JP2012012292A - Manufacturing method for group iii nitride crystal, and group iii nitride crystal and group iii nitride crystal substrate obtained by the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method for a group III nitride crystal to which silicon is homogeneously doped at a high concentration in an in-plane direction and a film thickness direction achieving excellent controllability and reproducibility.SOLUTION: The method of manufacturing the group III nitride crystal includes a process to prepare a ground substrate in a crystal growth furnace and a growth process to grow the group III nitride crystal on the ground substrate by reacting halides of group III elements with a compound including nitrogen element. The method of manufacturing the group III nitride crystal comprises supplying further a halogen element containing substance and a silicon containing substance to the crystal growth furnace at the growth process from the same lead-in tube.

Description

  The present invention relates to a method for producing a group III nitride crystal, a group III nitride crystal obtained by the production method, and a group III nitride crystal substrate.

  Group III nitride crystals have a high melting point, and the dissociation pressure of nitrogen near the melting point is high, so that bulk growth from the melt is difficult. On the other hand, it is known that a group III nitride crystal substrate can be manufactured by using a vapor phase growth method such as a hydride vapor phase growth (HVPE) method or a metal organic chemical vapor deposition (MOCVD) method. For example, when manufacturing a gallium nitride crystal substrate, a base substrate such as sapphire is set in a crystal growth furnace (reactor) of a vapor phase growth apparatus, and a gas containing a gallium compound and a nitrogen compound is contained in the reactor. By supplying a gas for forming a group III nitride crystal consisting of gallium nitride, a gallium nitride crystal is grown on the base substrate to a thickness of several μm to several cm. Then, a desired group III nitride crystal substrate can be obtained by removing portions such as the base substrate using a method of polishing or laser irradiation. Among the above-mentioned vapor phase growth methods, the HVPE method has a feature that can achieve a higher growth rate than other growth methods. Therefore, when a thick film growth of a group III nitride crystal is necessary or a sufficient thickness is required. This is effective as a method for obtaining a group III nitride crystal substrate having the same.

  On the other hand, as a GaN substrate used for manufacturing light emitting elements and power device elements, conductivity was increased by adding impurities in order to manufacture a device having an upper and lower electrode structure in which electrodes are also attached to the back surface of the substrate. Things are usually used. In designing the device structure, since it is often designed that the outermost surface of the epitaxial structure is a P-type layer, n-type conductivity is usually given to the GaN substrate.

  When growing an n-type GaN crystal by MOCVD, a method of doping silicon (silicon (Si)) using monosilane or disilane as a doping source gas is generally employed (for example, Patent Document 1). However, in the HVPE method, monosilane or disilane cannot be used as a doping gas. The HVPE method is a so-called hot wall type crystal growth method in which a source gas contacts a reactor wall heated to a high temperature, so that it decomposes before reaching a crystal on which monosilane or disilane is growing, and is effective. This is because it is not taken into the crystal.

Therefore, in Patent Document 2, an n-type nitride-based III-V group compound is doped with Si using SiH _x Cl _4-x (x = 1 to 3) as a doping source gas during vapor phase growth by the HVPE method. A method for forming a semiconductor layer is proposed. Patent Document 3 discloses a group III nitride semiconductor substrate containing silicon (Si) as an impurity element, and includes dichlorosilane (SiH ₂ Cl ₂ ), tetrachlorosilane (silicon tetrachloride (SiCl ₄ )). Is described for epitaxially growing a group III nitride semiconductor. Patent Document 4 describes that a group III nitride semiconductor crystal doped with silicon (Si) is epitaxially grown by using tetrachlorosilane (silicon tetrachloride (SiCl ₄ )) as a doping gas.
Furthermore, in Patent Document 5, a halogen element-containing substance is further introduced into the crystal growth furnace from a second supply pipe different from the halogen element-containing substance supply pipe for forming the group III metal halide, and the heat-resistant silicon-containing material is used. In this method, a group III nitride-based semiconductor crystal is doped with silicon contained in the flow pipe through the flow pipe.

JP-A-3-252175 JP 2000-91234 A JP 2006-193348 A JP 2009-126723 A JP 2005-223243 A

In order to control the n-type conductivity of the group III nitride crystal when the group III nitride semiconductor crystal is grown by a vapor phase growth method such as HVPE method or MOCVD method, the n-type in the group III nitride crystal is used. It is necessary to control the concentration of the impurity (dopant).
On the other hand, the present inventors have used silane (SiH ₄ ), disilane (Si ₂ H ₆ ), tetrachlorosilane (which are used as doping gases in Patent Documents 2 to 4 above to dope silicon as an n-type impurity ( SiCl ₄ ), trichlorosilane (SiHCl ₃ ), dichlorosilane (SiH ₂ Cl ₂ ), and monochlorosilane (SiH ₃ Cl) reach the underlying substrate on which the crystal grows at the group III nitride crystal growth temperature. It has been found that there is a problem that it decomposes before being adsorbed and is adsorbed in a reactor such as an introduction pipe to precipitate silicon.

In addition, the doping gas used in Patent Documents 2 to 4 also reacts with nitrogen gas or ammonia gas to generate a silicon nitride (SixNy (x and y are arbitrary integers))-based compounds. is there.
In the case where doping is performed by introducing a halogen element-containing substance into a flow pipe made of a heat-resistant silicon-containing material used in Patent Document 5, when the corrosion of the heat-resistant silicon-containing material progresses during growth, the doping concentration also increases. As a result, the silicon concentration in the group III nitride crystal cannot be controlled.

  The present invention solves such problems and provides a production method capable of doping silicon uniformly in a large-area crystal efficiently and stably. Furthermore, by using such a manufacturing method, a Group III nitride crystal having high uniformity in the plane and in the film thickness direction in the crystal and doped with a high concentration of silicon is also provided.

As a result of diligent investigations to achieve the above object, the inventors of the present invention simultaneously supplied a halogen-containing substance and a silicon-containing compound from the same introduction tube, and led the silicon into the reactor by introducing it onto a base substrate on which crystals grow. The present inventors have found that a group III nitride crystal can be doped with silicon at a high concentration without precipitating, and reached the present invention.
That is, the gist of the present invention is to prepare a base substrate in a crystal growth furnace, and to grow a group III nitride crystal on the base substrate by reacting a group III element halide and a nitrogen element-containing compound. The present invention relates to a method for producing a group III nitride crystal including a step, wherein a halogen element-containing material and a silicon-containing material are further supplied to a crystal growth furnace from the same introduction tube in the growth step.

