JPH0365585A - Production of compound semiconductor single crystal - Google Patents

Abstract

PURPOSE:To improve the conversion to single crystal and reduce the generation of dislocation in the growth of a group II-VI compound semiconductor single crystal having low thermal conductivity using a horizontal boat process by inserting a heat- insulation material between a reaction tube and a furnace core tube or the boat. CONSTITUTION:A reaction tube 5 containing a horizontal boat 2 holding raw materials (e.g. Cd, Zn and Te) is put into a furnace core tube 1 and a heat-insulation material 7 is placed between the reaction tube 5 and the furnace core tube 1 or between the reaction tube 5 and the boat 2. The boat is heated with a heater placed outside of the furnace core tube 1 to form a prescribed temperature zone to temporarily melt the raw material in the boat 2. The molten liquid in the boat 2 is slowly solidified from one end to the other end by transferring the heater relative to the boat. A group II-VI compound semiconductor single crystal is grown by this process. Since the heat- insulation material 7 is interposed between the tubes, etc., the amount of heat escaping through the crystal becomes larger than the heat escaping from the side or bottom face of the boat 2 in the generated latent heat of solidification. Accordingly, the solid-liquid interface can be flattened and the conversion to single crystal can be improved.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a technology for manufacturing compound semiconductor single crystals, and more particularly, to a technology for growing II-VI group compound semiconductor single crystals with low thermal conductivity by a horizontal boat method. The present invention relates to a technique that is effective when used in the production of CdTs-based single crystals.

[Prior Art] One of the conventional methods for manufacturing compound semiconductor single crystals such as GaAs and InP is the horizontal boat method.

FIG. 3 shows a schematic configuration of a general single crystal growth apparatus that implements the two-temperature horizontal Bridgman method, which is one of the horizontal boat methods.

That is, a quartz reaction tube 5 in which a boat 2 filled with raw materials, an element 3 for steam pressure control, and a convection prevention plate 4 are vacuum-sealed is inserted into the furnace core tube 1, and a divided tube is placed outside the furnace core tube 1. A heater 6 is disposed, and the heater 6 is configured to form two equal heats *TL and T2 along the axial direction inside the furnace core tube ↓. The quartz reaction tube 5 is initially arranged so that the boat 2 loaded with raw materials is located in the high-temperature soaking zone T□, and the element 3 for vapor pressure control is located in the low-temperature soaking zone T2. The high-temperature soaking zone T has a temperature slightly higher than the melting point of the raw materials in the boat 2, and the low-temperature soaking zone T2 has a temperature so that the inside of the reaction tube S has a desired pressure due to the vapor pressure of element 3. controlled. In this state, the raw materials in the boat 2 are first melted, and then the heater 6 is moved to the left so that the boat 2 moves from the high temperature soaking zone T1 to the low temperature soaking zone T2. The solid-liquid interface of the solid-liquid interface is moved relatively to grow the crystal from the right end to the left end.

[Problems to be Solved by the Invention] By the way, when producing a single crystal of a ■-■ group compound semiconductor such as CdTe in a crystal growth apparatus using the horizontal boat method as described above, CdTe is grown as shown in Table 1. ■-■ group compound semiconductors such as GaAs, -
Thermal conductivity is more than an order of magnitude lower than graphite and pBN, which are the materials for the boat inside the shell.

When a compound semiconductor single crystal with such a low thermal conductivity is grown in a boat, it becomes difficult for the latent heat of solidification to travel through the crystal and escape, resulting in a large proportion of the heat escaping through the boat. As a result, the solid-liquid interface shape becomes concave toward the melt side, as shown in Figure 5, and nuclei are formed in the area in contact with the boat, promoting polycrystalization and the generation of dislocations such as lineage and cell structures. There was a drawback to that.

The present invention was made in view of the above-mentioned problems, and its purpose is to reduce Cd by the horizontal boat method.
The purpose of this invention is to improve the single crystallization rate and reduce the occurrence of dislocations when growing a compound semiconductor single crystal with low thermal conductivity such as Te.

[Means for solving the problem] In a method of growing a compound semiconductor single crystal with low thermal conductivity such as CdTe by a horizontal boat method, it is necessary to A heat insulating material is interposed between the two.

[Function] According to the above means, since the heat insulating material is placed around the boat, the amount of conductive heat and radiant heat that escapes from the side or bottom of the boat among the solidification latent heat generated is reduced, and in contrast, the amount of conductive heat and radiant heat that is transmitted through the crystal is reduced. The proportion of heat that escapes increases,
As a result, the solid-liquid interface, which was concave on the melt side as shown in Fig. 5 in the conventional method, is flattened as shown in Fig. 4, improving the single crystallization rate and reducing the occurrence of dislocations. can be done.

[Embodiment] FIGS. 1 and 2 show essential parts of an embodiment of a crystal growth apparatus using a horizontal boat method according to the present invention.

In this embodiment, a bottom plate 8 and a heat insulating material 7 are provided inside the furnace core tube 1.
A quartz reaction tube 5 is disposed through the reaction tube 5, and a boat 2 containing raw materials is enclosed within the reaction tube 5. That is, the outer periphery of the reaction tube 5 is coated with a heat insulating material 7 so as to cover the side and bottom surfaces of the boat 2. Although not particularly limited, the reaction tube 5 covered with a heat insulating material 7 is supported by a bottom plate 8 so as to be located approximately at the center of the furnace core tube 1.

