JPH01103984A - Method for refining compound semiconductor crystal - Google Patents

Abstract

PURPOSE:To produce a group III-V compd. semiconductor single crystal which is free from contamination by impurities at a low temp. by melting the group III element in the upper part of a crucible, melting the group III-V compd. in the lower part successively, floating the group III-V compd. crystal onto the upper part of a melt zone, and bringing a seed crystal into contact with the melt zone. CONSTITUTION:A polycrystal of the group III-V compd., for example, InP, is put into the crucible and the group III element, for example, In is put into the upper part thereof. Said upper part is sealed by a liquid sealant such as B2O3 and the crucible is heated to melt the In. The InP begins to melt successively from the boundary face of the In and the InP as the In melts. The melt in which a large quantity of the In is incorporated is thus formed. Since this melt has the density larger than the density of the ordinary melt, the melt moves toward the lower side of the InP polycrystal. The concn. of P in this melt zone increases gradually and the crystal of the InP begins to deposit. This crystal has the density smaller than the density of melt and, therefore, floats in the upper part of the melt zone. The refining of the crystal is executed in such a manner. The seed crystal is set at this time and is brought into contact with the melt zone, by which the InP single crystal is grown.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for refining the crystals of compound semiconductors, particularly 1-V group compound semiconductors.

[Conventional technology]

Regarding methods for refining semiconductor crystals or growing single crystals using seed crystals, various methods including zone melting are already known.

FIGS. 3 and 4 are diagrams showing the principles of the zone refining method and the floating zone melting method (FZ method), which are known as typical examples thereof.

Figure 3 shows the zone purification method, where 1 is, for example, ■-v
The crystals of group compounds are stored in the boat 2, and a part of them is melted by the heater 3.

4 indicates the melting zone.

As the melting progresses, the boat 2 is pulled back inside the pressure vessel 5 in the direction of the arrow, so the melting zone 4 gradually moves to the rear of the boat 2.

By repeating this operation, the impurities in the crystal 1 are gradually pushed backwards based on the segregation phenomenon at the interface between the solid phase and the liquid phase, thereby purifying the crystal.

FIG. 4 shows the FZ method. The same reference numerals are used for parts corresponding to those in FIG.

In this method, the crystal 1 is held vertically, the melting zone 4 is moved vertically, and impurities are collected to one side as in the case of FIG. 3, thereby purifying the crystal. A feature of this method is that it does not use boats or crucibles, so there is no contamination caused by impurities transferred from these containers.

[Problems to be Solved by the Invention] As mentioned above, when refining semiconductor crystals, the zone refining method and the FZ method are used. , or in the case of ■-V group compounds such as gallium phosphide (GaP), the crystals of these compounds have very high melting points, and when zone refining methods are used, they can be contaminated by impurities from crystal storage vessels such as boats. There is a tendency to

To prevent this, the FZ method can be used, but in this case, V
Since the vapor pressure of the group elements is extremely high, when the normal FZ method is used, the group V elements dissociate from the crystal and the semiconductor is not purified.

An object of the present invention is to provide a compound semiconductor crystal purification method that purifies crystals at low temperatures and reduces contamination by impurities generated from containers and the like.

[Means for Solving the Problems] The present invention heats a part of a semiconductor crystal to form a molten zone, and moves the molten zone vertically within the crystal to remove internal impurities from one end of the semiconductor crystal. In the compound semiconductor crystal purification method of collecting and refining the semiconductor crystal, m-v
A group compound is placed in a crucible, a group (I) element is placed on top of the crucible, a liquid sealant is placed on top of the crucible, the crucible is sealed, and the group (I) element is melted using a heater; By the melting of the group (1) element, the group (1)-v compound is sequentially melted from the interface where the two contact, forming a molten zone, and this molten zone is moved below the group (1)-v compound, and the compound (2)-v A crystal of the group compound semiconductor is precipitated and floated above the melting zone, and in this state, a seed crystal is placed in the crucible and brought into contact with the melting zone to form a single crystal of the group III-V compound semiconductor. It aims to achieve its purpose by purifying crystals at low temperatures and at the same time preventing contamination from the surrounding area.

[Function] In the compound semiconductor crystal purification method of the present invention,
For example, a polycrystal of InP, a group ■-V compound, is placed in a pot, and on top of it, for example, In, a group II element, is placed, and then a liquid sealant is applied to the top, and boron oxide (B203), for example, is placed in a pot. The head of the crucible is sealed, and then the crucible is heated with a heater to melt the In. At this time I
Since the melting point of nP is higher than that of In, polycrystalline InP does not melt at this temperature, but when In starts to melt, it gradually starts to melt from the part that comes into contact with the melt, thus forming a melting zone.

As the melting progresses, this melting zone becomes an InP melt containing a large amount of In.

Since the InP melt containing a large amount of In has a much higher density than a normal InP melt, the InP melt zone gradually moves below the InP polycrystal.

In this case, the concentration of P in the melting zone of InP also gradually increases, and as the concentration of P increases, crystals of InP begin to precipitate. Since this crystal has a lower density than the melt, the crystal floats to the top of the melt zone. In this way, the crystals are purified.

At this time, by setting a seed crystal in the crucible and bringing it into contact with the melt zone, it becomes possible to grow a single crystal of InP.

