JP5629870B2 - AlGaN vapor deposition method and AlGaN crystal thick film substrate manufactured by AlGaN vapor deposition method - Google Patents

Description

The present invention relates to a method of epitaxially growing AlGaN used in ultraviolet lasers, LEDs, high-frequency / high-power electronic devices, and the like, and a thick film substrate of AlGaN crystal manufactured by the method .

  As an ordinary method for producing a bulk crystal, an HB (Horizontal Bridgiman) method and an LEC (Liquid Encapsulated Czochralski) method are known. However, these methods make it difficult to grow an AlGaN single crystal.

  For this reason, in recent years, growth of bulk crystals has been attempted by solution growth under a high temperature and high pressure, a sublimation method, or the like. However, even with such a method, an AlGaN crystal that can be used for a large substrate crystal has not been obtained.

Currently, as one of the most promising methods for producing an AlGaN single crystal substrate, the present inventors consider that AlGaN is heteroepitaxially grown on a substrate (for example, sapphire substrate) by HVPE (Hydride Vapor Phase Epitaxy) method. It is a method to make it.
In this method, an Al source gas, a Ga source gas, and an NH ₃ source gas are mixed in a mixing unit, and the mixed gas is fed into a growth unit (also referred to as a substrate unit because the substrate is located). Then, AlGaN is grown on the sapphire substrate accommodated in the growth part.

HVPE Method The advantage of the HVPE method that is a quartz reaction tube hot wall system is that the growth rate is particularly high. For this reason, the HVPE method has been conventionally used for manufacturing a high-sensitivity optical sensor that requires a thick film and a power device (particularly, a power supply device using GaAs) that requires a high-quality crystal with a thick film. Further, it is used as a method for producing the above-mentioned substrate, particularly a GaN substrate.

  This is described in, for example, the following Patent Document 1 “Crystal Growth Method of Gallium Nitride-Based Compound Semiconductor (Toyoda Gosei Co., Ltd.)” and the following Patent Document 2 “Epitaxial Wafer and Manufacturing Method (Sumitomo Electric Industries, Ltd.)”. Has been.

  The applicant of the present application has developed a technique for manufacturing a substrate of a group III-V compound containing Al by HVPE (method), and has filed another patent application (Japanese Patent Application No. 2002-106102) separately (patent) Reference 3).

Japanese Patent Laid-Open No. 10-215000 JP-A-10-316498 JP 2003-303774 A

Accordingly, the present inventors have proceeded research on binding AkiraNaru length of AlGaN with HVPE.

The inventors of the present invention have found a problem that the controllability of the composition ratio is poor when crystal growth of “thick film” of AlGaN is performed using HVPE.

  Hereinafter, it demonstrates in order.

Regarding AlGaN First, since AlGaN is a so-called mixed crystal (often referred to as a solid solution) of AlN and GaN, it is often described as Al _x Ga _1-x N in order to clarify the ratio. Here, x is a ratio of AlN in the AlGaN crystal and can take a value of 0 or more and 1 or less. And it couple | bonds at the atomic level with respect to all the values of 0 to 1, and forms what is called a solid solution. When x is 0, since the composition ratio of AlN is 0, all are GaN. On the other hand, when x is 1, all are AlN. The value of x needs to be determined accurately depending on the application of AlGaN.

However, when making a thick film of AlGaN by HVPE, so an effective method for setting the ratio x of the Al N in AlGaN crystal to a desired value is not conventionally known, the conditions variously changed by experiment Therefore, crystal growth is performed.

Accordingly, the present invention has been made to solve the above problems, and provides an epitaxial growth method capable of growing a high-quality AlGaN crystal on a HVPE sapphire substrate or Si substrate, and AlGaN. An object of the present invention is to realize a method and apparatus capable of setting the value of the AlN ratio x in the crystal to a desired value.

In view of the above problems, the inventors of the present application have conducted extensive research, and as a result, the ratio of the Al source gas to the Ga source gas and the value of the ratio x of AlN in the AlGaN crystal are not in a linear relationship. to have found that have a ratio x of AlN in the AlGaN crystals can be easily controlled to a desired value.

