JP2010118391A - METHOD OF GROWING AlxGal-xN CRYSTAL - Google Patents

Abstract

A method for growing Al _x Ga _1-x N (0 ≦ x ≦ 1) crystals having high crystallinity is provided.
The Al _x Ga _1-x N crystal growth method includes a step of preparing a base substrate 10 and a solution 7 in which nitrogen is dissolved 5 in a Ga melt 3 containing Al. And a step of growing at least one layer of Al _x Ga _1-x N crystal 20 on the base substrate 10. Here, an AlN crystal as the first layer Al _x Ga _1-x N crystal 21 and an Al _x2 Ga _1-x2 N as the second layer Al _x Ga _1-x N crystal 22 (0 < As the x2 <1) crystal and the third layer Al _x Ga _1-x N crystal 23, a GaN crystal can be grown sequentially.
[Selection] Figure 1

Description

In the present invention, a solution obtained by dissolving nitrogen in a Ga melt containing Al is brought into contact with the main surface of the base substrate, and Al _x Ga _1-x N (0 ≦ x ≦ 1) crystals are grown on the main surface. It relates to the method of making it.

AlN crystal, Al _x Ga _1-x N, such as GaN crystal (0 ≦ x ≦ 1, hereinafter the same) crystals, the light emitting device preferably used as a substrate for a semiconductor device such as an electronic device. Here, in order to improve the characteristics of the semiconductor device, an Al _x Ga _1-x N crystal having a low dislocation density and high crystallinity is required.

Here, a liquid phase method using a melt containing Al and Ga has a lower dislocation density than a vapor phase method such as an HVPE (hydride vapor phase epitaxy) method or an MOCVD (metal organic chemical vapor deposition) method. It is expected that Al _x Ga _1-x N crystals having high crystallinity can be grown.

  For example, re-published international publication WO2006 / 022302 (hereinafter referred to as Patent Document 1) describes a method for producing an AlN crystal under mild pressure and temperature conditions (for example, 0.01 to 1000 MPa and 300 to 2300 ° C.), In the presence of a nitrogen-containing gas, the component (A) which is at least one element of alkali metal and alkaline earth, and at least one element selected from the group consisting of Sn, Ga, In, Bi and Hg (B The present invention proposes a method of growing AlN crystals by reacting aluminum and nitrogen in a flux containing a component) or in a flux containing the component (B).

  In addition, the republished international publication WO2006 / 030718 (hereinafter referred to as Patent Document 2) describes at least gallium (Ga), aluminum (Al), and sodium (Na) as a method for growing a high-quality AlN single crystal. A method is proposed in which an AlN single crystal is grown by pressurizing the melt contained in a nitrogen-containing atmosphere, preferably at a nitrogen partial pressure of 50 atm or lower or at a temperature of 850 ° C. or higher and 1200 ° C. or lower.

Japanese Patent Application Laid-Open No. 2003-335600 (hereinafter referred to as Patent Document 3) discloses a method for producing a relatively large AlN single crystal easily and at low cost as a metal, Cr, Mn, Fe, Co, Cu and Cooling the melt of an abc alloy containing at least one selected from Ni, including at least one selected from Sc, Ti, V, Y, Zr and Nb as metal b, and further including Al as component c Or a method of growing an AlN single crystal by evaporation of at least one of the metals a and b.
Republished International Publication WO2006 / 022302 International publication WO2006 / 030718 JP 2003-335600 A

  However, the method of Patent Document 1 has a problem that only a thin AlN crystal having a thickness of about 2 μm or less can be obtained on the substrate under the crystal condition of the example, and it is easy to be polycrystallized and has low reproducibility. In the embodiment, since the alkali metal and / or alkaline earth metal having a high vapor pressure is used as the component (A), the crystal growth temperature is lowered to suppress the evaporation of the component (A) (for example, the embodiment In this case, it is necessary that the crystal growth temperature is 800 to 980 ° C.), and it is considered that the crystal growth rate is low. In addition, since the crystal growth temperature is low, the crystallinity is lowered and it is considered that the crystal is easily crystallized and the reproducibility is low.

  Further, in the method of Patent Document 2, Na having a high vapor pressure is used as the flux. Therefore, when the crystal growth temperature is increased, Na is evaporated and the reproducibility is lowered. On the other hand, if the crystal growth temperature is lowered to suppress the evaporation of Na, there is a problem that the crystallinity is lowered.

