JPH02111690A - Growth of compound semiconductor crystal and apparatus therefor - Google Patents

Abstract

PURPOSE:To obtain high-quality bulk crystal by passing upward an electric current through a compound semiconductor solution in a crucible so as to produce the electromigration for the solute to effect uniform distribution of each element in the solution containing elements liable to cause gravitational segregation. CONSTITUTION:The bottom of a crucible 1 made from e.g., boron nitride is fitted with a positive electrode 3, while the upper part facing the bottom with a vertically movable negative electrode 4 capable of contact with a compound semiconductor solution (or melt) when made to descend, and an electric current is passed through said solution (melt) with such an intensity as to develop the electromigration of the solute contained (e.g., In+Ga+As). Thence, the current is cut and a seed crystal (e.g., InP) 6 is brought into contact with the solution (melt) 2 to make a growth of the objective compound semiconductor crystal.

Description

[Detailed Description of the Invention] [Summary] Regarding a method suitable for growing a compound semiconductor crystal having a composition that tends to cause gravitational segregation, and an apparatus for carrying out the same, With the aim of uniformly distributing the compound semiconductor solution (or melt) by simple means and obtaining high-quality bulk crystals, a positive electrode is placed on the bottom of the crucible containing the compound semiconductor solution (or melt). Negative electrodes are provided above facing the bottom surface of the crucible, and are movable up and down and can contact the compound semiconductor solution (or melt) when lowered, and contact the compound semiconductor solution (or melt) in the crucible. A current sufficient to cause electromigration of the solute is applied to uniformly distribute the solute in the crucible, and then the current is stopped and a seed crystal is brought into contact with the compound semiconductor solution (or melt) to form a compound. Configure to grow semiconductor products.

[Industrial application field]

The present invention relates to a method suitable for growing a compound semiconductor crystal having a composition that tends to cause gravitational segregation, and an apparatus for carrying out the method.

Currently, various compound semiconductor crystals are being used to manufacture various compound semiconductor devices, and not only binary mixed crystals but also multi-component mixed crystals are required for bulk crystals. In general, growing high quality bulk crystals with uniform composition requires strict control of growth conditions.

[Conventional technology]

Conventional semiconductor bulk crystal growth uses silicon or GaA
It is often carried out for systems where gravitational segregation is hardly a problem, such as s.

In recent years, in the research stage, InGaAs, GaAs P%In
Examples have been reported in which ternary crystals such as AsP are grown by the pulling method.

[Problems to be Solved by the Invention] In the above-mentioned conventional techniques, composition control is not strict enough to make gravitational segregation a problem.

However, for example, when trying to grow InGaAs by the pulling growth method, compared to In, Ga and As
Since Ga is a light element, if left in solution, Ga
And As is concentrated in the upper part of the solution.

FIG. 3 is an explanatory diagram of the main parts of the growth apparatus for explaining the situation.

In the figure, ■ indicates a crucible, and 2 indicates a solution.

As shown in the figure, in the solution 2, Ga and As, which are light elements, move to the upper part of the solution 2, and the distribution of the elements becomes non-uniform as a whole.

Usually, the seed crystal for growing bulk crystals is crucible 1.
Since it is brought into contact with the solution 2 by descending from above, it goes without saying that if the composition above the solution 2 is not uniform, the grown bulk crystal will not be homogeneous either.

The present invention makes it possible to uniformly distribute each element by simple means in a solution containing elements that are prone to gravitational segregation, thereby making it possible to obtain bulk crystals of commercial quality.

[Means to solve the problem]

Generally, when a current is passed through a metal solution (or melt), a phenomenon called electromigration occurs.
It is known that elements move towards the electrode.

The present invention utilizes this electromigration effect to alleviate the gravitational segregation of solute elements.

FIG. 1 is an explanatory view of the main parts of a growth apparatus for explaining the present invention in detail, and the same symbols as those used in FIG. 3 indicate the same parts or have the same meanings. Also, in this case? It is assumed that the material is InGaAs.

In the figure, 3 indicates the positive side electrode, and 4 indicates the negative side electrode.

In this growth apparatus, when a voltage is applied with the polarity shown between the positive electrode 3 and the negative electrode 4 and a current is passed through the solution 2, Ga and As are generated due to the electromigration effect.
can be moved in the direction of the positive electrode 3.

Therefore, if a seed crystal is lowered in this state and a bulk crystal made of InGaAs is grown, its composition will be homogeneous as desired.

For this reason, in the compound semiconductor crystal growth method and the apparatus for carrying out the method according to the present invention, the compound semiconductor solution or melt (for example, solution 2) in the crucible (for example, crucible 1) is grown from below to above. A step of uniformly distributing the solute in the crucible by passing a current to the extent that electromigration of the solute occurs, and then, after stopping the current, a seed crystal (for example, seed crystal 6) is transferred to the compound semiconductor. In addition, a positive side electrode (for example, a positive side electrode) provided on the bottom of the crucible containing the compound semiconductor solution (or melt) is included. 3), and a negative electrode (e.g. negative electrode 4) which is provided so as to be movable up and down above facing the bottom surface of the crucible and which can come into contact with the compound semiconductor solution or melt when lowered. Be prepared.