Further, according to the present invention, in the supply of the halogen element-containing material and the silicon-containing material, the amount of halogen element in the supplied halogen element-containing material and the amount of silicon in the supplied silicon-containing material can be expressed by The group III nitride crystal satisfying the above).
A1 × ln (B1 × (X1−D1)) − (C1 × (X1−D1) + E1 <Y1 <A1 × ln (B1 × (X1−D1)) − (C1 × (X1−D1) + F1. Formula (1)
X1 Amount of silicon (molar ratio)
Y1 Amount of halogen element (molar ratio)
A1 9.682E-4
B1 8.000E-1
C1-7.400
D1-8.000E-6
E1 1.000E-2 (lower limit)
F1 1.480E-2 (upper limit)
However, if A1 * ln (B1 * (X1-D1))-(C1 * (X1-D1) + E1 <0, then A1 * ln (B1 * (X1-D1))-(C1 * (X1- D1) It is assumed that + E1 = 0.
Further, according to the present invention, there is provided the group III nitride crystal according to the above, wherein the halogen element-containing substance is hydrogen chloride, the silicon-containing substance is dichlorosilane, and each supply amount satisfies the following relational expression (2). It relates to a manufacturing method.
A × ln (B × (X−D)) − (C × (X−D) + E <Y <A × ln (B × (X−D)) − (C × (X−D) + F) Formula (2)
X Dichlorosilane supply (molar ratio)
Y Supply amount of hydrogen chloride (molar ratio)
A 9.682E-4
B 1.110
C -1.060E + 1
D-2.760E-6
E 8.706E-3 (lower limit)
F 1.861E-2 (upper limit)
However, when A × ln (B × (X−D)) − (C × (X−D) + E <0, A × ln (B × (X−D)) − (C × (X− D) Let + E = 0.
The present invention also relates to a method for producing the group III nitride crystal, wherein the silicon-containing substance is dichlorosilane.
The present invention also relates to a method for producing the Group III nitride crystal, wherein the halogen element-containing substance is hydrogen halide.
The present invention also relates to a method for producing a group III nitride crystal in which a carrier gas is further supplied from the same introduction tube in addition to a halogen element-containing material and a silicon-containing material.

Further, the present invention supplies the halide of the group III element and the compound containing the nitrogen element into the crystal growth furnace from the introduction pipe, and supplies the halogen element-containing substance and the silicon-containing substance from the introduction pipe different from the introduction pipe. , And relates to a method for producing the group III nitride crystal.
The present invention also relates to a method for producing the group III nitride crystal, wherein the growth step is performed by a hydride vapor phase epitaxy (HVPE) method.
The present invention also relates to a group III nitride crystal obtained by the method for producing a group III nitride crystal.
The present invention also relates to a group III nitride crystal substrate comprising the group III nitride crystal.

In the production method of the present invention, by devising the supply method of the halogen element-containing substance or controlling the supply amount, the silicon is gasified without precipitating silicon (silicon (Si)) in the reactor such as the introduction pipe. Since the substrate can be efficiently supplied to the base substrate, the group III nitride crystal can be stably doped with silicon at a high concentration. That is, by using the manufacturing method of the present invention, a group III nitride crystal in which silicon is uniformly doped at a high concentration in the in-plane direction and the film thickness direction in the crystal can be obtained while realizing excellent controllability and reproducibility. Can be manufactured. As a result, a thick film and a large area group III nitride crystal can be stably produced, and an improvement in productivity can be expected.

It is a phase diagram of chemical equilibrium of three elements of H, Cl, and Si in an atmosphere of 1000 ° C. It is a phase diagram of the chemical equilibrium of HCl and a chlorosilane type compound in 1000 degreeC atmosphere. It is the graph which showed the phase diagram of the chemical equilibrium of HCl and dichlorosilane, and Examples 1-4 and Comparative Examples 1 and 2. FIG. It is a schematic sectional drawing of the HVPE apparatus used by the Example and the comparative example. It is the graph which showed the phase diagram of the chemical equilibrium of chlorine and silicon, and Examples 1-4 and Comparative Examples 1 and 2. FIG.

  Hereinafter, a method for producing a group III nitride crystal of the present invention, a group III nitride crystal obtained by the method, and a group III nitride crystal substrate will be described in detail. The description of the constituent elements described below may be made based on typical embodiments of the present invention, but the present invention is not limited to such embodiments. In the present specification, a numerical range represented by using “to” means a range including numerical values described before and after “to” as a lower limit value and an upper limit value.

  In the method for producing a group III nitride crystal of the present invention, silicon is not deposited and deposited in an introduction tube or the like in a crystal growth furnace (hereinafter sometimes referred to as a reactor) of a vapor phase growth apparatus. This is a manufacturing method capable of doping a group nitride crystal with a high concentration. That is, a group III including a step of preparing a base substrate in a crystal growth furnace and a step of growing a group III nitride crystal on the base substrate by reacting a group III element halide with a nitrogen element compound. In the method for producing a nitride crystal, the halogen-containing material and the silicon-containing material are further supplied from the same introduction pipe to the crystal growth furnace in the growth step to obtain a group III nitride crystal doped with silicon. .

