JPS6287490A - Growth of semiconductor crystal - Google Patents

Abstract

PURPOSE:To form a GaAs layer of high quality having low dislocation, etc., by providing a specific buffer layer having composition gradually changing from the side of a substrate on an Si substrate in forming a GaAs layer or AlxGa1-xAs layer on the Si substrate. CONSTITUTION:A buffer layer 2 having a composition consisting of SiyGe1-y is formed on an Si substrate 1 by using a molecular beam epitaxial or vapor- phase growth method, etc., and the composition is formed so as to change from y=1 on the side of the substrate 1 gradually to y=0. A GaAs layer or AlxGa1-xAs layer 3 is then formed on the buffer layer 2. As a result, the lattice strain is absorbed in the buffer layer 2 and a strain is not taken over to the GaAs crystal 3 formed on the buffer layer 2. The aimed GaAs layer 3 having low dislocation can be formed.

Description

[Detailed Description of the Invention] [Industrial Field of Application] This invention provides a method for forming G a A s/AjxG on a st substrate.
The present invention relates to a crystal growth method for forming an a1-XA8 layer.

[Conventional technology]

Recently, technology for integrating conventional (7) ICs and optical semiconductor elements such as GaAs/AlGaAs systems has begun to be developed. For this reason, research is being carried out to form GaAs crystals on Si substrates using vapor phase epitaxy, molecular beam epitaxial methods, etc.;
) and GaAs (approximately 5.65), a low-dislocation GaA layer cannot be obtained. Therefore, as shown in FIG. 2, an attempt was made to deposit a Ge layer 5 having a lattice constant similar to that of GaAs on an 8i substrate 4 using an electron beam scattering method, thereby forming a Ga As layer 6 on the Ge layer. ing. (For example, Solid State Devices Conference,
Abstraf), pp. 115-119, Kobe, 198
4 years) [Problems to be solved by the invention] At this time, a GaAs layer with lower dislocations can be obtained compared to forming GaAsf directly on a Si substrate, but due to the lattice mismatch at the interface between Ge and Si, FET, The dislocation density is too thick for crystals for devices such as semiconductor lasers, and good device characteristics cannot be obtained.

The purpose of the present invention is to solve the above-mentioned problems and to fabricate low-dislocation, high-quality Ga A 8 /AlxGa 1 on an 81 substrate.
- To provide a crystal growth method for forming an XAS layer.

[Means for solving problems]

In the present invention, 5iyGex-y'f: is formed on the 8i substrate, and the buffer layer is gradually changed to y==Q with y=l on the 8i substrate side. It forms a layer. In this crystal growth method, it is necessary that the compositional change of the buffer layer 8iyGel-y be gentle enough to prevent dislocations from occurring within the buffer layer. 5iyGez-y
A molecular beam epitaxial method may be used as a method for forming (a vapor phase growth method using a gas such as 8iH4, GeH4, etc.) may be used.

[Effect]

As mentioned earlier, the lattice constant of 8i is 5.45 people.

The lattice constant of Ge and GaAs is approximately 5.65. S
Since t and Ge are Group 4 elements and have the same crystalline structure of the zinc oxide structure, 5iyGel-y can change the lattice constant between the lattice constants of Si and Ge while maintaining the zinc oxide structure. Therefore, if the yO value t-1 of 8iyGel-y on the Si substrate side is changed gradually and a nine buffer layer is formed, the lattice strain will be absorbed within the buffer layer, and the lattice strain will be absorbed on the buffer layer. Strain cannot be inherited by GaAs crystals formed in 1), 8 for the above reasons.
By interposing the i yGe ty buffer layer, a low dislocation GaAs layer or kl xGa 1 is formed on the 81 substrate
-xAs NI can be formed.

〔Example〕

Hereinafter, the crystal growth method of the present invention will be explained using the drawings.

In the following explanation, an example using the molecular beam epitaxial method will be described. FIG. 1 is a cross-sectional view of a semiconductor crystal manufactured by the method of the present invention. Sl substrate 1 55
While heated to 0° C., an 8i beam is applied to start epitaxial growth of St, the Ge beam is gradually increased, and the Si beam is decreased. In this way, an 8iyGet-y layer whose composition is gradually changed from Si is formed, and finally Get-grown. Thereafter, a GaAs layer 3 is grown by applying an As beam and a Ga beam. To grow an AlxGa t-xAs layer in place of the GaAs layer, As
, Ga, and ht beams.

〔Effect of the invention〕

GaAs, AxGa produced by practicing the present invention
Since the lattice strain of the 1-xAs layer is absorbed by the 8iyGel-y buffer layer, the 1-xAs layer has low dislocations and high quality. The present invention uses 8iIC and GaA1 IC, 8iIC and GaAs
/Aj It can be applied to the integration of GaAs-based optical semiconductor devices.

[Brief explanation of drawings]

Figure 1 shows a method for forming GmAs on a St substrate used as a 8iyGe1-y t-buffer layer according to the present invention, and Figure 2 shows a method for forming GmAs on a St substrate using Ge as a buffer layer according to the prior art.
G on the t board! The IA8 formation method is shown. 1, 4 =...-8i board, 2--8i yG
e ty layer. 3.6...G a As layer, 5...
Ge layer.

Claims (1)

[Claims] GaAs layer or Al_xGa_1_-_x on Si substrate
When forming the As layer, Si_y is used as a buffer layer.
Ge_i_-_y is provided, and from y=1 to y from the Si substrate side
1. A method for growing a semiconductor crystal, characterized by gradually changing the crystal value to 0.