JPS623097A - Production of iii-v compound semiconductor mixed crystal - Google Patents

Abstract

PURPOSE:To grow a semiconductor crystal of desired composition of a uniform mixed crystal, by bringing the solid phase into contact with a pseudobinary solution consisting of III-V compounds having different melting points and pulling up the mixed crystal for growth. CONSTITUTION:A pseudobinary solution is formed from the first III-V compound and the second III-V compound having a higher melting point than the first compound and one component common thereto. The solid phase of the compound having the higher melting point or mixed crystal slid phase of the pseudobinary system having the higher melting point than the solution is brought into contact with the above-mentioned solution to pull up the mixed phase from the solution. The reduction in the compound component of a larger segregation coefficient having the higher melting point can be prevented, and the aimed III-V compound semiconductor of uniform mixed crystal is obtained by this method. For example, two components InAs and GaAs, are used as the mixed crystal.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a mixed semiconductor crystal in which two types of III-V compound semiconductors are homogeneously mixed in a predetermined ratio.

Ultrahigh-speed devices using two-dimensional gas, semiconductor lasers,
In light emitting diodes, photodiodes, etc., indium phosphide (InP), gallium arsenide (GaAs), gallium phosphide (GaP), gallium antimonide (GaS)
Not only III-V compound semiconductors such as b), but also mixed crystal semiconductors (hereinafter referred to as mixed crystals) of two or more of these III-V compound semiconductors, and heterojunctions that combine these semiconductors are playing an important role. has come to occupy the majority of Various crystal growth methods have been developed so far, and if a substrate to serve as a seed crystal is supplied, there is a stage in which a mixed crystal of a desired composition can be epitaxially grown on it under lattice matching conditions. is reaching. However, currently only binary compounds such as GsAs, InP, GsSb, InAs, and GsP are available as crystal substrates that are essential for the growth of these mixed crystals and the growth of heterojunctions, and this limits the composition range in which mixed crystals can be used. ing.

The present invention was made with the aim of solving this problem. In other words, the present invention provides a method for growing a III-V compound mixed crystal that can be used as a substrate for epitaxial growth.

The mixed crystal for this substrate is required to be a large, homogeneous, high-quality single crystal that has a predetermined lattice constant, in other words, a composition.

The reason why we have not been able to obtain a mixed crystal that meets this requirement is because
This is due to the fact that it was difficult to keep the composition of the growth solution constant because the segregation coefficients of each component compound constituting the mixed crystal were different. In other words, the Bridgman method, the I
Rotational pulling method (LEC method; Liquid-En
capsulated-Czoch-ralski method)
Attempts have been made to grow large bulk mixed crystals in the solution, but components with large segregation coefficients precipitate out of the solution quickly, and as growth progresses, components with small segregation coefficients increase in the solution. A compositional gradient occurred, and the growth of homogeneous mixed crystals was not possible.

The present invention solves these problems and relates to an improved rotary pulling method using liquid encapsulation that makes it possible to pull up mixed crystals of uniform composition. The present invention was made with the aim of realizing that a requirement for homogeneous bulk mixed crystal growth is to control the composition of the growth solution to be constant. The principle of this composition control method is that in a quasi-binary alloy system consisting of two types of III-V compounds, not only the liquid phase and the solid phase but also the entire growth system are in thermal equilibrium and the system is sealed. If so, the degree of freedom is 1, which is based on the fact that the compositions of the liquid phase and solid phase are uniquely determined by temperature. That is, by bringing the growth system as close to thermal equilibrium as possible, the composition of the solid phase precipitated as a mixed crystal and the liquid phase composition corresponding to the solid phase can be controlled by temperature. Furthermore, in the present invention, a compound with a higher melting point among the two III-V group compounds constituting the mixed crystal, or a pseudo-binary system with a melting point higher than that of the growth solution is added to the mixed crystal growth solution. By keeping the mixed crystal in contact as a replenishing raw material and pulling the mixed crystal out of the growth solution, it is possible to prevent this high melting point compound component with a large segregation coefficient from decreasing.