In order to dope silicon (Si) into a group III nitride crystal at a high concentration, it is necessary to reach the surface of the crystal on which Si is grown as a gaseous silicon-containing substance. However, in a hot wall type apparatus such as HVPE, the entire reactor becomes a high temperature, which is the growth temperature of the group III nitride crystal, and therefore silane (SiH ₄ ) used as a doping gas for doping Si as an n-type impurity. , Disilane (Si ₂ H ₆ ), tetrachlorosilane (SiCl ₄ ), trichlorosilane (SiHCl ₃ ), dichlorosilane (SiH ₂ Cl ₂ ), and monochlorosilane (SiH ₃ Cl) are crystalline. Before reaching the growing base substrate, it decomposes under high temperature conditions, and Si is adsorbed and deposited in a reactor such as an introduction tube. Therefore, by supplying the halogen-containing material simultaneously with the silicon-containing material as a doping gas, it becomes possible for the silicon-containing material to stably exist as a gas in the reactor even at high temperatures, and to the surface of the crystal to be grown. It is considered that it reaches as a gas and can be doped with Si at a high concentration in the obtained crystal.
From the study by the present inventors, the phenomenon of Si precipitation can be estimated by chemical equilibrium in a reactor such as an introduction tube. Here, for the preparation of the chemical equilibrium diagram, GTT-Technologies Ltd. And Thermfact Ltd. Used the thermodynamic equilibrium calculation software “FactSage” and the thermodynamic database “Fact”.
Specifically, taking as an example the case of using a substance containing Cl as the halogen element-containing substance, FIG. 1 shows a phase diagram of the chemical equilibrium of three elements of H, Cl, and Si in an atmosphere of 1000 ° C. The horizontal axis represents the molar ratio of Si, and the vertical axis represents the molar ratio of Cl.
FIG. 2 shows a phase diagram of chemical equilibrium in an atmosphere of 1000 ° C., taking as an example the case of using HCl as the halogen element-containing material and chlorosilane-based compound as the silicon-containing material. In FIG. 2, the horizontal axis represents the molar ratio of the chlorosilane-based compound, and the vertical axis represents the molar ratio of HCl.
The curves on the graphs of FIG. 1 and FIG. 2 are the curves showing the boundary where Si is deposited as a solid, the region above the curve is in a gaseous state with Si as a compound, and the region below is It is considered that at least a part of Si is precipitated as a solid. For example, when only dichlorosilane as a silicon-containing substance as a doping gas and H ₂ as a carrier gas are supplied from an introduction tube and no halogen element-containing substance is introduced, the molar ratio of Cl as the vertical axis of the graph is It becomes zero, and even if dichlorosilane is introduced into a reactor such as an introduction pipe even a little, it is precipitated as Si in an atmosphere of 1000 ° C., and a sufficient concentration of Si cannot be doped in the obtained group III nitride crystal. . On the other hand, when HCl is simultaneously supplied from the introduction pipe, it is possible to reduce the rate of precipitation as Si from the relationship of chemical equilibrium, and doping of higher concentration Si into the obtained group III nitride crystal Will be able to.
Even when the halogen element contains an element other than Cl, such as Br or F, the chemical equilibrium diagrams similar to those in FIGS. 1 and 2 can be obtained by the above-described method. It can be said that there is an effect.
In the production method of the present invention, the introduction of the halogen-containing material is introduced in accordance with the amount of introduction of the silicon-containing material as the doping gas so as to enter the region above the curve on the graph from the phase diagrams of FIGS. It is preferable to adjust the amount and introduce both substances into the reactor because Si can be efficiently doped into the crystal at a higher concentration without precipitating Si in the reactor such as an introduction tube.
For example, in the supply of the halogen element-containing material and the silicon-containing material, the amount of halogen element in the supplied halogen element-containing material and the amount of silicon in the supplied silicon-containing material satisfy the following relational expression (1): It is preferable to adjust the supply amount.
A1 × ln (B1 × (X1−D1)) − (C1 × (X1−D1) + E1 <Y1 <A1 × ln (B1 × (X1−D1)) − (C1 × (X1−D1) + F1. Formula (1)
X1 Amount of silicon (molar ratio)
Y1 Amount of halogen element (molar ratio)
A1 9.682E-4
B1 8.000E-1
C1-7.400
D1-8.000E-6
E1 1.000E-2 (lower limit)
F1 1.480E-2 (upper limit)
However, if A1 * ln (B1 * (X1-D1))-(C1 * (X1-D1) + E1 <0, then A1 * ln (B1 * (X1-D1))-(C1 * (X1- D1) It is assumed that + E1 = 0.
Specifically, when the halogen element-containing substance is hydrogen chloride and the silicon-containing substance is dichlorosilane, the halogen element-containing substance so that the molar ratio of hydrogen chloride satisfies the following relational expression (2): It is preferable to supply the silicon-containing substance from the same introduction pipe.
A × ln (B × (X−D)) − (C × (X−D) + E <Y <A × ln (B × (X−D)) − (C × (X−D) + F) Formula (2)
X Molar ratio of dichlorosilane Y Molar ratio of hydrogen chloride A 9.682E-4
B 1.110
C -1.060E + 1
D-2.760E-6
E 8.706E-3 (lower limit)
F 1.861E-2 (upper limit)
However, when A × ln (B × (X−D)) − (C × (X−D) + E <0, A × ln (B × (X−D)) − (C × (X− D) Let + E = 0.

In formula (2), A × ln (B × (X−D)) − (C × (X−D)) is a formula representing a chemical equilibrium diagram of hydrogen chloride and dichlorosilane shown in FIG. 2. Therefore, the meaning of the lower limit value (E) and the upper limit value (F) of Y will be described.When the halogen element-containing material is supplied at a value exceeding the upper limit value, the growth rate is remarkably increased due to the excessive supply of the halogen element-containing material. Therefore, it is preferable to adjust the halogen-containing material below the upper limit for mirror growth, and when the halogen-containing material is flowed below the lower limit. Therefore, it is difficult to obtain a group III nitride crystal having a higher carrier concentration because the Si doping amount in the group III nitride crystal is remarkably reduced. The possibility of Si being deposited in a large amount in a reactor such as a tube increases the possibility of damage to the reactor, so the halogen element-containing material should be adjusted at the lower limit or higher from the viewpoint of improving Si doping efficiency and suppressing reactor deterioration. It is preferable.
FIG. 3 shows a phase diagram of chemical equilibrium in an atmosphere of 1000 ° C. and a curve representing the upper limit value and lower limit value of Y in the case of using HCl as the halogen element-containing material and chlorosilane-based compound as the silicon-containing material as an example. In Example 3 to be described later, a GaN crystal having a mirror growth surface and a carrier concentration of 6.31 × 10 ¹⁷ / cm ³ is obtained, but the Si precipitation rate is based on the amount of introduced dichlorosilane. It is 96.75 mol%. On the other hand, the lower limit value of Y described above is a value in the case where it is defined as the condition of the Si deposition ratio of 90.00 mol% with respect to the same amount of dichlorosilane introduced as in Example 3. Note that the Si precipitation ratio and the halogen element amount (Y value) in the halogen-containing material are calculated using thermodynamic equilibrium calculation software “FactSage”.
Here, the value of E in the formula (2) is preferably 1.1E-2, and more preferably close to the theoretical value of FIG. Moreover, 1.4E-2 is preferable and the value of F in Formula (2) is more preferable to approximate the theoretical value of FIG.
Since the phase diagram of the chemical equilibrium shown in FIG. 1 is obtained as the relationship between the halogen element and silicon, even when a substance other than HCl is used as the halogen element-containing substance and a substance other than dichlorosilane is used as the silicon-containing substance, The upper limit value and the lower limit value of Y can be considered similarly. For example, when a halogen-containing material containing Cl as a halogen element is used in FIG. 5 and a silicon-containing material is used, the phase diagram of chemical equilibrium and the upper limit value and lower limit value of Y1 in a 1000 ° C. atmosphere are expressed as Cl. A curve represented by the molar ratio of Si to Si is shown. Thus, since the chemical equilibrium relationship between the halogen-containing material and the silicon-containing material can be considered as the relationship between the halogen element and Si, the amount of the halogen element in the halogen-containing material to be supplied and the silicon-containing material to be supplied If the halogen element-containing material and the silicon-containing material are supplied in a range satisfying the relational expression (1) so that the amount of silicon in the substrate is not less than the lower limit value and not more than the upper limit value in FIG. This is preferable because the amount of Si doping can be ensured and the precipitation of Si in the reactor can also be suppressed.
Here, the value of E1 in Formula (1) is preferably 1.1E-2, and more preferably close to the theoretical value of FIG. Moreover, 1.3E-2 is preferable and the value of F1 in Formula (1) is more preferable to approach the theoretical value of FIG.

