US 4,767,494 A · Preparation process of compound semiconductor

Abstract

A compound semiconductor thin film is formed by growing a plurality of molecular layers one over another. According to the present invention, while a carrier gas and a small quantity of hydride containing an element in Group V or VI are normally flowed, an organometallic compound which is diluted with hydrogen and which contains an element in Group III or II and a hydride which is diluted with hydrogen and which contains an element in Group V or VI are alternately introduced over a substrate so that an atomic layer of an element in Group III or II and an atomic layer of an element in Group V or VI are alternately grown over the substrate. According to this method, grown layers having a high degree of purity can be obtained. A portion such as a Ga-Ga two-layer structure formed in the growth of a surface of an element in Group III or II can easily be eliminated by the introduction of a hydrogen halide so that the surface defects and deep levels are significantly decreased and perfect crystals can be obtained. According to the present invention, a high-concentration doping of a III-V compound semiconductor becomes possible. The method of the present invention is advantageous in the fabrication of high-speed FETs and multi-quantum-well lasers using compound semiconductors.

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Claims26

Dependent claims

A process for preparing compound semiconductor thin films in which an organometallic compound cotaining an element of Group III or II and a hydride containing an element of Group V or VI are transported over a heated substrate and are subjected to thermal decomposition, whereby a III-V or 11-VI compound semiconductor is grown over said heated substrate, the process comprising:

repeating a cycle consisting of the following steps, whereby a III-V or II-VI compound semiconductor is grown over said heated substrate by forming alternating layers of an element of Group III or II and an element of Group V or VI, respectively:
(a) introducing over said heated substrate a carrier gas comprising a hydride containing an element of Group V or VI and present in a first concentration, said carrier gas further comprising at least one organometallic compound containing an element of Group III or II and present in a concentration, to thermally decompose the organometallic compound and form a layer of at least one element of Group III or II, wherein said first concentration of said hydride is a molar fraction ranging from a value which corresponds to the equilibrium molar fraction of said element of Group V or VI on said III-V or II-VI compound semiconductor at the temperature of said heated substrate up to a value at which said element of Group V or VI is not substantially incorporated into said layer of at least one element of Group III or II;
(b) interrupting the introduction of said organometallic compound;
(c) introducing over said heated substrate a carrier gas comprising a hydride containing an element of Group V or VI and present in a second concentration, which second concentration is higher in hydride than said first concentration, to thermally decompose the hydride and form a layer of an element of Group V or VI on top of said layer of an element of Group III or II;
and
(d) interrupting the introduction of said hydride at said second concentration.

3 more elements

A process for preparing compound semiconductor thin films in which an organometallic compound containing an element of Group III or II and a hydride containing an element of Group V or VI are introduced over a heated substrate and are subjected to thermal decomposition, whereby a III-V or II-VI compound semiconductor is grown over said heated substrate, the process comprising:

repeating a cycle consisting of the following steps, whereby a III-V or II-VI compound semiconductor is grown over said heated substrate by forming alternating layers of an element of Group III or II and an element of Group V or VI, respectively:
(a) introducing over said heated substrate a first carrier gas comprising a hydride containing an element of Group V or VI and present in a first concentration, said first carrier gas further comprising at least one organometalIic compound containing an element of Group III or II and present in a concentration, to thermally decompose the organometallic compound and form a layer of at least one element of Group III or II, wherein said first concentration of said hydride is a molar fraction ranging from a value which corresponds to the equilibrium molar fraction of said element of Group V or VI on said III-V or II-VI compound semiconductor at the temperature of said heated substrate up to a value at which said element of Group V or VI is not substantially incorporated into said layer of at least one element of Group III or II;
(b) interrupting the introduction of said organometallic compound;
and
(c) introducing over said heated substrate a second carrier gas comprising a hydride containing an element of Group V or VI and present in a second concentration, which second concentration is higher in hydride than said first concentration, to thermally decompose the hydride and form a layer of an element of Group V or VI on top of said layer of at least one element of Group III or II;
and
(d) interrupting the introduction of said hydride at said second concentration;
and
(e) introducing over said heated substrate a third carrier gas comprising a hydrogen halide and present in halide which is diluted by a third carrier gas to a concentration of said hydrogen halide.

