JPS6260219A - Vapor growth for compound semiconductor crystal - Google Patents

Abstract

PURPOSE:To assure a growing crystal of quality improvement by a method wherein hydrogen compounds of group V elements are led into a reaction chamber through pipings inside of which is partly formed of alkyl compound mainly composed of elements with electrode potential not exceeding the lowest reference electrode potential out of group III elements. CONSTITUTION:AsH2 is carried through a piping 11a to a pressure regulator 108 by a high pressure cylinder 107 and then pressure-regulated by the pressure regulator 108 to be led into a reaction chamber 109 through another piping 11b, With the reaction chamber 109, the temperature of a single crystal substrate 110 arranged on a susceptor 111 is controlled by high-frquency coils 112 provided on the peripheral part of reaction chamber 109. Besides, the inside of pipings 11a, 11b is partially composed of Al because the reference electrode potential of Ga is at low level in Ga and Al of group III elements comprising (CH3)Ga 101 and (CH3)3Al 102. Through these procedures, a compound semiconductor crystal can be grown with excellent reproducibility to improve the luminous intensity of crystalline layer remarkably assuring the growing crystal of high quality.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to a method for vapor phase growth of compound semiconductor crystals,
In particular, the present invention relates to a method for vapor phase growth of a group 1-V compound semiconductor crystal using an organometallic compound of a group 1 element of the periodic table and a hydrogen compound of a group V element as raw materials.

[Technical background of the invention and its problems]

One method for epitaxially growing ■-V group compound semiconductor crystals is the vapor phase growth method, so-called thermal decomposition, which uses a ■-■ group alkyl compound and a hydrogen compound of a V group element as raw materials for the group ■ and V group elements, respectively. A vapor phase growth method is known.

This pyrolytic vapor phase growth method has the advantage that it is relatively easy to control the layer thickness of the vapor phase grown layer and the carrier concentration of the grown layer by doping with impurities. The method has become popular as a method for growing not only binary ■-■ group compound semiconductor crystals such as GaAg and InP, but also ternary or quaternary mixed crystals. Development of microwave elements and optical devices is actively underway.

However, GaAQA containing A2 as a constituent element among ■-v group compound semiconductor crystals using a conventional growth apparatus.
It is known that when pyrolytic vapor phase growth such as s is performed, the quality of the obtained crystal is significantly influenced by the purity of the hydrogen compound of the group V element used as the raw material for the group V element. For example, trimethylaluminum (hereinafter referred to as (CH3), Al2) and arsine (hereinafter referred to as AsH3) gas are used as the starting materials for group (I) and group V elements, respectively. In the pyrolytic vapor phase growth of GaAQAs, since the standard electrode potential of Al, which is a constituent element of (CH3A4), is relatively low, oxygen and moisture contained in AsH3 gas cause (C1(3)aAQ, (CH3) Aa produced by the decomposition of 3Aβ is easily oxidized, which has been an obstacle to obtaining a GeAQAs crystal layer having a desired mixed crystal ratio with good reproducibility.

In addition, in order to remove the effects of oxygen and moisture, for example, As
A method is known in which an adsorbent is disposed in a pipe made of stainless steel that introduces H3 gas from a supply source into a reaction vessel to adsorb and remove oxygen and moisture in AsH3 gas. However, such an adsorption reaction is close to a reversible equilibrium reaction, and the adsorbed molecules are desorbed in the same way as the adsorption action, so although oxygen and moisture can be reduced to a certain extent, it is difficult to remove them to a level that poses no practical problem. Not yet reached. Moreover, in order to consistently demonstrate the adsorption capacity of the adsorbent, it is necessary to heat the adsorbent and desorb the adsorbed oxygen etc. until the breakthrough time of the adsorbent is reached. By repeating this, the adsorbent itself deteriorates, that is, the adsorption efficiency of oxygen and moisture decreases, and oxidation reactions of (CH3) and All occur, which hinders the reproducible growth of GaA12As with the desired mixed crystal ratio. was.

[Purpose of the invention]

This invention eliminates the above-mentioned problems, and by steadily and reliably removing impurity components such as oxygen and moisture contained in hydrogen compounds of group Ⅰ elements, relatively standard electrode potentials such as AQ can be improved. To provide a vapor phase growth method capable of growing with good reproducibility a ■-■ group compound semiconductor crystal whose constituent element is a group ■ element that is easily oxidized because of its low-level position, and also significantly improving the quality of the grown crystal. .