  Further, in the method of Patent Document 3, there is a problem that cracks occur in the AlN single crystal when a different type substrate having a chemical composition different from that of an AlN single crystal grown like a SiC substrate is used under the crystal growth conditions of the example. . This is probably because the temperature of the melt for starting crystal growth is as high as 1500 to 1850 ° C., and a large thermal stress is generated due to the difference in thermal expansion coefficient between the dissimilar substrate and the AlN single crystal during cooling.

Therefore, an object of the present invention is to solve the above problems and provide a method for growing Al _x Ga _1-x N (0 ≦ x ≦ 1) crystals having high crystallinity. In order to achieve such an object, the present inventors use an alkali metal such as Na having a high vapor pressure or an alkaline earth metal such as Ca as the flux without particularly lowering the crystal growth temperature, and Cr as the flux. A high crystallinity Al _x Ga _1-x N crystal is obtained using a solution obtained by dissolving nitrogen in a Ga-containing melt containing Al without using a high melting point metal such as Sc and Sc. The present invention was completed by finding that it can be grown.

In the present invention, a step of preparing a base substrate, and a solution obtained by dissolving nitrogen in an Al-containing Ga melt is brought into contact with the base substrate, so that at least one layer of Al _x Ga _1-x N ( And 0 ≦ x ≦ 1) a step of growing a crystal, and a method for growing an Al _x Ga _1-x N crystal.

In the step of growing an Al _x Ga _1-x N crystal in the Al _x Ga _1-x N crystal growth method according to the present invention, an AlN crystal is formed as an Al _x Ga _1-x N crystal of the first layer on the base substrate. Can be grown. Further, on the take AlN crystal, Al _x2 Ga _1-x2 N as Al _x Ga _1-x N crystal of the second layer (0 <x2 <1) crystal, as Al _x Ga _1-x N crystal of the third layer GaN crystals can be further grown sequentially. Here, the crystal growth temperature can be set to 1000 ° C. or higher and 1300 ° C. or lower.

The present invention can provide a method for growing Al _x Ga _1-x N (0 ≦ x ≦ 1) crystals having high crystallinity.

Referring to FIG. 1, an embodiment of the Al _x Ga _1-x N (0 ≦ x ≦ 1) crystal growth method according to the present invention includes a step of preparing a base substrate 10, a Ga-containing Al-containing alloy. A solution 7 in which nitrogen is dissolved in the liquid 3 (5 dissolution of nitrogen in the melt) is brought into contact with the base substrate 10 to grow at least one layer of Al _x Ga _1-x N crystal 20 on the base substrate 10. A process.

According to the Al _x Ga _1-x N crystal growth method according to the present embodiment, by using a Ga melt 3 containing Al, an alkali metal or alkaline earth metal having a high vapor pressure, or a transition having a high melting point. Without using metal, a solution 7 in which nitrogen is dissolved in the melt 3 (dissolution of nitrogen in the melt 5) is formed, and the solution 7 is brought into contact with the base substrate 10 so that at least 1 is formed on the base substrate 10. A layer of Al _x Ga _1-x N crystal 20 can be grown.

(Process for preparing the base substrate)
With reference to FIG. 1, the Al _x Ga _1-x N crystal growth method of the present embodiment includes a step of preparing a base substrate 10. Here, the base substrate 10 is not particularly limited as long as the Al _x Ga _1-x N crystal 20 can be epitaxially grown thereon, and Al _x Ga _1-x N crystal grown with the starting substrate From the viewpoint of epitaxially growing a high crystallinity Al _x Ga _1-x N crystal by reducing the mismatch of the lattice constants, a sapphire substrate, SiC substrate, Si substrate, GaAs substrate, Al _s Ga _1-s N (0 ≦ s ≦ 1) A substrate or the like is preferable. From the same viewpoint, sapphire substrate, SiC substrate, a thin on a base substrate such as Si substrate or GaAs substrate _{Al t Ga 1-t N (} 0 ≦ t ≦ 1) Al layer was formed _t Ga _1-t N template substrates are also preferred.

(Step of growing Al _x Ga _1-x N crystal)
Referring to FIG. 1, the Al _x Ga _1-x N crystal growth method of this embodiment is a solution 7 in which nitrogen is dissolved in Al-containing Ga melt 3 (dissolving nitrogen 5 in the melt). Is brought into contact with the base substrate 10 to grow at least one layer of Al _x Ga _1-x N crystal 20 on the base substrate 10.