6 more elements

A process for preparing compound semiconductor thin films, comprising:

repeating a cycle consisting of the following steps, whereby a III-V compound semiconductor is grown over said heated substrate by forming alternating layers of an element of Group III and an element of Group V, respectively:
(a) introducing over said heated substrate a carrier gas comprising hydrogen and a hydride containing an element of Group V and present in a first concentration, said carrier gas further comprising at least one organometallic compound containing an element of Group III and present in a concentration, to thermally decompose the organometallic compound and form a layer of at least one element of Group III, wherein said first concentration of said hydride is a molar fraction ranging from a value which corresponds to the equilibrium molar fraction of said element of Group V on said III-V compound semiconductor at the temperature of said heated substrate up to a value at which said element of Group V is not substantially incorporated into said layer of at least one element of Group III;
(b) interrupting the introduction of said organometallic compound;
(c) introducing on said heated substrate a carrier gas comprising hydrogen and a hydride containing an element of Group V and present in a second concentration, which second concentration is higher in hydride than said first concentration, to thermally decompose the hydride and form a layer of an element of Group V on top of said layer of at least one element of Group III;
(d) interrupting the introduction of said hydride at said second concentration;
(e) introducing over said heated substrate a hydrogen halide which is diluted by said hydrogen carrier gas;
(f) interrupting the introduction of said hydrogen halide;
and
(g) introducing over said heated substrate said carrier gas comprising hydrogen together with a compound containing an element in Group IV, VI or II, thereby doping said III-V compound semiconductor.

6 more elements

Dependencies are inferred from the claim text.

Description18,837 words

Summary3,768 words

#1. Field of the Invention

#The present invention relates to a process for preparing compound semiconductor films and especially III-V or II-VI compound semiconductor films.

#2. Description of the Prior Art

Brief description of the drawings47 figures

#FIG. 1 is a view used to explain a conventional Metal-Organic Chemical Vapor Deposition (MOCVD) method;

#FIG. 2 shows the distribution of the thickness of a compound semiconductor formed by the MOCVD method;

#FIG. 3 is a time chart illustrating the timing for the introduction of source elements in the conventional molecular layer epitaxial (MLE) method;

Detailed description14,219 words

#Referring first to FIG. 5, the present invention will be described in connection with GaAs which is a typical III-V compound semiconductor Arsine which is diluted to a first concentration by hydrogen carrier gas is made to flow at a very small flow rate over the surface of a GaAs substrate (FIG. 5A) throughout the duration of growth. The amount of arsine is diluted to such an extent that even when trimethyl gallium is made to flow over the GaAs substrate, they fail to react with each other and consequently no GaAs is formed. When arsine is diluted by hydrogen carrier gas to a second concentration which is higher in arsine than the first concentration and is made to flow together with the hydrogen carrier gas, arsine is adsorbed by Ga atoms of the GaAs substrate over the surface of the substrate and then is subjected to thermal decomposition so that As atoms and Ga atoms are combined and a single As atomic layer is formed over the surface of the substrate (FIG. 5B). Adsorption and thermal decomposition continue until the surface of the substrate is completely covered with a single As atomic layer. After the formation of the As atomic layer, since the power of adsorption of As atoms for arsine is weak, the succeeding flow of arsine is not adsorbed and is discharged out of the system. Next, the flow of arsine at the second concentration is stopped and excess arsine is purged (FIG. 5C) and trimethyl gallium diluted with hydrogen is made to flow (FIG. 5D). Trimethyl gallium is strongly adsorbed by the single As atomic layer over the surface of the substrate and is subjected to thermal decomposition so that Ga atoms and As atoms are combined and consequently a single Ga atomic layer is formed over the single As atomic layer. After the formation of the single Ga atomic layer, the succeeding trimethyl gallium is discharged out of the system because the power of trimethyl gallium to combine with Ga atoms is weak. After the formation of the single Ga atomic layer, the flow of trimethyl gallium is stopped and excess trimethyl gallium is purged (FIG. 5A). Thereafter, arsine which is diluted with hydrogen to produce a relatively high concentration of arsine and trimethyl gallium diluted by hydrogen are made to flow repeatedly, a single GaAs molecular layer being formed uniformly over the whole surface of the GaAs substrate during each cycle. According to the present invention, arsine diluted to the first concentration is always made to flow as described above, so that As is prevented from desorption from GaAs grown. In addition, the hydrogen gas is also made to normally flow so that methyl radicals resulting from the decomposition of trimethyl gallium are reduced by hydrogen to became methane which is not incorporated to a compound and consequently no carbon acceptor is formed. So far, the alternate flows of arsine and trimethyl gallium have been described, but even when the flows of arsine and trimethyl gallium are reversed, the same result as described above is obtained except that trimethyl gallium is strongly adsorbed by As atoms over the surface of the GaAs substrate and then is subjected to thermal decomposition, thus forming a single Ga atomic layer.