Then, further research was conducted, and a condition was found where the ratio of the Al source gas to the Ga source gas and the value of x, which is the ratio of AlN in the AlGaN crystal , have a linear relationship. We developed a crystal growth method and apparatus that can easily control the value of x, which is the ratio of AlN in the AlGaN crystal, by allowing crystal growth under such conditions. This will be described below.

A. Invention of vapor phase growth method of Al _x Ga _1-X N (1) The present invention
An aluminum material supply step of arranging a substrate crystal in the growth section and supplying an aluminum raw material to the growth section together with a carrier gas; a gallium raw material supply step of supplying a gallium raw material to the growth section together with a carrier gas; A method of growing an AlGaN crystal on the substrate crystal by an HVPE method.
The total hydrogen partial pressure in the carrier gas in each raw material supply step is 0.01 atm or more and less than 0.1 atm, and the composition ratio of AlN and GaN in the AlGaN crystal according to the ratio of the aluminum raw material and the gallium raw material. Is a vapor phase growth method of an AlGaN crystal, characterized in that is set to a desired value.

With such a configuration, by maintaining the hydrogen partial pressure in the carrier gas at a certain value, the relationship between the supply ratio of the Al source gas and the Ga source gas and the composition of the resulting crystal is more linear. It becomes easy to control the composition ratio of the AlGaN crystal.

The carrier gas here is N ₂ A predetermined amount of H in an inert gas (Inert Gas: IG) such as He or Ar gas ₂ Is a mixed gas.

Such carrier gas is described in paragraph 0064 of the embodiment.

(2) Further, the present invention is characterized in that, in the vapor phase growth method according to the above (1), the aluminum raw material supply step is performed at 750 ° C. or lower, and the growth portion is set at 900 ° C. or higher and 1600 ° C. This is a vapor phase growth method for AlGaN crystals.

As will be described later in the embodiment, the raw material can be supplied if the temperature in the raw material supply step is within such a temperature range. In addition, the temperature in a raw material supply process is the temperature of each raw material supply part.

Similarly, crystal growth can be performed if the growth part is in the above temperature range.

B. _{Al x} Ga _1-x N Al obtained by the vapor phase growth method for x _{Ga 1-x} N invention (3) Further, the present invention, the above (1) to according to any one of (2) It is a thick film substrate of AlGaN crystal manufactured by a vapor phase growth method.

  According to each of the above methods, since the crystal composition can be easily controlled, a thick film substrate can be formed.

C. Reference invention of Al _x Ga _1-x N vapor phase growth apparatus ( 4 ) In order to solve the above problems, this reference invention grows a growth part in which a substrate crystal is arranged and an aluminum raw material together with a carrier gas. An aluminum raw material supply means for supplying to the growth section, a gallium raw material supply means for supplying a gallium raw material together with a carrier gas to the growth section, and a nitrogen raw material supply means for supplying a nitrogen raw material together with a carrier gas to the growth section. In the apparatus for crystal growth of AlGaN on the substrate crystal disposed in the growth part, the aluminum source supply means, the gallium source supply means, and the nitrogen source supply means are configured to supply hydrogen in the carrier gas. An AlGaN crystal vapor phase growth apparatus using the carrier gas having a pressure of 0 atm.

  With such a configuration, the crystal can be grown in a state where the relationship between the material supply ratio and the composition of the obtained crystal is placed in a more linear relationship. As a result, according to this apparatus, the control of the crystal composition becomes easy.

(5) In addition, this reference invention comprises a growing part of the substrate crystal is arranged, the aluminum raw material and the aluminum material supply means for supplying to the growth unit together with the carrier gas, a gallium raw material to the growth portion together with the carrier gas In the apparatus for crystal growth of AlGaN on a substrate crystal disposed in the growth section, comprising: a gallium source supply means for supplying; and a nitrogen source supply means for supplying a nitrogen source together with a carrier gas to the growth section. Aluminum raw material supply means,
And the gallium source supply means and the nitrogen source supply means use the carrier gas having a hydrogen partial pressure of 0 atm or more and less than 0.01 atm in the carrier gas. It is a growth device.