Here, the method 5 for dissolving nitrogen in the Ga-melt 3 containing Al is not particularly limited, and by supplying at least one of a nitrogen-containing gas, a nitrogen-containing liquid, and a nitrogen-containing solid to the melt. It can be carried out. From the viewpoint of easily adjusting the amount of nitrogen dissolved in the melt, it is preferable to supply a nitrogen-containing gas to the melt by pressurization. The nitrogen-containing gas is not particularly limited as long as the gas contains nitrogen that can be dissolved in the melt, and nitrogen (N ₂ ) gas, ammonia (NH ₃ ) gas, or the like is used. From the viewpoint of reducing the contamination of impurities into the crystal, the purity of each of the Al raw material and Ga raw material for forming the melt 3 is preferably 99 mol% or more, more preferably 99.99 mol% or more, and 99.9999 mol%. The above is more preferable. Further, from the same viewpoint, the purity of the nitrogen-containing gas is preferably 99.99 mol% or more, and more preferably 99.9999 mol% or more.

At this time, the dissolution 5 of nitrogen in the Al melt is more difficult than the Ga melt, but nitrogen dissolves in the Ga melt containing Al. In addition, an AlN crystal is very easy to grow as compared with a GaN crystal. Therefore, in a given crystal growth conditions, the solution 7 obtained by dissolving nitrogen in the Ga melt containing the Al, on underlying substrate 10, first, AlN as Al _x Ga _1-x N crystal 21 of the first layer Crystal grows. As the AlN crystal grows, the Al content in the Ga melt 3 containing Al decreases.

Further, when the crystal growth is continued, an Al _x2 Ga _1-x2 N (second layer Al _x Ga _1-x N crystal 22 is formed on the AlN crystal (first Al _x Ga _1-x N crystal 21). 0 <x2 <1) Crystal grows. The Al _x2 Ga _1-x2 N crystal (the second layer Al _x Ga _1-x N crystal 22) is an AlN crystal (the first layer Al _x Ga _1-x N crystal 21) and the next grown GaN crystal. It is positioned as an AlGaN composition transition crystal layer between the (third layer Al _x Ga _1-x N crystal 23). As the Al _x2 Ga _1-x2 N crystal (the second layer Al _x Ga _1-x N crystal 22) grows, the Al composition (x2) in the crystal decreases, and the Al content in the melt 3 further increases. It will eventually be eliminated.

Further, when the crystal growth is continued, a GaN crystal is formed on the Al _x2 Ga _{1 -x2} N crystal (the second layer Al _x Ga ₁ -xN crystal 22) as the third layer Al _x Ga _{1 -x} N crystal 23. Will grow. In this way, at least one Al _x Ga _1-x N crystal 20 is formed on the base substrate 10 as an AlN crystal (first Al _x Ga _1-x N crystal 21), Al _x2 Ga _1-x2. N crystal (second layer Al _x Ga _1-x N crystal 22) and GaN crystal (third layer Al _x Ga _1-x N crystal 23) can be grown sequentially and continuously.

Here, the above AlN crystal (first layer Al _x Ga _1-x N crystal 21), Al _x2 Ga _1-x2 N crystal (second layer Al _x Ga _1-x N crystal 22) and GaN crystal ( The presence of the third layer Al _x Ga _1-x N crystal 23) and their thickness are determined by the chemical composition of the cross section parallel to the growth direction of the obtained crystal using the EPMA (electron probe microanalysis) method. This can be confirmed by analysis.

As described above, according to the Al _x Ga _1-x N (0 ≦ x ≦ 1) crystal growth method of the present embodiment, the Al composition (x) in the Al _x Ga _1-x N crystal is increased along with the crystal growth. By reducing this, an AlN crystal, an Al _x2 Ga _1-x2 N crystal, and a GaN crystal can be grown sequentially and continuously on the base substrate. Therefore, an Al _x such as a SiC substrate or a sapphire substrate can be used as the base substrate 10. Even when a heterogeneous substrate having a chemical composition different from that of Ga _1-x N is used, a highly crystalline GaN crystal can be obtained.

