JP2002145700A - Sapphire substrate, semiconductor device, electronic component and crystal growth method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To use a nitride material such as a nitride semiconductor, for example, using InGaAlN as a constituent element, and to have better characteristics such as a nitride semiconductor device having excellent electrical and optical characteristics and a long life. The device can be obtained. SOLUTION: The surface of the sapphire M-plane off-substrate (heteroepitaxial growth surface) has an inclination rotated by 8 ° to 20 ° around the c-axis of the sapphire substrate (the inclination angle, ie, the off-angle is equal to the rotation angle). In this case, crystal steps are formed on the substrate in the direction in which the substrate is inclined. This step suppresses the generation of twins generated on the M-plane just surface.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a sapphire substrate having a heteroepitaxial growth surface, a semiconductor device having a group III nitride single crystal layer grown on the substrate, and a crystal substrate having a rhombohedral crystal structure. The present invention relates to an electronic component having a crystal layer of a nitride material and a crystal growth method.

[0002]

2. Description of the Related Art As a semiconductor material having a high band gap energy and a high melting point, a gallium nitride-based material has attracted attention. For example, devices using crystalline InGaAlN have been manufactured. In manufacturing this element, it is necessary to heteroepitaxially grow a crystal film on a substrate. This is because there is no crystal substrate made of gallium nitride-based crystals. Conventionally, corundum (sapphire) is mainly used as a substrate on which a crystal film is heteroepitaxially grown, and this (0001) plane (C plane) is used as a heteroepitaxial growth plane for growing a crystal of a nitride material as a dissimilar material. Have been.

[0003] Usually, first, GaN which is most likely to grow in the present crystal is grown on a sapphire substrate.
This is because (1) it is difficult to control the structure of mixed crystal growth, (2) AlN growth requires a high temperature of 1300 ° C. or higher, and (3) high N equilibrium vapor pressure for growth of InN. In order to realize the above, the supply ratio of the nitrogen raw material and the In raw material N /
In needs to be extremely large, about 1,000,000, and the growth rate becomes 100 nm / h or less, which is not industrial.

[0004] Even when growing GaN, if a single crystal is to be grown directly on a substrate, only a crystal having a highly uneven surface can be obtained. It is difficult to stack crystals on such a surface, and even if they are stacked, the thickness of the stacked layers becomes nonuniform, and growth with controlled layer thickness cannot be performed. In addition, if a single crystal is to be grown directly, a crystal grain boundary is generated, which becomes a defect, and greatly impairs the optical and electrical characteristics of the crystal. For these reasons, crystals grown directly cannot be used for device fabrication.

[0005] In order to solve this difficulty, a two-stage growth method has appeared. The two-step growth method will be briefly described below. Polycrystalline, amorphous, or GaN or A2 having a mixture of both states having a thickness of 20 to 50 nm is formed on a substrate.
InN is grown at a low temperature (low-temperature buffer layer growth), and thereafter, single crystallization is performed at a high temperature (annealing), on which high-quality single-crystal GaN is grown (main growth). In this case, threading dislocations having a density of 10 ⁸ to 10 ¹⁰ / cm ² exist in the film due to a lattice mismatch rate of 13.8% existing between the substrate and GaN. These dislocations degrade the electrical and optical characteristics of GaN.

In order to reduce the dislocation density, a method has been proposed which utilizes selective growth and lateral growth. That is, GaN having a submicron thickness is grown by the method described above. Next, as a selective growth mask,
A number of O ₂ strip patterns are formed in parallel. GaN is grown under conditions that allow easy growth in the direction (lateral direction) perpendicular to the film thickness direction between the bands. As a result, GaN extending from both ends of this band on one band of SiO ₂
Are combined, and the entire surface of the substrate surface is covered with GaN.

In order to obtain high quality crystals, it is necessary to increase the thickness of GaN to 100 to 200 μm. But,
Dislocations contained in the underlying GaN remain in the crystal on the window. Further, in the above-mentioned united portion of GaN, since the lattice constant of the substrate does not match the lattice constant of GaN as the epitaxial growth film, a number of defects are included. High quality crystals are present only between the united portion and the SiO ₂ window. However, this part also has a density of 10 ⁴ to 10 ⁶ / cm ²
There is a degree of dislocation. Further, the shape of the high-quality crystal part is only a belt-like shape having a width of about 5 μm. The reason this width cannot be increased is due to the limitations of lateral growth technology.

The G formed by the method described above
A semiconductor laser structure has been fabricated on a substrate on which aN has been deposited. However, in the case of application to a DVD device, which is regarded as the most important use of this element, the light output at an operating temperature of 50 ° C.
Although the device life of 100,000 hours under the condition of 0 mW is required, the longest device life at present is as short as several hundred hours or two digits or more. This is due to the strain existing in the high quality crystal part,
It is thought to be due to the dislocation extension present on both sides of this. Therefore, there is a problem that the above-described method is still insufficient in terms of crystallinity.

Further, in the above-described crystal growth method, (1) two-step growth including low-temperature buffer layer growth, annealing and main growth, (2) formation of a film for selective growth and formation of this pattern,
(3) Three processes of lateral growth are required, and the process is complicated.
There was a problem that the growth would be costly.

Examination of the existence of a lattice-matched substrate reveals that, in the same sapphire, the (01-10) plane (hereinafter referred to as the M plane)
There is. The M plane has been conventionally proposed as a heteroepitaxial growth plane by the inventors (Japanese Patent No. 270418).
No. 1). At the time of proposal (application date: February 13, 2001)
On the other hand, there was an era in which GaN was directly grown on a substrate at a high temperature without using a low-temperature-grown GaN layer, instead of a two-stage growth. In this era, GaN crystals have better properties than sapphire (0001) plane (hereinafter referred to as C plane) in terms of surface flatness, low residual carrier concentration, high mobility, and high intensity photoluminescence. Was obtained on the M surface.

[0011]

In order to further improve the crystallinity of GaN grown on the sapphire M plane, two-step growth was performed using the sapphire M plane. The inclination of the substrate surface used at this time from the M plane was 0.3 ° or less in each direction, and the present substrate had a surface that could be usually called a (01-10) just surface. However, the surface of the obtained GaN crystal had a rougher surface than the GaN crystal obtained by two-step growth on the sapphire C plane.

This is because, as shown in FIG. 8, on a substrate having a sapphire (01-10) just face, there is an inherent problem that twins are easily generated. The reason why twins are generated is that, in the (01-10) just-plane substrate, the c-axis of GaN is determined by the two directions of [2-1-10] and [-2110] of the sapphire substrate from the normal direction of the substrate surface. In each of the directions. In other words, the fact that the c-axis orientation can be taken in two ways generates twins. As a result, when a GaN buffer layer is formed on a substrate having a sapphire (01-10) just face, and gallium nitride is grown thereon, crystals grow in two directions as shown in FIG. It is formed.

