JPH05136056A - Molecular beam epitaxial growth method - Google Patents

Abstract

PURPOSE:To provide a molecular beam epitaxial method for manufacturing a III-V compound semiconductor by which a high-purity epitaxial film having a good surface condition can be obtained. CONSTITUTION:This method includes a cleaning process wherein a group V molecular beam of cleaning molecular beam strength Pc is applied to a substrate set at a cleaning temperature Tc, and a growth process wherein after the cleaning process, a group V molecular beam of growth molecular beam strength Pg which is lower than the cleaning molecular beam strength Pc and a specified group III molecular beam are applied to the substrate set at a growth temperature Tg which is lower than the cleaning temperature Tc.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to molecular beam epitaxial (MBE) growth of III-V group compound semiconductors, and more particularly to a method for cleaning a compound semiconductor substrate before epitaxial growth.

[0002]

2. Description of the Related Art Molecular beam epitaxial growth of III-V group compound semiconductors has conventionally been performed in the following steps.
The evaporation source cells for group III and group V elements are heated to a predetermined temperature with the shutter closed, and the substrate is mounted on the substrate holder in the high-vacuum growth chamber. First, the shutter of the evaporation source cell for the group V element is opened, and the substrate is heated to a predetermined temperature to clean the substrate surface. After that, open the shutters of the evaporation source cells for the III and V elements,
An epitaxial film of III-V compound semiconductor is grown.

[0003]

There is a problem in that the characteristics of the grown epitaxial film are not sufficient because the cleaning of the substrate surface in the growth chamber is not sufficient. In particular, when a III-V compound semiconductor containing phosphorus such as InP is used as the substrate,
When the substrate temperature during cleaning is increased, the surface condition is deteriorated such as the surface of the substrate is deteriorated, and there is a problem that a flat epitaxial film cannot be obtained.

The present invention has been made to prevent the above-mentioned drawbacks, and an object of the present invention is to provide a molecular beam epitaxial growth method capable of obtaining an epitaxial film having an excellent surface condition and a high purity.

[0005]

SUMMARY OF THE INVENTION The present invention is directed to V during cleaning.
This is based on the idea that sufficient cleaning can be achieved by making the group molecular beam intensity and the substrate temperature higher than those during growth.

The present invention relates to a method of epitaxially growing a III-V compound semiconductor on a substrate made of a III-V compound semiconductor by molecular beam epitaxial growth, wherein a V-group molecule having a cleaning molecular beam intensity Pc of the cleaning temperature Tc is used. And a predetermined group III molecular beam having a growth molecular beam intensity Pg lower than the cleaning molecular beam intensity Pc on the substrate having a growth temperature Tg lower than the cleaning temperature Tc. The gist is to include a growth step of irradiation.

When a III-V group compound semiconductor containing phosphorus such as InP is used as the substrate, the substrate temperature Tc in the cleaning step is
Is preferably 550 ° C. or higher.

Further, it is desirable that the intensity of the group III molecular beam in the growing step is 1/15 to 1/25 times the intensity Pg of the growing molecular beam of the group V molecular beam.

[0009]

[Operation and effect] Since the temperature during cleaning can be raised, contaminants on the surface of the substrate can be sufficiently removed, and at the same time, the smoothness of the substrate can be maintained. Further, since the epitaxial film can be grown with an appropriate group V molecular beam intensity, the characteristics of the epitaxial film can be dramatically improved.

[0010]

The growth of an InGaAs epitaxial layer on an InP substrate will be described below as an embodiment of the present invention.

The InP substrate used as the substrate is an iron-doped 2-inch diameter (100) wafer obtained by the LEC method after organic cleaning and acid etching.

A molecular beam epitaxial growth (MBE) apparatus is a growth chamber capable of evacuating to a high vacuum, a preparation chamber for introducing a substrate, and In each equipped with a shutter.
It consists of three types of evaporation source cells, Ga and As. In and G
The evaporation source cell of a was heated to adjust the composition ratio of In0.53Ga0.47As. The evaporation source cell of As, which is a group V element, has a molecular beam intensity of 3.3E-3Pa (3.3 m).
The heater temperature of the evaporation source cell was adjusted by using a molecular beam monitor so as to be Pa).

The substrate was preheated to about 100 ° C. in the preparation chamber and then transferred to the growth chamber. Open the shutter of the evaporation source cell of As, and irradiate the substrate with As molecular beam to 580 the substrate.
Cleaning was performed by raising the temperature to 0 ° C. and holding for 5 minutes.

After that, the substrate temperature is lowered to 500 ° C. and A
The molecular dose of s was set to 2.0E-3Pa (2.0mPa), the shutter of the evaporation source cell of In and Ga was opened, and the InGaAs layer was grown.

The InGaAs layer formed in the above steps is
Carrier concentration n = 1.1E14 / cm ³ , mobility μ = 920
It was 0 cm ² / V · s (measurement at room temperature).

The irradiation dose of As molecular beam during cleaning is
3.0E-3 to 3.5E-3Pa is desirable. The substrate temperature during growth may be 520 ° C. or lower.

As a comparative example, when the As molecular dose during cleaning and during growth was the same 2.0E-3 Pa, the substrate temperature during cleaning was 540 ° C., and the other conditions were the same as those in the above-mentioned examples, Carrier concentration of InGaAs layer n = 5.1E1
4 / cm ³ , mobility μ = 5500 cm ² / V · s (measured at room temperature), which was worse than in the examples.

FIG. 1 shows changes in the impurity concentration at the interface between the epitaxial layer and the substrate depending on the substrate temperature during cleaning. It can be seen that at a temperature of 550 ° C. or higher, the concentration of oxygen as an impurity is remarkably reduced. If the substrate temperature is 600 ° C. or higher, the surface smoothness is impaired, so the substrate temperature during cleaning is preferably 550 ° C. to 600 ° C. The impurities were analyzed by SIMS (secondary ion mass spectrometry) method.

Molecular beam intensity ratio of group V element and group III element (V
FIG. 2 shows changes in carrier concentration and mobility of the epitaxial film depending on the (/ III ratio). It is understood that this V / III ratio has an appropriate range, and in the case of 15 to 25, an epitaxial film having excellent carrier concentration and mobility can be obtained.
The group III molecular beam intensity is the sum of the molecular beam intensities of In and Ga.

The present invention is not limited to the above embodiment, and GaAs or GaP may be used instead of the InP substrate.
III-V group compound semiconductors such as can be used as a substrate, and III-V group compound semiconductors such as AlGaAs and InGaAsP can be grown instead of InGaAs as an epitaxial layer.

[Brief description of drawings]

FIG. 1 is a diagram showing the relationship between substrate temperature and impurity concentration during cleaning according to an example of the present invention.

FIG. 2 is a diagram showing a relationship between a molecular beam intensity ratio of a group III element and a group V element and a characteristic of an epitaxial film according to an example of the present invention.

Claims (1)

[Claims] 1. On a substrate made of a III-V compound semiconductor
In the method of epitaxially growing a group III-V compound semiconductor by molecular beam epitaxy, a V having a cleaning molecular beam strength Pc of V
A cleaning step of irradiating a group molecular beam, and then a growth molecular beam intensity Pg lower than the cleaning molecular beam intensity Pc on the substrate having a growth temperature Tg lower than the cleaning temperature Tc.
And a growth step of irradiating a predetermined group III molecular beam.