiconductor crystal, wherein the group nitride semiconductor is an aggregate of columnar crystals or island crystals.
(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.
[0017]
The present invention also provides:
(12) A group III nitride semiconductor crystal produced by the method described in (1) to (11) above.
It is.
[0018]
The present invention also provides:
(13) 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 (12).
It is.
[0019]
DETAILED DESCRIPTION OF THE INVENTION
In the method for producing a Group III nitride semiconductor crystal of the present invention, a Group III material is supplied onto a heated substrate with a V / III ratio of 1000 or less (including a case where the V / III ratio is 0), A first step of forming a compound semiconductor, 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. 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. In the present invention, the group III nitride semiconductor is represented by InGaAlN.
[0020]
A group III nitride semiconductor crystal manufactured under conditions of a low V / III ratio of V / III ratio of 1000 or less has a stoichiometric ratio of group V element to group III element (stoichiometry) of 1: 1 in the crystal. It seems that the group III element is shifted to the excessive side and the metal is excessive. In such a group III nitride semiconductor crystal layer, an excessive group III element exists as a metal crystal or a droplet. Therefore, it is considered that when a group III nitride semiconductor crystal is grown thereon, migration at the initial stage of the growth proceeds efficiently and two-dimensional growth in the lateral direction can be achieved. However, the details of the mechanism are unknown.
[0021]
Japanese Patent Laid-Open No. 9-64477 describes that an AlN film produced with a small V / III ratio is desirable for growing a good group III nitride semiconductor. However, in this document, it is desirable that the group III nitride semiconductor crystal to be produced is a single crystal with good crystallinity. Through repeated experiments and analyses, we found that aggregates of columnar crystals and island crystals function as a better buffer layer than single crystal films. This is thought to be because a metal-excess crystal tends to be generated more easily when a metal crystal or a droplet enters a grain boundary existing in a layer made of columnar crystals or island-like crystals. However, details are unknown.
[0022]
In this method, since the temperature rises and falls less than the conventional method using a low-temperature buffer layer, 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 element characteristics is improved. In addition, it is possible to produce a crystal exhibiting good device characteristics as compared with the growth method using an AlN layer grown at a high temperature disclosed so far.
[0023]
In the present invention, glass, SiC, Si, GaAs, 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.
[0024]
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.
[0025]
In the first step of the present invention, a Group III nitride semiconductor is formed by supplying Group V materials such as ammonia, alkylamines, hydrazines and the like 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 generated.
[0026]
In 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, even if the Group V raw material that is intentionally supplied is 0, a Group III nitride semiconductor is formed by nitrogen supplied from the decomposition of deposits adhering to the reactor wall, top plate, susceptor, etc. It is necessary to In this case, it is necessary to appropriately control the composition and amount of deposits attached 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 performing the previous growth, baking is not performed and thermal cleaning is performed at 600 ° C. for 10 minutes. Then, as a first step, the substrate is set to 1000 ° C., and only the metal-containing compound is circulated. As a result of crystal growth as the second step, a good group III nitride semiconductor crystal could be produced.
[0027]
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.
[0028]
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.
[0029]
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.
[0030]
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 specified, 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.
[0031]
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, a set of island-shaped crystal lumps in which island-shaped particle lumps having a width of 1 nm to 500 nm and a height of about 5 nm to 100 nm are densely formed. By making the group III nitride into an island-like crystal, many crystal 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 is obtained. It is done. Further, the structure may be such that the distribution of island crystals is not so dense that the substrate surface can be seen between the crystal lumps. In this case, since regions having different crystal growth rates are mixed on the surface, the density of threading dislocations is reduced by the effect of selective growth, and a better crystal can be manufactured.
[0032]
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. .
[0033]
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 is formed in the first step using a group III material and a nitrogen material. When the group III nitride semiconductor crystal to be grown is GaN, GaN is preferable among the group III nitride semiconductors because it tends to grow two-dimensionally and easily forms a flat crystal film. Once a flat and good crystalline film is made of GaN, it becomes easy to produce semiconductor device structures using Group III nitride semiconductor crystal layers of various compositions thereon.
[0034]
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 flattened substrate out of the reaction furnace.
[0035]
In the second step, the temperature of the substrate when the group III nitride semiconductor crystal is grown by the MOCVD method is 950 ° C. to 1200 ° C., and the pressure of the atmosphere is 1000 Pa to 1 × 10 6. ^Five Pa is preferable.