1) Preparation Step The manufacturing method of the present invention includes a step of preparing a base substrate in a crystal growth furnace of a vapor phase growth apparatus.
(Type of substrate)
The base substrate used in the present invention is not particularly limited as long as it has a growth surface capable of growing a group III nitride crystal, but the crystallinity of the obtained group III nitride crystal is good. To a hexagonal crystal, more preferably a hexagonal crystal having a lattice constant close to that of the group III nitride crystal to be grown, such as sapphire, zinc oxide crystal, and nitride crystal. . Of these, a nitride crystal is preferable, and a nitride crystal of the same type as the group III nitride crystal grown on the growth surface is more preferable. An example is gallium nitride. In particular, it is preferable that a growth surface of the base substrate contains a group III nitride crystal.
The lattice constant of sapphire is 4.758Å on the a axis and 12.983Å on the c axis. The lattice constant of gallium nitride is 3.189Å on the a-axis and 5.185Å on the c-axis.
The plane orientation of the base substrate is not particularly limited as long as it is a growth plane capable of growing a group III nitride crystal. For example, the {0001} plane, {10-10} plane, {11-20} plane, The {11-22} plane, the {20-21} plane, and the like can be preferably used, and the (0001) plane is more preferably used.

  In this specification, the “C plane” is a (0001) plane in a hexagonal crystal structure (wurtzite type crystal structure). In the group III nitride crystal, the “C plane” is a group III plane, and in gallium nitride, it corresponds to the Ga plane. Further, in this specification, the “C plane” refers to a growth surface of a base substrate having a growth surface in a range inclined by 25 ° from the C axis measured with an accuracy within ± 0.01 °. More preferably, it is a growth surface in a range inclined by 10 °, and further preferably a growth surface in a range inclined by 5 °.

  In this specification, the {10-10} plane is the “M plane” and is a plane equivalent to the {1-100} plane in a hexagonal crystal structure (wurtzite type crystal structure). A polar surface, usually a cleaved surface. The plane equivalent to {1-100} plane is (1-100) plane, (−1100) plane, (01-10) plane, (0-110) plane, (10-10) plane, (−1010) Surface. Further, in this specification, the “M plane” is a growth plane of a base substrate having a growth plane within a range inclined by 15 ° from the M axis to the A axis direction measured with an accuracy within ± 0.01 °. More preferably, it is a growth surface in a range inclined by 10 °, and more preferably a growth surface in a range inclined by 5 °. Further, the “M plane” means a growth plane of the base substrate having a growth plane within a range inclined by 25 ° from the M axis to the C axis direction measured with an accuracy within ± 0.01 °, more preferably. Is a growth surface within a range inclined by 10 °, more preferably a growth surface within a range inclined by 5 °.

  In this specification, the {11-20} plane is the “A plane” and is a plane equivalent to the {11-20} plane in the hexagonal crystal structure (wurtzite type crystal structure). It is a polar surface. The planes equivalent to the {11-20} plane are (11-20) plane, (-1-120) plane, (1-210) plane, (-12-10) plane, (-2110) plane, (2 -1-10) plane. Further, in this specification, the “A surface” is a growth surface of the base substrate having a growth surface in a range inclined by 15 ° from the A axis to the M axis direction measured with an accuracy within ± 0.01 °. More preferably, it is a growth surface in a range inclined by 10 °, and more preferably a growth surface in a range inclined by 5 °. Further, “A-plane” refers to a growth plane of the base substrate having a growth plane within a range inclined by 25 ° from the A-axis to the C-axis direction measured with an accuracy within ± 0.01 °, more preferably. Is a growth surface within a range inclined by 10 °, more preferably a growth surface within a range inclined by 5 °.

In this specification, the {11-22} plane is a plane equivalent to the {11-22} plane in the hexagonal crystal structure (wurtzite type crystal structure), which is a semipolar plane. The plane equivalent to the {11-22} plane is (11-22) plane, (-1-122) plane, (1-212) plane, (-12-12) plane, (-2112) plane, (2 -1-12) plane. Further, in this specification, the {11-22} plane has a growth plane within a range of a direction inclined by 15 ° from the <11-22> axis to the M-axis direction, which is measured with an accuracy within ± 0.01 °. It refers to the growth surface of the base substrate, more preferably a growth surface within a range inclined by 10 °, and still more preferably a growth surface within a range inclined by 5 °. Further, the {11-22} plane is measured with an accuracy within ± 0.01 °, and the growth surface of the base substrate has a growth surface in a range inclined by 25 ° from the <11-22> axis to the C-axis direction. More preferably, it is a growth surface in a range inclined by 10 °, and more preferably a growth surface in a range inclined by 5 °.
In this specification, the {20-21} plane is a plane equivalent to the {20-21} plane in a hexagonal crystal structure (wurtzite type crystal structure), which is a semipolar plane. The plane equivalent to the {20-21} plane is the (20-21) plane, (2-201) plane, (02-21) plane, (0-221) plane, (−2201) plane, (−2021). Surface. Further, in this specification, the {20-21} plane has a growth plane within a range of a direction inclined by 15 ° from the <20-21> axis to the A-axis direction measured with an accuracy within ± 0.01 °. It refers to the growth surface of the base substrate, more preferably a growth surface within a range inclined by 10 °, and still more preferably a growth surface within a range inclined by 5 °. Further, the {20-21} plane is measured with an accuracy within ± 0.01 °, and the growth surface of the base substrate has a growth surface in a range inclined by 25 ° from the <20-21> axis to the C-axis direction. More preferably, it is a growth surface in a range inclined by 10 °, and more preferably a growth surface in a range inclined by 5 °.

