JPS62138390A - Molecular beam epitaxy - Google Patents

Abstract

PURPOSE:To enable occurrence of rapid change of intensity of phosphorus molecular beam when a III-V compound semiconductor single crystal is prepd. by the molecular beam epitaxy by using diphosphin as feed for P and decomposing the diphosphin photolytically by the irradiation with ultraviolet rays. CONSTITUTION:A vacuum chamber 1 contg. an InP substrate 2 is evacuated to superhigh vacuum and molecular beam of the Group III starting material is generated by heating the starting material for the Group III element in a starting material cell 4 for the III group material. On one hand, AsH3 as a starting material for the Group V element is introduced from an introducing pipe 5a, which is decomposed thermally in a thermal decomposition furnace 7 to generate As molecular beam. Further, P2H4 is introduced through a gas introducing pipe 5b in the stage of the growth of InP layer, which is irradiated with ultraviolet rays having 100-260nm wavelength generated by a Hg lamp 8 through a light irradiating window 9, generating thus P molecular beam by causing photolysis. By this method, a growth layer having InP/InGaAs superstructure and satisfactory boundary surface is formed on the InP substrate 2.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a molecular beam epitaxial growth method, and particularly relates to a method for growing l-V group compound semiconductors using a group V element compound containing phosphorus (P) and a group II element. This article relates to the molecular beam epitaxial growth method for growing crystals.

: This conventional technique] The molecular beam epitaxial method is a method in which each constituent element of a crystal is placed in a separate crucible in an ultra-high vacuum and heated and evaporated to grow a single crystal thin film on a substrate. This molecular beam epitaxial method is currently expected to be the crystal growth method with the best control over thin films.

However, since conventional molecular beam epitaxial growth methods mainly use solid raw materials, the raw materials are depleted and the growth chamber must be exposed to the atmosphere in order to replenish the raw materials. This is a problem not only because it takes a long time to return the growth chamber to ultra-high vacuum, but also from the standpoint of the quality of the epitaxial film.

In addition, the conventional molecular beam epitaxial growth method, for example,
Although the growth of crystals containing only one type of group V element, such as As mixed crystal, is good, for example, TnG.

It has been difficult to grow crystals containing two or more types of Group V elements, such as ASP mixed crystals. The reason for this is that in order to obtain a mixed crystal with a desired composition ratio, two or more types of V.
It is necessary to precisely control the molecular beam intensity ratio of the groups.

However, when using Group Ⅰ solid raw material 3, the vapor pressure of the raw material is high, making it difficult to control the molecular beam intensity ratio.

Therefore, as a growth method to compensate for these drawbacks, a molecular beam epitaxial growth method using a gas source instead of the conventional solid source has been used.

For example, Ni R Karawa (^, RJ41awa)
) in the 1981 Applied Physics Letters (Applied Physics Iett, pr.
s), Volume 38, page 70], As series,
For P-based compounds, AsH3,P)! This is done using 3.

FIG. 2 shows a cross-sectional view of a typical introduction section for AsH3 and PH3. AsH3, P) 13 is introduced through the leak valve 6 at the introduction part of the ultra-high vacuum system, and the tantalum outer tube 1 is
As+, As2+AS4°P2 in a pyrolysis furnace (cassel) heated using tantalum filament 12 in 1
Growth is performed by forming a first-class molecular beam.

Also, M, B, Pan
1sb) and Nis-Sumski (S, Sumski) decomposed AsH3 and PH3 in a pyrolysis furnace as shown in Fig. 3 to grow IflG and ^5P-based mixed crystals. ．． Prototype of 1' DH laser was produced in 1984.
Journal of Applied Physics (Journal of Appiie + I Phys)
ics), Volume 55, page 3571. As shown in Fig. 3, this pyrolysis furnace has a hole for leakage at the tip of the gas introduction pipe 5 in the alumina resistance heating furnace 13, and the gas is supplied by changing the pressure of the gas (P) 13. The amount is controlled.

In this way, the molecular beam epitaxial growth method using a gas as the Group Ⅰ raw material can control the molecular beam intensity of the ~′ group compared to the conventional molecular beam epitaxial growth method using a solid material, and can grow two or more types of Group V elements. It is known that it is possible to grow mixed crystal systems containing

[Problem that the invention seeks to solve]

However, the conventional molecular beam epitaxial method using Group V gas raw materials has the drawback that it is difficult to rapidly switch the gas composition. In the conventional molecular beam epitaxial method using group III gas raw materials, the composition of group III elements is changed by changing the leak valve or gas pressure, but the molecular beam intensity in the ultra-high vacuum system does not change rapidly. Ta. This is especially true for P2. near the exit of the pyrolysis furnace. The phenomenon of P4 adhesion, adsorption, and re-evaporation occurs, and the pH rapidly increases.
This is thought to be due to the fact that even if the flow rate is cut off, molecular beams such as <P2 are generated for a while. When a shutter is used, this phenomenon is caused by adsorption in the form of P4 on the shutter and re-evaporation, and could not be completely prevented.

