JP2575948B2 - Method for growing ZnSe crystal - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for growing a semiconductor crystal, and more particularly to a crystal growth method suitable for stably and efficiently producing a high-quality ZnSe single crystal.

[Conventional technology]

FIG. 6 shows a liquid phase growth apparatus for a ZnSe semiconductor crystal. A heat sink 11 made of a material having good thermal conductivity such as carbon is provided on the bottom of a quartz crystal growth vessel 10 having an appropriate diameter.
And fix it. A polycrystalline ZnSe 12 serving as a source crystal is arranged on the upper portion of the growth vessel 10. Furthermore, ZnSe polycrystal 12
The space between the heat sink 11 is filled with the Se solvent 13.

The inside of the container 10 of the crystal growth apparatus having such a configuration is evacuated to a predetermined pressure and sealed. In the prior art, when the crystal growth apparatus of FIG. 6 is arranged in a temperature gradient as shown on the right side of FIG. 6, the source crystal 12 in the high temperature part (Ts) dissolves to the saturation solubility and the low temperature part (Tg) Spread toward.
Since the temperature of the low-temperature portion below the solvent is lower than that of the vicinity of the source crystal 12, ZnSe becomes supersaturated in the solvent 13, and ZnSe crystal grows on the heat sink 11 in bulk.

[Problems to be solved by the invention]

In such a liquid phase growth apparatus, the solvent is Zn.
The constituent element of Se, Zn or Se, can be considered.
As shown by the solubility curves of ZnSe for various solvents in the figure, when Zn is used as the solvent, the solubility of ZnSe is extremely low, and it is difficult to obtain bulk crystals. When Se is used as the solvent as shown in FIG. 6, the vapor pressure is very high as shown in the temperature dependence of the vapor pressure of various solvents in FIG. 3, and the temperature is increased to increase the solubility. Then, there is a danger that the vapor pressure will suddenly increase and the quartz container 10 will explode. If a device for applying pressure from the outside of the container 10 is prepared as a countermeasure, a large-scale and complicated crystal growth device as a whole is not preferable as a production device. Furthermore, as shown in the density comparison between ZnSe, Se and Te in FIG.
When 0) and ZnSe (dotted line) are compared in terms of specific gravity (density), ZnSe> Se, and during the growth process, a part of the source crystal may fall or a crystal that has nucleated during diffusion in a solvent may be generated. There is a problem that growth of a homogeneous bulk single crystal is hindered due to dropping on a crystal growth surface.

An object of the present invention is to solve the above-mentioned problems and to provide a high-quality ZnSe
An object of the present invention is to provide a crystal growth method for stably and efficiently producing a single crystal.

[Means for solving the problem]

The method for growing a ZnSe single crystal according to the present invention includes the steps of:
In a method of dissolving a source crystal of ZnSe in a solvent and growing and crystallizing ZnSe from the solvent, the upper portion of the crystal growth container is provided with a step having a larger diameter than the lower portion, and an ingot-shaped ZnSe is formed at the step. A source crystal is arranged, and a heat sink having a flat and mirror-finished surface for depositing a growth crystal with a good heat conductive material different from the growth container is provided at the lower part of the growth container, and the growth crystal has a thickness of 400 to 800 nm. ZnSe in the wavelength range of
A mixed solvent of Se and Te selected from a mixture ratio of Se in the mixed solution within a range of 30 to 60 mol% so as to emit a single peak of band edge emission of light is disposed between the heat sink and the source crystal, A predetermined temperature gradient is provided in the solvent so that the source crystal side becomes a high temperature portion of the temperature gradient, and a ZnSe single crystal is grown in the low temperature portion of the temperature gradient.

[Action]

As shown in the solubility curves of ZnSe in various solvents in FIG. 2, the solubility of Zn as a solvent in ZnSe is very high. Therefore, when a mixed solution with Se is used, the crystal growth of ZnSe crystals is faster than in the Se solvent. Become.