  With such a configuration, while maintaining the hydrogen partial pressure in the carrier gas at a certain value, the relationship between the supply ratio of the material and the composition of the obtained crystal is placed in a more linear relationship. Lets grow. As a result, according to this apparatus, the control of the crystal composition becomes easy.

(6) In addition, this reference invention comprises a growing part of the substrate crystal is arranged, the aluminum raw material and the aluminum material supply means for supplying to the growth unit together with the carrier gas, a gallium raw material to the growth portion together with the carrier gas In the apparatus for crystal growth of AlGaN on a substrate crystal disposed in the growth section, comprising: a gallium source supply means for supplying; and a nitrogen source supply means for supplying a nitrogen source together with a carrier gas to the growth section. The aluminum raw material supply means, the gallium raw material supply means, and the nitrogen raw material supply means use the carrier gas whose hydrogen partial pressure in the carrier gas is 0 atm or more and less than 0.1 atm. This is an AlGaN crystal vapor phase growth apparatus.

  With such a configuration, while maintaining the hydrogen partial pressure in the carrier gas at a certain value, the relationship between the supply ratio of the material and the composition of the obtained crystal is placed in a more linear relationship. Lets grow. As a result, according to this apparatus, the control of the crystal composition becomes easy.

D. Al _x Ga Reference Invention of _{1-x Al} obtained by the vapor phase growth apparatus of _{N x Ga 1-x N (} 7) this reference invention, (4) to according to any one of (6) It is a thick film substrate of AlGaN crystal manufactured by a vapor phase growth apparatus.

  According to each of the above apparatuses, since the crystal composition can be easily controlled, a thick film substrate can be produced.

As described above, according to the present invention, when an AlGaN crystal is grown, it becomes easy to set x , which is the ratio of AlN in the crystal in the AlGaN crystal, to a desired value. As a result, an AlGaN crystal having a desired composition ratio can be easily obtained as compared with the conventional case, and a thick film substrate can be produced.

Hereinafter, with reference to the drawings, a preferred embodiment of an AlGaN epitaxial layer growth method according to the present invention will be described in detail.
The diagram 1 of a vapor deposition apparatus, and schematic diagram of the vapor phase growth apparatus 10 utilized in this embodiment schematically showing is shown. With reference to FIG. 1, a vapor phase growth apparatus 10 for HVPE (Hydride Vapor Phase Epitaxy) method used in the present embodiment will be described.

  As shown in FIG. 1, the vapor phase growth apparatus 10 includes an aluminum source supply unit 12 that supplies an aluminum source, a gallium source supply unit 14 that supplies a gallium source, a nitrogen source supply unit 16 that supplies a nitrogen source, It has. The gas output from each supply unit is mixed in the mixing unit 18 and then used for crystal growth in the growth unit 20. The growth unit 20 is composed of a quartz reaction chamber and is provided with an exhaust port 20a.

As shown in FIG. 1, the aluminum material supply unit 12 is a reaction chamber in which metallic aluminum is accommodated in a predetermined reaction chamber. The aluminum material supply portion 12, the first gas introduction passage 12a is provided, and HCl through the first gas introducing passage 12a, and the hydrogen gas _{H 2,} IG is introduced. As a result, metal aluminum and HCl react to produce AlCl ₃ which is an AlGaN aluminum material. The reaction formula when AlCl ₃ is produced is as follows.

“Chemical 1”
Al + 3HCl → AlCl ₃ + 3 / 2H ₂
The AlCl ₃ obtained in this way is transferred to the mixing unit 18 together with the carrier gas.

What is characteristic in the present embodiment is that the value of the hydrogen partial pressure in the carrier gas used is within a predetermined value range. By setting this value within a predetermined range, it becomes easy to set the value of x , which is the ratio of AlN in the crystal, to a desired value. A specific value of the hydrogen partial pressure will be described in detail later.

The aluminum raw material supply unit 12 is maintained at a predetermined temperature using a heating device (not shown). Specifically, it is desirable to keep the temperature range (750 ° C. or less) at which AlCl ₃ is produced more than other substances (AlCl) by the reaction of Al metal and HCl. In this embodiment, the temperature is kept at 500 ° C.