(Base substrate manufacturing method)
The manufacturing method of the base substrate used in the present invention is not particularly limited, and can be manufactured by a generally known method.
For example, as a crystal growth method of the base substrate, HVPE (Hydride Vapor Phase Epitaxy) method, MOCVD (Meral-Organic Chemical Vapor Deposition) method, MBE (Molecular Beam Epitaxy) method and the like can be exemplified.

(Installation of base substrate)
The method for preparing the base substrate in the crystal growth furnace (reactor) of the vapor phase growth apparatus is not particularly limited. For example, when an HVPE apparatus as shown in FIG. 4 is used, it is placed on the substrate holder 107. be able to. Specifically, it will be described in detail in the description of the growth process described later.

2) Growth process The production method of the present invention comprises reacting a compound containing a halide of a group III element and a nitrogen element (hereinafter, these may be collectively referred to as a group III nitride crystal forming gas) to form the base. A growth step of growing a group III nitride crystal on the substrate; In the growth step, a group III nitride crystal doped with a high concentration of silicon is obtained by supplying a halogen-containing material and a silicon-containing material from the same introduction tube to the crystal growth furnace.
When supplying the halogen element-containing material and the silicon-containing material into the crystal growth furnace (reactor) of the vapor phase growth apparatus, if not supplied from the same introduction pipe, the temperature inside the reactor becomes a high temperature condition that becomes the growth temperature. Therefore, decomposition occurs in the middle of the introduction pipe for supplying the silicon-containing substance, and Si is adsorbed and deposited. Therefore, a large amount of Si is precipitated in the reactor, particularly around the introduction pipe, which is not preferable.
When supplying the halogen-containing material and silicon-containing material into the reactor, the flow rate in the introduction tube can be increased and the silicon-containing material can be uniformly introduced into the base substrate. It is preferable to supply from.

In addition, when the group III nitride crystal forming gas is supplied into the reactor from each introduction pipe, the silicon-containing material reaches the base substrate without generating a silicon compound before reaching the base substrate. In view of this, it is preferable to supply the halogen-containing material and the silicon-containing material from an introduction pipe different from the introduction pipe that supplies the group III nitride crystal forming gas.
(Group III nitride crystal)
The type of group III nitride crystal for crystal growth is not particularly limited. For example, GaN, InN, AlN, InGaN, AlGaN, AlInGaN, etc. can be mentioned. Preferred is GaN, AlN, AlGaN, and more preferred is GaN.
The group III nitride crystal of the present invention preferably has a carrier concentration of 5E + 17 / cm ³ or more, more preferably 8E + 17 / cm, for the purpose of ensuring conductivity in device characteristics.
cm ³ or more, more preferably 1E + 18 / cm ³ or more. The carrier concentration is preferably 4E + 18 / cm ³ or less, more preferably 3E + 18 / cm ³ or less, and even more preferably 1 for reasons such as a decrease in mobility, an increase in absorbance, and an increase in defects due to impurities.
. 4E + 18 / cm ³ or less. In particular, according to the manufacturing method of the present invention, the Si doping concentration can be 5E + 17 / cm ³ or more, preferably 8E + 17 / cm ³ or more, and more preferably 1E + 18 / cm ³ or more. In addition, the Si doping concentration is preferably 4E + 18 / cm ³ or less, more preferably 3E + 18 / cm ³ or less, and even more preferably 1.4E + 18 from the viewpoint of maintaining mirror growth in the production method of the present invention.
/ Cm ³ or less.

(Halogen element-containing substances)
The halogen element-containing substance that can be used in the present invention is not particularly limited. For example, hydrogen halides such as HCl, HBr, and HF; halogen gases such as Cl ₂ , Br ₂ , and F ₂ ; gases that release halogen elements, and the like Is mentioned. Of these, hydrogen halides such as HCl, HBr, and HF are preferable, and HCl is more preferable because the silicon-containing material is easily stabilized as a gas. From another viewpoint, when the silicon-containing substance used as the doping gas contains a halogen element, it is preferable that the silicon-containing substance contains the same halogen element as the halogen element.

(Silicon-containing substance)
The silicon-containing substance that can be used in the present invention is not particularly limited as long as it contains silicon, and any substance may be used as long as it becomes a Si doping gas that functions as an n-type impurity in the reactor. For example, Si solid; monosilane; chlorosilane compounds such as SiH ₃ Cl, SiH ₂ Cl ₂ , SiHCl ₃ , SiCl ₄ ; bromosilane compounds such as SiH ₃ Br, SiH ₂ Br ₂ , SiHBr ₃ , SiBr ₄ ; SiH ₃ F, Fluorosilane compounds such as SiH ₂ F ₂ , SiHF ₃ , and SiF ₄ ; and halosilane compounds such as iodide silane compounds such as SiH ₃ I, SiH ₂ I ₂ , SiHI ₃ , and SiI ₄ are included. Of these, chlorosilane compounds such as SiH ₃ Cl, SiH ₂ Cl ₂ , SiHCl ₃ , and SiCl ₄ are preferable, and dichlorosilane (SiH ₂ Cl ₂ ) is more preferable because of its stability as a doping gas.

(Group III nitride crystal growth process)
As a crystal growth method that can be used in the method for producing a group III nitride crystal of the present invention, there are a Hydrogen Vapor Phase Epitaxy (HVPE) method, a M-Organic Chemical Vapor Deposition (MOCVD) method, a Molecular Beam Epix method, A gas phase method such as a sublimation method can be given. The HVPE method and the MOCVD method are preferable because the high-purity crystal can be obtained, and the HVPE method is most preferable. Next, the process of growing a group III nitride crystal using the method for producing a group III nitride crystal of the present invention will be described.