Next, the method for producing the compound mixed crystal of the present invention will be specifically explained using the drawings. Figure 1 is a cross-sectional structural diagram of a crystal growth apparatus used to carry out the manufacturing method of the present invention.
Contains growth solution 3. 1 is a seed crystal, 2 is a pulled III-V group compound mixed crystal, and 6 is a support rod for the crucible, which allows the crucible to rotate.

7 is a sealing agent such as B2O3, 9 is a flange, and the space between the reaction tube 8 and the reaction tube 8 is sealed by an appropriate method. Reference numeral 11 denotes a pulling rod, which rotates and pulls up the compound mixed crystal 2 through a chuck 12 that fixes the seed crystal 1. Of course, the spaces between the flanges 9 and 9' and the mixed crystal pulling rod 11 and the crucible support rod 6 are sealed so that these rods can rotate, respectively. The interior of the reaction tube is filled with a high-purity inert gas such as argon, nitrogen, or hydrogen gas pressurized at an appropriate pressure.

The crucible 5 is made of a suitable material such as boron nitride or graphite, and an internal crucible 5' made of high-purity quartz, PBN, corundum, etc. is appropriately used inside the crucible 5 to prevent contamination by impurities from the crucible. Figure 2 is for explaining the principle of composition control in the present invention.

The figure shows a pseudo-binary system phase diagram consisting of one type of III-V group compound AB and another type of III-V group compound CD having a higher melting point. Here, A and C correspond to group III elements, and B and D correspond to group V elements. Furthermore, in Figure 2, Tm1 and Tm2 represent the melting points of compounds AB and CD, respectively. Now AB
Mixed crystal A made by alloying CD and CD with a molecular ratio of (1-X):X
The case of growing 1-XCXB1-XDX will be explained. As shown in Figure 2, the growth temperature Tg of the mixed crystal (however, T
m1≦Tg≦Tm2) is determined, the solution composition X and solid phase composition X are uniquely determined by the liquidus line L and the solidus line S in this AB-CD pseudo-binary system equilibrium phase diagram I understand that. In this method, if the rate of replenishment of the CD component to the solution is set to be higher than the rate of precipitation of the CD component precipitated in the pulled mixed crystal, the solution composition can always be controlled to be constant.

In the present invention, in order to achieve this, a predetermined amount of the CD compound raw material polycrystalline 4 is placed at the bottom of the crucible 5 as shown in Figure 1, and the CD component is rapidly converted into the growth solution from below using the difference in specific gravity. Made it possible to replenish. This is due to the fact that the higher the concentration of the CD component with a higher melting point in the solution, the lower the specific gravity of the solution. As a result of this, A-
A1-XCXB1- from growth solution 3 consisting of B-C-D
When the XDX mixed crystal 2 is pulled up, the CD component with a large segregation coefficient tends to decrease from the solution 3, but an amount of CD component corresponding to this precipitation is immediately replenished from the CD raw material polycrystal 4, so that the solution 3 The composition of the mixed crystal 2 is always kept constant, so the composition of the pulled mixed crystal 2 is also always controlled to be constant,
The objectives of the invention are achieved. In particular, the present invention provides that the elements A and C or the elements B and D are the same, that is, A=C
Alternatively, it is effective for growing a ternary mixed crystal in which B=D, AB1-XDX or A1-XCXB.

Example 1 First, a predetermined amount of GaSb was formed into a predetermined shape in the crucible 5 shown in FIG.
A polycrystalline ingot is inserted as raw material crystal 4. If the shape of the ingot does not match the shape of the crucible, boron oxide (B) is placed on top of the raw material crystal to prevent dissociation of antimony.
Add an appropriate amount of liquid opcell material such as 2O3) or sodium chloride (NaCl). Next, high-purity argon gas, nitrogen gas, or hydrogen gas is passed into the reaction tube 8 using valves 13 and 13' and heated to about 750°C to melt the GaSb raw material crystals, and the GaSb raw material is placed at the bottom of the crucible. Crystal 4 is cast and placed. And after cooling,
The liquid encapsulant is removed using a suitable method, such as methanol, and a predetermined amount of polycrystalline (In, Ga) Sb for a growth solution having a predetermined composition adjusted in advance is added thereon. For example, when the purpose is to grow a (In, Ga)Sb mixed crystal with X=0.7, (I
The composition of n, Ga)Sb may be set to X=0.2. Of course, the composition of the polycrystalline (In, Ga)Sb for growth solution 3 must have sufficient uniformity for practical use, and oxide films and contaminants must be sufficiently removed from its surface by etching or the like. Furthermore, (In, Ga)Sb for growth solution 3
Add liquid encapsulant material such as B2O3 onto the polycrystal. It is necessary to moderate the viscosity of this liquid capsule during growth, and for this purpose, an appropriate amount of an alkali metal fluoride or oxide may be added.