Further, as shown in the vapor pressure characteristics of the various solvents in FIG. 3, since the vapor pressure of Te is low, the vapor pressure can be made lower than that of the Se solvent by using a mixed solution with Se.

Further, as shown in the density comparison of ZnSe, Se and Te in FIG. 4, a mixture ratio of Se (the intersection of the solid line and the dotted line, Se60: Te4
0) Below (to the right of the intersection), the specific gravity (density) of the Se-Te mixed solution (solid line) exceeds that of ZnSe (dotted line), and therefore, source crystals and crystal growth nuclei grow during the ZnSe crystal growth process. No more falling on the surface.

Then, by selecting the ratio of Se in the solution to substantially 30 to 60 mol%, a ZnSe semiconductor device which emits pure blue spectrum light can be obtained as described in detail later.

〔Example〕

Hereinafter, a method according to an embodiment of the present invention will be described with reference to FIG.

In FIG. 1, a heat sink 11 made of a material having good thermal conductivity such as carbon is stored at the bottom of a quartz crystal growth vessel 10 having an appropriate diameter, and a notch is formed at a predetermined position of the growth vessel 10. The heat sink 11 is fixed by leverage. The surface of the heat sink 11 where crystals are deposited is flat and mirror-finished. The heat sink 11 is formed of, for example, cylindrical high-purity carbon having a diameter of 8 to 20 mm and a length of 5 to 200 mm. The upper portion of the quartz growth vessel 10 is made larger in diameter than the lower portion as shown in the figure, and this can be made by connecting a small-diameter quartz tube and a large-diameter quartz tube. An ingot-like polycrystalline ZnSe 12 serving as a source crystal is arranged on an upper portion of a quartz growth vessel 10. ZnSe polycrystal
The diameter of the growth vessel 10 is made larger than the small diameter of the growth vessel 10 and smaller than the large diameter, and is fixed using the step between the upper and lower parts of the growth vessel 10. Furthermore, the space between the ZnSe polycrystal 12 and the heat sink 11
It is filled with a Se—Te mixed solvent 14.

The inside of the container 10 of the crystal growth apparatus having such a configuration,
Evacuate to a degree of vacuum higher than 2 × 10 ⁻⁶ Torr and seal. When the above crystal growth apparatus is placed in a furnace having a temperature gradient having a source crystal part temperature Ts and a crystal growth part temperature Tg as shown on the right side of FIG. 1, the source crystal 12 in the high temperature part becomes solvent until the solubility becomes saturated. It is dissolved in and diffused and transported through the temperature gradient, and the low temperature part (temperature Tg) of the heat sink 11 becomes a supersaturated solution. Therefore, a single crystal of ZnSe is deposited and grown on the mirror surface of the heat sink 11.

Under the conditions of a growth temperature Tg = 950 ° C. and a temperature gradient ΔT = 10 ° C./cm, crystal growth was attempted by changing the ratio of Se in the solvent 14.
At a mixing ratio of Se of 0 to 60 mol%, a bulk ZnSe single crystal having a convex growth front was obtained.
If it exceeds mol%, polycrystallization of the grown crystal occurs. This is considered to be due to the decrease in the solubility of ZnSe and the reversal of the specific gravity of the solvent and ZnSe as the Se ratio of the solvent increases. In addition, as the Se content increases, the vapor pressure also increases, increasing the risk of explosion. Considering the pressure resistance of the quartz container 10, the pressure (steam pressure) in the container 10 is desirably 10 atm or less, and from this aspect, the Se ratio of the solvent is substantially 60 mol.
% Is considered to be the upper limit.

FIG. 5 shows the measurement results of cathodoluminescence spectra of crystals grown under different Se—Te solvent mixing ratios. In FIG. 5, (a), (b), (c),
(D) and (e) show that the ratio of Se—Te in the solvent 14 is 6
0:40, 45:55, 30:70, 10:90, 0: 100 (mol%).

