JPH05175146A - Epitaxial growth method - Google Patents

Abstract

PURPOSE:To provide a method for growing a flat and high-quality Gap layer on a silicon substrate. CONSTITUTION:Aluminum phosphorus layer 2 is low-temperature grown on the surface of a silicon substrate 1 in such manner that the whole surface is covered with a growing nucleus at a temperature where the growing nucleus is formed flatly, aluminum phosphorus layer 3 is consecutively grown at a high temperature, and gallium phosphorus layer 4 is grown on this upper layer 3.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an epitaxial growth method, and more particularly to an epitaxial growth method of a gallium phosphide (GaP) layer on the surface of a single crystal silicon substrate.

[0002]

2. Description of the Related Art III-V compound semiconductors are attracting attention as materials used in high-speed electronic devices, optical devices, etc., but they are mechanically fragile and it is difficult and expensive to obtain a large-area substrate. have.

Therefore, in order to solve such a problem,
A method of growing an epitaxial growth layer of a desired III-V compound on a surface of a single crystal substrate such as a silicon substrate which is inexpensive and has excellent mechanical and thermal characteristics is widely used.

For example, in the case of a solar cell, a large area can be obtained by epitaxially growing a gallium phosphide (GaP) layer having a wide band gap on the surface of a silicon substrate which is inexpensive, has excellent mechanical and thermal characteristics, and has a narrow band gap. Attempts are being made. In this structure, silicon not only supports the gallium phosphide layer as a substrate, but also forms a pn junction to operate as a solar cell, which is a laminated structure of solar cells made of semiconductor materials having different band gaps. Therefore, a highly efficient solar cell having a plurality of absorption wavelength bands can be obtained.

When forming such a solar cell, it is necessary to epitaxially grow a GaP layer on a silicon substrate. Although it is said that silicon and GaP have good lattice matching and are capable of epitaxial growth, there is a problem that the crystallinity and surface state are not sufficient when actually manufacturing a device.

Therefore, a two-step growth method in which a GaP layer having a thickness of several tens of nm is epitaxially grown at a relatively low temperature and then the desired GaP layer is grown by raising the substrate temperature is also considered.

However, since the crystallinity and the surface flatness are not sufficient, there is a problem that excellent characteristics cannot be obtained.

[0008]

As described above, the conventional method has a problem that a GaP layer having excellent crystallinity and a good surface condition cannot be grown on the surface of the silicon substrate.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an epitaxial growth method for forming a high-quality GaP layer excellent in crystallinity and surface flatness on a silicon substrate.

[0010]

Therefore, in the present invention, the aluminum phosphorus layer is formed on the surface of the silicon substrate at a low temperature so that the growth nuclei are formed flat on the surface of the silicon substrate and the film thickness is such that the growth nuclei are entirely covered. The growth is carried out, and then the aluminum phosphorus layer is grown at a high temperature, and the GaP layer is grown on top of this.

[0011]

According to the above method, the aluminum phosphorus layer is grown at a low temperature on the surface of the silicon substrate at a temperature at which the growth nucleus of the aluminum phosphorus crystal covers the entire surface by about 5 to 50 nm and is flat. The aluminum phosphide layer is grown at a high temperature of 0.1 to 1 μm so that the strain does not propagate, and the gallium phosphide layer is grown on this. Obtainable.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A method for forming a gallium phosphorus epitaxial growth layer according to an embodiment of the present invention will be described in detail below with reference to the drawings.

In this method, as shown in FIG. 1, an aluminum phosphorus layer is formed as a buffer layer on the surface of the silicon substrate 1, and a gallium phosphorus layer is epitaxially grown on the aluminum phosphorus layer. That is, the aluminum phosphorus layer 2 is grown at a low temperature at a substrate temperature of about 450 ° C. so that the growth nuclei of the crystal cover the entire surface by 5 to 50 nm, and then the substrate temperature is raised to about 750 ° C. so that strain does not propagate. 0.1-1
This is characterized in that the aluminum phosphorus layer 3 is grown to a thickness of μm, and the gallium phosphorus (GaP) layer 4 is grown thereon.

