JPH0412092A - Compound semiconductor and method for growing the same - Google Patents

Abstract

PURPOSE:To obtain a compound semiconductor having low dislocation density and improved crystallinity by growing a compound semiconductor on a porous silicon substrate free from surface-modification layer. CONSTITUTION:A silicon substrate is anodized in a solution such as hydrofluoric acid at a current density of 0.1-200mA/cm<2> to form a porous layer having a thickness of 5-300mum and pore diameter of 20-300Angstrom near the surface of the silicon substrate. The surface modification layer is removed by etching, mechanical grinding, etc., to expose the porous layer to the surface. A compound semiconductor is grown on the silicon substrate.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to compound semiconductors such as ■-v group, ■-■ group, IV-IV group, etc. grown on a porous silicon substrate and a method for manufacturing the same. .

(Prior Art) Attempts have been made to grow compound semiconductors on silicon substrates because they are easy to grow in area, are light and heavy, have high thermal conductivity, and are inexpensive.

However, since there is a difference in crystal lattice constant of about 4% between silicon and GaAs, for example, when performing heterogeneous growth of compound semiconductors with different lattice constants on a substrate, normal growth methods are not suitable. However, attempts have been made to use, for example, an off-angle silicon substrate in which the plane index of the substrate single crystal is slightly shifted, or a silicon substrate with a Ge haphazard layer.

Additionally, r 5solid 5tate Technol
ogy (198g-1) Japanese version p, 41-49'', heat-treated at a high temperature of about 850 to 900°C/Recon board is coated with a layer of 200 Å or less at a low temperature of about 400 to 450'C. A two-step temperature growth method has also been attempted in which a thin GaAs layer is grown and then normal high-temperature growth is performed, but it has not always been possible to grow a good crystal. Further, methods using a silicon substrate or the like having a GaAs strained superlattice have been attempted, but the residual dislocations in the grown layer have only been reduced to about 10'/cm'.

Furthermore, “Applied Physics Vol. 57 No. 11 (1988) No. 1
710-1720, a porous layer with micropores is formed on the surface of a silicon substrate by an anodization method, and GaAs However, the crystallinity of the epitaxial layer was not as good as that of the bulk crystal.

(Problems to be Solved by the Invention) The present invention aims to provide a compound semiconductor with excellent crystallinity and a method for growing the same by improving the above porous silicon substrate.

(Means for Solving the Problems) The present invention provides a compound semiconductor grown on a porous silicon substrate, characterized in that a porous silicon substrate without a surface metamorphism layer is used, and a porous In a manufacturing method for growing a compound semiconductor on a silicon substrate, a silicon substrate made of a silicon single crystal made porous by an anodization method is processed in advance by etching, etching, mechanical polishing, etc. to remove a metamorphosed layer on the surface of the substrate. This method of manufacturing a compound semiconductor is characterized by growing a compound semiconductor after removing the compound semiconductor.

(Function) Conventionally, in research into the formation mechanism of porous silicon layers by anodization, a metamorphic layer (surface layer) was formed on the surface of the porous layer.
Although it is known that the metamorphic layer (porous fila+) exists, no study has been done on the influence of this metamorphic layer on the growth of different materials.

The present inventors focused on this metamorphic layer and investigated its relationship with the growth of compound semiconductors, and found that this metamorphic layer has polycrystalline or amorphous properties and is weak against heat. It is not suitable for normal high-temperature growth of thin film crystals in the metamorphic layer, and in addition, unlike the porous layer below, there are only about 10 pores on the surface of the metamorphic layer, so there is no mechanism to reduce misfit dislocations. I found it.

Therefore, in the present invention, a compound semiconductor with excellent crystallinity was successfully obtained by growing a compound semiconductor using a silicon substrate from which a metamorphic layer on the surface of a porous layer had been removed. That is, in a solution such as hydrofluoric acid, the current density is 0.1 to 200.
By anodizing in the mA range of 7 cm', a porous layer with a thickness of 5 to 300 μm having a pore diameter of 20 to 300 μm is generated near the surface of the silicon substrate, and then the surface is modified by etching, mechanical polishing, etc. After the layer is removed to expose the pore size at the surface, a compound semiconductor is grown on the silicon substrate.

In this way, when a compound semiconductor is grown on a porous layer from which the metamorphic layer has been removed, even if the lattice constants are different, the strain caused by lattice mismatch is alleviated by growing with the pores bridged. It is considered that the introduction of misfit dislocations can be prevented. Also,
The porous silicon layer has a Young's modulus of about 1/10 that of normal silicon, making it highly flexible, so when cooling a compound semiconductor growth layer with significantly different coefficients of thermal expansion from the growth temperature to room temperature. However, since the strain of the two substances is absorbed, dislocations and residual stress in the compound semiconductor growth layer can be significantly reduced.

(Example) According to the procedure shown in Figure 1, a porous layer is formed on a silicon substrate as shown in (a), a metamorphosed layer on the surface of the porous layer is removed as shown in (b), and the metamorphic layer is removed as shown in (C). A GaAs single crystal thin film was grown on it and its crystallinity was examined.

First, to form a porous layer on a silicon substrate, the surface of the silicon substrate is brought into contact with a hydrofluoric acid solution, and the current density is set to 20 mA.
/cm" and anodized to obtain a porous layer with a thickness of 30 μm. Figure 1 (a) shows this state, and a metamorphosed layer exists on the surface of the porous layer. Next, the metamorphic layer was removed by etching the surface of the porous layer to a thickness of 0.57 μm.Thereafter, a GaAs single crystal thin film with a thickness of 2.5 μm was grown by OMVPE.

The dislocation density of the obtained GaAs single crystal thin film is lXl0'
It was possible to significantly reduce it to ``ell-''.

(Comparative Example 1) The surface of a conventional silicon substrate has a thickness of 2.5 mm as in the example.
When a μm-thick GaAs single crystal thin film was grown (FIG. 2) and the dislocation density was examined, it showed a large value of 4×10'cm-'.

(Comparative Example 2) Using the porous silicon substrate (FIG. 2(a)) before removing the metamorphic layer in the example, a GaAs single crystal thin film with a thickness of 2.517 m was deposited on the substrate as in the example. 2 (b)), and when we investigated the dislocation density, we found that IXIO7cm-
' showed a large value.

(Effects of the Invention) By adopting the above configuration, the present invention allows compound semiconductors with different lattice constants and coefficients of thermal expansion to grow on a silicon substrate, and even when cooled from the growth temperature to room temperature, the compound semiconductor grows. It has become possible to suppress the residual stress in the layer and provide a compound semiconductor with low dislocation density and excellent crystallinity.

[Brief explanation of drawings]

Figures 1 (a) to (c) are explanatory diagrams showing the procedure for growing a GaAs layer on a porous silicon substrate from which a metamorphic layer has been removed; Figure 2 is a diagram showing a GaAs layer grown directly on a silicon substrate; FIGS. 3(a) and 3(b) are explanatory diagrams showing the procedure for growing a GaAs layer on a porous silicon substrate on which a metamorphosed layer is formed. Figure 2 Figure 3

Claims (2)

[Claims] (1) A compound semiconductor grown on a porous silicon substrate, characterized in that a porous silicon substrate without a surface metamorphism layer is used. (2) In a manufacturing method in which a compound semiconductor is grown on a porous silicon substrate, a silicon substrate made of silicon single crystal made porous by an anodization method is etched or mechanically polished in advance, so that the surface of the substrate is 1. A method for manufacturing a compound semiconductor, comprising growing a compound semiconductor after removing a metamorphic layer.