JP2008021889A - Nitride semiconductor single crystal - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a nitride semiconductor single crystal wherein a nitride semiconductor film of non-polar (10-10) plane is formed on an Si substrate in thickness of ≥1 μm, and it is preferably used also for a light emitting device. <P>SOLUTION: There are formed on an Si(211) substrate a single crystal film of GaN(10-10), AlN(10-10) or InN(10-10) or a superlattice structure of GaN(10-10) and AlN(10-10) via a buffer layer consisted of any one kind or more of 3C-SiC(211) or BP(211) and via an AlN(10-10) buffer layer. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a nitride semiconductor single crystal made of gallium nitride (GaN) and aluminum nitride (AlN) which is suitably used for a light-emitting diode, a laser light-emitting element, an electronic element capable of high-speed high-temperature operation, and the like.

  Nitride semiconductors typified by GaN and AlN have a wide band gap, and are compound semiconductors having excellent characteristics such as high electron mobility and high heat resistance. It is a material that is expected to be applied to high-temperature operable electronic devices.

Since the nitride semiconductor has a high melting point and a very high equilibrium vapor pressure of nitrogen, bulk crystal growth from the melt is not easy. For this reason, a single crystal is produced by heteroepitaxial growth on a heterogeneous substrate.
Conventionally, a GaN (0001) or AlN (0001) single crystal film is formed on a substrate of sapphire (0001), 6H—SiC (0001), Si (111) or the like via a buffer layer.

Among these substrates, the Si substrate is excellent in crystallinity, obtained in a large area, and low in price as compared with other substrates. is there.
Moreover, since the formation of the nitride semiconductor film on the Si substrate can inherit the current silicon technology, it is required to be put into practical use also from the advantage in the development cost of industrial technology.

  However, when the nitride semiconductor single crystal is formed on the Si substrate, the nitride semiconductor single crystal film is cracked due to the difference in thermal expansion coefficient between Si and the nitride semiconductor. Due to the difference in the crystal lattice constant, a large number of crystal defects occur, and it was difficult to form a single crystal film having a thickness of 1 μm or more.

For this reason, when forming a nitride semiconductor single crystal on a Si substrate, it is necessary to form it through an appropriate buffer layer.
As such a buffer layer, for example, it has been proposed to employ an AlN and GaN superlattice structure or a 3C—SiC (111) layer.

Further, when a 3C-SiC layer is formed on a Si substrate, the use of a Si (211) substrate results in a lower defect density more efficiently than when a Si (100) or Si (111) substrate is used. It is known that a 3C—SiC (211) film can be formed (for example, see Patent Document 1). It is considered that the same effect can be obtained by BP having a lattice constant close to that of 3C-SiC.
JP 2005-223215 A

By the way, when a nitride semiconductor is used for a light-emitting device, in the nitride semiconductor single crystal having the (0001) plane, recombination of electron holes is hindered by the spontaneous polarization of the crystal, resulting in a decrease in luminous efficiency. Had problems.
For this reason, in order to improve luminous efficiency, it is required to use (10-10) or (11-20) planes that are nonpolar crystal planes.

  On the other hand, the present inventors, when forming a nitride semiconductor film such as GaN (10-10), AlN (10-10), 3C-SiC (on the Si (211) substrate described above) 211) or using BP (211), it has been found that the nitride semiconductor film can be formed with a thickness of 1 μm or more.

  That is, the present invention has been made to solve the above technical problem, and a (10-10) plane nitride semiconductor film having a thickness of 1 μm or more is formed on a Si substrate. An object of the present invention is to provide a nitride semiconductor single crystal that can be suitably used for a light emitting device.

The nitride semiconductor single crystal according to the present invention has a buffer layer composed of at least one of 3C—SiC (211) and BP (211) and an AlN (10-10) buffer layer on a Si (211) substrate. And is made of GaN (10-10), AlN (10-10), or InN (10-10).
According to the above configuration, a (10-10) plane nitride semiconductor single crystal having a thickness of 1 μm or more and excellent crystallinity can be formed on a Si substrate.

In addition, a nitride semiconductor single crystal according to another aspect of the present invention includes a buffer layer composed of at least one of 3C—SiC (211) and BP (211) on a Si (211) substrate, and AlN (10 -10) It is formed through a buffer layer and has a superlattice structure of GaN (10-10) and AlN (10-10).
Thus, the crystallinity of the nitride semiconductor single crystal can be further improved by forming a superlattice structure of GaN and AlN.

As described above, according to the present invention, a GaN, AlN or InN single crystal film having excellent crystallinity of a (10-10) plane which is a nonpolar crystal plane can be obtained on a Si substrate with a thickness of 1 μm or more. Can do.
Furthermore, the crystallinity of the nitride semiconductor single crystal can be further improved by forming a superlattice structure of GaN and AlN.
Therefore, the nitride semiconductor single crystal according to the present invention can be suitably used for a light-emitting diode, a laser light-emitting element, an electronic element capable of high-speed and high-temperature operation, and is particularly suitable for a light-emitting device. Can be achieved.