Details of the apparatus used for crystal growth are not particularly limited. For example, an HVPE apparatus as shown in FIG. 4 can be used. The HVPE apparatus shown in FIG. 4 includes a substrate holder (susceptor) 107 on which a base substrate 109 is placed and a reservoir 105 into which a group III nitride crystal material to be grown is placed. In addition, introduction pipes 101 to 104 for introducing gas into the reactor 100 and an exhaust pipe 108 for exhausting are installed. Further, a heater 106 for heating the reactor 100 from the side surface is installed.
As a material of the reactor 100, quartz, polycrystalline boron nitride (BN) stainless steel or the like is used. A preferred material is quartz, and synthetic quartz is more preferred because the carrier concentration of the crystal obtained is stable. The reactor 100 is filled with atmospheric gas in advance before starting the reaction. Examples of the atmospheric gas include H ₂ gas, N ₂ gas, inert gas such as He, Ne, and Ar. These gases may be mixed and used.

  Carbon is preferable as the material of the substrate holder 107, and a material whose surface is coated with SiC is more preferable. The shape of the substrate holder 107 is not particularly limited as long as the substrate substrate 109 of the present invention can be installed, but there is no structure upstream of the growing crystal when the crystal is grown. It is preferable. If there is a structure in which a crystal may grow on the upstream side, a polycrystal adheres to the structure, and HCl gas is generated as a product, which adversely affects the crystal to be grown. The size of the base substrate placement surface of the substrate holder 107 is preferably smaller than the base substrate to be placed. That is, it is more preferable that the substrate holder 107 is sized to be hidden by the size of the base substrate when viewed from the gas upstream side.

  When placing the base substrate on the substrate holder 107, it is preferable to place the base substrate so that the growth surface of the base substrate faces the upstream side of the gas flow (above the reactor in FIG. 4). That is, the gas is preferably placed so as to flow toward the crystal growth surface of the base substrate, and more preferably, the gas flows from a direction perpendicular to the crystal growth surface of the base substrate. By placing the base substrate in this way, a group III nitride crystal having more uniform and excellent crystallinity can be obtained.

The reservoir 105 is charged with a raw material to be a group III source. Examples of such a group III source material include Ga, Al, and In.
A gas that reacts with the raw material put in the reservoir 105 is supplied from an introduction pipe 103 for introducing the gas into the reservoir 105. For example, when a raw material that is a group III source is put in the reservoir 105, hydrogen halide such as HCl gas can be supplied from the introduction pipe 103. Here, the raw material serving as the group III source of the reservoir 105 reacts with the gas supplied from the introduction pipe 103, and a group III element halide is supplied into the reactor as the group III source gas G3. At this time, the carrier gas may be supplied from the introduction pipe 103 together with hydrogen halide such as HCl gas. Examples of the carrier gas include H ₂ gas, N ₂ gas, inert gas such as He, Ne, and Ar. These gases may be mixed and used. The carrier gas may be the same as or different from the atmospheric gas, but is preferably the same.

From the introduction pipe 104, a compound containing a nitrogen element is supplied as the group V source gas G4. Usually, NH ₃ gas is supplied. A carrier gas is supplied from the introduction pipe 102. As the carrier gas, the same carrier gas supplied from the introduction pipe 103 can be exemplified. The carrier gas supplied from the introduction pipe 102 and the carrier gas supplied from the introduction pipe 103 are preferably the same. Further, from the introduction pipe 101, a silicon-containing material and a halogen element-containing material, which are dopant gases, are supplied simultaneously. For example, an n-type dopant gas such as SiH ₄ or SiH ₂ Cl ₂ can be supplied. The carrier gas can also be supplied from the introduction pipe 101. As the carrier gas, the same carrier gas supplied from the introduction pipes 102 and 103 can be exemplified, and these are preferably the same.

  The gases supplied from the introduction pipes 101, 102, and 104 may be exchanged with each other and supplied from different introduction pipes. In addition, the source gas and the carrier gas serving as a nitrogen source may be mixed and supplied from the same introduction pipe. Further, a carrier gas may be mixed from another introduction pipe. These supply modes can be appropriately determined according to the size and shape of the reactor 100, the reactivity of the raw materials, the target crystal growth rate, and the like.

As described above, the doping gas G1, the group V source gas G4, and the group III source gas G3 are preferably supplied from separate introduction pipes.
The gas discharge pipe 108 is generally installed so that it can be discharged from the reactor inner wall on the opposite side to the introduction pipes 101 to 104 for gas introduction. In FIG. 4, a gas discharge pipe 108 is installed on the bottom surface of the reactor located opposite to the top surface of the reactor where the introduction pipes 101 to 104 for gas introduction are installed. When the introduction pipe for introducing gas is installed on the right side of the reactor, the gas discharge pipe is preferably installed on the left side of the reactor. By adopting such an aspect, a gas flow can be stably formed in a certain direction.

  Crystal growth by the HVPE method is usually performed at 800 ° C. to 1200 ° C., preferably 900 ° C. to 1100 ° C., more preferably 925 ° C. to 1070 ° C., and more preferably 950 ° C. to 1050 ° C. preferable. The pressure in the reactor is preferably 10 kPa to 200 kPa, more preferably 30 kPa to 150 kPa, and even more preferably 50 kPa to 120 kPa.

  The group III nitride crystal obtained after crystal growth may have a polycrystal at the boundary of the crystal plane. The polycrystal here means, for example, a crystal in which a hexagonal crystal lattice cannot be formed and there is no atom at an appropriate position. That is, it refers to a collection of minute crystals with disordered crystal orientation, meaning a collection of very small single crystal grains. In the case of having such a polycrystal, after performing the step of removing the polycrystal, a step of growing a group III nitride crystal on the surface of the crystal from which the polycrystal has been removed is further performed. When the group III nitride crystal thus obtained still has a polycrystal at the boundary of the crystal plane, the step of removing the polycrystal is performed again, and a group III nitride crystal is further grown on the surface. Perform the process. By repeating such an operation, a group III nitride crystal having no polycrystal can be obtained.

  The crystal system of the group III nitride crystal obtained by the production method of the present invention is preferably a hexagonal system. Further, the obtained group III nitride crystal is preferably a single crystal. The thickness of the group III nitride crystal grown on the base substrate is preferably 1 mm to 10 cm. When grinding, polishing, laser irradiation, etc. are performed after crystal growth, a crystal of a certain size is required. Therefore, the thickness of the group III nitride crystal grown on the base substrate is preferably 5 mm to 10 cm, and preferably 1 cm. 10 cm is more preferable.

