JPS62138389A - Molecular beam epitaxy - Google Patents

Abstract

PURPOSE:To cause growth of crystal of high quality on a substrate with high reproducibility by causing epitaxial growth of a semiconductor single crystal on an InP substrate with cleaned surface stabilized by the formation of a Group III element by irradiating the substrate with molecular beam. CONSTITUTION:An InP substrate 4 is set in a substrate holder 3 which is half- fixed at a growth position of a crystal in a molecular beam epitaxial growth chamber 2 provided with an evacuation line 1 to superhigh vacuum, and the substrate 4 is irradiated with >=2X10<-5>Torr As molecular beam generated by a power source 12 for heating the cell after measuring the internsity of the As molecular beam radiated from a cell 11 attached to a boat 10 by fixing a mano-meter 9 held perpendicularly to the holder 3 for a while by revolving a manipulator 8. Then, the manipulator 8 is put back in the growth position, and the substrate 4 is heated with a heater 13 while irradiating with the As molecular beam, forming thus the stabilized surface of the Group III element on the surface of the substrate 4. After confirming the stabilized surface with reflection type fast electron beam pattern formed on a fluorescent screen 15, the semiconductor single crystal is grown on the substrate 4 by the molecular beam epitaxy.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for growing high quality crystals on an InP substrate by molecular beam epitaxial growth.

[Conventional technology]

Conventionally, in order to grow a semiconductor single crystal on an InP substrate by molecular beam epitaxial growth, a thin oxide film is formed on the substrate surface by chemical etching, and the oxide film is removed by heating the substrate in a vacuum just before the growth, and at the same time, A substrate cleaning process was used to remove contaminants from the surface (Journal φ Op-Ken Applied Fixtures (J, pp1.
Phys-) Vol. 52, 1981, p. 1015).

Further, at this time, an arsenic molecular beam was irradiated onto the substrate surface in order to prevent the substrate surface from being decomposed due to evaporation of group V elements with high vapor pressure contained in the substrate (same as above). The cleaning of the substrate shows that the observation of the reflection-type high-speed electron diffraction pattern shows that the superstructure and the turns are twice as large in the (TTo) azimuth.
It was also confirmed by the appearance of a group V stabilizing surface exhibiting a four-fold superstructure/mother turn in the [110] azimuth (Journal Otsu Applied Fixtures (J, Appl.
.

Phys, Volume 52, 1981, Page 4033).

[Problem that the invention seeks to solve]

By the way, 9-turn reflection high-speed electron diffraction is not sensitive to the presence of a slight oxide film or group II microdroplets on the surface of the substrate crystal, but on the other hand, the surface Moho-)- and the crystallinity of the interface are It is sensitive to oxide films and group II microdroplets. Especially in
In the case of a P substrate, the temperature at which the surface oxide film is removed is almost the same as the temperature at which In and P decompose and evaporate on the surface, and the temperature at which the surface oxide is removed depends on cleaning methods and chemical etching. Since slight differences in processing conditions can make a big difference, even if the substrate is deoxidized at the same temperature, a clean surface and a high-quality growth layer can be obtained, and in some cases, an oxide film remains on the outermost surface layer. However, InP decomposes and generates minute droplets of In, which may result in surface defects or interface defects in the grown layer. It was difficult to identify by the appearance of a stabilizing surface. For this reason, Gao and 47In are lattice-matched to InP using the conventional method. , 53A8
When grown on an InP substrate crystal, its mobility is at most 9,000cn1"/V-B@C at room temperature, 77
10,000 cm2/V' sec to 40,000 cm2/V-sec, which is small compared to other growth methods (Electro Letters).
n Lett) Volume 18, 1982, page 758),
Although high-mobility crystals can sometimes be obtained, the reproducibility is not good. Moreover, in order to obtain a crystal with high mobility, it is necessary to grow a film with a thickness of 3 μm or more due to poor interface.

Since a film thickness of 3 μm consumes time and raw materials for molecular beam epitaxial growth, which is performed at a slow growth rate of about 1 μm per hour, a fundamental solution was needed.

The purpose of the present invention is to eliminate such conventional drawbacks and to
An object of the present invention is to provide a molecular beam epitaxial growth method that allows high-quality crystals to be grown on a substrate with good reproducibility.

[Means for solving problems]

According to the present invention, in a molecular beam epitaxial growth method in which InP is used as a substrate, the substrate is heated to clean the surface, and then a molecular beam is irradiated onto the substrate, a group (III) stabilizing surface is applied to the substrate surface during the cleaning. This is a molecular beam epitaxial growth method characterized by forming.

[For production]

The present inventor performed reflective high-speed electron diffraction (high-speed electron diffraction) on the group V stabilizing surface during cleaning of the InP substrate. It was discovered by secondary ion mass spectrometry that, even if confirmed by a test, trace amounts of oxygen and other impurities were actually deposited on the surface of the substrate. This remaining trace amount of oxygen is absorbed by I2O3 and P2O3, which exist as oxidation layers on the InP surface, and I
I thought it was n203. Furthermore, it was thought that merely checking the V-group stabilizing surface would miss the presence of oxygen atoms surrounding the In atoms. So this trace amount of I n20s
In order to remove this, we believe it is important to observe the normal superstructure near the In atoms, that is, to observe the In stabilization plane, and form the In stabilization plane without damaging the substrate due to heat. Invented a cleaning method.