  Here, the Al content in the Ga melt 3 containing Al is not particularly limited, but from the viewpoint of promoting the growth of AlN crystals, it is 0.01 mol% or more and 10 mol% or less with respect to the Ga content. preferable. When the Al content with respect to the Ga content is less than 0.01 mol%, AlN crystals hardly grow. When the Al content is more than 10 mol, dissolution of nitrogen in the melt decreases and the growth of AlN crystals is suppressed. Here, the dissolution of nitrogen in the melt decreases due to the decrease in the Ga composition ratio accompanying the increase in the Al composition ratio, while the AlN crystal increases on the melt surface other than on the substrate due to the increase in the composition of Al that easily forms nitrides. It tends to occur and grow. In order to suppress this, it is necessary to lower the nitrogen pressure, and the reduction of the nitrogen pressure reduces the amount of nitrogen dissolved in the melt.

Further, by adjusting the Al content in the Ga melt 3 containing Al, the above AlN crystal (first layer Al _x Ga _1-x N crystal 21), Al _x2 Ga _1-x2 N crystal ( The thickness of each crystal growth of the second layer Al _x Ga _1-x N crystal 22) and the GaN crystal (third layer Al _x Ga _1-x N crystal 23) can be adjusted. That is, the thickness of the AlN crystal (the Al _x Ga _1-x N crystal 21 of the first layer) can be increased by increasing the Al content in the Ga melt 3 containing Al. By reducing the Al content in the Al-containing Ga melt 3, AlN crystal (first layer Al _x Ga _1-x N crystal 21) and Al _x2 Ga _1-x2 N crystal (second layer Al) The thickness of the GaN crystal (the third layer Al _x Ga _1-x N crystal 23) can be increased by reducing the thickness of the _x Ga _1-x N crystal 22).

In the Al _x Ga _1-x N crystal of this embodiment, the crystal growth temperature in the step of growing the Al _x Ga _1-x N crystal is not particularly limited, but it is easy to form a layered continuous AlN crystal From 1000 ° C. to 1300 ° C. is preferable. When the crystal growth temperature is lower than 1000 ° C., it is difficult to grow layered continuous AlN crystals. When the crystal growth temperature is higher than 1300 ° C., the substrate (Al _x Ga _1-x N crystal) that has a different chemical composition from the growing crystal Cracks are likely to occur in the layered AlN crystal due to the difference in thermal expansion coefficient from the substrate.

The crystal growth pressure in the step of growing the Al _x Ga _1-x N crystal is not particularly limited, but from the viewpoint of efficiently growing the Al _x Ga _1-x N crystal having high crystallinity, the pressure is 100 atm (10 .1 MPa) or more and 2000 atmospheres (202.7 MPa) or less. If the crystal growth pressure is lower than 100 atm, the crystal growth rate becomes too low, and if it is higher than 2000 atm, crystals grow on the surface of the melt and selective crystal growth on the underlying substrate becomes impossible. . Here, the AlN crystal grows easier than the GaN crystal, and a crystal with high crystallinity grows even at a pressure lower than the crystal growth pressure of the GaN crystal. Therefore, when an AlN crystal is grown as the Al _x Ga _1-x N crystal 21 of the first layer, the crystal growth pressure of the GaN crystal is prevented from reliably preventing the growth of the GaN crystal and preventing the GaN from entering the AlN crystal. It is necessary to grow AlN crystals at a sufficiently lower pressure. Since the crystal growth pressure of such an AlN crystal varies depending on the crystal growth temperature, it may be searched according to the crystal growth temperature.

Further, from the viewpoint of growing Al _x Ga _1-x N crystal having high crystallinity, it is preferably grown at a temperature of 1000 ° C. or higher, preferably 1100 ° C. or higher. However, when an Al _x Ga _1-x N crystal is grown on the underlying heterogeneous substrate, cracks are generated due to the difference in thermal expansion coefficient between the underlying heterogeneous substrate and the Al _x Ga _1-x N crystal. It is not preferable to make it too high. From this viewpoint, a crystal growth temperature of 1300 ° C. or lower is preferable.

Example 1
1. Step of Preparing Substrate Referring to FIG. 1, a SiC substrate having a principal surface with a plane orientation of (0001) and a 6H type diameter of 3 inches (7.62 cm) × thickness of 300 μm was prepared as base substrate 10.

2. _1. Growth of Al _x Ga _1-x N crystal Referring to FIG. 1, the above SiC substrate (crystal growth vessel 1) is placed in a crystal crucible (crystal growth vessel 1) having an inner diameter of 10 cm and a height of 5 cm. Underlying substrate 10), 450 g of 99.9999 mol% metal Ga and 1.7 g of 99.9999 mol% metal Al (1 mol% metal Al with respect to metal Ga) were arranged.