In general, in epitaxial growth, an off-substrate inclined at an appropriate angle (called an off-angle) with respect to a just surface is used to improve crystallinity. The off-angle in this case is usually not as large as about 1 to 5 °. Actually, when GaN was epitaxially grown on a sapphire M substrate having such an off angle, it was found that there was no effect in suppressing twinning.
This is evident only after actual crystal growth.

As described above, since it is conventionally difficult to obtain a nitride semiconductor having good crystallinity, characteristics using a nitride material having characteristics such as a wide gap semiconductor having a wide band gap energy are obtained. It was difficult to obtain a good device. The present invention has been made in order to solve the above problems, and uses a nitride material such as a nitride semiconductor, for example, has InGaAlN as a constituent element, has excellent electrical and optical characteristics, and has a long life. It is an object of the present invention to obtain an element having better characteristics, such as a nitride semiconductor device having a longer length.

[0015]

According to one aspect of the present invention, a sapphire substrate has a heteroepitaxial growth surface rotated on the (01-10) plane of the sapphire substrate and a c-axis of the sapphire substrate rotated in a crystal lattice of the sapphire substrate. The axis is parallel to a plane rotated by 8 ° to 20 °. In this sapphire substrate, twin growth on the heteroepitaxial growth surface is suppressed.

In a sapphire substrate according to another embodiment of the present invention, the heteroepitaxially grown surface has a (01-10) plane of the sapphire substrate in a crystal lattice of the sapphire substrate and a rotation angle of 13 ° with respect to the c-axis of the sapphire substrate. It is in a state parallel to the plane rotated by 18 ° from. In this sapphire substrate, twin growth on the heteroepitaxial growth surface is suppressed.

In a sapphire substrate according to another embodiment of the present invention, the heteroepitaxially grown surface has a (01-10) plane of the sapphire substrate in a crystal lattice of the sapphire substrate, and has a c-axis of the sapphire substrate of 8 ° as a rotation axis. , And without any rotation around the c axis,
This is a state parallel to a plane inclined at 0.1 ° to 20 ° with respect to the c-axis. In this sapphire substrate,
The twin growth on the heteroepitaxial growth surface is suppressed, and the generation of a stripe pattern (striped pattern) extending in the direction parallel to the c-axis of the substrate on the crystal growth surface is suppressed.

In a sapphire substrate according to another embodiment of the present invention, the heteroepitaxially grown surface has a (01-10) plane of the sapphire substrate in the crystal lattice of the sapphire substrate, and has a c-axis of the sapphire substrate of 8 ° as a rotation axis. , And without any rotation around the c axis,
This is in a state parallel to a plane inclined from 0.1 ° to 2 ° with respect to the c-axis. In this sapphire substrate, twin growth on the heteroepitaxial growth surface is suppressed, and the occurrence of a striped pattern extending in the direction parallel to the c-axis of the substrate on the crystal growth surface is suppressed.

A semiconductor device according to one embodiment of the present invention is a group III nitride I grown on the sapphire substrate described above.
nN, GaN, AlN single crystal layer or its mixed crystal In
_1-XY Ga _X Al _Y N single crystal (where 0 ≦ X <1, 0 ≦
Y <1, 0 <X + Y ≦ 1).

An electronic component according to an embodiment of the present invention has a size of $ 0.
A crystal substrate having a rhombohedral crystal structure having a main surface rotated from 8 ° to 20 ° about the c-axis as a rotation axis from a 1-10 ° plane, and a nitride crystal grown on the main surface of the crystal substrate And a crystal layer of a material. According to this electronic component, generation of twins is suppressed in the crystal layer grown on the main surface of the crystal substrate.

An electronic component according to another aspect of the present invention includes:
A crystal substrate having a rhombohedral crystal structure whose main surface is a plane rotated from 13 ° to 18 ° with the c-axis as a rotation axis from the {01-10} plane, and crystals grown on the main surface of this crystal substrate And a crystal layer of a nitride material.
According to this electronic component, generation of twins is suppressed in the crystal layer grown on the main surface of the crystal substrate.

In the above electronic component, the main surface of the crystal substrate is, for example, a surface inclined at 0.1 ° to 20 °, more preferably 0.1 ° to 2 ° with respect to the c-axis, so that the crystal layer is formed. The generation of a striped pattern extending in the direction parallel to the c-axis of the crystal substrate on the surface of is suppressed. In the electronic component, for example, a corundum substrate can be used as the crystal substrate. Further, as the nitride material, for example, a semiconductor material containing nitrogen and gallium can be used, and a semiconductor material containing indium and aluminum in addition to nitrogen and gallium can be used.

According to one embodiment of the present invention, there is provided a crystal growth method comprising:
The main surface is 8 ° from the {01-10} plane with the c-axis as the rotation axis
A crystal substrate having a rhombohedral crystal structure having a plane rotated by 20 ° is prepared, and a nitride material is crystal-grown on the main surface of the crystal substrate by a vapor phase epitaxy method. A crystal layer of a material is formed. According to this crystal growth method, the nitride material grows on the main surface of the crystal substrate in a state where twinning is suppressed.

According to another embodiment of the present invention, there is provided a crystal growth method in which a main surface is a plane rotated from 13 ° to 18 ° with respect to a c-axis as a rotation axis from a {01-10} plane. Is prepared, a nitride material is crystal-grown on the main surface of the crystal substrate by a vapor phase growth method, and a layer of the nitride material is formed on the crystal substrate. According to this crystal growth method, the nitride material grows on the main surface of the crystal substrate in a state where twinning is suppressed.

In the above-mentioned crystal growth method, the crystal is grown by setting the main surface of the crystal substrate to a plane inclined from 0.1 ° to 20 °, more preferably from 0.1 ° to 2 ° with respect to the c-axis. The generation of a stripe pattern extending in the direction parallel to the c-axis of the crystal substrate on the surface of the nitride material layer can be suppressed. In addition, as the crystal substrate, for example, a corundum substrate may be used. The nitride material is, for example, a semiconductor material containing nitrogen and gallium, and is a semiconductor material containing indium and aluminum in addition to nitrogen and gallium.

[0026]

Embodiments of the present invention will be described below with reference to the drawings. Hereinafter, a case where a gallium nitride-based crystal film such as InGaAlN is grown on a crystal substrate such as sapphire (corundum) will be described as an example. First, the features of the present embodiment will be briefly described. In the present embodiment, a surface formed by rotating the M-plane of sapphire around a rotation axis in a specific direction is referred to as a heteroepitaxial growth surface, and in the crystal growth of a gallium nitride-based crystal film,
The generation of twins was suppressed. By suppressing the generation of twins,
A gallium nitride-based crystal having a flat surface and good crystallinity can be grown, and an electronic component having good characteristics can be obtained.