[Summary of the invention]

The method for vapor phase growth of compound semiconductor crystals according to the present invention includes:
When an alkyl compound of a group I element and a hydrogen compound of a group V element are introduced into a reaction vessel and an m-v group compound semiconductor crystal is grown in a vapor phase, at least a part of the inner surface of the j- group forms an alkyl compound. A hydrogen compound of a group V element is introduced into the reaction vessel (109) through a conduit (lla, 1 lb) whose main component is an element having an electrode potential lower than the lowest standard electrode potential among the group elements. It is.

[Embodiments of the invention]

Hereinafter, vapor phase growth of GaAQAs according to an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 schematically shows a Ga1As vapor phase growth apparatus constructed based on the present invention. In the figure, 101 represents trimethyl Ga ((CH3)aGa), which is a Ga source, and 102
respectively represent trimethyl Al1((CH3)3A) which is an AQ source.

(CH,)3Ga 101 and (CH3)3A111
02 are housed in stainless steel bubbler containers 103 and 104, respectively, and the bubbler containers 103 and 104 are controlled to have a desired temperature by constant temperature baths 105 and 106. 1
07 is a concentration of 10 diluted with hydrogen (H2) that serves as an As source
% of arsine (AsH3) gas. AsH3 gas is supplied to the pressure regulator 1 by the high pressure container 107.
08, the pressure is adjusted by the pressure regulator 108, and the sample is introduced into the reaction vessel 109 via the pipe 11b. Inside this reaction vessel 109, gallium arsenide (Ga
As) A single crystal substrate 110 is placed on a susceptor 111, and the temperature of the substrate 110 can be adjusted by a high frequency coil 112 provided around the reaction vessel 109. In addition, (CHa)3Ga 101 and (C
H3) As shown in Table 1, the standard electrode potential of Ga is −0,
560V (Handbook of Chemistry
y and Physics, 50th Edition
n.

The Chen+1cal Rubsr Co,,1
969), whereas that of AQ is -1,6
6V (Chemical Data Book.

2nd Editlon 1966), at least a part of the inner surface of the pipes 11a and llb is made of Aa. Therefore, all As
It may be a pipe, an Aff pipe whose outside is coated with, for example, a stainless steel pipe (clad type), or a pipe in which the above-mentioned pipe whose inner surface is Al is joined to a part of the pipe.

Using a vapor phase growth apparatus with piping as described above, the temperature of aGa was maintained at a temperature of 0.degree. C. in a constant temperature bath 105.
The flow rate of H2 gas bubbled was approximately 10 ce/min, and the temperature was maintained at 20°C by a constant temperature bath 106 (C1 (3), A
The flow rate of H2 gas bubbled in Q was set to about 7 buttons/min, and the flow rate of As1 was set to about 320 cc/min, and the temperature of the substrate 110 was set to 700°C.
The crystals were grown in a vapor phase. In addition, the flow rate of each of these gases is
The mixed crystal ratio of Ga and AQ in GaAQAs is 0.8 each.
It was set with the intention of achieving a growth rate of 5.0.15. Further, as the substrate] 10, an undoped high-resistance GaAs crystal with a plane orientation of (100) was used.

The AQ mixed crystal ratio obtained under the conditions described above is shown in FIG. 2 for each growth cycle. That is, the present invention is plotted with black circles in the same figure, and the piping 11a and 1.1b are Ga1A grown in the vapor phase using conventional stainless steel pipes.
The AQ mixed crystal ratio for each growth cycle of s is plotted with white circles. Second
As shown in the figure, when the piping system is made of stainless steel, as has been widely used in the past, the average value of the AQ mixed crystal ratio is about 0.13, which is smaller than the desired AQ mixed crystal ratio.
Moreover, the fluctuation range of the i-mixture ratio for each growth cycle is ±1 from the average value.
It reaches 0%.

Furthermore, in addition to stainless steel, when the piping that introduces AsH and gas into the reaction vessel 109 during the growth of GaAQAs described above is constructed of members whose main components are nickel, lead, zinc, etc., the resulting Ga19As crystal can be The Aff mixed crystal ratio is always smaller than the desired Afi mixed crystal ratio, and the fluctuation range of the AQ mixed crystal ratio for each growth cycle is large, so that a constant AQ
GaAQAs crystals having a mixed crystal ratio could not be obtained with good reproducibility.

Considering the above results from a chemical perspective, the main components of the piping member that did not lead to stably obtaining the desired AI2 mixed crystal ratio, namely chromium, nickel, lead and zinc, are also listed in Table 1. As shown, both (CH3)3A
It has a higher standard electrode potential than l that constitutes Q. This means that even if AsH3 gas is brought into contact with a piping member made up of an element with a potential higher than the standard electrode potential of AQ, as has been widely done in the past, the oxygen contained in the AsH3 gas will be absorbed by the piping member. This shows that the oxidation reaction of (coa)3Aρ, which can be constantly consumed by the oxidation reaction of the main elements constituting GaAQ, but rather easily oxidized (coa)3Aρ, proceeds preferentially.
This reduces the number of (CH3)3Aρ molecules that contribute to the growth of As, and is one of the reasons why it is difficult to obtain a desired mixed crystal ratio.