[Effect]

By adopting the above method, the composition of the entire solution can be made uniform by moving the solute in the solution that tends to segregate by gravity in the opposite direction by electromigration, and as a result, the resulting crystal The composition also becomes uniform. In addition, to realize this, it is sufficient to flow a current to an extent that electromigration is generated in the solution, so it can be easily implemented.

〔Example〕

FIG. 2 shows an explanatory diagram of the main parts of the growth apparatus for explaining one embodiment of the present invention, and the same symbols as those used in FIGS. 1 and 3 indicate the same parts or have the same meaning. Shall have.

In the figure, 5 indicates a seed crystal moving rod, 6 indicates a seed crystal, and 7 indicates a conductor.

In the illustrated example, the material of crucible 1 is boron nitride, and the solution 2 is I
n + Ga + As (X+n=0.738.XA
s=0.212. X, , = 0.05), electrodes 3 and 4
The material is carbon and the seed crystal is InP. The composition of the solution 2 is an equilibrium composition with a crystal having a composition lattice-matched to InP at 840 ('C). Further, the electrode 4 is movable downward in the same manner as the seed crystal moving rod 5.

Now, when the temperature of the entire crucible 1 is gradually raised to 860 ('C), the electrode 4 is immersed in the solution 2 near 840 ('C), and a current is passed in the direction from the electrode 3 to the electrode 4.

In this case, the current density is, for example, 10 (A/cm"3~
50 (A/cm”), preferably 20 (A/cm”), preferably 20 (A/cm”)
A/am''), and the operation of turning on the current for, for example, 5 [minutes] and then cutting off for 3 [minutes] is repeated until the start of crystal growth.

The temperature increase of the crucible 1 is 1! Subsequently, when the temperature reaches 860 ("C), it is left in that state for 30 [minutes], and then, when the temperature is lowered to 840 ("C) again, crystal growth is started.

By performing such an operation, the composition of the solution 2 is kept uniform by the gravitational effect and electromigration effect until the growth starts, and InP is lattice-matched to InP.
High quality GaAs crystals can be obtained.

〔Effect of the invention〕

In the compound semiconductor crystal growth method and the apparatus for carrying out the same according to the present invention, a positive electrode is provided on the bottom surface of the crucible, and the positive electrode is movable up and down in an upward direction opposite to the bottom surface of the crucible, and when lowered. A negative electrode capable of contacting the compound semiconductor solution (or melt) is provided at each of the electrodes, a current is applied to the compound semiconductor solution (or melt) to an extent that electromigration of the solute occurs, and then the current is stopped. Thereafter, a seed crystal is brought into contact with the compound semiconductor solution (or melt) to grow a compound semiconductor crystal.

By adopting the above configuration, the composition of the entire solution can be made uniform by moving the solute in the solution that tends to segregate by gravity in the opposite direction by electromigration, and as a result, the resulting crystal The composition also becomes uniform. In addition, to realize this, it is sufficient to flow a current to an extent that electromigration is generated in the solution, so it can be easily implemented.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of the main parts of a compound semiconductor crystal growth apparatus for explaining the present invention in detail, FIG. 2 is an explanatory diagram of the main parts of the growth apparatus for explaining one embodiment of the present invention, and FIG. Each of the drawings shows an explanatory view of the main parts of a compound semiconductor crystal growth apparatus for explaining gravitational segregation of a compound semiconductor solution. In the figure, 1 is a crucible, 2 is a solution, 3 is a positive electrode, and 4 is a crucible.
5 indicates a negative electrode, 5 a seed crystal moving rod, 6 a seed crystal, and 7 a conductor. Patent Author: Fujitsu Limited Representative Patent Attorney Shoji Utoya

Claims (2)

[Claims] (1) A step of uniformly distributing the solute in the crucible by passing a current to the extent that electromigration of the solute occurs from below to above the compound semiconductor solution (or melt) in the crucible, and then distributing the solute uniformly in the crucible. A method for growing a compound semiconductor crystal, the method comprising the step of: stopping the current, and then bringing a seed crystal into contact with the compound semiconductor solution (or melt) to grow a compound semiconductor crystal. (2) a positive electrode provided on the bottom surface of a crucible containing a compound semiconductor solution (or melt); and a positive electrode provided upwardly facing the bottom surface of the crucible so as to be movable up and down, and when lowered, 1. A compound semiconductor crystal growth apparatus comprising: a negative electrode capable of contacting a compound semiconductor solution (or melt);