JPH1075019A - Manufacture of gan compound semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing high-quality GaN compound semiconductor device, wherein a high-quality InGaN light-emitting layer of a good crystallinity can be formed. SOLUTION: When depositing (Ga1-x N/Alx )1-y Iny N (0<=x<=1, 0<=y<=1) crystal material, by vapor phase epitaxial technology, an atmosphere of at least one growth interruption process to interrupt the growth of a layer being formed, whether it is the same layer or hetero layer, is made the group V gas included one and carrier gas other than group V gas is inactive gas. By this method, the sublimation of a layer exposed in the growth interruption process can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a semiconductor light emitting device, and more particularly to a method for manufacturing an InGaAlN-based heterostructure LED, LD, etc. used for light emitting devices ranging from ultraviolet to green.

[0002]

2. Description of the Related Art Taking a GaN-based light-emitting device used for a display or a full-color display as an example, a method of manufacturing a GaN-based semiconductor device based on a conventionally proposed manufacturing example. Will be described.

FIG. 1 is a sectional view schematically showing a structural example of a GaN-based light emitting device. FIG. 9 is a time chart showing the processing temperature and the passage of time. As a growth method of each layer,
Metal organic chemical vapor deposition (hereinafter referred to as MOCVD) is used.

First, before growing the buffer layer, the sapphire substrate 1 is subjected to thermal cleaning using only a hydrogen carrier gas. Then, 5
The temperature is lowered to 20 ° C., and then the carrier gas is switched as follows. That is, the carrier gas is switched so that the ratio of nitrogen and hydrogen becomes 1: 3, and NH ₃ which is a group V material is
And a fixed amount of Group III raw material TMG
A GaN buffer layer 2 of nm is grown. NH ₃ , which is a group V raw material, is set so as to be always supplied during the subsequent process, not only during growth but also during suspension of growth.

[0005] Thereafter, the carrier gas is changed to 11 without switching.
The temperature is raised to 00 ° C., TMG and SiH ₄ are supplied, and a Si-doped n-type GaN clad layer 3 having a thickness of 4 μm is grown. After the growth of the Si-doped n-type GaN clad layer 3, the temperature is lowered to 800 ° C. while keeping the carrier gas as it is. With the temperature kept constant at 800 ° C., the ratio of nitrogen and hydrogen as carrier gases was switched to 1: 1 and TMI and TMG as growth layer materials and SiH as emission center material were changed.
₄ and DMZn, and Zn, Si having a thickness of 0.2 μm.
A doped InGaN light emitting layer 4 is grown. Here, in the present specification, a case where the ratio of nitrogen: hydrogen is 1: 1 is also defined as a nitrogen-rich state.

After the growth of the Si-doped InGaN light-emitting layer 4, the ratio of nitrogen to hydrogen as a carrier gas is returned to 1: 3 (that is, in a hydrogen-rich state), and the temperature is raised to 1100 ° C. After the temperature was raised to 1100 ° C., the carrier gas was left as it was, TMA and TMG and Cp ₂ Mg as a dopant were supplied, and a 0.2 μm-thick Mg-doped p was added.
A type AlGaN layer 5 is grown. Finally, TMG and Cp
₂ Mg is supplied to grow a p-type GaN layer 6 having a thickness of 0.3 μm. Further, by lowering the temperature to room temperature while the growth is interrupted while the carrier gas is kept, a GaN-based light emitting device as shown in FIG. 1 is obtained.

The InGaN light emitting layer thus obtained has an equilibrium pressure of nitrogen of InN which is about two orders of magnitude higher than that of GaN, and is grown at a temperature lower than that of GaN by about 200 ° C. AlGaN on top of the layer
When growing the layer, the growth had to be interrupted once, and the temperature had to be further raised to grow the AlGaN layer on the InGaN layer.

Therefore, it is necessary to stably maintain the InGaN light emitting layer in a high temperature state (ie, when the temperature is raised from 800 ° C. to 1100 ° C.). However, according to the findings of the present inventors, in the above-described conventional method,
Since a hydrogen-rich gas having a ratio of nitrogen to hydrogen of 1: 3 was used as a carrier gas in the temperature increasing process, I
It has been found that the nGaN light emitting layer cannot be stably held. That is, since NH ₃ has a large diffusion coefficient of twice or more that of nitrogen in a hydrogen atmosphere, the NH ₃ concentration in the vicinity of the substrate is reduced under the hydrogen-rich condition. Phenomenon occurs,
Therefore, N of the InGaN light emitting layer is easily dissociated,
There has been a problem that the decomposition of the InGaN light-emitting layer causes the deterioration of the crystal or the reduction or disappearance of the thickness. Therefore,
The light-emitting element obtained by the above-described method has an extreme
Since there was no nGaN light-emitting layer, or even if this layer remained, it remained as a layer with significantly reduced crystallinity, resulting in reduced luminous efficiency and reliability.