The sapphire substrate in this embodiment is
It differs from the conventional semiconductor device substrate containing at least one layer of InGaAlN in the following points. Conventionally, the sapphire M-plane just surface has been a heteroepitaxial growth surface. In contrast, in the present embodiment, the sapphire M
A surface inclined at an angle larger than the normal off angle with respect to the surface is defined as a heteroepitaxial growth surface, for example, GaN
A crystal film of a nitride material such as the above is formed.

Therefore, the characteristic sapphire substrate in this embodiment is called a sapphire M-plane off-substrate, and this heteroepitaxially grown surface is called an M-plane off-plane. In the following description, the front surface of the substrate (the surface distinguished from the back surface and the side surface) is a heteroepitaxial growth surface. Here, the M plane will be described. A hexagonal system having a rhombohedral structure such as corundum (sapphire)
It has a hexagonal prism type structure. The M surface corresponds to the six rectangular side walls of the hexagonal column. Since the c-axis in the crystal is parallel to the direction perpendicular to the hexagonal top and bottom surfaces, the M-plane is, of course, parallel to the c-axis. When the plane orientation of the M plane is expressed using a “Miller-Bravais” index, (1−100), (−1110)
0), (01-1-10), (0-1110), (1
0-10) and (-1 0 10). This can be collectively written as {01-1-10}.

The sapphire M according to the present embodiment
A semiconductor device fabricated on a plane-off substrate uses a conventional InG
It differs from a semiconductor element containing at least one layer of aAlN in the following points. Since the semiconductor element in this embodiment is formed on a sapphire M-plane off-substrate, there are few crystal defects in a semiconductor layer forming the element. Therefore, good characteristics can be obtained and the element life is long. In the prior art, when crystals are grown by lateral growth, high-quality crystals can only be obtained in the form of strips. However, when a sapphire M-plane off-substrate is used, good characteristics are obtained over the entire surface of the substrate. Therefore, there is no limitation on the arrangement and size of the elements.

When the surface (heteroepitaxial growth surface) of the sapphire M-plane off-substrate has an inclination rotated by 8 ° to 20 ° about the c-axis of the sapphire substrate (the inclination angle, ie, the off-angle is equal to the rotation angle). A crystal step is formed on the substrate in the direction in which the substrate is inclined. This step suppresses the generation of twins generated on the M-plane just surface.

This operation will be described with reference to FIG.
FIG. 1 is a cross-sectional view of sapphire perpendicular to the c-axis. The dotted line indicates the surface of the GaN buffer layer formed on the sapphire substrate. The angle θ between the dotted line and the solid line is the inclination angle from the M plane of the substrate. Since the sapphire M plane is a stable plane, the M plane appears on the surface of the substrate regardless of the tilt angle. Further, the step height _DS is constant from the crystal structure, and it is appropriate to consider it as shown in FIG. Therefore, D _S becomes _{D S = a × sin60 ° (} 1). Here, a is the length of the a-axis of the sapphire crystal. Now, the width W _S of the step is estimated to _{W S = D S / tanθ (} 2). Table 1 shows the relationship between the inclination angle of the substrate and the step width.

[0032]

[Table 1]

From this table, it can be seen that when the inclination angle is small, the step width is large. That is, the flat portion (terrace portion) of the step becomes wider. Therefore, nuclei having c-axes in arbitrary directions, that is, directions in which twins are formed in FIG. 8 can be generated on the same step. Therefore, twins are easily generated. Table 1 shows that when the inclination angle of the substrate is large, the step width becomes narrow. In this case, since the center (terrace portion) of the step is narrow, nuclei are hardly generated, and two-dimensional crystal growth in the step is hard to occur. On the other hand, the atoms supplied from the growth material tend to adhere to the kink portion, which is a place formed by vertically adjacent steps, so that growth from the kink portion becomes dominant.

Generally, to obtain a flat growth surface, it is preferable that the lateral diffusion distance of the attached atoms is large. However,
As described above, since the nucleus is generated on the surface with many steps and the crystal grows on the M surface which is greatly inclined, the distance to the next step is short, and the lateral diffusion distance of the attached atoms is short. . Therefore, according to the present embodiment, there is a great advantage in that the margin of the growth condition is widened and a flat growth surface can be more easily obtained.

Assuming that the inclination of the substrate is in the [2-1-10] direction, it is considered whether a crystal having a c-axis inclined by 32 ° in the [-2110] direction from the normal direction of the step can be grown. The angle between the sapphire M plane existing between the normal direction of the step and the step above it is 30 °. Since this angle is narrower than the above-mentioned angle of 32 °, the crystal of the gallium nitride-based material is difficult to grow. Therefore, a crystal whose c-axis is inclined in the [2-1-10] direction starts to grow from the kink portion, and grows on the step in the [2-1-10] direction. As a result, this growth form governs the growth on the inclined plane having large crystal nuclei. In the above description, the inclination of the sapphire M-plane off-substrate is described as [2-1-10], but the same can be said for the inclination in the opposite direction of [-2110].

Further, the crystal growth will be considered from the viewpoint of the movement of the attached molecules. In actual crystal growth, usually, a two-dimensional growth mode, in which steps are easily extended, is used instead of a three-dimensional growth mode. Under this condition, the steps extend to the left side (down step) in FIG. In order to reach the right side of FIG. 1, the above steps (up steps)
This is because the attached molecule must advance. In order for the attached molecules to migrate in the up step, larger kinetic energy is required than in the down step. The growth nucleus that easily extends to the down step side must be a growth nucleus in which the inclination direction of the c-axis direction is directed to the down step side. As a result, generation of twins is suppressed, and a single crystal of a single domain grows.

[0037]

Next, an embodiment of the present invention will be described.
The embodiment is merely an example, and it goes without saying that various changes or improvements can be made without departing from the spirit of the present invention.

<Example 1> Next, an actual GaN growth method will be described below. (1) Substrates Used Two types of sapphire substrates were used: sapphire M-plane just substrates and sapphire M-plane off substrates. The sapphire M-plane off substrate has 15
° The surface rotated is the surface. The size of each substrate was 1 inch square and the thickness was 400 μm. The back surface of the substrate is lapping-finished, and the growth surface (substrate surface) is mirror-finished. This face is c
The inclination about the axis as the rotation axis is within 0.3 °, and the inclination is not intentionally performed.

(2) Substrate cleaning After each substrate was ultrasonically cleaned in acetone for 5 minutes,
It was washed with water, blown with nitrogen gas, and dried. (3) Transferring the substrate to the growth furnace Place the substrate in the load lock chamber of the metal organic chemical vapor deposition apparatus,
After evacuation to a level of 1.3 × 10 ⁻⁴ Pa (10 ⁻⁶ Torr), the substrate was transferred to a growth furnace.

