JPS62207795A - Molecular beam crystal growth method for iii-v compound semiconductor - Google Patents

Abstract

PURPOSE:To obtain a high-quality crystal growth layer of a III-V compd. semiconductor contg. Al with less incorporation of oxygen and carbon by forming the III-V compd. contg. Al while irradiating hydrogen plasma. CONSTITUTION:The molecular beam source 2 of Al having 99.99999% purity, the molecular beam source 3 of Ga having 99.9999% purity, the molecular beam source 4 of As having 99.99999% purity, and an H2 plasma generator 5 are firstly mounted in an ultrahigh-vacuum vessel 1. The plasma is formed by electron cyclotron resonance method, and irradiated on a substrate. The temp. of the substrate 7 consisting of GaAs is set at 600 deg.C, and a layer of the material shown by the formula is formed at 1mu/h growth velocity. Namely, the layer is firstly grown in 0.5mu thickness without irradiating hydrogen plasma, and then H2 is introduced by regulating a variable-leak valve 6 so that the H2 partial pressure in the ECR plasma generator is adjusted to 10<-4>mmHg, and the layer is further grown in 1mu thickness while irradiating hydrogen plasma.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for molecular beam crystal growth of ■-V compound semiconductors, particularly Aj7-V group compounds or Ae-V group compounds and other III-V group compounds. This invention relates to a method for molecular beam crystal growth of compound semiconductors consisting of mixed crystals.

[Conventional technology]

□Conventionally, Ae xGal-xAs, (0< x≦1
) 1 class ^J7-V group compound semiconductor or a semiconductor consisting of a mixed crystal of Af-V group compound and Ike's ■~■ group compound (hereinafter simply referred to as In-V group compound semiconductor containing Ae) is a molecular beam crystal. When grown using a growing method.

For example, metal Ga, all belongings! , solid arsenic was placed in separate crucibles, heated in vacuum to form molecular beams, and supplied to the substrate crystal surface to form a growth layer on top. Such methods are described, for example, in "Crystals: Growth, Properties, and Applications" edited by H.C. Freihart.
grorLh, Properties.

and applications)," published by Springer Verlag, page 93, in Mr. Plouffe's review.

In this way, high quality GaAs and Gaxlnl-x
A molecular beam crystal growth layer of As has been obtained, but it contains 17■
-V group compound semiconductors, such as ke xGal-xAs and ^1! In xln1-xAs ^! Because these atoms have strong bonding energy with oxygen and carbon, there is a high probability that these atoms will be incorporated into the crystal during growth. Such impurities form levels with acceptors and deep impurities in the crystal, resulting in poor crystal quality. Therefore, if these crystals are grown without intentionally doping with n+ impurities, they will have high resistance. Furthermore, when the amount of impurities is large, an n-type crystal cannot be obtained unless a large amount of n-type impurity is doped, making it difficult to control the carrier concentration. Furthermore, since non-radiative recombination processes due to these impurity levels increase, the optical properties of the crystal are also poor.

It has been reported that the quality of Ae xGal-xAs crystals is improved by introducing hydrogen. For example, Kondo et al.
AI! 0.2
It is stated that the photoluminescence intensity was improved several times by irradiating 10-'nm IIg of hydrogen during the growth of Gao4^S.

However, in the inventor's experiments, even with this method, Ae x
The quality of lnl-xAs has not improved much.

The reason why the crystal quality of Ae xGal-xAs is improved by using hydrogen is that hydrogen
This is because it bonds with oxygen or carbon on the -x^S surface and becomes molecules such as H2O or C114 and is desorbed. However, ^l! It is conceivable that the impurity concentration cannot be effectively reduced in materials such as In1-xAs, which cannot be oxidized by raising the substrate temperature, because the above-mentioned molecules are not generated or desorbed. Since the ease with which these reactions occur is thought to be determined thermodynamically, it would be better to increase the partial pressure of hydrogen, but if this were done, the partial pressure would become too high and molecular flow would no longer occur. Alternatively, problems such as the inability to use a reflection electron beam diffraction device may occur.

[Problem that the invention seeks to solve]

The conventional ■-■ molecular beam crystal growth method for compound semiconductors described above does not take measures to effectively prevent oxygen and carbon from being trapped in the crystal growth layer, so high-quality ^l-containing ■
-■ There was a drawback that a crystal growth layer of compound semiconductor could not be obtained.

An object of the present invention is to provide a method for molecular beam crystal growth of compound semiconductors that can obtain a high-quality crystal growth layer of IV group compound semiconductors that incorporates less oxygen and carbon and that contains 8L. There is a particular thing.