The heat insulating material 7 is a material with lower thermal conductivity than the crystal to be grown.
For example, alumina (Af1203) and silica (SiO2)
A cloth-like material made of fibers whose main component is Also,
The heat insulating material 7 is open at both ends, protrudes outward by Δa from both ends of the boat 2, and is formed such that its upper end protrudes upward by Δh from the upper end of the boat 2.

Here, the protrusion amount Δ(is O~80+nm, Δh is O~10
It is preferable to set the range to +ni.

Although not shown, a convection prevention plate 4 is disposed in the center of the reaction tube 5 as in the conventional apparatus shown in FIG. Elements of the same family are included as vapor pressure control elements. Further, a split type heater is arranged around the furnace core tube 1, and the reaction tube 5 and the heater are configured to be movable relative to each other in the axial direction.

In the above embodiment, the heat insulating material 7 is disposed around the outer periphery of the reaction tube 5, but the heat insulating material 7 may be interposed between the outer wall of the boat 2 and the inner wall of the reaction tube 5. However, if it is placed inside the reaction tube 5, a long baking process or other treatment must be performed in advance to prevent the components of the heat insulating material 7 and impurities attached to the heat insulating material from being mixed into the grown crystal. Therefore, it is preferable to provide a heat insulating material on the outside of the reaction tube 5 as in the above embodiment.

- As an example, a pBN with a total length of 400 nn+ and a height of 42 nn
The total weight of Cd, Te, and Zn as raw materials is 2 in the manufactured boat 2.
．． 2 kg, and this boat was sealed in a quartz reaction tube 5 together with Cd as an element for controlling vapor pressure.A heat insulating material 7 with a total length of 450 mm and a height of 42.5 ua+ was placed around the outer periphery of the reaction tube 5 on the sides of the boat 2 and It was placed in the furnace core tube 1 with a coating covering the bottom surface.

Then, by applying the two-temperature zone horizontal Bridgman method, crystals were grown while controlling the high-temperature soaking zone to 1105° C. and the low-temperature soaking zone to 819° C. while moving the heater at a relative speed Q of 5 mm/hr. As a result, the maximum grain size is approximately 35X4
Cd Z n T with 0x120m and 4 crystal grains
e crystals were obtained.

As the heat insulating material 7, a cloth-like material made of fibers containing alumina and silica as main components was used.

For comparison, the device shown in Figure 1 without using insulation material,
A Cd ZnTe crystal weighing 2.1 kg was grown by applying the two-temperature horizontal Bridgman method under the same conditions as in the above example. As a result, the maximum grain size is approximately 25X3
CdZnTe consisting of several dozen crystal grains at 0x40an
Crystals were obtained.

[Effects] As explained above, in the above embodiment, in the method of growing a compound semiconductor single crystal with low thermal conductivity such as CdZnTe by the horizontal boat method, the Since a heat insulating material is interposed between the reaction tube and the reaction tube, the amount of heat escaping through the crystal is larger than the amount of heat escaping from the side or bottom of the boat, which is different from the conventional method. The method has the effect of flattening the solid-liquid interface, which was concave on the melt side, improving the single crystallization rate, and reducing the occurrence of dislocations.

In addition, because the dimensions of the insulation material were set to be slightly longer than the overall length of the boat and slightly higher than the height of the boat, it was possible to suppress heat radiation from the boat, while heat radiation due to radiation from the melt surface Since there is almost no change in the amount of heat transmitted through the crystal, it is possible to increase the proportion of heat dissipated through the crystal, thereby improving the single crystallization rate and reducing dislocations.

In the examples, a CdZnTe crystal was grown as an example, but the present invention can be used to manufacture a CdTe crystal or an n-vt group compound semiconductor single crystal having low geothermal conductivity.

[Brief explanation of drawings]

Fig. 2 is a cross-sectional front view showing the essential parts of an embodiment of the compound semiconductor single crystal manufacturing apparatus according to the present invention, Fig. 2 is a cross-sectional side view of the apparatus shown in Fig. 1, and Fig. 3 is a crystallization by the horizontal boat method. 4(A) and (B) are a plan view and a front view showing the shape of the solid-liquid interface during crystal growth when the present invention is applied; FIG. 5 is a sectional front view showing the entire growth apparatus; (A) and (B) are an explanatory plan view and an explanatory front view showing the shape of a solid-liquid interface when grown by a conventional method. 1...Furnace core tube, 2...Boat, 5...Reaction tube, 6...Heater, 7...Insulating material. Figure 1 (A) FB) Figure (Al

Claims (1)

[Claims] (1) A reaction tube containing a horizontal boat containing raw materials is installed inside the furnace core tube, a heater is placed outside the furnace core tube to form a desired temperature zone, and the raw materials in the boat are temporarily removed. In a crystal growth method in which a II-VI group compound semiconductor single crystal is grown by melting and then moving a heater relative to each other to gradually solidify the melt in a boat from one end to the other, the above-mentioned furnace core tube and A method for producing a compound semiconductor single crystal, characterized in that a heat insulating material is interposed between the reaction tube and the boat and the reaction tube.