[Example] Hereinafter, one embodiment of the present invention will be described with reference to the drawings.

FIG. 1 shows a longitudinal sectional view of a crystal refining apparatus used in an embodiment of the compound semiconductor single crystal refining method of the present invention.

In the figure, 6 is a crucible and the material is P B N (Pyro
It has a diameter of 30 mm and a height of 50 mm. 7 is a polycrystalline compound of the ■-v group, and polycrystalline InP is used. 8 is a group Ⅰ element and In is used. 9 is a liquid sealant and is B2O3. 10 is a heater, and 11 is a graphite susceptor.

In this example, 1400 g of InP polycrystal 7, I
290 g of n8 6N (nine).

B2039 is 70g, and the pressure vessel 5 is filled with argon (Ar).
) Gas was sealed to make the internal pressure 40 Kg/am2.

In this state, the inside of the crucible 6 is heated by the heater 10 for about 50 minutes.
It was heated to 00°C to dissolve In8 and B2039. In this case, the melting point of 1nP polycrystalline 7 is 1068°C, so normally it does not melt at this temperature, but I
The portion of n8 that comes into contact with the melt will gradually dissolve. In this way, a melting zone is gradually formed by the In8 and InP polycrystalline 7 solutions.

The melt in this melting zone contains a large amount of In,
Therefore, its density is extremely large and about twice as high as that of InP before melting, and as it melts the InP polycrystal 7, it gradually moves below it.

In this case, since P is also melted in the melting zone, its concentration gradually increases. When the concentration of P increases, InP crystals start to precipitate, but since the density of the InP crystals is smaller than the density of the melt, the crystals float above the melting zone.

The precipitated InP crystals have a stoichiometric composition, and by continuing the above melting-transfer operation, purified InP crystals can be obtained.

Figure 2 shows the situation during refining, where 12 is the melting zone;
13 indicates an InP crystal. In the case of taking out the purified bamboo crystals in the figure, the crucible is heated and then left for 18 hours, then slowly cooled for 24 hours, and about 30a+i of the lower part of the crystals are removed before being taken out.

Regarding the InP crystal obtained in this way, the hole (
Hall mobility μ and carrier concentration n were determined at room temperature by measuring the Hall effect and compared before and after purification. Before purification, the Hall mobility μm was 3100 cm2/V −
S, carrier concentration n-1 × 101B101B after purification Hμm3900cm/V-S, n
-2X 1015 cm-3, μ.

It was recognized that both n and n were improved.

In addition, under the same conditions as in the case of crystal refining described above, a seed crystal with crystal orientation <111> was placed in the upper part of the melting zone to grow the crystal, and as a result, an InP single crystal ingot with a height of 110 cm was obtained. was completed.

In this example, an open-top crucible was used, but a closed crucible may also be used.

When moving the melting zone 12, the heater 4 may be moved in the direction of the arrow as shown in FIG. 5, and various shapes of the heater can be considered.

Further, by rotating the crucible, the shape of the melting zone can be made uniform, and by tilting the crucible, the moving speed of the melting zone can be adjusted.

The moving speed of the melting zone can be adjusted by adjusting the heater temperature.
An induction heating type heater can be used, and a crystal with a uniform composition can be obtained by applying a magnetic field.

As described above, by melting In as shown in this embodiment, it becomes possible to refine and grow crystals at low temperatures, and the following effects can be obtained.

(1) It is possible to prevent the contamination of contaminants generated from the crucible and other surrounding areas.

(2) It is possible to reduce the dissociation of group V elements, such as P.

(3) It is economically advantageous because less electric power is required for the heater and the entire device can be simplified.

[Effects of the Invention] According to the present invention, it is possible to provide a compound semiconductor single crystal purification method that purifies the crystal at a low temperature and reduces contamination by impurities generated from a container or the like.

[Brief explanation of the drawing]

FIG. 1 is a vertical cross-sectional view of a crystal refining apparatus used in an embodiment of the compound semiconductor single crystal refining method of the present invention, and FIG.
3 and 4 are longitudinal sectional views showing the conventional crystal purification apparatus, and FIG. 5 shows another embodiment of the crystal purification apparatus used in the method of the present invention. FIG. 6: Crucible, 7: I[[-V group compound, 8: ■group element, 9: Liquid sealant, 10: Heater, 12: Melting zone, 13: InP crystal. 1 bite of ivy

Claims (1)

[Claims] (1) A compound semiconductor crystal in which a part of the semiconductor crystal is heated to form a molten zone, and the molten zone is moved in the vertical direction within the crystal, while internal impurities are collected at one end to refine the semiconductor crystal. In the purification method, a III-V group compound is stored in a crucible, a group III element is placed on top of the crucible,
Furthermore, a liquid sealant is placed above the crucible to seal the crucible, and then the group III element is melted by a heater, and the group III element is melted to separate the group III-V compound at the boundary where the two contact each other. The crystals of the III-V compound are precipitated and floated above the melting zone by sequentially melting from the surface to form a melting zone, and moving the melting zone below the III-V compound. . A compound semiconductor single crystal refining method, further comprising disposing a seed crystal in the crucible in this state and bringing it into contact with the melting zone to grow a single crystal of the III-V compound semiconductor.