(4) Hydrogen Cleaning of Substrate The substrate was cleaned by heating it to 1050 ° C. for 5 minutes in a hydrogen atmosphere. At this time, the pressure in the furnace is 8.
It is 6 × 10 ⁴ Pa (650 Torr). The pressure in the furnace in the following steps was 8.6 × 10 ⁴ Pa (650 To
rr) It was constant.

(5) GaN buffer layer growth The temperature was lowered to 550 ° C., and a mixture of amorphous and polycrystalline G
aN was grown to a thickness of 25 nm (vapor phase growth method). As a source gas, ammonia was used as a nitrogen source, and triethylgallium (hereinafter abbreviated as TEGa) was used as a gallium source. The carrier and the bubbling gas of TEGa are hydrogen. At this time, the supply ratio V / III of the raw materials of ammonia and TEGa is 61200. Growth pressure is 8.6 ×
10 ⁴ Pa (650 Torr). (6) Single crystallization of buffer layer The heating temperature was increased to 1050 ° C., and the mixture was kept in a mixed gas of nitrogen and ammonia for 20 minutes to achieve single crystallization of the buffer layer.

(7) GaN High Temperature Growth GaN was grown at 1010 ° C. for 1 hour. The formed film thickness was 0.95 μm. The source gas used was
The nitrogen source is ammonia, and the gallium source is trimethylgallium (hereinafter abbreviated as TMGa). TMG
The carrier and the bubbling gas of a are hydrogen. The supply ratio V / III of the raw material at this time is 2800. (8) Removal of Substrate After growth, the temperature was lowered at a rate of 40 ° C. per minute and the substrate was removed. The reason why the cooling rate is 40 ° C./min is that if the cooling rate is about 100 ° C./min or more, the substrate may be broken due to thermal strain.

Subsequently, the characteristics of the obtained crystal are shown below. FIG. 2 shows a differential interference optical microscope surface photograph of the grown GaN crystal. FIG. 2A shows Ga on a M-plane just substrate.
The surface state of a gallium nitride crystal film grown through an N buffer layer is shown. FIG. 2B shows a surface rotated by 15 ° about the c-axis of sapphire (M-off surface).
The surface state of a gallium nitride crystal film grown above via a GaN buffer layer is shown.

Both the sapphire M-plane just substrate and the sapphire M-plane off substrate have a tilt angle of 0.3 ° due to rotation about the [2-1-10] axis (a-axis).
And is not intentionally tilted as described above. In FIG. 2B, a striped pattern is observed.
This orientation is parallel to the sapphire c-axis. It is considered to be generated from the GaN hexagonal prism observed by obliquely observing the side wall of the hexagonal prism of GaN. This striped pattern appears on the photograph because the step is emphasized and observed with a differential interference microscope. However, when the actual unevenness was measured by an atomic force microscope, it was 1 nm or less and was extremely flat.

For the same sample as FIGS. 2A and 2B showing photographs of the surface, a pole figure was measured using a four-crystal X-ray diffractometer to determine whether the sample was twin or single crystal. (FIGS. 3A and 3B). The pole figure measurement is X
In this method, the X-ray diffraction intensity is measured by setting the position of a line detector at a position where reflection from the (0002) plane of GaN can be detected, and rotating the sample for both in-plane rotation and tilting. Thus, regardless of the orientation of GaN (0002), all GaN (000)
2) can be detected.

In FIGS. 3A and 3B showing the pole figures, the orientation shown in a ring shape corresponds to the in-plane rotation of the sample. Further, the directions described as 0 °, 30 °, 60 °, and 90 ° correspond to the tilting rotation directions. In FIG. 3A corresponding to FIG. 2A, two peaks are observed. This means that GaN (000
2) is included in the crystal while being oriented in two different directions. Therefore, in the case of FIG.
It is clear that twinning has occurred.

On the other hand, FIG. 3 corresponding to FIG.
In (b), it is unimodal. That is, GaN (0002) is oriented in one direction in the crystal. Therefore, in the case of FIG. 3B, it can be said that a single crystal is grown. From the above experimental results, it is clear that twin crystals are clearly generated on the M-plane just substrate, while single-crystal growth can be realized on the substrate inclined by 15 ° from the M-plane. 3 (c) and FIG. 3 (d)
3A and 3B are schematic views showing the state of crystal orientation corresponding to FIGS. 3A and 3B, respectively.

FIG. 4 shows the relationship between the tilt angle of the substrate and the photoluminescence characteristics measured at room temperature. As the inclination angle is larger, the wavelength 50, which is light emission from a deep level (deep), is larger.
Yellow light emission near 0 nm is weak. On the other hand, band edge emission (edge) near a wavelength of 360 nm is dominant. Looking at the intensity ratio (deep / edge) between the deep level emission and the band edge emission, the effect of the tilt angle can be clearly seen.

As described above, a good GaN crystal could be obtained by tilting the substrate about 15 °. As shown in FIG. 4, better characteristics are expected at tilt angles of 8 ° to 20 ° than with no tilt, and particularly good characteristics are expected to appear at tilt angles of 13 ° to 18 °. You.

Here, the case where the substrate is inclined using the c-axis, which has the greatest effect, as the rotation axis has been described. By using such a sapphire M-plane off-substrate, twins completely disappeared, but a striped pattern was generated in GaN in an orientation parallel to the c-axis of the substrate. In order to eliminate this and make it even more flat, the surface of the substrate (heteroepitaxial growth surface)
Using a substrate inclined by 1 ° with respect to the c-axis without rotation about the c-axis, a GaN buffer layer was formed thereon, and then GaN was crystal-grown. As a result, steps flowed during the crystal growth of GaN, and a mirror surface was obtained.

The flatness of the formed gallium nitride crystal film is as follows:
Even with a differential interference optical microscope, no pattern could be observed. In this case, the inclination of the surface is performed by rotation about a direction parallel to the surface and perpendicular to the c-axis as a rotation axis. In this case, the surface is c
It tilts without rotation around the axis, and the tilt angle is equal to the rotation angle. Here, the inclination angle is set to 1 °, but this angle is not strictly limited. The required tilt angle is determined by the ratio of the step flow speed to the growth speed in the film thickness direction, and the tilt angle depends on the growth conditions.

The angle of inclination relative to the c-axis without rotation about the c-axis is preferably 0.1 ° to 20 °, more preferably 0.1 ° to 2 °. In the above description, GaN was used as the buffer layer, but the effect of the tilt angle of the substrate can be similarly observed with AlN. Where Al
The growth temperature of the N buffer layer is 600 ° C., and the annealing temperature is 1250 ° C., which is higher than that of the GaN buffer layer.

In the above description, an example of crystal growth of GaN has been described. However, the present invention is not limited to this example, and crystal growth of InGaN and AlGaN can be similarly performed as described below. First, the crystal growth of InGaN will be described. First, sapphire M
A surface-off substrate is prepared, and a GaN buffer layer is formed thereon. The formation of the buffer layer was performed as follows.