#FIG. 6 is a schematic view of an apparatus used to carry out the present invention. Reference numeral 1 designates a substrate; 2, a reaction chamber; 3, a substrate holder; 4, a heating device such as a high frequency induction coil; 5, a pipe line; and V.sub.1 -V.sub.12, valves. The valves V.sub.1 and V.sub.2 are so adjusted that a small quantity of hydride of an element in group V which is diluted by a carrier gas and the carrier gas are always made to flow continuously through the reaction chamber 2. The valves V.sub.3 -V.sub.12 are used to introduce source gases for forming a compound semiconductor, hydrogen halide to be described in detail hereinafter and an impurity gas used for doping into the reaction vessel 2. Such gases in FIG. 6 are described as an example. The valves V.sub.3 -V.sub.12 are controlled by a control unit 6 so that a predetermined gas is introduced in a predetermined quantity and for a predetermined time interval into the reaction vessel 2. Reference numeral 7 designates a pipe line for discharging the gases. The reaction vessel 2 shown in FIG. 6 is a vertical type, but it is of course possible to use a horizontal reacticn vessel. With the reaction apparatus of the type described, special care has been directed to permit the flow of the carrier gas in large quantities at a high flow rate and to suppress turbulent flows.

#A thin GaAs film was grown over the surface of a GaAs substrate. Arsine (AsH.sub.3) was used as a hydride of an element in group V, while trimethyl gallium (CH.sub.3).sub.3 Ga was used as an organometallic compound containing an element in group III.

Facts

Application

06/909,287Filed 19 Sep 1986

Priority

JP 61-1562604 Jul 1986

Granted

30 Aug 1988

Term ended

19 Sep 2006

Estimated · how

Pre-1995 term; greater of 17 years from grant or 20 years from filing when eligible. Maintenance-fee lapses, terminal disclaimers and statutory extensions have not been checked. The continuity chain may be incomplete; this is not an enforceability determination.

Classification14 codes

C30B 25/02
Single-crystal growth by chemical reaction of reactive gases, e.g. chemical vapour-deposition growth: epitaxial-layer growth
C30B 29/40
Inorganic compounds or compositions: aIIIBV compounds wherein A is B, Al, Ga, In or Tl and B is N, P, As, Sb or Bi
C30B 29/48
Sulfur-, selenium- or tellurium-containing compounds: aIIBVI compounds wherein A is Zn, Cd or Hg, and B is S, Se or Te
C30B 29/68
Characterised by shape: crystals with laminate structure, e.g. "superlattices"

Preparation process of compound semiconductor

Life of this patent

Preparation process of compound semiconductor

Life of this patent

Life of this patent

Abstract

Drawings

Drawings

Claims26

Description18,837 words

Drawings

Classification14 codes

Life of this patent

Description18,837 words