Next, while the inside of the crystal growth chamber 110 is evacuated to 1 × 10 ⁻⁵ atm (1.01 Pa), the temperature is raised from room temperature to 700 ° C. using the heater 120 and held at 700 ° C. for 1 hour, and then the gas is supplied. Nitrogen gas with a purity of 99.9999 mol% was supplied into the crystal growth chamber 110 from the port 110e, and the crucible (crystal growth vessel 1) was pressurized from atmospheric pressure to 10 atm (1.01 MPa). Next, the crucible was held at 10 atm, and the temperature was raised from 700 ° C. to 1200 ° C. over 1 hour using the heater 120. Next, the crucible was held at 1200 ° C. and pressurized from 10 atm to 500 atm (50.7 MPa). At this time, the metal Ga and the metal Al arranged in the crucible are melted to form a Ga melt 3 containing Al (Al content is 1 mol% with respect to the Ga content). The obtained solution 7 is in contact with the SiC substrate (underlying substrate 10). Here, the depth from the surface 7 m of the solution 7 to the main surface 10 m of the base substrate 10 is about 5 mm. The crucible was then held at 1200 ° C. and 500 atmospheres for 10 hours. Next, the temperature was lowered from 1200 ° C. to 100 ° C. over 1 hour while maintaining the crucible at 500 atm. Next, the crucible was held at 100 ° C. and the pressure was reduced from 500 atm to atmospheric pressure, and then the temperature was lowered from 100 ° C. to room temperature (30 ° C.).

In this way, an Al _x Ga _1-x N single crystal (Al _x Ga _1-x N crystal 20) having a thickness of 5 to 10 μm and grown in layers on the entire main surface 10m of the SiC substrate (underlying substrate 10). Obtained. When the chemical composition of the cross section parallel to the growth direction of the obtained Al _x Ga _1-x N single crystal was analyzed by the EPMA method, an AlN single crystal (the first layer Al _x Ga _1-x N crystal 21) was formed. It had been. Such an AlN single crystal had a high crystallinity with a half-value width of an X-ray diffraction peak in a rocking curve with respect to the (0002) plane being 150 to 200 arcsec. In addition, no cracks were observed in the AlN single crystal.

(Example 2)
1. Preparation of Base Substrate With reference to FIG. 1, a SiC substrate similar to Example 1 was prepared as the base substrate 10.

2. _1. Growth of Al _x Ga _1-x N crystal Referring to FIG. 1, the above SiC substrate (crystal growth vessel 1) is placed in a crystal crucible (crystal growth vessel 1) having an inner diameter of 10 cm and a height of 5 cm. Underlying substrate 10), 450 g of 99.9999 mol% metal Ga and 0.17 g of 99.9999 mol% metal Al (0.1 mol% metal Al with respect to metal Ga) were placed.

Next, while the inside of the crystal growth chamber 110 is evacuated to 1 × 10 ⁻⁵ atm (1.01 Pa), the temperature is raised from room temperature to 700 ° C. using the heater 120 and held at 700 ° C. for 1 hour, and then the gas is supplied. Nitrogen gas with a purity of 99.9999 mol% was supplied into the crystal growth chamber 110 from the port 110e, and the crucible (crystal growth vessel 1) was pressurized from atmospheric pressure to 10 atm (1.01 MPa). Next, the crucible was held at 10 atm, and the temperature was raised from 700 ° C. to 1200 ° C. over 1 hour using the heater 120. Next, the crucible was held at 1200 ° C. and pressurized from 10 atm to 500 atm (50.7 MPa). At this time, the metal Ga and the metal Al arranged in the crucible are melted to form a Ga melt 3 containing Al (the Al content with respect to the Ga content is 0.1 mol%), and the dissolution of nitrogen into the melt 3 5 is in contact with the SiC substrate (underlying substrate 10). Here, the depth from the surface 7 m of the solution 7 to the main surface 10 m of the base substrate 10 is about 5 mm. The crucible was then held at 1200 ° C. and 500 atmospheres for 10 hours. Next, the crucible was held at 1200 ° C. and pressurized from 500 atm to 1950 atm (197.6 MPa) over 3 hours. The crucible was then held at 1200 ° C. and 1950 atm for 20 hours. Next, the temperature was lowered from 1200 ° C. to 100 ° C. over 1 hour while maintaining the crucible at 1950 atm. Next, the crucible was held at 100 ° C., and the pressure was reduced from 1950 atm to atmospheric, and then the temperature was lowered from 100 ° C. to room temperature (30 ° C.).