[0036]
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. . Moreover, it is preferable that the V / III ratio when growing the group III nitride semiconductor crystal in the second step is 500 to 20000.
[0037]
In the present invention, the group III nitride semiconductor crystal having the first and second steps described above is used for the group III nitride with high uniformity and good crystallinity on the substrate by a short time and power saving process. A physical semiconductor crystal 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.
[0038]
【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 the first embodiment, as a first step on a sapphire substrate, 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 to produce a GaN layer made of gallium nitride crystals on the sapphire substrate. The V / III ratio under the conditions used in the first step is about 85.
[0039]
The sample including the GaN layer was produced by the following procedure using the MOCVD method.
First, before introducing the sapphire substrate, the deposits adhering to the inside of the reactor in the previous growth performed in the same apparatus are heated in a gas containing ammonia and hydrogen to be nitrided, so that it is difficult to decompose further. I made it. 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 pipes 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.
[0040]
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.
[0041]
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 into the furnace, and GaN growth 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.
[0042]
Through the above steps, a metal-excessed group III nitride semiconductor layer having a columnar structure was formed on a sapphire substrate, and an undoped GaN layer having a thickness of 2 μm was formed thereon. 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 was a mirror surface.
[0043]
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-value width of 230 seconds in the (0002) plane measurement and a half-value width of 350 seconds in the (10-12) plane.
[0044]
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.
[0045]
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.
[0046]
(Example 2)
In Example 2, the experiment was performed using almost the same process as Example 1, except that the growth of the group III nitride semiconductor was made 2 minutes in the first process. Also in this case, the surface of the taken-out wafer was specular. The color was colorless and transparent.
[0047]
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.
[0048]
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.
[0049]
(Example 3)
In Example 3, after the previous experiment, the sapphire substrate was introduced into the reactor without performing the baking before the growth, and a gas containing trimethylaluminum (TMAl) vapor was circulated as the first step. Then, as a second step, TMGa and ammonia were distributed to grow gallium nitride, and a GaN layer made of gallium nitride crystal was produced on the sapphire substrate. Although the intended V / III ratio in this embodiment is 0, a small amount of N atoms is supplied on the substrate due to decomposition of deposits adhering to the wall of the reactor and the top plate.
[0050]
The sample including the GaN layer was produced by the following procedure using the MOCVD method.
First, the sapphire substrate 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 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 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 the supply of hydrogen gas into the reactor was started.
[0051]
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.
[0052]
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 into the furnace, and GaN growth 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.
[0053]
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 2 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.
[0054]
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 200 seconds in the (0002) plane measurement and a half-value width of 330 seconds in the (10-12) plane.
[0055]
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.
[0056]
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.
[0057]
(Example 4)
In Example 4, as a first step on the sapphire substrate, a gas containing a gas obtained by mixing a vapor of trimethylaluminum (TMAl) and a vapor of trimethylindium (TMIn) at a molar ratio of 2: 1 is used as a carrier gas. As a second step, TMGa and ammonia were passed as a second step to grow gallium nitride to produce a GaN layer made of gallium nitride crystals on a sapphire substrate. 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.
[0058]
The sample including the GaN layer was produced by the following procedure using the MOCVD method.
First, before introducing the sapphire substrate, the deposit adhered to the inside of the reaction furnace in the previous growth performed in the same apparatus was heated in a gas containing ammonia and hydrogen to be nitrided so as not to be decomposed. 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.
[0059]
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.
[0060]
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 into the furnace, and GaN growth 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.
[0061]
Through the above steps, a metal-excessed group III nitride semiconductor layer having a columnar structure was formed on a sapphire substrate, and an undoped GaN layer having a thickness of 2 μm was formed thereon. The substrate taken out was colorless and transparent. The growth surface was a mirror surface.
[0062]
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.
[0063]
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.
[0064]
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.
[0065]
(Example 5)
In Example 5, a method for manufacturing a gallium nitride-based compound semiconductor light-emitting element using the method for manufacturing a 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. That is, the epitaxial wafer is formed by forming the metal-excess AlN layer 8 having a columnar structure on the sapphire substrate 9 having the 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 Ｉｎ In with an electron concentration of _0.1 Ga _0.9 N-cladding layer 5, 6 layers of GaN barrier layer 3 having a layer thickness of 70 mm, and 5 layers of non-doped In-layer having a layer thickness of 20 mm starting from the GaN barrier layer and ending with the GaN barrier layer _0.2 Ga _0.8 Multiple quantum well structure 20 and 30 な る non-doped Al composed of N well layer 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.