Further, in the present embodiment, AlCl ₃ is generated as described above, but it is also preferable that the AlCl ₃ powder is sublimated and fed into the mixing unit 18.

As shown in FIG. 1, the gallium source supply unit 14 is a reaction chamber in which metallic gallium is accommodated in a predetermined reaction chamber. The gallium material supply portion 14, the second gas introduction passage 14a is provided, and HCl through the second gas introducing passage 14a, and the hydrogen gas _{H 2,} IG is introduced. As a result, metal gallium and HCl react to generate GaCl, which is a gallium raw material for AlGaN. The reaction formula when GaCl is generated is as follows.

"Chemical 2"
Ga + HCl → GaCl + 1 / 2H ₂
The GaCl thus obtained is transferred to the mixing unit 18 together with the carrier gas.

What is characteristic in the present embodiment is that the value of the hydrogen partial pressure in the carrier gas used is within a predetermined value range. By setting this value within a predetermined range, it becomes easy to set the value of x , which is the ratio of AlN in the AlGaN crystal, to a desired value. The specific value of the hydrogen partial pressure will be described in detail later.

Nitrogen source supply unit Nitrogen source supply unit 16 is a predetermined reaction chamber as shown in FIG. The nitrogen material supply portion 16 has a third gas introduction passage 16a is provided, and the hydrogen gas _{H 2} and IG through the third gas introduction passage 16a, ammonia NH ₃ is introduced.

Although not shown, a heating device is provided around the nitrogen raw material supply unit 16 and is heated to a predetermined temperature. With this heat, the ammonia NH ₃ in the nitrogen raw material supply unit 16 is placed in a state of being decomposed at a predetermined rate. A mixed gas of ammonia NH ₃ decomposed at such a predetermined ratio, hydrogen gas H ₂ and IG is transferred to the mixing unit 18. Similarly to the above , when the value F ⁰ of the hydrogen partial pressure in the carrier gas in the nitrogen raw material supply unit 16 is within a predetermined range, x which is the ratio of AlN in the AlGaN crystal is set to a desired value. be able to.

The mixing unit mixing unit 18 is a mixture of the Al source gas, the Ga source gas, and the NH ₃ source gas supplied from the respective source units of the aluminum source supply unit 12, the gallium source supply unit 14, and the nitrogen source supply unit 16 described above. Is done. Moreover, in order to maintain at predetermined temperature, the predetermined heating apparatus not shown is provided.

The growth part growth part 20 accommodates a substrate crystal 22 for crystal growth. In order to obtain a temperature suitable for crystal growth, a predetermined heating device (not shown) is provided. Such a heating apparatus can employ various configurations that have been known in the past. For example, heating with a heating wire or high-frequency heating can be used.

In particular, in the present embodiment, high-frequency heating is used to intensively heat the substrate crystal 22. It is also very preferable to use light heating in order to heat the substrate crystal 22 intensively. These heating devices are heating devices are well known in the art.

  In the present embodiment, the substrate crystal 22 is a sapphire substrate. The substrate crystal 22 is placed on the carbon susceptor 24.

Crystal Growth With the above-described configuration, a solid solution of Al _x Ga _1-x N (0 ≦ x ≦ 1), which is a mixed crystal of AlN and GaN, can be grown on the substrate crystal 22.

Adjustment of Composition Ratio In the present embodiment, a device for facilitating the setting of the value of x, which is the ratio of AlN in the AlGaN crystal, has been made. Qualitatively speaking, in order to increase x, the ratio of the aluminum raw material may be increased compared to gallium, and in order to decrease x, the ratio of the gallium raw material is increased relative to aluminum. I can imagine what I should do.

However, since the relationship between the “raw material ratio” and x is generally not a linear relationship, it is often very difficult to adjust the crystal composition to a desired value .