Here, the growth temperature is such a low temperature (450) that the growth nuclei of the aluminum phosphorus layer 2 are formed flat.
C.), and subsequently, at a higher temperature (750.degree. C.), an aluminum phosphorus layer 3 is grown to a thickness of 0.1 to 1 .mu.m at which strain does not propagate, and gallium phosphorus (GaP ) Layer 4 is grown and p is deposited in this gallium phosphide layer.
It is characterized in that an n-junction is formed.

Next, this manufacturing method will be described. Figure 2
FIG. 4 is a diagram showing a growth temperature profile.

Turned off twice in the <011> direction (100)
After cleaning the silicon substrate 1 and performing thermal cleaning at 960 ° C. for about 15 minutes, phosphine (PH ₃ ) and trimethylaluminum (TMA) at a substrate temperature of 450 ° C.
l: Using Al (CH ₃ ) ₃ ) as a raw material, a first aluminum phosphorus layer 2 having a thickness of 10 to 20 nm is grown.

Then, the substrate temperature is raised to 750 ° C. and the second aluminum phosphorus layer 3 having a thickness of about 0.1 μm is grown under the same conditions.

After this, trimethyl aluminum (TMA
l: Al (CH ₃ ) ₃ ) is replaced with trimethylgallium (TMGa:
Instead of Ga (CH ₃ ) ₃ ), a 1 μm thick GaP layer 4 with a thickness of 1 μm
Grow.

The thus-obtained epitaxial growth substrate has a flat surface and extremely excellent crystallinity.

As a result of measuring the rocking curve of the GaP layer on the surface of the gallium phosphide layer thus formed and calculating the full width at half maximum, it is remarkably improved by the inclusion of the AlP layer.

The results are shown in Table 1.

[0022]

[Table 1] According to these comparisons, a GaP layer was grown directly on a silicon substrate in two steps from low temperature growth to high temperature growth (2
It can be seen that the characteristics are remarkably improved as compared with the step growth method). Here, FIG. 3 shows a copy of a surface photograph of the surface of the GaP layer formed by these methods as observed by a Nomarski microscope. From these comparisons as well, in the method of the present invention, since the aluminum phosphorus layer formed by two-step growth is interposed as the buffer layer on the substrate surface, GaP having good surface flatness can be obtained.

Pattern formation is performed using this epitaxial growth substrate to form a device such as a solar cell. For example, when forming a solar cell, in practice, first, a diffusion layer is formed on the surface of a silicon substrate to form a pn junction to form a first solar cell. Then, a p-type layer and an n-type gallium phosphorus layer are sequentially formed on the upper layer through an aluminum phosphorus layer as a buffer layer to form a pn junction to form a second solar cell. In this way, a stacked body of solar cells composed of materials having different band gaps of silicon and gallium phosphide is formed, so that a solar cell having a wide absorption wavelength region and high efficiency can be obtained.

Although the compound semiconductor layers used in solar cells and the like have been described in the above embodiments, it goes without saying that the present invention can also be applied to the formation of other devices such as HBTs.

[0025]

As described above, according to the present invention, the first aluminum phosphorus layer is formed flat at low temperature, and the second aluminum phosphorus layer having good crystallinity is formed on the first aluminum phosphorus layer. Since the flat gallium phosphide layer having excellent crystallinity is formed on the top surface, the gallium phosphide layer having flatness and excellent crystallinity can be obtained.

[Brief description of drawings]

FIG. 1 is a diagram showing an epitaxial growth substrate according to an embodiment of the present invention.

FIG. 2 is a temperature profile diagram in manufacturing the epitaxial growth substrate.

FIG. 3 is a surface structure comparison diagram of an epitaxial growth substrate of an example of the present invention and an epitaxial growth substrate of a conventional example.

[Explanation of symbols]

 1 Silicon Substrate 2 First Aluminum Phosphorus Layer 3 Second Aluminum Phosphorus Layer 4 Gallium Phosphorus Layer

Claims (1)

[Claims] 1. A first aluminum phosphorus (AlP) layer is grown on a surface of a single crystal silicon substrate while maintaining the temperature of the single crystal silicon substrate at a low temperature, and then the temperature of the substrate is raised to increase the temperature. An aluminum phosphorus growth step of growing a second aluminum phosphorus layer on the first aluminum phosphorus layer, and a gallium phosphorus growth step of growing a gallium phosphorus (GaP) layer on the second aluminum phosphorus layer. Characteristic epitaxial growth method.