The present invention takes advantage of the feature of the molecular beam epitaxial growth method using a group V gas source, which is that it is possible to accurately control the molecular beam intensity of group The purpose of this invention is to provide a molecular beam epitaxial growth method that allows for changes in line intensity.

[Means for solving problems]

The molecular beam epitaxial growth method of the present invention uses a group V element compound containing phosphorus (P) and a group
In the molecular beam epitaxial growth method for growing group compound semiconductor crystals, diphosphine (P
2H4), which has been photodecomposed using an excitation light source with a wavelength of 1100 nm or more and 260 nm or less.

[Effect]

Diphosphine is a more unstable substance than phosphine and is known to be decomposed by irradiation with ultraviolet light at room temperature. According to Kawasaki, it is known that the absorption wavelength of the photolysis reaction of P2H4 is 260 nm or less, and the maximum absorption wavelength is 220 nm or less (Masahiro Yozaki: Applied Physics, 5
3, 1985.603). As a power source for optical excitation process, for example, as shown in Nikkei Microdevice, Spring 1985 issue, 1G1-78, currently 1000 m
The reality is that it is difficult to obtain materials with wavelengths below.

Therefore, by irradiating diphosphine with light of the above wavelength using P feedstock gas, 2
Molecular beams can be stably obtained. In addition, since the light irradiation is carried out in the space within the ultra-high vacuum system, P
2. No adsorption phenomenon of P4 occurs. For this reason, rapid changes in the P molecular beam intensity are possible.

5 Embodiments Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram of a molecular beam epitaxial growth apparatus for explaining one embodiment of the present invention. In the following, using FIG. 1, InP/T, G is formed on an InP substrate.

The case of creating an AS superlattice structure will be explained.

In FIG. 1, an InP substrate 2 was placed in a vacuum chamber 1 evacuated to an ultra-high vacuum of about 10 −9 Torr, and the substrate temperature was set at 300° C. using a heater 3 .

For the group (2) raw material, high purity 1° Ga is heated in an ordinary cell 4 to obtain a molecular beam. As for the V group element, A5H for As was introduced into an ultra-high vacuum system through an inlet pipe 5a through a leak valve 6af:, and an arsenic molecular beam was obtained in an ordinary pyrolysis furnace 7. P
For P2H4, connect it to the leak valve 6b from the inlet pipe 5b.
was introduced into an ultra-high vacuum system through a mercury lamp 8, and the Pa1 (4 raw material beam) was irradiated with ultraviolet rays through a light irradiation window 9 using a mercury lamp 8.

When growing the InP layer, G and molecular beams are exposed to shutter 1.
Shut off at 0, ^5) Close the leak valve for I3 raw material,
Furthermore, it was shut off at the shutter. When growing the 1nCIA three layer, the P2I+4 source was closed and the light irradiation was interrupted.The As1I3 pyrolysis furnace was
The temperature was set at 00°C.

In this way, rnG of 50A cycle, person 5. ．． /InP superlattice structure was grown in 20 layers. As a result, a grown layer with a good mirror surface was obtained.

Furthermore, the concentration of As and P atoms was measured in the depth direction using a secondary ion mass spectrometer (SIMS), and the results showed that the interface was very good. It was confirmed that it had changed.

〔Effect of the invention〕

■- Using a group V element compound containing P and a group ■ element
In performing molecular beam epitaxial growth of ~' group compound semiconductor crystals, P2H4 (diphosphine) is used as the P source gas, and the P2H4 (diphosphine) is photodecomposed in a space within an ultra-high vacuum system using an excitation light source with a wavelength of 1100 nm or more and 260 nm or less. Therefore, there is no need for a pyrolysis furnace when the molecular beam intensity of group Ⅰ elements changes rapidly. There is no spreading phenomenon, and a grown crystal with a good interface can be obtained.

[Brief Description of the Drawings] Fig. 1 is a block diagram of a molecular beam epitaxial growth apparatus for explaining an embodiment of the present invention, and Fig. 2 is a cross-sectional view of the AsH3°PH3 introduction part of a conventional molecular beam epitaxial growth apparatus. , FIG. 3 is a sectional view of a pyrolysis furnace used by Pa-nish. 1... Vacuum chamber, 2... InP substrate, 3...
・Heater, 4... Group ■ raw material cell, 5a, 5b...
Gas introduction pipe, 6a, 6b...leak valve, 7...
Ordinary pyrolysis furnace, 8...Mercury lamp, 9...Light irradiation window, lO...Shutter, 11...Tantalum outer tube, 12...Tantalum filament, 13...Alumina resistor heating furnace. Tacita/Refilament AsH3 PH. Figure 2 Figure 3

Claims (1)

[Claims] In the molecular beam epitaxial growth method of growing a III-V compound semiconductor crystal using a group V element compound containing phosphorus and a group III element, diphosphine is used as the phosphorus source gas and an excitation light source with a wavelength of 100 nm or more and 260 nm or less is used. A molecular beam epitaxial growth method characterized by photolysis.