On the other hand, when growing GaAffAs, if at least a part of the inner surfaces of the pipes 11a and llb shown in FIG. 1 are made of AQ based on the present invention, as shown in FIG.
In addition to obtaining the desired value of the i-mixture ratio of the As crystal layer, which is about 0.15, which is the average value of the 10 times of growth,
It has been made possible to keep fluctuations for each growth cycle within ±3.5% of the average value, and this fluctuation range is significantly smaller than in the case of the conventional example described above.

Furthermore, according to the present invention, it has been found that the luminous efficiency of the GaA15 light emitting diode is significantly superior to that of the conventional one. Such an effect was also observed when the introduction piping for hydrogen compounds of group Ⅰ elements, that is, AsH3 gas, into the reaction vessel was constructed with a member containing magnesium (Mg) as the main component, and the results of ultra-trace impurity analysis showed that It has been revealed from the above that this improvement in luminous efficiency is due to a decrease in the concentration of oxygen impurities in the GaAQAs growth layer. Based on this result, we conclude that the internal material of the pipe, which is sufficient to provide high-quality GaAQAs crystals, is mainly composed of Mg or An, and both of these elements constitute (CH,)BAQ. It has a standard electrode potential equal to or lower than Al1.

However, when a member mainly composed of Mg or i is brought into contact with AsH gas, the standard electrode potential is extremely low as shown in Table 1, so it is easily oxidized by moisture, oxygen, etc. contained in AsH3. Can be oxidized.

(Left below) This potential in Table 1 is Hand book of Che+++
1stry and Physics, 50th, E
dition, The Chemical Rube
rCo, 1969.

Other potentials can be found in Chemical Data Book,
2nd.

Quoted from Edition 1966.

As described above, AsH, moisture, etc. in the gas can be removed through this oxidation reaction much more efficiently than adsorption and removal of oxygen by an adsorbent, and as a result, (CH3), AQ itself, and (C
H3), i generated by thermal decomposition of i becomes As in the reaction system.
h. It has a remarkable effect on preventing oxidation by oxygen and moisture in the gas.

In the above embodiments, the present invention was explained in detail by taking the vapor phase growth of Ga1lAs as an example. However, the present invention is not limited to GaAs, and other compound semiconductor crystals such as InA
The effects of the present invention are also exhibited in the crystal growth of QAs, InGa1P, and the like.

Also, the member with which the hydrogen compound of group V element comes into contact is A4.
Needless to say, the material is not limited to Mg, and any member that satisfies the scope of the claims of the present invention may be used.

〔Effect of the invention〕

As described above, according to the present invention, an m-v group compound semiconductor crystal, particularly easily oxidized GaAQAs, etc., is grown in a pyrolytic vapor phase using an alkyl compound of a group I element and a hydrogen compound of a group V element. In addition to being able to grow a GaAgAs crystal layer with a desired AQ mixed crystal ratio with good reproducibility, it is also possible to significantly improve the luminous efficiency of the crystal layer.
Growth of high quality GaAgAs crystal layers can be achieved. This greatly contributes to improving the quality and yield of optical devices such as lasers using GaAl1As crystal layers as a base material.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view schematically showing an apparatus used in the vapor phase growth method according to the present invention, and FIG. 2 is an AR mixed crystal for each growth cycle of a GaA4As crystal layer grown by the vapor phase growth method according to the present invention. This is a diagram showing the ratio, and the Aff mixed crystal ratio for each growth cycle of the Ga/u2Ag crystal layer obtained by the conventional vapor phase growth method is also shown for comparison. 1.1a, 11. b ・(CH,), i piping 101
・-・-----・(CH,)30a102・・・・・・
...(cHa)zAI1103.1.04...Stainless steel bubbler container 105.106...Thermostatic chamber 107...AsH, gas high pressure container 108
......Pressure regulator 109...Piping

Claims (1)

[Claims] When a group III-V compound semiconductor crystal is grown in a vapor phase by introducing an alkyl compound of a group III element and a hydrogen compound of a group V element into a reaction vessel, at least a part of the inner surface forms an alkyl compound. 1. A method for vapor phase growth of compound semiconductor crystals, characterized in that a hydrogen compound of a group V element is introduced into a reaction vessel through a conduit whose main component is an element having an electrode potential lower than the lowest standard electrode potential among the elements.