JPH0712030B2 - (II)-(VI) Group compound semiconductor crystal growth apparatus - Google Patents

Description

TECHNICAL FIELD The present invention relates to crystal growth, and more particularly to crystal growth of a II-VI group compound semiconductor using a Zn solvent.

[Prior Art] FIG. 2 shows a liquid crystal growth apparatus for a compound semiconductor according to the prior art. At the bottom of the quartz crystal growth ampoule 1,
A heat sink 9 made of a material having a good thermal conductivity such as carbon is housed, a part of the heat sink 9 is notched, and the growth ampoule is deformed accordingly, thereby fixing the heat sink. The substrate crystal 7 is arranged on the heat sink 9, and the substrate crystal 7 is fixed by the substrate stopper 5. The substrate stopper 5 is made of quartz or the like similar to the growth ampoule 1. The solvent 2 is accommodated on the substrate 7, and the source crystal 3 serving as a growth raw material is disposed on the substrate stopper 5. In the case of crystal growth of a III-V group compound semiconductor, the solvent 2 is a compound semiconductor such as Ga or In that grows.
Group III constituent elements are selected. Further, in the case of chalcogenide crystals of II-VI group compound semiconductors, chalcogenide elements such as Se and Te have been often used conventionally. Substrate 7, substrate stopper 5, solvent 2, source crystal 3 in growth ampoule 1
After housing, the ampoule is evacuated to a vacuum and sealed. An ampoule having such a configuration is arranged in a temperature gradient as shown on the right side of the figure, the source crystal in the high temperature portion is dissolved in the solvent 2, the temperature gradient is transported, and the crystal is deposited on the substrate 7. Let

However, when an attempt is made to grow a II-VI group compound semiconductor or the like having Zn as a constituent element using a liquid crystal growth apparatus such as that shown in FIG. It does not grow, or even if it grows, a flat growth layer cannot be obtained.

[Problems to be Solved by the Invention] In comparison with the solvent used for the growth of III-V group compound semiconductors, Z
The n solvent has good thermal conductivity. Therefore, it is difficult to form a temperature gradient in the solvent. The specific gravity of emissivity becomes relatively large. The emissivity of the heat sink carbon at high temperature is 0.
There is about 86 (1050 ℃), and the emissivity of Zn is, for example, 1000
It has a very large value compared with the value estimated to be about 0.1 at ℃. Therefore, the heat sink becomes like a heating element, and there is a tendency to create an opposite temperature gradient in the vicinity of the substrate. If a temperature gradient cannot be formed on the substrate surface, crystal growth will not occur, and if a reverse temperature gradient is formed, the substrate will dissolve into the solvent.

The surface of the substrate is in contact with the Zn solvent and is surrounded by a quartz substrate stopper. Around the substrate stop is a quartz ampoule. In such a structure, the temperature distribution in the solvent is high in the central portion and becomes lower toward the periphery. That is, the isotherm has a downwardly convex shape. The growing crystal will have a concave surface according to the shape of the isotherm.

An object of the present invention is to provide a II-VI group compound semiconductor crystal growth apparatus capable of efficiently performing crystal growth using a Zn solvent.

Another object of the present invention is to provide a II-VI group compound semiconductor crystal growth apparatus capable of obtaining a flat growth layer on a substrate by using a Zn solvent.

[Means for Solving the Problems]

According to the present invention, a solvent containing Zn as a main component is used, a temperature difference is provided between the upper and lower sides, and II- is formed on the substrate arranged on the heat sink.
In an apparatus for growing a Group VI compound semiconductor crystal in liquid phase,
The heat sink is formed of a material whose emissivity at the growth temperature is about 1/2 or less of that of carbon, and the substrate stopper for closely fixing the substrate on the heat sink is formed of a material having an emissivity equal to or higher than that of quartz. A characteristic II-VI group compound semiconductor crystal growth apparatus is provided.

Further, according to the present invention, there is provided a substrate stopper for stopping a substrate placed on a heat sink, the substrate stopper being made of a material having an emissivity at a growth temperature which is about twice or more that of quartz. A II-VI compound semiconductor crystal growth apparatus is provided.

[Operation] When performing crystal growth using Zn as a solvent, it is necessary to consider the thermal properties of Zn. Zn has an extremely low emissivity at a high temperature near the crystal growth temperature, whereas
Carbon has a very high emissivity. Therefore, if Zn and carbon are arranged in the vicinity, a large amount of heat radiation will be generated from carbon. Zn which receives this radiation causes a temperature rise. That is, when carbon is used as a heat sink, it does not work as a heat sink but rather works as a heat generator. For this reason, it becomes difficult to create a temperature gradient in the vertical direction, which hinders crystal growth. By using a material whose thermal emissivity is less than about 1/2 of the thermal emissivity of carbon at the crystal growth temperature, the tendency to create a reverse temperature gradient is significantly weakened, making it easier to create a vertical temperature gradient. . Therefore, crystal growth becomes easy.

Further, by using a material whose emissivity at the growth temperature is about twice or more the emissivity of quartz as a substrate stopper, thermal radiation is generated from the surroundings to the solvent and is radiated to the surroundings, so that the peripheral part from the solvent central part is radiated. Can prevent the tendency for the temperature to drop.

[Embodiment] FIG. 1 shows a II-VI group compound semiconductor crystal growth apparatus according to an embodiment of the present invention. As a representative of II-VI group compound semiconductors having Zn as a constituent element, ZnSe will be described below as an example.

A heat sink 8 made of a solid quartz rod having a small emissivity at high temperature is attached to the lower part of the growth ampoule 1.
In the internal space of the growth ampoule 1, the substrate 7 is housed so as to be mounted on the heat sink 8 and the emissivity at high temperature is much better than the emissivity of Zn which is a solvent as the substrate stopper 4 that holds down the substrate 7. More specifically, a material having an emissivity of about twice or more of quartz, for example, carbon is used. Solvent 2
Zn is used as the material, and ZnSe polycrystal synthesized at low temperature is used as the source crystal 3.