  The group III nitride crystal obtained by the production method of the present invention may be used as it is, or may be used after processing such as grinding or slicing. Here, slicing means (1) processing to make the quality of the surface uniform so that the grown crystal can be used as a base substrate, and (2) that there is stress generated from dislocations in the initial stage of growth. This refers to the processing that is performed in order to cut off the portion in consideration. Specifically, the slicing can be performed using an inner peripheral slicer, a wire source slicer, or the like. In the present invention, it is preferable to produce a crystal having substantially the same shape, lower dislocation density, and fewer surface defects by slicing.

The group III nitride crystal substrate made of the group III nitride crystal of the present invention can also be obtained by performing processes such as grinding and slicing as described above, and general polishing and cleaning.
According to the production method of the present invention, a group III nitride crystal having a C-plane or M-plane with a surface roughness of 1 nm or less can be obtained. In particular, a group III nitride crystal having a C-plane or M-plane with a surface roughness of 1 nm or less can be produced without polishing after crystal growth. In addition, the surface roughness (Rms) in this invention is calculated | required by calculating with a root mean square from the data which measured the surface roughness of 10 micrometers square using atomic force microscope (AFM). Further, the C plane and the M plane are used in the same meaning as described above for the base substrate.

  The group III nitride crystal produced by the production method of the present invention can be used for various applications. In particular, it is useful as a substrate for semiconductor devices such as light emitting diodes of ultraviolet, blue or green, etc., light emitting elements having relatively short wavelengths such as semiconductor lasers, and electronic devices. It is also possible to obtain a larger group III nitride crystal by using the group III nitride crystal manufactured by the manufacturing method of the present invention as a base substrate.

The features of the present invention will be described more specifically with reference to examples and comparative examples. The materials, amounts used, ratios, processing details, processing procedures, and the like shown in the following examples can be changed as appropriate without departing from the spirit of the present invention. Therefore, the scope of the present invention should not be construed as being limited by the specific examples shown below.
In the following examples and comparative examples, crystal growth was performed using the HVPE apparatus shown in FIG.
<Evaluation method>
(1) Carrier concentration The carrier concentration in the GaN crystal obtained by the present invention was determined by performing hole measurement by the van der Pauw method. A substrate made of a 5 mm × 5 mm square GaN crystal was prepared as a sample, and an electrode was formed on the sample surface near the apex of the square with indium-containing solder, and measurement was performed.

<Example 1>
As a base substrate, a template substrate in which GaN was grown to about 15 μm by MOCVD on a sapphire substrate was prepared.
The base substrate was placed on a SiC-coated carbon substrate holder 107 having a diameter of 70 mm and a thickness of 20 mm, and placed in the reactor 100 of the HVPE apparatus as shown in FIG.

After raising the temperature in the reactor to 1040 ° C., H ₂ carrier gas G 1, N ₂ carrier gas G 2, GaCl gas G ₃ which is a reaction product of Ga and HCl, and NH ₃ gas G 4 are introduced into the introduction pipes 101- 104 respectively. Here, HCl was supplied from the introduction tube 103 to Ga in the reservoir 105, and GaCl gas G3 was supplied into the reactor. Further, dichlorosilane (SiH ₂ Cl ₂ ) and hydrogen chloride (HCl) are simultaneously supplied to the H 2 carrier gas G 1 of the introduction tube 101 in order to dope silicon into the crystal to be grown, and a GaN layer is formed on the template substrate 109. Grow for 23 hours. In this GaN layer growth step, the growth pressure is 1.01 × 10 ⁵ Pa, the partial pressure of the GaCl gas G3 is 7.36 × 10 ² Pa, and the partial pressure of the NH ₃ gas G4 is 7.03 × 10 ³ Pa. The partial pressure of dichlorosilane (SiH ₂ Cl ₂ ) was 6.74 × 10 ⁻¹ Pa, and the partial pressure of hydrogen chloride (HCl) was 4.49 × 10 ¹ Pa.
After completion of the GaN layer growth step, the temperature in the reactor was lowered to room temperature to obtain a GaN crystal that was a group III nitride crystal. Almost no Si deposition was observed in the reactor.
The obtained GaN crystal had a growth surface with a mirror surface, and the thickness measured by a stylus type film thickness meter was 3.1 mm. Moreover, it was 1.07 * 10 < ¹⁸ > / cm < ³ > when carrier concentration was measured by the hole measurement.

<Example 2>
In the GaN layer growth process of Example 1, the partial pressure of NH ₃ gas G4 is set to 7.02 × 10 ³ Pa, the partial pressure of dichlorosilane (SiH ₂ Cl ₂ ) is set to 6.73 × 10 ⁻¹ Pa, and chlorination is performed. A GaN crystal that is a group III nitride crystal was obtained in the same manner as in Example 1 except that the partial pressure of hydrogen (HCl) was set to 6.73 × 10 ¹ Pa. No Si deposition was observed in the reactor. The obtained GaN crystal had a growth surface with a mirror surface, and the thickness measured with a stylus type film thickness meter was 3.0 mm. Further, the carrier concentration was measured by hole measurement and found to be 1.03 × 10 ¹⁸ / cm ³ .

<Example 3>
The growth time of the GaN layer of Example 1 was 24 hours, the partial pressure of GaCl gas G3 was 7.37 × 10 ² Pa in the GaN layer growth step, and the partial pressure of dichlorosilane (SiH ₂ Cl ₂ ) was 1.35. × and ¹⁰ 0 Pa, except that the partial pressure of hydrogen chloride (HCl) was 6.74 × ¹⁰ 0 Pa, to obtain a GaN crystal a group III nitride crystal in the same manner as in example 1. A large amount of Si deposition was observed in the reactor. As a result of simulation of chemical equilibrium using the thermodynamic equilibrium calculation software “FactSage” and the thermodynamic database “Fact”, 96.75 mol% of Si was precipitated with respect to the amount of introduced dichlorosilane. It is thought that there is.
The obtained GaN crystal had a growth surface with a mirror surface, and the thickness measured with a stylus type film thickness meter was 3.0 mm. Further, the carrier concentration was measured by hole measurement and found to be 6.31 × 10 ¹⁷ / cm ³ .

