JPH0817739A - Crystal growth method - Google Patents

Abstract

(57) [Summary] [Object] An object of the present invention is to make it possible to form a laminated structure of a III-V compound semiconductor thin film having a steep hetero interface without diffusion of different V elements. [Constitution] As is formed on the surface of the already formed GaAs layer.
In the state where the source gas is not supplied, first Ga and In
The source gas is supplied (step S4), and the crystal surface is moved to II.
After being made to be in a state of being coated with a Group I element, immediately after that, a P source gas is supplied to grow an InGaP thin film (step S
5).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a crystal growth method for producing a laminated structure of two or more III-V group compound semiconductor thin films having different V group elements by crystal growth.

[0002]

2. Description of the Related Art A laminated structure of two or more different III-V group compound semiconductor thin films is called a so-called heterostructure and is used for an optical element such as a semiconductor laser, an electronic element such as a field effect transistor, or a heterojunction bipolar transistor. Has been applied. In particular, InGaP / GaAs
Compared with the AlGaAs / GaAs system, the system has been actively researched recently because it is easy to obtain a high quality crystal because it does not contain Al and the recombination rate of the heterojunction surface is small. .

[0003]

However, InGaP /
The GaAs system has its advantages, but it has two of As and P.
It is a system in which a group V element of a kind is completely switched at the heterojunction interface, and it is difficult to manufacture it by crystal growth. This is the metalorganic vapor phase epitaxy (M
The OVPE method will be described.

For example, trimethylgallium (TMG) as a Ga raw material and arsine (AsH ₃ ) as an As raw material.
Is used to form a GaAs film, and Ga is a raw material of triethylgallium (TEG), an In raw material is trimethylindium (TMI), and a P raw material is phosphine (P).
Consider the case of forming an InGaP film using H ₃ ).
FIG. 3 is a timing chart showing the supply timing of the source gas in this vapor phase growth.

This shows a simple process which has been used conventionally. After supplying trimethylgallium and arsine at the same time to grow a GaAs film, the supply of these gases is stopped, and at the same time, triethyl is added. It is a simple process such as starting the supply of gallium, trimethylindium, and phosphine. However, in this method, the group III raw material of the previous layer remains in the stage of growing the next layer, which becomes a factor to inhibit the growth of the next layer.

FIG. 4 is a timing chart showing the supply timing of the source gas in the vapor phase growth, which is carried out in order to eliminate this state. That is, when the growth of the GaAs film and the growth of the InGaP film are switched, the supply of the group III gas is first stopped and the group III gas is not supplied, and a group V gas such as arsine and phosphine is supplied. It is designed to switch between. Usually, in this vapor phase growth, in order to prevent the surface of the growing crystal from being roughened, the supply of the group V gas is not stopped but is continuously supplied.

However, although this method solves the above-mentioned problems, a steep heterojunction interface cannot be obtained. Similarly, a steep hetero interface cannot be obtained by the method described with reference to FIG. 3, and it is considered that As and P interdiffuse at the hetero interface. At such a hetero interface, there is a problem that a desired band discontinuity cannot be obtained and an expected device (electronic element) characteristic cannot be obtained.

The present invention has been made to solve the above problems, and has a laminated structure of a III-V group compound semiconductor thin film having a steep hetero interface without diffusion of different V group elements. The purpose is to be able to form.

[0009]

In the crystal growth method of the present invention, first, a first gas as a raw material of a first group III element and a second gas as a raw material of a first group V element are used. And supplying at least a first group III element and a first group III element on the semiconductor substrate.
A first III-V group compound semiconductor layer composed of the group V element of is formed on the semiconductor substrate by vapor phase epitaxy.
Then, after a lapse of a predetermined time after the supply of the first gas is stopped, the supply of the second gas is stopped and the supply of the third gas, which is a raw material of the second group III element, is started on the semiconductor substrate. . Then, after the predetermined time, the supply of the fourth gas, which is the source of the second group V element, onto the semiconductor substrate is started,
Forming a second III-V group compound semiconductor layer composed of at least a second group III element and a second group V element on the first group III-V compound semiconductor layer by vapor phase epitaxy Is characterized by.