Using TEGa (trimethylgallium) as a source gas for Ga, the temperature of the raw material cylinder containing TEGa is set to about 11 ° C., and hydrogen is bubbled at a flow rate of 25 sccm into the TEGa stored in the raw material cylinder.
A Ga gas is generated, and the supply amount of the gas is 3.85 μmo.
1 / min, carrier gas (hydrogen gas: flow rate 1.5 sl)
m) and supplied into the growth chamber of the crystal growth apparatus. On the other hand, ammonia gas was used as a nitrogen source gas at a flow rate of 5%.
Supply to the above growth chamber by slm. As the raw material supply ratio, V
Group / III becomes 57960.

Under the above conditions, each source gas is supplied into the growth chamber, and the sapphire M-plane off-substrate placed in the growth chamber is set to 55 with the pressure in the growth chamber at 650 Torr.
By heating to about 0 ° C., an amorphous gallium nitride buffer layer is formed on the sapphire M-plane off substrate. Next, the formed buffer layer was treated with ammonia (flow rate 0.1
In an atmosphere (pressure 650 Torr) of nitrogen (supplied at a flow rate of 15 slm) and nitrogen (supplied at a flow rate of 15 slm), the mixture is heated to 1010 ° C. for 20 minutes to perform single crystallization.

Next, InGaN is grown on the GaN buffer layer as follows. First, TEGa was used as a source gas of Ga, the temperature of the raw material cylinder containing TEGa was set to about 11 ° C., and nitrogen was bubbled into the TEGa stored in the raw material cylinder at a flow rate of 50 sccm to generate TEGa gas. Gas supply 7.
At about 7 μmol / min, it is supplied into a growth chamber of a crystal growth apparatus together with a carrier gas (nitrogen gas flow rate: 1.5 slm).

The source gas of indium is T
Using MIn (trimethylindium), the temperature of the raw material cylinder containing TMIn was set to about 20 °, and nitrogen gas was bubbled into the TMIn stored in the raw material cylinder at a flow rate of 600 sccm to generate TMIn gas. A supply amount of about 60.3 μmol / min is supplied together with a carrier gas (nitrogen gas) into a growth chamber of a crystal growth apparatus. In addition, ammonia gas is supplied into the growth chamber at a flow rate of 15 slm as a nitrogen source gas. The raw material supply ratio is 9715 for Group V / Group III.

Under the above conditions, each source gas was supplied into the growth chamber, and the sapphire M-plane off-substrate placed in the growth chamber was placed under the pressure of 650 Torr.
By heating to about 0 ° C., In is deposited on the GaN buffer layer.
_A crystal of _0.114 Ga _0.886 N is grown. Even if InGaN is grown as described above,
As with N, an extremely flat crystal film can be obtained. The InGaN crystal film having a crystal growth had an emission wavelength at room temperature of 400 nm.

Incidentally, InGaN can be grown at a lower temperature of about 500 ° C. However,
When the temperature is low, the activation rate of ammonia decreases, so it is necessary to use a high V / III ratio. For example, when the growth temperature is 500 ° C., the V / III ratio is 1600.
00 may be set.

Next, the crystal growth of AlGaN will be described. First, a sapphire M-plane off-substrate is prepared in the same manner as described above, and a GaN buffer layer is formed thereon in the same manner as described above. Next, AlGaN is crystal-grown on the GaN buffer layer as described below. First, using TEGa as a source gas of Ga,
The temperature of the raw material cylinder containing TEGa was set to about 11 ° C., and the flow rate of TEGa stored in the raw material cylinder was 84%.
bubbling nitrogen with sccm to generate TEGa gas,
This gas is supplied at a supply rate of about 12.9 μmol / min together with a carrier gas (hydrogen gas flow rate 1.5 slm) into the growth chamber of the crystal growth apparatus.

Further, TMAl (trimethylaluminum) is used as an aluminum source gas, and TMIn
At a temperature of about 17.2 ° C., and bubbling hydrogen at a flow rate of 4 sccm into TMAl contained in the raw material cylinder to generate a TMAl gas, and supply the gas at a rate of about 1.87 μmol / min. And supply it into the growth chamber of the crystal growth apparatus together with the carrier gas (hydrogen gas). The TMA gas supply amount / (TMA gas supply amount + T
(EGa gas supply amount) = 0.13. In addition, ammonia gas was used as a nitrogen source gas at a flow rate of 1
Supply into the above growth chamber at 5 slm. As the raw material supply ratio,
Group V / III becomes 15117.

Under the above conditions, each source gas is supplied into the growth chamber, and the sapphire M-plane off-substrate placed in the growth chamber is placed in the growth chamber at a pressure of 650 Torr.
By heating to about 10 ° C., A
A crystal of l _0.15 Ga _0.85 N is grown. Even if AlGaN is grown as described above,
As with N, an extremely flat crystal film can be obtained.

In the same manner as described above, InGaAlN can form a flat crystal film with good crystallinity on a sapphire M-plane off substrate. In the above description, the GaN buffer layer is provided on the sapphire M-plane off-substrate before crystal growth is performed.
Crystal growth may be performed directly on the off-plane substrate.

When InGaAlN is grown on a sapphire M-plane off-substrate, for example, the lattice constants can be matched by appropriately setting the composition ratios. The lattice constant of the _{In 1-XY Ga X Al Y} N is "lattice constant = InN lattice constant × (1-XY) + lattice constant × Y of GaN lattice constant × X + AlN".

<Embodiment 2> FIGS. 5, 6 and 7 are views for explaining a second embodiment of the present invention. FIG. 5 is a perspective view for explaining an outline of the element in the present embodiment. This light-emitting element is configured by stacking a plurality of crystal layers such as a GaN layer and an InGaAlN layer on a sapphire substrate whose M plane is rotated by 15 ° about the c-axis as a rotation axis. Reference numeral 1 denotes a sapphire substrate whose M plane is rotated by 15 ° about the c axis as a rotation axis. Reference numeral 2 denotes a layer including a plurality of semiconductor layers. Reference numeral 3 denotes an SiO ₂ insulating layer for current confinement. Reference numeral 4 denotes a metal electrode layer in which Ni and Au are sequentially stacked on a semiconductor layer. Reference numeral 5 denotes a metal electrode layer in which Ti and Al are sequentially stacked on a semiconductor layer.

Here, the details of the semiconductor layer 2 will be described with reference to the schematic sectional view of FIG. In FIG. 6, 6 is a GaN buffer layer, 7 is a silicon-doped n-type GaN layer,
8 is a silicon-doped n-type Al _0.1 Ga _0.9 N cladding layer,
9 is a silicon-doped n-type GaN waveguide layer, 10 is In
_An active layer having a quantum well structure of _0.2 Ga _0.8 N / In _0.05 Ga _0.95 N, 11 is a magnesium-doped p-type Al _0.2 Ga
_0.8 N barrier layer, 12 is magnesium-doped p-type GaN
Waveguide layer 13 is magnesium-doped p-type Al _0.15 Ga
_0.85 N cladding layer, 14 is magnesium-doped p-type Ga
This is an N contact layer.