<Example 4>
In Example 1, after raising the temperature in the reactor to 1020 ° C., the growth time of the GaN layer was 56 hours, the partial pressure of the GaCl gas G3 was 6.02 × 10 ² Pa in the GaN layer growth step, and the NH ₃ gas G4 Is set to 7.58 × 10 ³ Pa, the partial pressure of dichlorosilane (SiH ₂ Cl ₂ ) is set to 5.35 × 10 ⁻¹ Pa, and the partial pressure of hydrogen chloride (HCl) is set to 8.92 × 10 ^1. A GaN crystal, which is a group III nitride crystal, was obtained in the same manner as in Example 1 except that Pa was used. No Si deposition was observed in the reactor. However, abnormal growth occurred in the obtained GaN crystal, and it was impossible to obtain a GaN crystal having a mirror growth surface.

<Comparative Example 1>
As a base substrate, a polished C-plane GaN free-standing substrate having a Ga surface was prepared.
A GaN free-standing substrate was used instead of the ELO substrate of Example 1, the temperature inside the reactor was raised to 1020 ° C., and then a GaN layer was grown for 24 hours. In this GaN layer growth step, the partial pressure of GaCl gas G3 was 7.37. A GaN crystal, which is a group III nitride crystal, was obtained in the same manner as in Example 1 except that the pressure was × 10 ² Pa and dichlorosilane (SiH ₂ Cl ₂ ) and hydrogen chloride (HCl) were not used. No Si deposition was observed in the reactor. The obtained GaN crystal had a growth surface with a mirror surface and had a thickness of 2.3 mm as measured by a stylus thickness meter. Further, the carrier concentration was measured by hole measurement and found to be 3.71 × 10 ¹⁷ / cm ³ .

<Comparative example 2>
In Example 1, after raising the temperature in the reactor to 1020 ° C., the growth time of the GaN layer was set to 24 hours, and the partial pressure of the GaCl gas G3 was set to 7.37 × 10 ² Pa in the GaN layer growth step, and dichlorosilane (SiH ₂ Cl ₂ ) was set to 1.35 × 10 ⁰ Pa and hydrogen chloride (HCl) was not used to obtain a GaN crystal as a group III nitride crystal in the same manner as in Example 1. A large amount of Si deposition was observed in the reactor. The obtained GaN crystal was a growth surface surface state mirror surface, and the thickness measured by a stylus type film thickness meter was 3.0 mm.
Further, the carrier concentration was measured by hole measurement and found to be 5.72 × 10 ¹⁷ / cm ³ .

According to the method for producing a group III nitride crystal of the present invention, a group III nitride crystal in which silicon is uniformly doped in the in-plane direction and the film thickness direction in the crystal can be obtained. As a result, a thick film and a large area group III nitride crystal can be stably produced, and an improvement in productivity can be expected.
The obtained group III nitride crystal is useful as a substrate for semiconductor light emitting devices such as light emitting diodes and semiconductor lasers, and semiconductor devices such as electronic devices. Usually, the GaN substrate used to manufacture light-emitting elements is one that has increased conductivity by adding impurities in order to manufacture a device with an upper and lower electrode structure in which electrodes are also attached to the back surface of the substrate. Has been. Therefore, the present invention capable of producing a group III nitride crystal doped with a high concentration of silicon and having enhanced conductivity has high industrial applicability.

DESCRIPTION OF SYMBOLS 100 Reactor 101-104 Introduction pipe 105 Reservoir 106 Heater 107 Substrate holder 108 Gas exhaust pipe
109 Substrate G1 Doping gas G2 Carrier gas G3 Group III source gas G4 Group V source gas

Claims (10)

  A group III nitride including a step of preparing a base substrate in a crystal growth furnace and a growth step of growing a group III element halide and a compound containing a nitrogen element to grow a group III nitride crystal on the base substrate. A method for producing a group III nitride crystal, characterized in that a halogen element-containing substance and a silicon-containing substance are further supplied from the same introduction pipe to the crystal growth furnace in the growth step. In the supply of the halogen element-containing material and the silicon-containing material, the amount of halogen element in the supplied halogen element-containing material and the amount of silicon in the supplied silicon-containing material satisfy the following relational expression (1): Item 3. A method for producing a Group III nitride crystal according to Item 1.
A1 × ln (B1 × (X1−D1)) − (C1 × (X1−D1) + E1 <Y1 <A1 × ln (B1 × (X1−D1)) − (C1 × (X1−D1) + F1. Formula (1)
X1 Amount of silicon (molar ratio)
Y1 Amount of halogen element (molar ratio)
A1 9.682E-4
B1 8.000E-1
C1-7.400
D1-8.000E-6
E1 1.000E-2 (lower limit)
F1 1.480E-2 (upper limit)
However, if A1 * ln (B1 * (X1-D1))-(C1 * (X1-D1) + E1 <0, then A1 * ln (B1 * (X1-D1))-(C1 * (X1- D1) It is assumed that + E1 = 0. The group III nitride crystal according to claim 1, wherein the halogen element-containing substance is hydrogen chloride, the silicon-containing substance is dichlorosilane, and the supply amounts thereof satisfy the following relational expression (2). Method.
A × ln (B × (X−D)) − (C × (X−D) + E <Y <A × ln (B × (X−D)) − (C × (X−D) + F) Formula (2)
X Dichlorosilane supply (molar ratio)
Y Supply amount of hydrogen chloride (molar ratio)
A 9.682E-4
B 1.110E + 0
C -1.060E + 1
D-2.760E-6
E 8.706E-3 (lower limit)
F 1.861E-2 (upper limit)
However, when A × ln (B × (X−D)) − (C × (X−D) + E <0, A × ln (B × (X−D)) − (C × (X− D) Let + E = 0.   The method for producing a group III nitride crystal according to claim 1 or 2, wherein the silicon-containing substance is dichlorosilane.   The method for producing a group III nitride crystal according to claim 1 or 2, wherein the halogen element-containing substance is hydrogen halide.   The method for producing a group III nitride crystal according to any one of claims 1 to 5, wherein a carrier gas is further supplied from the same introduction tube in addition to the halogen element-containing material and the silicon-containing material.   The group III element halide and the nitrogen element-containing compound are supplied from an introduction pipe into a crystal growth furnace, and a halogen element-containing substance and a silicon-containing substance are supplied from an introduction pipe different from the introduction pipe. 7. The method for producing a group III nitride crystal according to any one of 6 above.   The method for producing a group III nitride crystal according to claim 1, wherein the growth step is performed by a hydride vapor phase epitaxy (HVPE) method.   A group III nitride crystal obtained by the method for producing a group III nitride crystal according to any one of claims 1 to 8.   A group III nitride crystal substrate comprising the group III nitride crystal according to claim 9.

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