Further, according to the vapor phase growth method of the present invention, when the growth of the above-mentioned second III-V group compound semiconductor layer is completed,
After a predetermined time from stopping the supply of the third gas, the supply of the fourth gas is stopped and the supply of the first gas onto the semiconductor substrate is started, and after the predetermined time, the semiconductor substrate of the second gas is stopped. Starting the supply to the above, and forming a third III-V group compound semiconductor layer having the same structure as the first III-V group compound semiconductor layer on the second III-V group compound semiconductor layer. Characterize.

[0011]

In the initial stage of the crystal growth stage of the second III-V compound semiconductor layer, the surface of the first III-V compound semiconductor layer is covered with the group III element, and
Even if the above gas is supplied, mutual diffusion of the first group V element of the first III-V group compound semiconductor and the second group V element by the fourth gas does not occur. In addition, even in the initial stage of the crystal growth stage of the third III-V compound semiconductor layer, the surface of the second III-V compound semiconductor layer is covered with the group III element, and the second gas is supplied. Even the second I
Mutual diffusion between the second group V element of the II-V group compound semiconductor layer and the first group V element by the second gas does not occur.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Before explaining one embodiment of the present invention,
The concept of the invention will be described. Here, InGaP /
A description will be given using GaAs as an example. The crystal growth is usually performed in an excessive supply state of the group V source gas in order to secure a good surface morphology. Therefore, the crystal surface immediately after growing GaAs is in a state of being covered with As atoms. When the P source gas is supplied to this, mutual diffusion of As and P occurs, and a steep hetero interface cannot be obtained.

Therefore, as shown in FIG. 1, Ga and In raw material gases are first supplied to the surface of the GaAs layer coated with As to make the crystal surface coated with the group III element, and immediately thereafter. InGaP by supplying P source gas
Grow thin film. The same applies to GaAs growth after InGaP growth. The details will be described later. If you do this,
A steep hetero interface can be obtained without mutual diffusion of As and P.

FIG. 2 shows a film thickness 2.
InG with 8 nm and 5.7 nm GaAs wells
It is sectional drawing (a) which shows aP / GaAs quantum well structure, and the spectrum characteristic figure (b) which shows PL (Photo Luminescence) characteristic in 4.2K. In the same figure (a), 21 is a GaAs substrate, 22 is In having a thickness of 100 nm.
GaP layer, 23 is a GaAs layer having a thickness of 5.7 nm, 24 is an InGaP layer having a thickness of 50 nm, 25 is a GaAs layer having a thickness of 2.8 nm, and 26 is an InGaP layer having a thickness of 100 nm. Further, in FIG. 2B, H1 is a PL spectrum of the InGaP / GaAs structure according to the present invention, and H2 is a PL spectrum of the InGaP / GaAs structure according to the conventional method shown in FIG.

As shown in FIG. 2B, in the PL spectrum H1, light emission from the two GaAs layers 23 and 25, which are quantum wells, is clearly observed. However, in the case of the similar method formed by the conventional method, as shown in the PL spectrum H2, the emission from the quantum well is not observed, and only the peak with a wide half width is observed in the long wavelength region. . That is, in the conventional method, even if an attempt is made to form a similar layer structure, no quantum well is formed in the manufactured one. The reason for this is that
It is considered that s and P are mutually diffused to form InGaAsP or the like.

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows one embodiment of the present invention, InGa
6 is a timing chart showing gas supply timing when a P / GaAs stacked structure is formed by a vapor phase growth method. Hereinafter, a method of manufacturing the InGaP / GaAs laminated structure according to the present invention will be described. First, the GaAs substrate is heated to 650 ° C. in an atmosphere of arsine to remove the oxide film on its crystal surface (step S1).

Then, the GaAs substrate is cooled to, for example, 500 ° C., trimethylgallium is supplied to the growth chamber in which the GaAs substrate is placed, and a GaAs thin film is grown to a desired film thickness (step S2). The supply of gallium is stopped (step S3). After the fixed time, the supply of arsine is stopped, and at the same time, the supply of triethylgallium and trimethylindium is started (step S4).