Hereinafter, the present invention will be described in more detail.
The nitride semiconductor single crystal according to the present invention is a GaN, AlN or InN single crystal formed on a Si single crystal substrate via a 3C-SiC or / and BP buffer layer and an AlN buffer layer.
In this nitride semiconductor single crystal, a (211) -plane Si substrate is used as the Si single crystal substrate, and a buffer layer made of at least one of 3C—SiC (211) and BP (211) is formed thereon. By forming, it is obtained as a (10-10) plane single crystal having excellent crystallinity.
Further, this (10-10) plane nitride semiconductor single crystal is formed on a Si substrate, so that the apparatus and technology used in the conventional Si semiconductor manufacturing process can be utilized, and the large diameter In addition, it has an advantage that it can be obtained at low cost.

  The manufacturing method of the Si single crystal substrate used in the present invention is not particularly limited. Those produced by the Czochralski (CZ) method or those produced by the floating zone (FZ) method may be used. An epitaxially grown crystal layer (Si epi substrate) may be used.

  The Si (211) substrate is cleaned by hydrogen gas or the like before forming a buffer layer made of at least one of 3C-SiC (211) and BP (211) on the surface of the Si (211) substrate. It is preferable to remove the water and keep it in a clean state.

Furthermore, it is preferable that the surface of the Si substrate is carbonized by heat treatment at 1000 to 1350 ° C. using a hydrocarbon-based gas such as propane.
By performing such carbonization in advance, it is possible to prevent Si from being detached from the Si substrate surface when the 3C—SiC or BP buffer layer is formed.

Further, as described above, since the 3C-SiC or BP layer can be efficiently formed on the Si single crystal substrate as a film having a low defect density, as described above, the conventionally used Si (111 ) Instead of the substrate, a buffer layer composed of at least one of 3C—SiC (211) and BP (211) is formed using a Si (211) substrate.
This buffer layer may be only the 3C—SiC (211) layer or only the BP (211) layer, or may be formed of two types of 3C—SiC (211) and BP (211).

In the case of selecting two types of 3C—SiC and BP in the buffer layer, it is preferable to form the 3C—SiC (211) layer after forming the BP (211) layer.
Since BP has an intermediate lattice constant between Si and SiC, the effect as a buffer layer can be improved by adopting a two-layer structure disposed between the Si substrate and the 3C—SiC layer.

Further, an AlN (10-10) buffer layer is formed on the 3C-SiC (211) or BP (211) buffer layer.
The AlN (10-10) buffer layer includes a substrate and a 3C-SiC (211) buffer layer, and GaN (10-10), AlN (10-10) or InN (10-10) formed thereon. It plays a role in relaxing crystal lattice mismatch.

The thickness of the AlN buffer layer is preferably as thin as possible from the viewpoint of manufacturing cost. However, the above-described substrate and a buffer layer made of any one or more of 3C—SiC (211) or BP (211) are used. And GaN (10-10), AlN (10-10), or InN (10-10) formed thereon are formed to such an extent that the effect of relaxing the crystal lattice mismatch is sufficiently obtained. Specifically, the thickness is preferably about 1 to 500 nm.
The AlN buffer layer can be formed, for example, by epitaxial growth on a buffer layer made of at least one of 3C-SiC and BP (211) by vapor phase growth.

  By epitaxially growing GaN (10-10), AlN (10-10) or InN (10-10) on the AlN buffer layer, these nitride semiconductor single crystals have an excellent thickness of 1 μm or more. It can be formed as a film having crystallinity.

  Furthermore, GaN (10-10) and AlN (10-10) are alternately laminated as a thin film on the AlN buffer layer, and the crystallinity of these nitride semiconductor single crystals can be improved by forming a superlattice structure. This can be further improved.

EXAMPLES Hereinafter, although this invention is demonstrated further more concretely based on an Example, this invention is not restrict | limited by the following Example.
[Example 1]
The Si (211) substrate was set in a growth region in the reaction tube, and while supplying hydrogen as a carrier gas, the Si (211) substrate was heated to 1100 ° C. to clean the substrate surface.
Then, propane was supplied to set the substrate temperature to 1000 to 1350 ° C., and the surface of the Si substrate was carbonized, and then propane and silane were supplied to form a 3C—SiC (211) layer having a thickness of 100 to 2000 nm.
Next, trimethylaluminum (TMA) and ammonia are supplied as raw materials while maintaining the substrate temperature, and an AlN (10-10) buffer layer having a thickness of 1 to 500 nm is formed on the 3C-SiC (211) layer. Filmed.
Furthermore, the substrate temperature was lowered to about 1000 ° C., trimethylgallium (TMG) and ammonia were supplied as raw materials, and a GaN (10-10) single crystal layer was formed.
Even when the GaN single crystal layer was formed to a thickness of 1 μm or more, no cracks or defects were observed.

[Example 2]
In the same manner as in Example 1, a 3C—SiC (211) layer and an AlN (10-10) buffer layer were formed on a Si (211) substrate.
The substrate temperature was raised to 1200 ° C. or higher, TMA and ammonia were supplied as raw materials, and an AlN (10-10) single crystal layer was formed.
Even when the AlN (10-10) single crystal layer was formed to a thickness of 1 μm or more, no cracks or defects were observed.

Claims (2)

  GaN (10-10) is formed on a Si (211) substrate via a buffer layer composed of at least one of 3C-SiC (211) and BP (211) and an AlN (10-10) buffer layer. A nitride semiconductor single crystal comprising AlN (10-10) or InN (10-10).   GaN (10-10) is formed on a Si (211) substrate via a buffer layer composed of at least one of 3C-SiC (211) and BP (211) and an AlN (10-10) buffer layer. And a nitride semiconductor single crystal comprising a superlattice structure of AlN (10-10).