FIG. 1 is a block diagram of the equipment necessary to accomplish this method. In the figure, a substrate holder 3 is semi-fixed at a crystal growth position in a molecular beam epitaxial growth chamber 2 having an ultra-high vacuum evacuation system of 1 tl, so that four InP substrates set in the substrate holder 3 can be monitored with a camera 7. It has become.

By rotating the if manifold and hierator 8, the vacuum gauge 9 held at right angles to the substrate holder 3 is temporarily fixed at the crystal growth position, and the arsenic cell 1 attached to the port 10 is
The intensity of the arsenic molecular beam irradiated from the arsenic cell heating power source 12 is measured, and the arsenic molecular beam intensity (2X1
0””Torr or more). Then, the manipulator 8 is returned to the growth position, and the source of irradiation with the arsenic molecular beam is the heater 13 for heating the substrate and the heater power source 1 for heating the substrate.
4 was used to perform the deoxidation film treatment while controlling the surface temperature of the substrate, and after confirming the appearance of the In stabilization surface using four turns of reflection-type high-speed electron diffraction that appeared on the fluorescent screen 15, the growth was stopped. Start.

〔Example〕

Examples of the present invention are shown below.

(Example 1) Using the substrate cleaning method according to the present invention, G
High quality crystals were obtained by growing 1InAs (high purity). In the examples, the substrates were subjected to a conventional chemical etching process before being placed into the growth apparatus.

For the experiment, 99.99999% Ga source, 99.9
A 999% In source and a 99.999999% As source were used. During cleaning of the substrate surface and during growth, the substrate surface was continuously irradiated with an arsenic molecular beam of 2×10” Torr.The substrate surface temperature was raised from room temperature to 570°C by heating with a heater on the back side of the substrate, and the In stabilized surface was heated. After confirming the appearance of , and holding this temperature for a while, the growth temperature is set to 5.
The temperature was lowered to 00°C and growth started. On the other hand, from 5 minutes before the start of growth, all the group ■ molecular beams were blocked and the main shutter located approximately one distance away from the opening of the group ■ molecular beam was closed.
■The shutter of the group molecular beam source was opened to stabilize the molecular beam intensity. Then, the main shutter was opened and growth began. When GaInAa lattice-matched to the substrate was grown to a thickness of 5000 cm at a growth rate of 0.5 μm/h, the mobility was 11000 cm”/vs at room temperature, 77.
The result was a very large value of 6000m''/V'8.

(Example 2) Using the substrate cleaning method according to the present invention, a Fe-Dog insulating InP (100) substrate crystal was lattice-matched to the substrate.
High quality crystals were obtained by growing tInA1 (Sl doped). The substrate was subjected to a conventional chemical etching process before being placed in the growth apparatus. A of 99.99991 for the experiment
T source, 99.9999% In source, 99.99
A 999% As source and a high purity 81 source were used.

3X10 on the substrate surface during substrate cleaning and during growth.
Irradiation continued with Torr's arsenic molecules. The substrate surface temperature was raised from room temperature to 580° C. by heating the back side of the substrate to confirm the appearance of an In-stabilized surface, and after this temperature was maintained for a while, the growth temperature was lowered to 500° C. to start growth. On the other hand, from 5 minutes before the start of growth, all group ■ molecular beams are blocked, and ■
While the main shutter located approximately 5 crn away from the opening of the group molecular beam source was closed, the shutter of the group ■ group molecular beam source was opened to stabilize the molecular beam intensity. Then, the main shutter and Sl source shutter were opened and growth started. AtInA lattice matched to the substrate
a (Sl-doped) at a growth rate of 0.7 μm/h to 1 μm
grown. Photoluminescence measurements of the grown layer revealed strong band edge emission. Further, the carrier concentration at that time was 8.42X10"cIn-' in the dark state, 8.43X10"crIt-3 in the light irradiation state, and 8.42
．． A value of 42X10 cm was obtained.

The fact that the carrier concentration did not change before and after irradiating the source revealed that there was no photoconductivity at all.

〔Effect of the invention〕

As described above, according to the present invention, in molecular beam epitaxial growth using InP as a substrate, crystals having high mobility and excellent optical properties can be grown with good reproducibility in a grown thin film of 1 μm or less. .

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of a molecular beam epitaxial growth apparatus used for crystal growth using the present substrate cleaning method. 4... InP substrate, 7... Infrared temperature camera, 11
...Arsenic cell, 15...Fluorescent screen, 16...
・Reflection-type high-speed electron beam diffraction electron gun. 4=-11P substrate crystal 71--red light tS rotary camera 11- arsenic upper 15--Se luminous screen

Claims (1)

[Claims] (1) In a molecular beam epitaxial growth method in which InP is used as a substrate, the substrate is heated to clean the surface, and then a molecular beam is irradiated onto the substrate, a group III stabilizing surface is attached to the substrate surface during the cleaning. A molecular beam epitaxial growth method characterized by forming.