Accordingly, the present invention is directed to overcoming the problems associated with the above-described conventionally proposed methods, and is directed to a high-quality, highly crystalline InGaAs.
It is an object of the present invention to provide a method for manufacturing a high-quality GaN-based compound semiconductor device capable of forming an 1N light emitting layer.

[0010]

As described above, as described above, GaN
In the case of growing a compound semiconductor in a vapor phase at a high temperature of about 1000 ° C., or growing a mixed crystal containing In which is thermally unstable such as an InGaAlN layer at a temperature of about 800 ° C. Due to the dissociation of N from the InGaAlN layer and the reduction action by the H ₂ carrier gas, the growth layer once formed is exposed to crystal deterioration and film thickness fluctuation due to a remarkable sublimation action in the growth interruption step. (Emission efficiency and light output).

In the present invention, the above problem is solved by actively focusing on this growth interruption step, and in particular, controlling the process conditions in all the growth interruption steps accompanying the temperature increase, temperature decrease, and flow rate change to an optimum state. It is assumed that.

That is, the method of manufacturing a GaN-based compound semiconductor device according to the present invention comprises the steps of (Ga _1-x Al _x ) _1-y In _y
In vapor phase growth of an N (0 ≦ x ≦ 1, 0 ≦ y ≦ 1) crystal structure, at least one growth interruption step of interrupting the growth of a layer to be formed in either the same layer or the hetero layer. By using an atmosphere containing a group V gas as the atmosphere in the interruption step and using an inert gas as a carrier gas other than the group V gas, the decomposition of the layer exposed in the growth interruption step is prevented. It is characterized by the following.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Specific embodiments of the method of manufacturing a GaN-based semiconductor device according to the present invention will be described with reference to a GaN-based light-emitting device used for a display or a full-color display as an example.

FIG. 1 is a sectional view schematically showing a structural example of a GaN-based light emitting device. FIG. 3 is a time chart showing the processing temperature and the passage of time. In this example, a metal organic chemical vapor deposition (MOCVD) method is used as a method for growing each layer.

First, before the growth of the buffer layer, the sapphire substrate 1 is subjected to thermal cleaning using only a hydrogen carrier gas. Then, 5
The temperature is lowered to 20 ° C., and then the carrier gas is switched as follows. That is, the carrier gas is switched so that the ratio of nitrogen and hydrogen becomes 1: 3, and NH ₃ which is a group V material is
And a fixed amount of Group III raw material TMG
A GaN buffer layer 2 of nm is grown. NH ₃ , which is a group V raw material, is set so as to be always supplied during the subsequent process, not only during growth but also during suspension of growth.

Thereafter, the carrier gas is switched without switching.
The temperature is raised to 00 ° C., TMG and SiH ₄ are supplied, and a Si-doped n-type GaN clad layer 3 having a thickness of 4 μm is grown. After the growth of the Si-GaN layer, the temperature is lowered to 800 ° C. while keeping the carrier gas. With the temperature kept constant at 800 ° C., the ratio of nitrogen and hydrogen as carrier gases was changed to 1: 1 and TMI and T
MG, SiH ₄ and DMZn, which are emission center materials, are supplied, and a Zn and Si-doped InGaN emission layer 4 having a thickness of 0.2 μm is grown.

After the growth of the InGaN layer, the ratio of nitrogen to hydrogen as a carrier gas is set to 3: 1 and the temperature is raised to 1100 ° C. After the temperature was raised to 1100 ° C., the ratio of the carrier gas nitrogen and hydrogen was returned to 1: 3, and TMA and T
MG and a dopant Cp ₂ Mg are supplied to grow a Mg-doped p-type AlGaN layer 5 having a thickness of 0.2 μm. Finally, TMG and Cp ₂ Mg are supplied to achieve a thickness of 0.
A 3 μm p-type GaN layer 6 is grown. Further, by lowering the temperature to room temperature while the growth is interrupted while the carrier gas is kept as it is, the GaN as shown in FIG.
A system light emitting device is obtained.