Hereinafter, a specific method for manufacturing the present element will be described.
The substrate 1 has a thickness of 400 μm with a c-axis serving as a rotation axis.
A sapphire substrate whose surface is rotated by 15 ° (sapphire M-plane off substrate) is used.

For growing a semiconductor layer such as InGaAlN, a metal organic chemical vapor deposition apparatus is used. An organic metal material is used as the metal material, TEGa and TMGa are used for the low-temperature-grown GaN buffer layer 6 and gallium for high-temperature-grown GaN, respectively, TMIn is used as the indium material, and TMAl is used as the aluminum material. The organic metal carrier gas is nitrogen for a system containing indium, hydrogen for a system not containing indium, and ammonia as a nitrogen source.

First, a low-temperature grown GaN buffer layer 6 is grown at 550 ° C. The thickness of the grown film is 20
nm. This layer acts as a buffer layer with less than ± 2% lattice mismatch between the substrate and GaN. Next, the GaN buffer layer 6 is placed in a mixed atmosphere of nitrogen and ammonia for 10 minutes.
Anneal at 50 ° C. for 20 minutes.

Next, a silicon-doped n-type GaN layer 7 is grown at 1010 ° C. to a thickness of 3 μm for drawing out an n-type electrode. The carrier concentration is 3 × 10 ¹⁸ / cm ³ . On this, a silicon-doped n-type Al _0.1 Ga _0.9 having a thickness of 0.5 μm is formed.
N clad layer 8, 0.1 μm thick silicon-doped n-type GaN waveguide layer 9, non-doped In _0.2 G as active layer
a _0.8 N (thickness 3 nm) / In _0.05 Ga _0.95 N (thickness 6
nm) quantum well structure 10 composed of three pairs, magnesium-doped p-type Al _0.2 Ga _0.8 N barrier layer 1 having a thickness of 20 nm
1. Magnesium-doped p-type GaN waveguide layer 12 having a thickness of 0.1 μm, magnesium-doped p-type Al _0.15 Ga _0.85 N cladding layer 13 having a thickness of 0.5 μm, and magnesium-doped p-type GaN contact layer having a thickness of 0.1 μm 14 grow continuously.

Before the formation of the p-type electrode, an insulating film 3 is formed as a current confinement layer as shown in FIG. 5 in order to concentrate the injected current. The width of the exposed portion of the p-type GaN layer (the direction perpendicular to the axial direction of the resonator) is 3 μm. Next, nickel / gold (layer 4 in FIG. 5) is deposited on p-type GaN as a metal electrode. Next, using a photolithography technique, the metal layer 4 and the semiconductor layers 8 to 14 are partially etched and removed, and the n-type GaN
The layer 7 is exposed. At this time, a part of the layer 7 may be etched. Thereafter, as shown in FIG. 5, an n-type metal electrode layer 5 is formed on the electrode-drawing n-type GaN layer 7 by titanium / metal.
Aluminum is deposited and patterned.

Next, a method of forming a laser resonator will be described. The resonator is formed so that the axial direction (the direction in which light reciprocates) is arranged parallel to the sapphire c-axis. The reason for this is that when the sapphire substrate is cleaved, an R-plane, which is an easy cleavage plane, appears. In forming the cavity end face, the stacked semiconductor layers were etched using a dry etching technique. In chip formation, the substrate was cleaved. FIG. 7A shows the light-current characteristics of the laser diode obtained as described above. It oscillated continuously at room temperature, and the threshold current of laser oscillation was 68 mA.

For comparison, FIG. 7B shows sapphire C
4 shows light-current characteristics of a laser having the same structure manufactured on a surface substrate. Obviously, the threshold current of the semiconductor laser device formed on the sapphire M-plane off-substrate in this embodiment is lower than that of the laser on the sapphire C-plane substrate. Also, the external differential quantum efficiency of the laser on the sapphire M-plane off-substrate is higher. This is because the use of the sapphire M-plane off-substrate reduces the lattice mismatch by about one digit compared to the sapphire C-plane substrate and improves the crystallinity.

As described above, when InGaAlN is grown on a sapphire M-plane off-substrate, twins are generated in InGaAlN on an M-plane just substrate, while twins are not generated and the reproducibility is reduced. Can grow in a good and simple process. Therefore, it is possible to obtain flat InGaAlN exhibiting good crystallinity, and this InGaAlN can be obtained.
By using N, a semiconductor element having excellent electric and optical characteristics and a long element life can be manufactured. Also, InGaAs
Since the direction of the c axis of 1N is inclined from the normal direction of the substrate surface,
As compared with the case where a sapphire C-plane substrate is used, it is possible to suppress the piezo effect which causes a reduction in luminous efficiency.

In the above embodiment, sapphire M
Although a combination of a sapphire M-plane off-substrate having a surface inclined at an angle larger than a normal off-angle with respect to the plane and a gallium nitride-based semiconductor material has been described, the present invention is not limited to this. Another crystal having a rhombohedral crystal structure, a plane rotated from 8 ° to 20 °, more preferably 13 ° to 18 ° about the c-axis as a rotation axis from the {01-10} plane as a main surface, In addition, the present invention can be applied to a combination of a crystal substrate having a main surface inclined at 0.1 ° to 20 °, more preferably 0.1 ° to 2 ° with respect to the c-axis, or another nitride material. Needless to say.

As an example of a plane rotated in the range of 8 ° to 20 ° from the {01-10} plane (M plane) with the c axis as a rotation axis, {12-30}, {13-4} 0｝,
{23-50}, {14-50}, {34
−70 °, {45−90}, {25−7}
0}, {27-9] 0}, {35-8
0}, {37-10}, {38-11}
0｝, {3 10 −130}, {3 13 -16}
0｝, ｛47 １１11 0｝, ｛49９-13
0｝, ｛4 11 -15 0｝, ｛4 13-17
0｝, ｛4 15-19 0｝, ｛4 17-21
There is 0｝. Also in this, {13-40},
{25−70}, {27−90}, {3
7−100}, {38−110}, {31}
0−130 °, {4 11−150}, {4
13-170} is {01-1} with the c-axis as the rotation axis.
This is a plane rotated in the range of 13 ° to 18 ° from the 0 ° plane.

Note that, in the content indicated by {h k l 0}, first, l =-(h + k). Also, a surface in which the order of h, k, and l in 変 え is changed, (h k l
0), (hlk 0), (khl0), (k
l h 0), (l hk 0), (l k h
0). In each of these planes, the planes in which the signs of all exponents are changed, (−h−k−1−0), (−h
−l −k −0), (−k −h −l −0),
(−k −l −h −0), (−l −h−k −
0) and (-l-k-h-0).