(In, Ga) Sb for seed crystal 1 required for pulling is obtained by processing an (In, Ga) Sb single crystal with the desired mixed crystal composition and axial orientation into a predetermined shape, and then forming a processed layer by polishing, etching, etc. , and thoroughly remove the oxide film and contamination on the surface. The seed crystal thus prepared is attached to the seed crystal fixing chuck 12 of the growth apparatus. As described above, after the materials are charged into the growth apparatus, high-purity hydrogen is flowed into the reaction tube at a predetermined flow rate and kept as it is for a certain period of time, for example, about one hour, to remove residual moisture, oxygen, etc. inside the reaction tube. The pressure of the gas applied inside the reaction tube is the same as that of (In, Ga)S at the growth temperature.
Since the dissociation pressure of b is low, about 1 atm is sufficient. Next, an electric current is passed through the electric furnace 10, and the (In, Ga) for the growth solution 3 is
) Raise the temperature until the Sb polycrystals just melt. The temperature varies depending on the In-Ga-Sb melt composition X, but X=0
．． In the case of 5, the temperature is 675°C. After the temperature in the growth system reaches a steady state, the seed crystal is lowered and the tip of the seed crystal is immersed in the In-Ga-Sb growth solution 3 until the tip is slightly dissolved in the growth solution. After that, start lifting. Of course, known techniques used in the usual LEC method, such as applying so-called necking at the initial stage of pulling this (In, Ga)Sb mixed crystal, can be applied. A specific example of the (In, Ga)Sb mixed crystal pulled in this manner will be shown. Composition and amount of In-Ga-Sb growth solution 3, X = 0.2 and 50 g, polycrystalline GaS for raw material 4
Charge amount of b 100 g, pulling axis direction (111), rotation speed 20 rpm, pulling speed 5 mm/h, growth temperature 595
As a result of pulling at .degree. C., an (In, Ga)Sb mixed crystal having a diameter of 25 mm, a length of 10 cm, and a mixed crystal composition of X=0.7 was obtained.

In carrying out this mixed crystal growth, (I
This article describes how the n,Ga)Sb seed crystals were obtained. Initially, (I
n, Ga) There is no Sb mixed crystal. Therefore, first, using GaSb as a seed crystal and using this method, (In
, Ga)Sb mixed crystal was pulled up. It has thus been found that a sufficiently good mixed crystal can be grown if the difference in composition between the seed crystal and the (In, Ga)Sb to be pulled is within 5%. Next, using this (In, Ga)Sb with a composition of X=0.95 as a seed crystal, it was possible to pull up an (In,Ga)Sb mixed crystal with a composition of X=0.9. In this way, the seed crystals (I
By pulling up a mixed crystal with X slightly smaller than n, Ga)Sb, it was possible to pull up the desired (In, Ga)Sb mixed crystal with X=a7. Of course, by repeating this process further, it is possible to grow an (In, Ga)Sb mixed crystal of any desired composition. A similar procedure can also be performed using the Bridgman method.

The composition range in which a high quality mixed crystal could be easily grown by the method of the present invention described here was the range of X≧0.7. This corresponds to a composition range in which the gradient of the solidus line in the pseudo-binary phase diagram is large, and it was found that this range is suitable for the mixed crystal growth method of the present invention.

Example 2 GaAs was used as the raw material polycrystalline 4, and a predetermined composition was used as the growth solution 3, for example, (In, Ga with X=0.35).
) As the seed crystal 1, an (In, Ga) As mixed crystal having a predetermined solid phase composition, e.g., X=0.85, and a pulling axis direction, e.g. , for example, at 1100° C., it was possible to grow an (In, Ga)As ternary mixed crystal with a composition of X=0.85.