After a certain period of time, the supply of phosphine is started to grow the InGaP thin film to a desired thickness (step S5), and then the supply of triethylgallium and trimethylindium is immediately stopped (step S6). Then, after a fixed time, the supply of phosphine is stopped and the supply of trimethylgallium is started at the same time (step S7), and the supply of arsine is started after the fixed time and the next GaA
s A thin film is grown to a desired thickness (step S2). After that, the above steps S2 to S7 may be repeated as necessary. Finally, the temperature of the substrate is lowered while supplying the source gas of the V-group element of the uppermost layer to complete the crystal growth.

[0019]

As described above, according to the present invention, in the crystal growth stage of the next layer, the source gas of the group III element is supplied and then the source gas of the different group V element is supplied. . Therefore, there is an effect that a laminated structure of a III-V group compound semiconductor thin film having a steep hetero interface can be formed without mutual diffusion of different V group atoms.

[Brief description of drawings]

FIG. 1 is a timing chart showing a gas supply timing when an InGaP / GaAs laminated structure is formed by a vapor phase growth method.

FIG. 2 GaAs with a film thickness of 2.8 nm and 5.7 nm
Schematic diagram showing an InGaP / GaAs quantum well structure having wells and its PL (Photo Luminesc) at 4.2K.
ence) is a spectrum characteristic diagram showing characteristics.

FIG. 3 is a timing chart showing a supply timing of a source gas in conventional vapor phase growth.

FIG. 4 is a timing chart showing another supply timing of the source gas in the conventional vapor phase growth.

[Explanation of symbols]

21 ... GaAs substrate, 22, 24, 26 ... InGaP
Layers, 23, 25 ... GaAs layers, H1, H2 ... PL spectra.

Claims (3)

[Claims] 1. A first gas, which is a raw material of a first group III element, and a second gas, which is a raw material of a first group V element, are supplied onto a semiconductor substrate to provide at least the first III group gas. A first III-V composed of a group element and a first group V element
A group compound semiconductor layer is formed on the semiconductor substrate by a vapor phase epitaxy method, and then, after a predetermined time after the supply of the first gas is stopped, the supply of the second gas and the second I
The supply of the third gas, which is the raw material of the group II element, to the semiconductor substrate is started, and after a predetermined time, the supply of the fourth gas, which is the raw material of the second group V element, is supplied to the semiconductor substrate. Starting, at least the second group III element and the second V
A crystal growth method comprising forming a second III-V group compound semiconductor layer composed of a group element on the first III-V group compound semiconductor layer by a vapor phase growth method. 2. The crystal growth method according to claim 1, wherein after the supply of the third gas is stopped for a predetermined time, the supply of the fourth gas is stopped and the semiconductor substrate of the first gas is supplied. The supply of the second gas to the semiconductor substrate is started after a predetermined time has elapsed, and the third III- having the same configuration as the first III-V compound semiconductor layer is formed. The group V compound semiconductor layer is formed on the second II
A method for crystal growth, which is characterized in that it is formed on a group IV compound semiconductor layer. 3. A first Ga source gas serving as a Ga source is first supplied onto a semiconductor GaAs substrate, and then an As source gas serving as an As source is supplied to form a first GaAs thin film on the GaAs substrate. After the crystal growth, and after a predetermined time after the supply of the first Ga source gas is stopped, the supply of the As source gas is stopped and the second Ga source gas serving as the Ga source and I serving as the In source are supplied.
The supply of the n source gas to the semiconductor GaAs substrate is started, and after a predetermined time, the supply of the P source gas serving as the P source to the semiconductor GaAs substrate is started to change the InGaP thin film to the first GaAs thin film. After the crystal growth, the supply of the P source gas is stopped and the semiconductor Ga of the first Ga source gas is stopped a predetermined time after the supply of the second Ga source gas and the In source gas is stopped.
The supply onto the As substrate is started, and after a predetermined time, the above A
A second source gas is supplied onto the InGaP thin film by supplying a source gas.
A crystal growth method, which comprises crystal-growing an aAs thin film.