The crystals having the rhombohedral crystal structure described above include, for example, α-Fe ₂ O ₃ , Ga ₂ O ₃ , Rh
_{There are 2} O ₃ and Ti ₂ O ₃ . The crystal lattice constants of the main rhombohedral crystal structure and the lattice mismatch with gallium nitride are shown below. Corundum (Al ₂ O ₃ ) lattice constant a: 0.476 nm, b: 1.294 nm, lattice mismatch GaN [03-32]: 2.64%, GaN
[2-1-10]: -1.41% α-Fe ₂ O ₃ lattice constant a: 0.504 nm, b: 1.372 nm, lattice mismatch GaN [03-32]: -2.98%, GaN
[2-1-10]: - 7.52% · Ga 2 O 3 lattice constant a: 0.498nm, b: 1.343nm, lattice mismatch GaN [03-32]: - 1.84% , GaN
[2-1-10]: - 5.24% · Rh 2 O 3 lattice constant a: 0.511nm, b: 1.382nm, lattice mismatch GaN [03-32]: - 4.51% , GaN
[2-1-10]: - 8.31% · Ti 2 O 3 lattice constant a: 0.515nm, b: 1.364nm, lattice mismatch GaN [03-32]: - 5.29% , GaN
[2-1-10]: -6.87%

In the above description, the crystal is grown by the metalorganic vapor phase epitaxy, but the present invention is not limited to this. For example, molecular beam epitaxy (MBE)
May be used to grow the crystal. in this case,
Metal In, metal Ga, and metal Al are used as group III raw materials, and nitrogen or ammonia is used as the nitrogen raw material. MB
In the E method, these gases are introduced into an ECR plasma cell or an rf plasma cell, and these materials are decomposed by discharge in the cells and introduced into a growth furnace as nitrogen atom radicals, nitrogen molecule radicals, and the like.

In the crystal growth by the MBE method, the pressure in the growth furnace is such that the mean free path is longer than the distance from the cell supplying the raw material to the substrate because the raw material reaches the growth substrate as a beam. Is used. Generally, this pressure is a vacuum greater than 10 ^-6 Torr. In addition,
In the MBE method, when a gas is used as a group V raw material, it may be distinguished by using a gas source MBE.

As a technique for growing a crystal, a chemical beam epitaxial growth method (CBE) may be used. In this case, the same organic raw material as in the above-described metal organic chemical vapor deposition method may be used as the group III raw material, and the same nitrogen or ammonia as in the MBE method may be used as the nitrogen raw material. As described above, various vapor deposition methods can be used for forming the crystal layer of the nitride material in this embodiment.

[0082]

According to the present invention, it is possible to provide a substrate for epitaxial growth in which a group III nitride semiconductor InGaAlN can be grown with a high reproducibility and a simple process.
By using InGaAlN as a constituent element, it is possible to provide a semiconductor device which can be manufactured at low cost and with high yield, has excellent electric and optical characteristics, and has a long element life.

In general, semiconductor materials are required to have a large band gap energy and a high melting point. Since a semiconductor material having a large band gap energy has a high withstand voltage and can apply a high electric field, a transistor which can operate at high speed can be realized. In addition, when a semiconductor material having a high melting point is used, operation at a high temperature becomes possible, and in addition, high-power operation becomes possible. Among such properties required for semiconductor materials, gallium nitride-based nitride semiconductor materials and the like have attracted attention.

Conventionally, devices have been manufactured using crystalline InGaAlN. Such a nitride semiconductor is
It is used for light emitting elements having a shorter wavelength than green. As a light emitting element using a nitride semiconductor, an LED has been put to practical use, and is used for an optical memory, a full color display device, a traffic signal, and the like. It is also used in deodorizing equipment using a method of decomposing chemical substances by irradiation with ultraviolet light. However, a semiconductor laser using a gallium nitride based semiconductor has not been put to practical use. This is because the lifetime of the device is short due to a large number of crystal defects contained in the crystal.

On the other hand, a nitride semiconductor is expected to be a semiconductor material that can realize higher characteristics in terms of high speed, high output, and high-temperature operation than transistors conventionally used in AlGaAs or silicon. Have been. Since the nitride semiconductor is a wide gap semiconductor, it has a high dielectric breakdown voltage and a high melting point, so that the above-described characteristics can be obtained.

Further, when a HEMT (High Electron Mobility Transistor) is considered, GaAs is used due to a difference in crystal structure.
The electron density of the two-dimensional electron gas layer is increased by the piezoelectric effect caused by distortion due to lattice mismatch in the upper and lower layers of the crystal, which is an effect not found in s-based semiconductors and silicon, and the natural polarization generated by the wurtzite crystal structure. As a result, high current operation can be expected. For example, it has been reported that an element manufactured experimentally using a nitride semiconductor operates at a maximum of 140 GHz. However, since the life of the element is short, it has not reached a practical stage. Moreover,
It is in a state where a large electric field cannot be applied as expected from the width of the band gap.

The nitride semiconductor is also expected to be applied to a special light receiving element. Since a nitride semiconductor has a wide band gap, a light-receiving element which does not react to sunlight can be manufactured. A major application of this light receiving element is a flame monitoring device (flare detector) used in a combustion device. However, since there are many crystal defects contained in the material, the dark current of the device becomes large, and the device has not been put to practical use.

The nitride semiconductor is also expected to be applied to a cathode material for electron emission. There is an expectation that the electron affinity of AlN is negative, and the characteristics are investigated by actually fabricating a cathode, and it is shown that a large current is drawn at a low voltage. This cathode is industrially expected to be applied to an electron emission source such as a plasma display and an electron microscope. However, again, since there are many crystal defects in the material of the manufactured device, low voltage and large current operation as expected from the physical properties has not been obtained.

In manufacturing an element using the nitride semiconductor described above, it is necessary to heteroepitaxially grow a crystal of the nitride semiconductor on the substrate. This is because these crystal substrates (bulk materials) have not been obtained. This is because the vapor pressure of nitrogen on the solid phase is high, so that it is not easy to grow a nitride semiconductor crystal by an ordinary method. By applying a high pressure of 15000 atmospheres,
There is also a method of growing a crystal of a nitride semiconductor, but in this case, only a small crystal of about several mm square is obtained, which is not practical for forming an element.

In one embodiment of the present invention, compared with the above-described conventional technique, for example, a nitride semiconductor crystal is grown on a sapphire M-plane off-substrate. As a result, first, a crystal layer of a nitride semiconductor can be obtained with little lattice mismatch. Further, by using a sapphire M-plane off-substrate having a large area, it is easy to obtain a crystal layer having a large area. Further, according to one embodiment of the present invention, a surface of a nitride semiconductor crystal layer can be obtained with a flat surface. Therefore, according to the present invention, many of the above-described elements can be obtained in a practical state.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a sapphire M-plane substrate that is perpendicular to the c-axis.