In this case, the reaction tube was filled with 1.5 atmospheres of high-purity nitrogen gas to prevent dissociation of arsenic.

Example 3 GaP was used as the raw material polycrystal 4, Ga(As, P) polycrystal having a predetermined liquid phase composition, for example, X = 0.15, was charged as the growth solution 3, and a predetermined amount A Ga(As,P) mixed crystal with a solid phase composition, e.g. . In this example, since the dissociation pressure of phosphorus is high, a pulling device capable of applying a gas pressure of 30 to 50 atmospheres to the entire growth system was used.

Example 4 GaP is used as the raw material polycrystal 4, and the growth solution 3 has a predetermined liquid phase composition, for example, (
In, Ga) P polycrystals are charged and pulled using (In, Ga) P having a predetermined solid phase composition, for example, X = 0.75, and an axial direction, for example (111), as a seed crystal, In0.25Ga0.75P ternary mixed crystal could be pulled up. Note that the applied gas pressure was 30 atm.

Although the four embodiments of the present invention have been described above, the method for producing mixed crystals of the present invention can be applied to other ternary and quaternary mixed crystals of III-V group compounds, such as (Ga, Al)As, (G
a, Al) P, (Ga, Al) Sb, (Ga, Al) (
It goes without saying that this method can be applied to the growth of not only As, P), etc., but also mixed crystals of II-VI group compounds and other mixed crystals.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional structural diagram of an apparatus used to implement the manufacturing method of the present invention. FIG. 2 is an equilibrium phase diagram of a pseudo-binary system containing two compounds for explaining the principle of the present invention. In addition, 1 is a seed crystal, 2 is a mixed crystal pulled by the manufacturing method of the present invention, 3 is a mixed crystal growth solution, 4 is a polycrystalline raw material for replenishing the ingredients lacking in the growth solution, 5 and 5 ' is a growth crucible, 6 is a support rod for the crucible, 7 is a liquid capsule for sealing the growth system, 8 is a reaction tube, 9 and 9' are flanges, 10 is an electric furnace, 11 is a support rod for the pulled crystal, 12 is a chuck for fixing seed crystals, 13, 13' gas valve L is a liquidus line, S is a solidus line, X is a composition of mixed crystal (solid phase), and X is a growth solution (liquid phase).
The composition of

Claims (6)

[Claims] (1) A second III-V compound is added to a pseudo-binary solution composed of a first III-V compound and a second III-V compound whose melting point is higher than that of the first III-V compound. A mixed crystal homogeneously containing the first compound and the second compound in a predetermined ratio is obtained from the solution in a state in which the solid phase of the group compound or the pseudo-binary mixed crystal solid phase having a higher melting point than the solution is in contact with the solid phase. 1. A method for producing a III-V group compound semiconductor mixed crystal, which comprises pulling and growing a III-V group compound semiconductor mixed crystal. (2) Place the solid phase of the second III-V compound in contact with the lower side of the pseudo-binary solution composed of the first and second compounds, and pour the mixed crystal from the top surface of the solution. A method for producing a III-V group compound semiconductor mixed crystal according to claim (1), characterized in that the mixed crystal is pulled up. (3) A III-V compound semiconductor according to claim (1), wherein the III-V compound semiconductor mixed crystal to be grown is composed of two components: indium antimonide and gallium antimonide. Method for producing mixed crystals. (4) Claims characterized in that the III-V group compound semiconductor mixed crystal to be grown is composed of two components of indium arsenide and gallium arsenide (1) III-V group compound semiconductor mixed crystal Production method. (5) A III-V compound semiconductor mixed crystal according to claim (1), characterized in that the III-V compound semiconductor mixed crystal to be grown is composed of two components of gallium arsenide and gallium phosphide. Crystal manufacturing method. (6) The III-V compound semiconductor according to claim (1), wherein the III-V compound semiconductor mixed crystal to be grown is composed of two components: gallium phosphide and indium phosphide. Method for producing mixed crystals.