Further, FIG. 2 shows a plan view of the electrode structure of the semiconductor light emitting device manufactured in Example 5. FIG.
[0066]
Fabrication of a wafer having an epitaxial layer having the above-described semiconductor light emitting device structure 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.
After the AlN layer 8 having a columnar structure was formed 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 GaN layer was grown for about 1 hour and 15 minutes. SiH _Four The amount to be distributed is examined in advance, and the electron concentration of the low Si-doped GaN layer is 1 × 10 6. ¹⁷ cm ^-3 It adjusted so that it might become.
In this way, a low Si-doped GaN layer 7 having a thickness of 2 μm was formed.
[0067]
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, TMGa and Si 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 high Si-doped GaN layer is 1 × 10 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 having a thickness of 1.8 μm was formed.
[0068]
After growing the high 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 800 ° 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 is 1 × 10 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 to 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. Si-doped In that continues to supply for about 10 minutes and has a thickness of 100 mm _0.1 Ga _0.9 An N clad layer 5 was formed.
Then TMIn, TEGa and Si ₂ H ₆ The supply of these raw materials was stopped.
[0069]
Next, the barrier layer 3 made of GaN and In _0.2 Ga _0.8 A multiple quantum well structure 20 composed of a well layer 4 made of N was produced. In manufacturing a multiple quantum well structure, Si-doped In _0.1 Ga _0.9 First, a GaN barrier layer 3 is formed on the N clad layer 5, and an In layer is formed on the GaN barrier layer. _0.2 Ga _0.8 An N well layer 4 was formed. After repeating this structure five times, the fifth In _0.2 Ga _0.8 A sixth GaN barrier layer was formed on the N well layer, and the GaN barrier layer 3 was configured on both sides of the multiple quantum well structure 20.
That is, Si-doped In _0.1 Ga _0.9 After the growth of the N-cladding layer is stopped for 30 seconds, the TEGa valve is supplied to the TEGa by switching the TEGa valve without changing the substrate temperature, the pressure in the furnace, and the flow rate and type of the carrier gas. It was. After supplying TEGa for 7 minutes, the valve was switched again to stop the supply of TEGa and the growth of the GaN barrier layer was completed. Thereby, the GaN barrier layer 3 having a thickness of 70 mm was formed.
[0070]
During the growth of the GaN barrier layer, the flow rate of TMIn flowing through the piping to the exclusion equipment was adjusted to be twice the molar flow rate compared to the growth of the cladding layer. It was.
After stopping the growth of the GaN barrier layer, the supply of the group III raw material was stopped for 30 seconds, and the TEGa and TMIn valves were switched by changing the TEGa and TMIn valves while maintaining the substrate temperature, the pressure in the furnace, and the flow rate and type of the carrier gas. And TMIn were supplied into the furnace. After supplying TEGa and TMIn for 2 minutes, the valve is switched again to stop supplying TEGa and TMIn. _0.2 Ga _0.8 The growth of the N well layer was completed. As a result, In having a thickness of 20 mm _0.2 Ga _0.8 An N well layer 4 was formed.
[0071]
In _0.2 Ga _0.8 After the growth of the N-well layer is completed, supply of Group III raw materials is stopped for 30 seconds, and then supply of TEGa into the furnace is started with the substrate temperature, furnace pressure, carrier gas flow rate and type unchanged. Then, the GaN barrier layer was grown again.
This procedure is repeated 5 times, 5 layers of GaN barrier layers and 5 layers of In _0.2 Ga _0.8 An N well layer was fabricated. In addition, the last In _0.2 Ga _0.8 A GaN barrier layer was formed on the N well layer.
[0072]
On the multiple quantum well structure 20 terminated with this GaN barrier layer, non-doped Al _0.2 Ga _0.8 N diffusion prevention layer 2 was produced.
Distribution of the carrier gas to the bubbler of trimethylaluminum (TMAl) was started in advance. The TMAl vapor generated by the bubbling was circulated to the piping to the detoxifying apparatus together with the carrier gas until the growth process of the diffusion preventing layer started, and was discharged out of the system through the detoxifying apparatus.
[0073]
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 prevention layer was stopped. Thereby, non-doped Al having a thickness of 30 mm. _0.2 Ga _0.8 N diffusion prevention layer 2 was formed.