Characteristic matters in the present embodiment are that the H ₂ concentration in the carrier gas is set to a range described later, and the ratio of the aluminum raw material to the gallium raw material, the ratio of aluminum to gallium in the generated crystal, , Can be placed in a more linear relationship. As a result, according to the present embodiment, it becomes easy to set x to a desired value.

Crystal Growth Reaction First, the temperature of the aluminum material supply unit 12 is maintained at a temperature of 500 ° C. as described above. As a result, the generation of AlCl is suppressed and a large amount of AlCl ₃ is generated. As a result, even when the reaction vessel is made of quartz, there is little risk of corroding quartz.

Moreover, the gallium raw material supply part 14 is hold | maintained at the temperature of 700 degree | times using the heating apparatus (illustration omitted) . The nitrogen raw material supply unit 16 is also maintained at a predetermined temperature using a heating device (not shown) . The temperature may be the same as that of the aluminum raw material supply unit 12, or is preferably controlled to another temperature.

Further, the mixing unit 18 is preferably maintained at a temperature at which AlCl ₃ generated in the aluminum raw material supply unit 12 does not precipitate in the quartz container, and in a temperature range in which precipitation of AlN and GaN does not occur in the mixing unit 18. . This is because, by maintaining such a temperature, the raw material can be sent to the growth region 20 without being deposited in the middle. In the present embodiment, the temperature of the mixing part is specifically maintained in a temperature range of 160 ° C. or higher and 750 ° C. or lower. In order to maintain such a temperature range, a heating device (not shown) is also provided around the mixing unit 18.

  The substrate crystal is set to a predetermined temperature in the temperature range of 900 ° C. to 1600 ° C. In the present embodiment, the substrate crystal of the growth unit 20 is maintained at 1000 ° C.

  By intensively heating the substrate crystal 22, it is possible to prevent AlN and GaN from being precipitated before reaching the substrate crystal 22, and to efficiently grow the crystal on the substrate crystal 22.

In this embodiment, high-frequency heating is adopted, but a heating method other than high-frequency heating (for example, light heating / resistance heating) may be adopted. In the case of resistance heating, by providing a resistance wire sufficiently close to the substrate crystal 22, it is possible to realize that the surrounding gas is not heated much while the substrate crystal 22 is mainly heated. In the case of heating by light, it is also preferable to adopt a configuration in which light is irradiated onto the surface of the substrate crystal 22 from the outside of the quartz reaction chamber. According to such a configuration, it is possible to increase mainly the temperature of the substrate crystal 22 without substantially increasing the temperature of quartz through which light passes or the surrounding gas. In addition, the furnace by light irradiation is known conventionally, and the furnace using a halogen lamp, a xenon lamp, etc. as a light source is put into practical use.
Further, a support member other than the carbon susceptor 24 may be used.

  In addition to the sapphire substrate, a Si crystal can be used as the substrate crystal 22.

  In particular, when a sapphire substrate is used, for example, it is preferable to install a sapphire substrate on a thin carbon plate and heat by irradiating light from the carbon side. It is possible to heat the sapphire substrate through the carbon thin plate by installing a thin plate of carbon on the back surface of the sapphire substrate and irradiating light from the carbon side. As a result, it is possible to easily raise only the temperature of the sapphire substrate without substantially raising the temperature of the surrounding gas or reaction region.

After growing the Al _x Ga _1-x N crystal layer in this way, a thick AlGaN substrate can be obtained by removing the sapphire or Si substrate used for the initial substrate.

Carrier gas As the carrier gas in the present embodiment, a gas in which a predetermined amount of H ₂ is mixed with IG such as N ₂ , He, or Ar gas is used.

What is characteristic in the present embodiment is that the ratio of the aluminum raw material to the gallium raw material and the ratio of aluminum to gallium in the generated crystal are set by setting the H ₂ concentration in the carrier gas to a range described later. , Can be placed in a more linear relationship. As a result, it is easier than before to set x , which is the ratio of AlN in the AlGaN crystal, to a desired value .

That is, it becomes easier to set the value of x , which is the ratio of AlN in the AlGaN crystal, to a desired value.