In this way, an Al _x Ga _1-x N single crystal (Al _x Ga _1-x N crystal 20) having a thickness of 10 to 15 μm which is grown in a layered manner on the entire main surface 10m of the SiC substrate (underlying substrate 10). Obtained. When the chemical composition of the cross section parallel to the growth direction of the obtained Al _x Ga _1-x N single crystal was analyzed by the EPMA method, an AlN single crystal having a thickness of 2 to 3 μm (the first layer of AlN) was observed from the SiC substrate side. _x Ga _1-x N crystal 21), Al _{x 2} Ga _{1-x 2} N (0 <x2 <1) single crystal (second layer Al _x Ga _1-x N crystal 22) and thickness of 2 to 3 μm A GaN single crystal (third layer Al _x Ga _1-x N crystal 23) of 5 to ₁₀ μm was sequentially formed. Here, the Al composition (x2) of the Al _x2 Ga _1-x2 N single crystal (the second layer Al _x Ga _1-x N crystal 22) is the AlN single crystal (the first layer Al _x Ga _1-x N crystal). From the main surface on the crystal 21) side to the main surface on the GaN single crystal (third layer Al _x Ga _1-x N crystal 23) side, the value decreased from 1 to 0.

In addition, the GaN single crystal (third layer Al _x Ga _1-x N crystal 23) has an extremely high crystallinity because the half-value width of the X-ray diffraction peak in the rocking curve with respect to the (0002) plane is 120 to 150 arcsec. Was. Also, AlN single crystal (first layer Al _x Ga _1-x N crystal 21), Al _x2 Ga _1-x2 N (0 <x2 <1) single crystal (second layer Al _x Ga _1-x N crystal) No occurrence of cracks was observed in any of 22) and the GaN single crystal (third layer Al _x Ga _1-x N crystal 23).

The Al _x Ga _1-x N crystal obtained in the present invention is of high quality, and according to the present invention, it is possible to simultaneously grow a large number of dozens of Al _x Ga _1-x N crystals. A large number of high-quality Al _x Ga _1-x N crystals can be efficiently produced at low cost. Using the Al _x Ga _1-x N crystal obtained in the present invention as a base substrate, a semiconductor device can be produced by depositing a single-layer or multilayer III-nitride thin film according to the purpose. In this case, since a high-quality Al _x Ga _1-x N crystal is used at low cost, a high-quality semiconductor device can be produced at low cost. Here, if necessary, before forming the group III nitride thin film, a step of polishing the surface of the Al _x Ga _1-x N crystal used as the base substrate to improve the surface flatness is introduced. May be.

  It should be understood that the embodiments and examples disclosed herein are illustrative and non-restrictive in every respect. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

Is a schematic sectional view showing an embodiment of a Al _x Ga _1-x N growth process of crystals according to the present invention.

Explanation of symbols

1 crystal growth vessel, 3 melt, nitrogen dissolved in the 5 melt 7 solution, 7m surface, 10 underlying substrate, 10m main _{surface, 20 Al x Ga 1-x} N crystal, 21 Al _x Ga of the first layer _1-x N crystal, 22 second layer Al _x Ga _1-x N crystal, 23 third layer Al _x Ga _1-x N crystal, 110 crystal growth chamber, 110e gas supply port, 120 heater.

Claims (4)

Preparing a base substrate;
A solution in which nitrogen is dissolved in an Al-containing Ga melt is brought into contact with the base substrate to grow at least one layer of Al _x Ga _1-x N (0 ≦ x ≦ 1) crystals on the base substrate. And a method of growing an Al _x Ga _1-x N crystal. The Al _x Ga _1-x In N step of growing the crystal, Al _x Ga _1-x according to claim 1 for growing the AlN crystal as Al _x Ga _1-x N crystal of the first layer to the underlying substrate N crystal growth method. In the step of growing said Al _x Ga _1-x N crystal, on the AlN crystal, the Al _x Ga _1-x N crystal of the second layer _{Al x2 Ga 1-x2 N (} 0 <x2 <1) crystal, The method for growing an Al _x Ga _1-x N crystal according to claim 2, wherein a GaN crystal is further grown as a third layer Al _x Ga _1-x N crystal. Growth of the _{Al x Ga 1-x N Al} x Ga 1-x N crystal according to any one of crystals claims 1 crystal growth temperature of 1000 ° C. or higher 1300 ° C. or less in the step of growing up claims 3 Method.

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