As an additional effect, the use of an inert gas atmosphere during temperature lowering allows the Mg-doped GaN layer to be formed as
It can also be made into a P-type by -grown.

In the above embodiment, a mixed gas of nitrogen-rich nitrogen and hydrogen was used as the group V source gas using NH ₃ as the carrier gas. However, as described above, Ne, Ar, Kr, and Xe other than nitrogen were used. And an inert gas such as SF ₆ can be used similarly.

As described above, the InGaN layer is a light emitting layer,
In the manufacture of a double heterostructure device having an AlGaN layer as a cladding layer, a hydrogen-rich gas having a ratio of nitrogen and hydrogen of 1: 3 is used as a carrier gas used in a temperature increasing process after growth of an InGaN layer. It had been. The reason why the hydrogen-rich gas is used is that hydrogen can purify a carrier gas with higher purity than nitrogen.

However, as described above, under such conditions, there is a problem that the InGaN layer is decomposed and the film disappears or decreases, or the crystallinity decreases. This is because the diffusion coefficient of NH ₃ is much larger in the hydrogen gas than in the nitrogen gas, and when the carrier gas is rich in hydrogen as in the prior art, the NH ₃ diffuses and the NH ₃ concentration becomes lower. This is considered to be because the effect of suppressing the decomposition of “N” in the layer is reduced.

By using the above-mentioned inert gas as the carrier gas as in the present invention, the NH ₃ concentration can be kept high, and the decomposition of the InGaN light emitting layer during the temperature rise can be significantly suppressed. be able to.

Next, changes in the surface of the InGaN layer caused by annealing will be described for the devices obtained in the above-described embodiment of the present invention and the comparative example described at the beginning.

First, each of the same wafers after the growth of the InGaN layer was heated from room temperature to 1100 ° C. under nitrogen-rich conditions (Examples) and hydrogen-rich conditions (Comparative Examples) in accordance with the temperature profile shown in FIG. Annealing was performed, and an SEM photograph of the surface of the InGaN layer was taken. FIG. 4 is a SEM photograph of the surface of the InGaN layer before annealing. FIG. 5 (Comparative Example) shows the surface state after annealing in a hydrogen-rich atmosphere, and FIG. 6 (Example) shows the surface state after annealing in a nitrogen-rich atmosphere. From these results, it can be seen that the surface of the InGaN layer is significantly deteriorated in the case of hydrogen-rich, but hardly changes in the case of nitrogen-rich.

FIG. 7 is a graph showing a change in X-ray intensity depending on the annealing time of the InGaN layer. In the X-ray intensity, when the hydrogen-rich gas is used as in the comparative example, the intensity is reduced by about 70%, whereas in the example using the nitrogen-rich gas, the X-ray intensity is substantially reduced. Not confirmed.

FIG. 8 shows measured values of LED relative luminance. From this graph, it can be seen that the luminance of the light emitting element according to the example of the present invention is 10 times or more higher than that of the comparative example.

FIG. 10 is a sectional view schematically showing a structural example of a GaN-based MQW blue laser device.

FIG. 11 is a time chart showing the processing temperature and the passage of time. Also in this example, a metal organic chemical vapor deposition method is used as a method for growing each layer.

First, before growing the buffer layer, the sapphire substrate is subjected to thermal cleaning using only a hydrogen carrier gas. Thereafter, the carrier gas is left as it is, and 52
The temperature is lowered to 0 ° C., and then the carrier gas is switched as follows. That is, the carrier gas is switched so that the ratio of nitrogen to hydrogen becomes, for example, 1: 3, and NH ₃ which is a group V material is
And a fixed amount of Group III raw material TMG
A GaN buffer layer of mm is grown. Here, NH ₃ which is a group V material is set so as to be always supplied during the subsequent process, not only during the growth but also during the suspension of the growth.

After that, the temperature is raised to 1050 ° C., and before the temperature is raised, the carrier gas is switched at a ratio of nitrogen to hydrogen of, for example, 3: 1. After the temperature rise, TMG and SiH ₄ are supplied to grow a Si-doped n-type GaN layer having a thickness of 4 μm. Thereafter, an AlGaN cladding layer is grown, and NH ₃ and T
Since the intermediate reaction with MA is likely to occur, it is necessary to change the total flow rate. Therefore, the growth is interrupted, and the total flow rate is increased, for example, by 1.5 times while keeping the composition ratio of the carrier gas to the ratio of nitrogen to hydrogen at 3: 1.