FIG. 2 is a photograph of the surface of a GaN crystal layer grown on a sapphire M-plane just substrate (a) and a sapphire M-plane off substrate (b) via a GaN buffer layer, observed with a microscope.

FIG. 3 is a characteristic diagram showing a result of a pole figure measurement of a crystal using a four-crystal X-ray diffractometer. The reflecting surface used is the (0002) plane.

FIG. 4 is a characteristic diagram showing a relationship between a tilt angle of a sapphire M-plane substrate and a photoluminescence characteristic of a GaN crystal layer grown thereon on the GaN crystal layer measured at room temperature.

FIG. 5 is a perspective view schematically showing a configuration example of a semiconductor device according to an embodiment of the present invention.

FIG. 6 is a cross-sectional view showing a detail of a portion of the semiconductor device shown in FIG. 5;

FIG. 7 is a characteristic diagram showing light-current characteristics (a) of a semiconductor device formed on a sapphire M-plane off-substrate and light-current characteristics (b) of a semiconductor device formed on a sapphire C-plane substrate. .

FIG. 8 is a perspective view schematically showing a state in which a GaN crystal is grown on a sapphire M-plane just substrate via a GaN buffer layer.

[Explanation of symbols]

1: Sapphire M-plane 15 ° off substrate, 2: InGaAl
Stacked region of N layers, 3 ... electric insulating layer, 4 ... metal electrode for p-type semiconductor, 5 ... metal electrode for n-type semiconductor, 6 ... G
aN buffer layer, 7... silicon-doped n-type GaN layer, 8
... silicon-doped n-type Al _0.1 Ga _0.9 N cladding layer 9
... silicon-doped n-type GaN waveguide layer, 10 ... undoped _{In 0.2 Ga 0.8 N / In 0.05} Ga 0.95 N quantum well layer,
11 ... magnesium-doped p-type Al _0.2 Ga _0.8 N barrier layer, 12 ... magnesium-doped p-type GaN waveguide layer, 1
3 ... magnesium-doped p-type Al _0.15 Ga _0.85 N cladding layer, 14 ... magnesium-doped p-type GaN contact layer.

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4G077 AA02 AA03 BB01 BE11 BE13 BE15 DB08 ED06 HA02 5F045 AB09 AB14 AB18 AC08 AC09 AC12 AD09 AD10 AD14 AE25 AF09 AF13 BB12 CA07 CA12 DA53 HA06 5F073 AA04 AA45 AA74 CA07 CB05 DA07 CB05 DA07

Claims (19)

[Claims] 1. A sapphire substrate having a heteroepitaxial growth surface, wherein the heteroepitaxial growth surface rotates the (01-10) plane of the sapphire substrate and the c-axis of the sapphire substrate in a crystal lattice of the sapphire substrate. A sapphire substrate characterized by being parallel to a plane rotated by 8 to 20 degrees as an axis. 2. A sapphire substrate having a heteroepitaxial growth surface, wherein the heteroepitaxial growth surface rotates a (01-10) plane of the sapphire substrate and a c-axis of the sapphire substrate in a crystal lattice of the sapphire substrate. A sapphire substrate parallel to a plane rotated by 13 to 18 degrees as an axis. 3. A sapphire substrate having a heteroepitaxial growth surface, wherein the heteroepitaxial growth surface rotates a (01-10) plane of the sapphire substrate and a c-axis of the sapphire substrate in a crystal lattice of the sapphire substrate. Rotate from 8 ° to 20 ° as axis,
Further, the sapphire substrate is parallel to a plane inclined by 0.1 ° to 20 ° with respect to the c-axis without rotating around the c-axis. 4. A sapphire substrate having a heteroepitaxial growth surface, wherein the heteroepitaxial growth surface rotates a (01-10) plane of the sapphire substrate and a c-axis of the sapphire substrate in a crystal lattice of the sapphire substrate. Rotate from 8 ° to 20 ° as axis,
Further, the sapphire substrate is parallel to a plane inclined at 0.1 ° to 2 ° with respect to the c-axis without rotation around the c-axis. 5. A group III nitride InN, Ga grown on the sapphire substrate according to claim 1.
N, AlN single crystal layer or its mixed crystal In _{1-X- Y} Ga _X Al
_YN single crystal (where 0 ≦ X <1, 0 ≦ Y <1, 0 <X
+ Y ≦ 1) at least one layer. 6. A crystal substrate having a rhombohedral crystal structure having a main surface rotated from 8 ° to 20 ° with the c-axis as a rotation axis from the {01-10} plane; An electronic component comprising at least a crystal layer of a nitride material grown on a crystal. 7. A crystal substrate having a rhombohedral crystal structure having a main surface rotated from 13 ° to 18 ° with the c-axis as a rotation axis from the {01-10} plane, and a main surface of the crystal substrate. An electronic component comprising at least a crystal layer of a nitride material crystal-grown thereon. 8. The electronic component according to claim 6, wherein the main surface of the crystal substrate is a surface inclined from 0.1 ° to 20 ° with respect to a c-axis. 9. The electronic component according to claim 6, wherein the main surface of the crystal substrate is a surface inclined from 0.1 ° to 2 ° with respect to a c-axis. 10. The electronic component according to claim 6, wherein the crystal substrate is a corundum substrate. 11. The electronic component according to claim 6, wherein the nitride material is a semiconductor material containing nitrogen and gallium. 12. The electronic component according to claim 11, wherein the nitride material is a semiconductor material containing indium and aluminum in addition to nitrogen and gallium. 13. A crystal substrate having a rhombohedral crystal structure in which a main surface is a surface rotated from 8 ° to 20 ° about a c-axis as a rotation axis from a {01-10} plane is provided. Crystal growth of a nitride material on a main surface of the substrate by a vapor phase growth method, and forming a crystal layer of the nitride material on the crystal substrate. 14. A crystal substrate having a rhombohedral crystal structure whose main surface is a surface rotated from 13 ° to 18 ° with the c-axis as a rotation axis from the {01-10} plane is provided. Crystal growth of a nitride material on a main surface of the substrate by a vapor phase growth method, and forming a layer of the nitride material on the crystal substrate. 15. The crystal growth method according to claim 13, wherein the main surface of the crystal substrate is a surface inclined from 0.1 ° to 20 ° with respect to a c-axis. Method. 16. The crystal growth method according to claim 13, wherein the main surface of the crystal substrate is a surface inclined from 0.1 ° to 2 ° with respect to a c-axis. Method. 17. The crystal growth method according to claim 13, wherein the crystal substrate is a corundum substrate. 18. The crystal growth method according to claim 13, wherein the nitride material is a semiconductor material containing nitrogen and gallium. 19. The crystal growth method according to claim 18, wherein the nitride material is a semiconductor material containing indium and aluminum in addition to nitrogen and gallium.