[Means for solving problems]

The method for molecular beam crystal growth of compound semiconductors of the present invention includes:
This method includes at least a step of forming a 1-2 compound semiconductor layer containing ^l while irradiating hydrogen plasma.

[Effect]

When hydrogen plasma is used, there are very few active species in the hydrogen plasma in an equilibrium state, so the hydrogen partial pressure that must be balanced against it becomes very large. In other words, from the viewpoint of chemical reactions, this is equivalent to the presence of a large partial pressure of hydrogen, which greatly accelerates the removal of carbon and oxygen. In fact, it has been confirmed that carbon and oxygen on the GaAs substrate are removed by this method (Mr. Kawai et al., Proceedings of the 45th Annual Conference of the Japan Society of Applied Physics, 19
1984, p. 617). This report has been reported as a technique for cleaning the surface of GaAs once exposed to the atmosphere, but the inventor of this application has further developed this technique into
It was confirmed that this method can be applied to the growth of 1-X^S and Ae xlnl-xAs.

〔Example〕

Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a schematic diagram of a molecular beam crystallization apparatus suitable for use in the method of molecular beam crystal growth of a -V compound semiconductor of the present invention. ``First, a first example will be described.

First, in ultra-high vacuum container 1, there is a substance with a purity of 99.99999%.
r molecular beam source 2, Ga molecular beam source 3 with purity 99.9999%, As molecular beam source 4 with purity 99.99999%, H
2. A plasma generator 5 was attached. Plasma was created by electron cyclotron resonance method (ECR method) and was irradiated onto the substrate. The temperature of the substrate 7 made of GaAs is set to 600°C, and a 3G;5o-tAS layer is formed at a growth rate of 1 μm/h. Then, by adjusting the variable leak valve 6 and flowing II2 so that the 11□ partial pressure inside the ECR plasma generator becomes 10-'mm l1g, a 1μIn thick film is grown while irradiating hydrogen plasma.
Made it grow.

When we investigated the distribution of carbon and oxygen concentrations in the film using a secondary ion mass spectrometer, we found that these concentrations were 11% higher in films formed while irradiating hydrogen plasma than in films that were not.
The ratio was reduced to about 5 to 17/8, and it was possible to reduce the amount of impurities mixed in. In addition, the photoluminescence intensity was five times brighter than in the case where hydrogen plasma was not applied.

Next, a second example will be described.

The same equipment as in the first example was used, but instead of the Ga molecular beam source, an In molecular beam source containing In with a purity of 99.9999% was installed. Set the substrate temperature to 550°C,
51nl), +; An AS layer is formed at a growth rate of 1 u, m/h, but first it is grown to a thickness of 0.5 μm without hydrogen plasma irradiation, and then hydrogen plasma is applied as in the first example. The film was irradiated to a thickness of 1.0 μm using this method. When we investigated the concentration distribution of carbon and oxygen using a secondary ion mass spectrometer, we found that these concentrations were reduced by 1/6 to 1/12 in films grown while applying hydrogen plasma.
It was possible to reduce the amount of impurities mixed in. In addition, when we performed Hall measurements, we found that hydrogen plasma was applied^47 g.
, 5In0.5AS layer exhibits n-type conduction even without doping with impurities, and the carrier concentration is 6 X 1 , O1
5C1ll-3. Do not apply hydrogen plasma ^(
! It was found that the a-5■no-5ks layer exhibited high resistance and that the deep levels could be reduced by hydrogen plasma.

In addition, 1. In the second example, the film was formed without irradiating hydrogen plasma for comparison purposes, and is not absolutely necessary. In practical terms,
Needless to say, this is unnecessary.

〔Effect of the invention〕

As explained above, the present invention provides AJ? by growing a crystal layer while irradiating hydrogen plasma. Including ■−
Since the concentration of carbon and acid in the V group compound semiconductor can be reduced, a high-quality grown layer free of deep-level impurities can be obtained.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of a molecular beam crystallization apparatus suitable for use in the molecular beam single crystal growth method of compound semiconductors of the present invention. 1... Ultra-high vacuum container, 2... Ke molecular beam source, 3G
Molecular beam source of a, 4... Molecular beam source of As, 5...11
2 plasma generator, 6... barrier pull leak valve,
7 boards.

Claims (1)

[Claims] A method for growing molecular beam crystals of a III-V compound semiconductor, the method comprising at least the step of forming a III-V compound semiconductor layer containing Al while irradiating hydrogen plasma.