Thereafter, TMG, TMA, and SiH ₄ are supplied, and 0.25 μm Si-doped n-type Al _0.15 Ga
_{A 0.85} N cladding layer is grown.

Then, the total flow rate of the carrier gas is returned to its original value while the ratio of nitrogen to hydrogen is kept at 3: 1, and the temperature is lowered to 700 ° C. Thereafter, an undoped GaN layer of 0.1 μm is grown.

Thereafter, an interval for a predetermined time is inserted, and T
MG and TMI are supplied according to the In composition of each of the well layer and the barrier layer, and undoped In _0.20 Ga _{0.80 of} 20 A is supplied.
10 pairs of N well layers and 40A undoped In _0.05 Ga _0.95 N barrier layers are alternately grown.

Next, the temperature is raised to 1050 ° C. with the ratio of nitrogen to hydrogen being 3: 1. Thereafter, the total flow rate is increased by a factor of 1.5 while maintaining the ratio of nitrogen to hydrogen. Furthermore, TM
G, TMA and Cp2Mg are supplied and Mg-doped p-type Al
_{A 0.15} Ga _0.85 N layer cladding layer is grown.

After that, the growth is interrupted, the total flow rate is returned to the original value, and the ratio of the carrier gas nitrogen and hydrogen is adjusted to 3:
As 1, a Mg-doped GaN layer having a thickness of 0.1 μm is grown. After the growth layer is completed, the temperature is lowered to room temperature while keeping the ratio of nitrogen to hydrogen carrier gas at 3: 1. In this way,
A GaN-based MQW blue laser diode is formed.

As an additional effect, the use of an inert gas atmosphere during temperature lowering allows the Mg-doped GaN layer to be formed as
It can also be made into a P-type by -grown.

In the above embodiment, a mixed gas of nitrogen-rich and hydrogen-rich was used as a group V source gas with NH ₃ as a carrier gas. However, as described above, Ne, Ar, Kr, Xe and inert gas, such as SF ₃ may be used as well. Further, NH ₃ , N ₂ H ₄ , N ₂ H ₃ CH ₃ and N ₂ H are used as group V source gases.
A raw material selected from the group consisting of ₂ (CH ₃ ) ₂ can be used.

In the conventional method, even at the same temperature, the growth is interrupted and the total flow rate is increased at the time of transition from GaN growth to AlGaN layer growth or at the time of transition from InGaN MQW layer to AlGaN layer growth. In such a case, a hydrogen-rich gas in which the ratio of nitrogen to hydrogen is 1: 3 has been used as the carrier gas. This is because hydrogen can purify a carrier gas with higher purity than nitrogen.

However, as described above, under such conditions, there is a problem that the CaN layer is decomposed and the film is reduced and the crystallinity is reduced. This is because the diffusion coefficient of NH ₃ is much higher in hydrogen gas than in nitrogen gas, and when the carrier gas is a hydrogen carrier gas as in the prior art, NH ₃ is diffused to lower the NH ₃ concentration. C
This is probably because the effect of suppressing the decomposition of “N” in the aN layer, the NMQW layer, and the AlGaN layer is reduced.

The hydrogen gas is a GaN layer, InGaN
This has the effect of chemically reducing the AlGaN layer and the AlGaN layer, and this also causes a problem that the film is reduced and the crystallinity is reduced.

In the method of the present invention, the use of the above-mentioned inert gas as the carrier gas not only keeps the NH ₃ concentration in the system high and suppresses the escape of “N” but also reduces the carrier gas. It is possible to suppress the reduction action by hydrogen gas.

Next, an ultraviolet light LE having a GaN layer as a light emitting layer
Another preferred embodiment of the present invention will be described by taking a D light emitting element as an example.

FIG. 12 is a sectional view schematically showing a structural example of a GaN-based ultraviolet light emitting device. FIG. 13 is a time chart showing the processing time and elapsed time. In this example, the same metal organic chemical vapor deposition (MOCVD) as described above is used as a method for growing each layer.