The inventors of the present application grow Al _x Ga _1-x N for ₁ to 10 hours using the temperature range as described above, thereby forming Al _x Ga on the substrate crystal 22 (sapphire substrate). _{A 1-xN} thick film crystal was grown. Then, the _Al x _{Ga 1-x} N obtained experiment was conducted to measure the composition of the crystal.

This experiment
-Ratio of Al source gas and Ga source gas-It carried out by changing each hydrogen partial pressure in carrier gas. Graphs representing the results of the experiment are shown in FIGS.

Graph of FIG. 2 (when hydrogen partial pressure F ⁰ = 0)
In the graph of FIG. 2, when the hydrogen partial pressure F ⁰ = 0 in the carrier gas, the value of the gas phase supply ratio R ([AlCl ₃ ] / {[AlCl ₃ ] + [GaCl]}) is changed. the _Al x _{Ga 1-x} N is sintered AkiraNaru length is a graph showing the X-ray diffraction pattern when the resulting _Al x _{Ga 1-x} N crystals were examined by XRD (X-ray analyzer). In this graph, the vertical axis represents diffraction intensity (unit is arbitrary). The horizontal axis represents the angle (2θ (degrees)).

In the graph of FIG. 2, since the hydrogen partial pressure F ⁰ = 0, the carrier gas is all IG . Under the condition of F ⁰ = 0 (inert carrier gas), Al _x Ga _1-x N crystals are grown at three gas phase supply ratios R.

First, when the vapor phase supply ratio R is 0, it means that there is no aluminum material, the resulting crystals diffraction pattern (solid line in the graph), it was found that crystals are all GaN.

Next, when the vapor phase supply ratio R is 0.25, it means that the aluminum raw material ratio is 0.25. From the peak position of the diffraction pattern (broken line in the graph) of the obtained crystal, it was found that the crystal was a mixed crystal having a composition of Al _0.32 Ga _0.68 N.

When the gas phase supply ratio R is 0.50, it means that the aluminum raw material ratio is 0.5. From the peak position of the diffraction pattern of the obtained crystal (the one-dot chain line in the graph), it was found that the crystal was a mixed crystal having a composition of Al _0.54 Ga _0.46 N.

Thus, as the gas phase supply ratio R increases, the peak shifts to the high angle side, and the ratio x of AlN in the AlGaN crystal increases.

Graph of FIG. 3 (in the case of hydrogen partial pressure F ⁰ = ^0, 0.01, 0.1, 1)
In the graph of FIG. 3, when the hydrogen partial pressure F ⁰ in the carrier gas is ⁰ , 0.01, 0.1, and 1, respectively, the vapor phase supply ratio R and the composition of the grown crystal (specifically, in the crystal The relationship between the AlN ratio and x ) is shown. In this graph, the vertical axis represents x (solid phase composition ratio) which is the ratio of AlN in the AlGaN crystal , and the horizontal axis represents the gas phase supply ratio R.

  In this graph, the solid line is the theoretical calculated value. Each plot ● ▲ ■ ▼ is an experimentally measured value.

In this graph, the graph when F ⁰ = 0 is represented by a solid line passing through ● and ●. From the graph represented by ●, when F ⁰ = 0, it is understood that the gas phase supply ratio R and the ratio x of AlN in the AlGaN crystal have a substantially linear relationship (linear relationship). Let's be done.

In this graph, the graph in the case of F ⁰ = 0.01 is represented by a solid line passing through ▲ and ▲. From the graph represented by ▲, when F ⁰ = 0.01, the gas phase supply ratio R and the ratio x of AlN in the AlGaN crystal are in a substantially linear relationship (linear relationship). However, some nonlinearity appears.

That is, when the absolute value of the gas phase supply ratio R is small, the change in x , which is the ratio of AlN in the AlGaN crystal, due to the change in R is relatively large. On the other hand, when the absolute value of the gas phase supply ratio R is large, the change in x , which is the ratio of AlN in the AlGaN crystal, due to the change in R is relatively small, and nonlinearity appears.