Here, the thermal characteristics of the solvent Zn, the quartz constituting the heat sink, and the carbon constituting the substrate stopper are compared as shown in the following table.

(Exact data on the emissivity of Zn in the molten state cannot be found, but it can be inferred to be about 0.1 at 1000 ° C.) The size of the crystal growth apparatus is, for example, the diameter D of the heat sink 8. Is 8 to 12 mm, and the length l1 of the heat sink 8 is about 80 to 100 m
m, length l2 of ampoule is about 70-100mm, crystal for source 3
The distance d between the substrate 7 and the substrate 7 is set to 5 to 15 mm. Also,
The growth ampoule 1 has a cylindrical shape, and the heat sink 8 has a cylindrical shape.

In the crystal growth apparatus having such a structure, the heat sink absorbs heat at the crystal growth temperature, but the emissivity is low, and therefore heat is less applied to the solvent 2. On the other hand, since the substrate stopper 4 has a high emissivity, it serves to heat the solvent 2 from the surroundings.

In use, first, the substrate 7 made of ZnSe single crystal is placed on the heat sink 8 and the substrate stopper 4 made of carbon is used.
Then, the substrate 7 and the heat sink 8 were surely brought into close contact with each other, then the source crystal 3 and the solvent Zn2 were inserted, and vacuum sealing was performed at 1 × 10 −6 Torr or less. After that, a growth ampoule was placed in a furnace in which a temperature gradient was set as shown on the right side of the figure, and crystal growth was performed. The conductivity type can be controlled by adding impurities to the Zn solvent.

Note that quartz can be used as the substrate stopper 4.

In order to compare the embodiment described above with the prior art, the growth rates of the case where quartz is used as the substrate stopper and the case where carbon according to the conventional technology is used as the heat sink 8 and the case where quartz is used according to the above-mentioned embodiment are shown. Compared.

The results obtained are shown in FIG. When carbon is used, the growth rate sometimes becomes negative (the grown crystal melts) and is unstable, and its absolute value is also limited. When the heat sink was made of quartz, the growth rate did not become negative and the value increased.

It should be noted that quartz has a higher emissivity than Zn, but when quartz is used as a substrate stopper, the film thickness distribution of the growth layer obtained on the substrate is shown by the white circles (○) in FIG. It was as shown. The sample points A, B, C, D and E were taken along one diameter as shown in the upper part of the figure. In the central portion C of the substrate, the grown film thickness is 10 μm or less, while in the peripheral portions A and E, it is 50 μm or less.
It is about μm. Thus, although the entire surface growth was obtained, the film thickness difference was as large as 5 times or more.

When carbon having a higher emissivity was used as the substrate stopper, the film thickness distribution of the growth layer obtained on the substrate was as shown by the black circles (●) in FIG. That is, the film thickness was thickest in the central portion C and gradually decreased toward the peripheral portions, but in the peripheral portions A and E, a film thickness of 40 μm or more was obtained. That is, the growth over the entire surface was obtained, and the growth layer having extremely good homogeneity was obtained.

Although the case where quartz is used as the heat sink has been described, if the material has an emissivity that is about 1/2 or less of the emissivity of carbon, a temperature gradient in the vertical direction is formed to obtain the entire surface growth on the substrate. Will be possible.

Although the case where quartz and carbon are used as the substrate stopper has been described, it is considered that suitable results can be obtained as long as the material has a sufficiently high emissivity as compared with the emissivity of the solvent Zn. For the material, a material having an emissivity equal to or higher than that of quartz is used. More preferably, a material having an emissivity about twice or more that of quartz is used. A combination of quartz and carbon may be used.

Although the present invention has been described above with reference to the embodiments, the present invention is not limited thereto. For example, various changes,
It will be apparent to those skilled in the art that modifications, combinations and the like are possible.

[Effects of the Invention] As described above, according to the present invention, when Zn is used as a solvent and a II-VI group semiconductor crystal is grown, it is easy to obtain the entire surface growth on the substrate.

Furthermore, by using a board stopper with high emissivity,
The film thickness distribution in the growth layer can be homogenized.

[Brief description of drawings]

FIG. 1 is a sectional view and a temperature distribution diagram for explaining a II-VI group semiconductor crystal growth device according to an embodiment of the present invention, and FIG. 2 is a sectional view and a temperature distribution diagram for explaining a conventional semiconductor crystal liquid phase growth device. FIG. 3 is a graph comparing the growth rates of the conventional technique and the example of the present invention, and FIG. 4 is a graph showing the film thickness distribution obtained by the example of the present invention. In the figure, 1 ... Ampule for growth 2 ... Zn solvent 3 ... Crystal for source 4 ... Stopping substrate 7 ... Substrate 8 ... Heat sink

Claims (2)

[Claims] 1. An apparatus for growing a II-VI group compound semiconductor crystal in a liquid phase on a substrate placed on a heat sink by using a solvent containing Zn as a main component with a temperature difference between the upper and lower sides, and the emissivity at the growth temperature. Characterized in that the heat sink is formed of a material that is less than about 1/2 of carbon, and the substrate stopper for closely fixing the substrate on the heat sink is formed of a material having an emissivity equal to or higher than that of quartz II- Group VI compound semiconductor crystal growth equipment. 2. A substrate stopper for stopping a substrate placed on the heat sink, comprising a substrate stopper made of a material having an emissivity at a growth temperature which is about twice or more that of quartz. Item 2. A II-VI compound semiconductor crystal growth apparatus according to Item 1.