When the Se ratio is 0 to 10 mol% (FIGS. 5 (e) to 5 (d)), the peak at the band edge is shifted to the longer wavelength side and has a subpeak at a longer wavelength side. .
This is because the grown crystal is a mixed crystal system of ZnSe _1-X Te _X ,
Further, it is considered that a level in the gap is generated. The mixing ratio of Se is 30 mol% or more (Fig. 5 (c) ~
In the case of (a)), only a single peak, which is considered to be the intrinsic band edge emission of ZnSe, disappeared, and emission including a deep level disappeared, and pure blue emission was obtained. In the EPMA (EDS) analysis, when the Se ratio was 0% and 10%, the Te concentrations were 2.8 at% and 0.6 at%, respectively. However, when the Se ratio was 30 mol%, Te was not detected. . Therefore, it can be considered that a ZnSe single crystal that can be practically used as a light emitting element is obtained when the ratio of Se is substantially 30 mol% or more.

From the above, a practical ZnSe single crystal can be obtained, and a bulk single crystal can be grown, in a Se-Te mixed solution.
The ratio of Se is preferably substantially 30 to 60 mol%, and in particular, 30 to 45 mol% has been found to be optimal from the viewpoint of the pressure in the container and the stability of crystal growth.

Although the present invention has been described with reference to the embodiments, the present invention is not limited to these embodiments. For example, it will be apparent to those skilled in the art that various modifications, improvements, combinations, and the like can be made.

〔The invention's effect〕

As described above, according to the present invention, a mixed solution of Se and Te is used as a solvent for dissolving and dispersing ZnSe, and the ratio of Se in the mixed solution is substantially set to 30 to 60 mol%, whereby crystal The crystal growth rate increases.

 Since the vapor pressure can be reduced, there is no danger of explosion.

Furthermore, the specific gravity of the Se—Te mixed solution exceeds the specific gravity of ZnSe, and therefore, during the growth process, the source crystal and the crystal growth nucleus do not fall on the growth surface, so that a bulk single crystal can be obtained.

Then, by selecting the ratio of Se in the solution to be substantially 30 mol% or more, a practical ZnSe semiconductor device that emits pure blue spectrum can be obtained.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing a growth apparatus for performing a crystal growth method according to an embodiment of the present invention, together with a temperature gradient. FIG. 2 is a view showing the mole fraction of ZnSe in various saturated solutions showing the solubility of ZnSe in various solvents. Graph, FIG. 3 is a graph showing the temperature dependence of the vapor pressure of various solvents, FIG. 4 is a graph showing a density comparison between ZnSe, Se and Te, and FIG. 5 is a Se-Te solvent having a different mixing ratio. Zn grown in
Cathodoluminescence spectrum of Se crystal. FIG. 6 is a sectional view of a ZnSe crystal growth apparatus. In the figure, 10: crystal growth container 11: heat sink 12: ZnSe polycrystal (source crystal) 13: Se solvent 14: Se-Te mixed solvent

Continuation of the front page (72) Inventor Yasuo Okuno 2-32-2 Fujigaoka, Midori-ku, Yokohama-shi, Kanagawa A302 (56) References JP-B-60-37076 (JP, B2)

Claims (1)

(57) [Claims] 1. A method for dissolving a source crystal of ZnSe in a solvent in a crystal growth vessel and growing and growing ZnSe from the solvent, wherein an upper portion of the crystal growth container is made larger in diameter than a lower portion and a step is formed. An ingot-shaped ZnSe source crystal is disposed at the step, and a heat sink having a flat and mirror-finished surface for depositing the grown crystal with a good thermal conductive material different from the growth container is provided at the lower part of the growth container. In the mixed solution, the grown crystal emits a single peak of ZnSe band edge emission in a wavelength range of 400 to 800 nm.
A mixed solvent of Se and Te selected from a mixing ratio of 30 to 60 mol% is arranged between the heat sink and the source crystal, and the solvent is mixed with the solvent such that the source crystal side becomes a high temperature portion of a temperature gradient. A method for growing a ZnSe single crystal, wherein a predetermined temperature gradient is provided, and a ZnSe single crystal is grown in a low temperature portion of the temperature gradient.