First, before the growth of the buffer layer, the sapphire substrate is subjected to thermal cleaning using only a hydrogen carrier gas. After that, the carrier gas is left as it is 52
The temperature is lowered to 0 ° C., and then the carrier gas is switched as follows. That is, the carrier gas is switched so that the ratio of nitrogen to hydrogen becomes, for example, 1: 3, and a fixed amount of NH _{3 as} a group V source gas and TMG as a group III source gas is supplied.
A 0 nm GaN buffer layer is grown. Here, NH ₃ , which is a group V source gas, is always supplied not only during growth but also during interruption of growth in the subsequent processes.

Thereafter, the growth is interrupted so that the ratio of carrier gas nitrogen to hydrogen is, for example, 3: 1. Thereafter, the temperature is raised to 1100 ° C.

Thereafter, TMG and SiH ₄ are supplied to grow a Si-doped n-type GaN layer having a thickness of 4 μm. This Si-GaN growth is interrupted, and the total flow rate is increased to 1.5 times while maintaining the carrier gas ratio.

Thereafter, TMG, TMA and SiH ₄ are supplied, and a Si-doped n-type Ai3Ga _1-z having a thickness of 0.2 μm is provided.
A N layer (0 <z ≦ 1) is grown. This Si-AlzG
After growing the a1-zN layer (0 <z≤1), the growth is interrupted and the total flow rate is returned to the original flow rate while maintaining the carrier gas flow rate ratio.

Thereafter, TMG and SiH ₄ are supplied to grow a GaN active layer having a thickness of 0.1 μm. Again, the growth is interrupted and the total flow rate is increased by a factor of 1.5 while keeping the carrier gas ratio.

Thereafter, TMG, TMA and Cp2Mg are supplied, and a 0.2 μm-thick Mg-doped p-type Al _z Ga
_{A 1-z} N layer (0 <z ≦ 1) is grown. The growth is interrupted again, and the total flow rate is returned to the original flow rate while maintaining the carrier gas flow rate ratio.

Thereafter, a predetermined amount of TMG and Cp2Mg are supplied, and a 0.1 μm-thick Ng-doped GaN layer is grown. Thereafter, the temperature is lowered while the growth is interrupted while leaving the carrier gas as it is, thereby obtaining the GaN-based ultraviolet light emitting device shown in FIG.

As an additional effect, the use of an inert gas atmosphere during temperature lowering allows the Mg-doped GaN layer to be formed as
It can also be made into a P-type by -grown.

In the above-described embodiment, the ratio between the inert gas and the H ₂ gas in the interruption of the growth is set, but the ratio may be 1: 1 or more, and it is particularly intended to limit the ratio to 3: 1. Not something. In the above embodiment, the growth interrupting step is performed and the carrier gas atmosphere is defined. However, depending on the function of the growth layer, it is not always necessary to apply the present invention to all the interrupting steps. It suffices to apply to the growth interruption step.

Focusing on the crystal state of each of the obtained forming layers, the forming layers according to the present invention all have an X-ray diffraction pattern having a clear peak, and have a high peak without rounding of the peak and crystal deterioration. A quality crystal layer can be obtained.

In particular, as shown in FIG. 14, the crystal pattern of the InGaN-based MQW layer obtained by the conventional method is rounded, whereas the InGaN-based MQW layer formed by the above-described method of the present invention is distorted. The layer has an X-ray diffraction pattern with satellite peaks indicating that high quality crystals have been formed.

[0055]

According to the present invention, there is provided a method of manufacturing a high-quality GaN-based compound semiconductor device capable of forming an InGaN light emitting layer having high quality and excellent crystallinity.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view schematically showing a structural example of a GaN-based light emitting device.

FIG. 2 is a time chart showing a processing temperature and a lapse of time in an embodiment of the present invention.

FIG. 3 is a temperature profile showing annealing conditions.

FIG. 4 is an SEM photograph showing a crystal state of a surface of an InGaN layer before annealing.

FIG. 5 is an SEM photograph showing a crystal state of a surface of an InGaN layer after annealing in a comparative example.

FIG. 6 is an SEM photograph showing a crystal state of a surface of an InGaN layer after an annealing process in an example.

FIG. 7 is a graph showing a change in X-ray intensity with time of annealing of an InGaN layer.

FIG. 8 is a graph showing measured values of LED relative luminance.

FIG. 9 is a time chart showing the processing temperature and the passage of time in a conventional example.