In the case of F ⁰ = 0.1, this nonlinearity becomes somewhat remarkable. In FIG. 3, a graph in the case of F ⁰ = 0.1 is represented by a solid line passing through ■ and ■. From the graph represented by (2), when F ⁰ = 0.1, the gas phase supply ratio R and the ratio x of AlN in the AlGaN crystal are approximately 0. It will be understood that the graph is bent with the portion 2 as the boundary. Thus, in the case of F ⁰ = 0.1, the nonlinearity becomes remarkable, and it becomes difficult to control x, which is the ratio of AlN in the AlGaN crystal, by adjusting the gas phase supply ratio R.

When F ⁰ = 1, the graph shows significant nonlinearity. In FIG. 3, the graph in the case of F ⁰ = 1 is represented by a solid line passing through ▼ and ▼. From the graph represented by ▼, in the case of F ⁰ = 1, the vapor phase supply ratio R and the ratio x of AlN in the AlGaN crystal are about 0.05. It will be understood that the graph is bent sharply with the part as the boundary. Thus, in the case of F ⁰ = 1, the nonlinearity becomes more remarkable, and it becomes difficult to control x , which is the ratio of AlN in the AlGaN crystal, by adjusting the gas phase supply ratio R. In particular, it is considered extremely difficult to control x to a predetermined value between 0.0 and 0.8.

From the hydrogen partial pressure above results, from the viewpoint of controllability of the composition ratio of the crystal, the hydrogen partial pressure 0 is preferable.

However, the completely when the hydrogen partial pressure is 0, since in some cases would be adversely affected by impurities, the accuracy of a typical device, the hydrogen partial pressure in consideration of the quality, etc. of the material is greater than 0 0.01 It is considered that it is often preferable to keep the value at a value less than about.

In addition, depending on variations in apparatus performance and material quality, it may be better to place the hydrogen partial pressure in the range of more than 0 and less than 0.1.

Summary As described above, in the present embodiment, by setting the hydrogen partial pressure value F ⁰ in the carrier gas to a predetermined range, the vapor-phase supply ratio R and the ratio of AlN in the AlGaN crystal The relationship with a certain x could be made more linear. As a result, according to the present embodiment, it is easier than ever to set x , which is the ratio of AlN in the AlGaN crystal, to a desired value.

It is a schematic diagram of the vapor phase growth apparatus of this Embodiment. X-ray diffraction of the growth layer obtained when growing the crystal of Al _x Ga _1-x N by changing the gas phase supply ratio R when the hydrogen partial pressure F ⁰ = 0 in the carrier gas It is a pattern. It is a graph which shows the relationship between the gaseous-phase supply ratio R and the ratio of AlN in an AlGaN crystal in case hydrogen partial pressure F0 in carrier gas is ⁰ , 0.01, 0.1, and 1, respectively.

DESCRIPTION OF SYMBOLS 10 Vapor growth apparatus 12 Aluminum raw material supply part 12a 1st gas introduction path 14 Gallium raw material supply part 14a 2nd gas introduction path 16 Nitrogen raw material supply part 16a 3rd gas introduction path 18 Mixing part 20 Growth part 20a Exhaust port 22 Substrate crystal 24 carbon susceptor

Claims (3)

An aluminum material supply step of arranging a substrate crystal in the growth section and supplying an aluminum raw material to the growth section together with a carrier gas; a gallium raw material supply step of supplying a gallium raw material to the growth section together with a carrier gas; and a nitrogen raw material together with a carrier gas A method of growing an AlGaN crystal on the substrate crystal by an HVPE method.
  The total hydrogen partial pressure in the carrier gas in each raw material supply step is 0.01 atm or more and less than 0.1 atm, and the composition ratio of AlN and GaN in the AlGaN crystal according to the ratio of the aluminum raw material and the gallium raw material. Is set to a desired value. A method for vapor phase growth of an AlGaN crystal. The vapor phase growth method according to claim 1 ,
Performing the aluminum raw material supply step at 750 ° C. or lower,
A method for vapor phase growth of an AlGaN crystal, wherein the growth portion is set to 900 ° C. or more and 1600 ° C. Thick film substrate of the prepared AlGaN crystal by a vapor deposition method according to any one of claims 1 or 2.

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