[0074]
This non-doped Al _0.2 Ga _0.8 An Mg-doped GaN layer 1 was formed on the N diffusion prevention layer.
Stop supply of TEGa and TMAl, and undoped Al _0.2 Ga _0.8 After the growth of the N diffusion preventing layer 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 started, the Mg vapor was circulated through the piping to the abatement apparatus together with the carrier gas, and was discharged out of the system through the abatement apparatus.
[0075]
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 circulated is examined in advance, and the hole concentration of the Mg-doped GaN cladding layer 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 was stopped. Thereby, the Mg-doped GaN layer 1 having a thickness of 0.15 μm was formed.
[0076]
After completing the growth of the Mg-doped GaN layer, the 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 the volume is 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.
[0077]
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 showed p-type even without annealing for activating p-type carriers.
[0078]
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.
About the produced wafer, the light transmission which consists only of the p-electrode bonding pad 12 with the structure which laminated | stacked titanium, aluminum, and gold | metal | money in order from the surface side on the surface 14 of a Mg dope GaN layer by well-known photolithography, and Au joined to it. P-type electrode 13 was formed to produce a p-side electrode.
Thereafter, the wafer was dry-etched to expose the portion 11 where the n-side electrode of the highly Si-doped GaN layer was formed, and an n-electrode 10 composed of four layers of Ni, Al, Ti, and Au was produced on the exposed portion. Through these operations, an electrode having a shape as shown in FIG. 2 was produced on the wafer.
[0079]
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, placed on the lead frame so that the electrodes were on top, and connected to the lead frame with gold wires to obtain a light emitting device.
When a forward current was passed between the p-side and n-side electrodes of the light-emitting diode produced as described above, the forward voltage at a current of 20 mA was 3.0V. Moreover, when light emission was observed through the translucent electrode of the p side, the light emission wavelength was 470 nm and the light emission output showed 6 cd. 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.
[0080]
【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 crystal characteristics is improved.
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.
[0081]
In addition, according to the method described in the present invention, a crystal having a low columnarity and a low dislocation density as compared with a conventional method using AlN grown at a high temperature, and a device structure produced thereon has good device characteristics. Can be produced.
[Brief description of the drawings]
FIG. 1 is a schematic view showing a cross section of an epitaxial wafer having an epitaxial layer structure 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 Non-doped Al _0.2 Ga _0.8 N diffusion prevention layer
3 GaN barrier layer
4 In _0.2 Ga _0.8 N well layer
5 In _0.1 Ga _0.9 N clad layer
6 High Si-doped GaN layer
7 Low Si-doped GaN layer
8 Metal excess 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 (7)

On a heated sapphire (Al ₂ O ₃ ) substrate, the V / III ratio (the ratio of the number of moles of a molecule containing a group III element and the number of moles of a molecule containing a group V element intentionally flowing to the reactor) A group III raw material is supplied as 0, a group V raw material is supplied from decomposition of deposits adhering to the reactor wall, top plate, and susceptor, and a group III nitride semiconductor containing at least Al (hereinafter referred to as a group III nitride semiconductor) Is represented by InGaAlN.), And then using the group III material and the nitrogen material, the substrate temperature is 950 ° C. to 1200 ° C. and the first step. A method for producing a group III nitride semiconductor crystal by MOCVD, which includes a second step of vapor-phase-growing a group III nitride semiconductor crystal at a substrate temperature equal to or lower than the substrate temperature. 2. The method for producing a group III nitride semiconductor crystal according to claim 1, wherein ammonia (NH ₃ ) is used as a nitrogen source in the second step. 3. The method for producing a group III nitride semiconductor crystal according to claim 1, wherein thermal cleaning is not performed before the first step. 4. The method for producing a group III nitride semiconductor crystal according to claim 1, wherein the group III nitride semiconductor formed in the first step is an island-like crystal lump. 5. The method for producing a group III nitride semiconductor crystal according to any one of claims 1 to 3, wherein the group III nitride semiconductor formed in the first step is a columnar crystal. 5. The group III nitride semiconductor crystal according to claim 4, wherein the island-shaped crystal is an island-shaped crystal lump in which island-shaped particle lumps having a width of 1 nm to 500 nm and a height of 5 nm to 100 nm are concentrated. Production method. 6. The method for producing a group III nitride semiconductor crystal according to claim 5, wherein the columnar crystal is a crystal in which columnar particles having a width of 0.1 nm to 100 nm and a height of 10 nm to 500 nm are aggregated.

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