FIG. 10 is a sectional view schematically showing a structural example of a GaN-based MQW blue laser device.

FIG. 11 is a time chart showing a processing temperature and a lapse of time in an example of the present invention.

FIG. 12 is a cross-sectional view schematically showing a structural example of a GaN-based ultraviolet light emitting device.

FIG. 13 is a time chart showing a processing temperature and a lapse of time in the embodiment of the present invention.

FIG. 14 is a graph showing an X-ray diffraction pattern of a GaN-based MQW structure obtained by a conventional method and the method of the present invention.

[Explanation of symbols]

 Reference Signs List 1 sapphire substrate 2 buffer layer 3 Si-GaN layer 4 Zn, Si-InGaN layer 5 Mg-AlGaN layer 6 Mg-GaN layer

Claims (13)

[Claims] (1) (Ga _{1 -x} Al _x ) _{1 -y} In _y N (0 ≦ x
≦ 1, 0 ≦ y ≦ 1) In the vapor phase growth of the system crystal material, in any one of the same layer and the hetero layer, the atmosphere in at least one of the growth interruption steps of the growth interruption step of interrupting the growth of the layer to be formed. , An atmosphere containing a group V gas, and the use of an inert gas as a carrier gas other than the group V prevents decomposition of the layer exposed in the growth interruption step. , A method of manufacturing a GaN-based compound semiconductor device. 2. The method according to claim 1, wherein, during the growth of the material system, the method according to claim 1 is applied to a temperature lowering process after completion of a final layer.
The method described in. 3. The method according to claim 1, wherein the step of interrupting the growth includes not only a step of keeping the temperature constant, but also a step involving raising or lowering the temperature. 4. The method according to claim 1, wherein the group V source gas is NH ₃ , N ₂ H ₄ ,
N ₂ include H ₃ CH ₃ and _N 2 _H 2 _(CH 3) at least one member selected from the group consisting of 2, the inert _{gas, N 2, He, Ne,} Ar, Kr, Xe and SF ₆
The method according to claim 1, comprising at least one member selected from the group consisting of: 5. The method according to claim 1, wherein the carrier gas contains a predetermined amount of H ₂ . 6. The method according to claim 1, wherein the ratio of the inert gas to the H ₂ carrier gas is 1: 1 or more.
The method described in the section. Diffusion coefficient for said carrier gas wherein said group V material gas is smaller than the diffusion coefficient for H _2, the method according to any one of claims 1 to 6. 8. The method according to claim 1, wherein the InGaN-based MQW layer formed by the method has an X-ray diffraction pattern having a satellite peak. 9. _{In x Ga 1-x N (} 0 <x ≦ 1) / Al y
In the step of vapor-growing a Ga _1-y N (0 ≦ y ≦ 1) -based crystal material, after growing an In _x Ga _1-x N layer at a temperature T ₀ , a predetermined atmosphere containing a group V source gas is applied. Lower, temperature T ₁
(Where T ₀ ≦ T ₁ ) During a growth interruption step including a temperature holding step or a temperature raising step until the Al _y Ga _1-y N layer is grown at T ₀ ≦ T ₁ , an inert gas is used as a carrier gas of the group V source gas. To suppress the diffusion of the group V source gas from the vicinity of the surface of the I _x nGa _1-x N layer into the atmosphere, and the vapor of the group V material near the surface of the I _x nGa _1-x N layer. The method of claim 1, wherein the pressure is substantially increased to prevent sublimation of the I _x nGa _1-x N layer. 10. The method according to claim 9, wherein the temperature T ₀ and the temperature T ₁ satisfy the following range conditions. 400 ° C ≦ T ₀ ≦ 950 ° C. 600 ° C. ≦ T ₁ ≦ 1300 ° C. 11. The group V source gas is NH ₃ , N
_At least one selected from the group consisting of ₂ H ₄ , N ₂ H ₃ CH ₃ and N ₂ H ₂ (CH ₃ ) ₂ , wherein the inert gas is N ₂ , He, Ne, Ar, Kr, Xe and at least one selected from the group consisting of SF ₆ ,
The method according to claim 9. 12. The method according to claim 9, wherein the carrier gas contains a predetermined amount of H ₂ . 13. A diffusion coefficient of the group V source gas with respect to the carrier gas is smaller than a diffusion coefficient with respect to H ₂ .
A method according to any one of claims 9 to 12.