JP3215798B2 - Method for growing II-VI compound semiconductor crystal - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to ZnSe, Zn
The present invention relates to a method for growing a II-VI compound semiconductor crystal such as S, CdTe, and CdS.

[0002]

2. Description of the Related Art II-VI compound semiconductor crystal growth methods are broadly classified into four types: melt growth method, solid phase growth method, solution growth method, and vapor phase growth method. Among them, the vapor phase growth method includes a sublimation method (PVT method: Physical VapourTransport method) in which crystal growth is performed by utilizing the sublimation and coagulation of the raw material, and a method in which a halogen is generated by reacting a halogen with a raw material. Chemical transport method (CVT: Chemical Vapor Trans
port method).

As for the growth of ZnSe crystal by the PVT method, 5 g of ZnSe powder and a ZnSe single crystal as a seed crystal are sealed in an ampoule as described in J. Crystal Growth 94 (1989) pp. 1-5. Heat the ampoule to ZnS
e By maintaining the temperature on the powder side at about 1080 ° C. and the temperature on the seed crystal side at about 1070 ° C., ZnSe is deposited on the seed crystal.
A crystal was grown. Thereafter, it is reported that the specific resistance could be reduced to about 0.2 Ωcm by subjecting the grown ZnSe crystal to heat treatment in a Zn melt.

As for ZnSe crystal growth by the CVT method, J. Crystal Growth 91 (1988) pp. 639-646.
In a ZnSe powder in a quartz tube, in addition to the ZnSe single crystal as a seed crystal, ampoule volume 1 cm ³ per 5.4mg
Was sealed in an ampoule, and the ampoule was heated to maintain the temperature on the ZnSe powder side at 850 ° C. and the temperature on the seed crystal side at 840 ° C., thereby growing a ZnSe crystal on the seed crystal. Since this crystal contains about 100 to 200 ppm of iodine,
It has been reported that by performing heat treatment in a Zn melt for 130 hours, the specific resistance could be reduced by 0.03 Ωcm.

[0005]

As described above, a ZnSe crystal having a specific resistance of about 0.03 Ωcm can be grown by the CVT method. However, in order to grow a large crystal, it is necessary to use a large ampoule. This method tends to generate gas convection in the ampoule, and if you use a large ampoule,
Since the tendency further increases, crystal growth could not be performed in a stable state, and single crystal could not be grown.

On the other hand, in order to suppress convection in the ampoule, a lattice plate or a bundle of thin tubes for suppressing generation of convection of gas is arranged in an intermediate region between the raw material filling region and the crystal growth region in the ampoule. (Japanese Patent Laid-Open No. 5-489)
In order to grow a large crystal in this method as well, it is necessary to enlarge the crystal growth region where the above-mentioned convection suppressing means does not exist. Convection occurred, making it difficult to grow single crystals.

[0007] The gas convection is natural convection induced by a temperature difference in the ampoule. Generally, the strength of the natural convection is defined by the following Grashof number (Gr). When the ampoule increases, R in the equation increases and the Grashof number increases, so that the gas convection increases. Gr = gβ _T R ³ ΔT ρ ² / μ ² where g: gravity β _T : body expansion coefficient R: ampule diameter ΔT: temperature difference in the ampoule ρ: gas density μ: viscosity coefficient

Here, if the gas density can be reduced by lowering the internal pressure of the ampoule, the number of Grashof can be reduced. Therefore, in order to grow a large crystal, even if the inner diameter of the ampoule is increased, the number of Grashof is too large. Therefore, crystal growth is possible without natural convection. However, in general, in the case of ZnSe crystal growth by the CVT method using iodine as a transport medium, the internal pressure is as high as several atmospheres, and natural convection is easily generated. Is a problem.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to solve the above-mentioned drawbacks when growing a crystal of a II-VI compound semiconductor by a vapor phase method, and to provide a halogen-doped low-pressure growth method.

[0010]

SUMMARY OF THE INVENTION The present invention relates to a method for preparing II-
In the method of growing a group VI compound semiconductor crystal, a growth chamber for growing a crystal and a reservoir containing a halide of a group II element constituting the grown crystal are connected by a thin tube, and a II-VI compound raw material is connected to the growth chamber. It is characterized in that polycrystals are arranged and crystal growth is performed while controlling the heating temperature of the reservoir
This is a method for growing a II-VI compound semiconductor crystal.

According to the present invention, there is provided the above-mentioned II-VI compound semiconductor crystal, wherein the halide of the group II element is disposed at a lowest temperature portion of the reservoir, and the lowest temperature portion is provided in a uniform temperature zone. Is the way.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Group II-VI compound semiconductor crystals grown in the present invention are ZnSe, ZnS, ZnTe, CdT.
e, CdS, CdSe, and the like.
As halides of group elements, ZnCl ₂ , Zn
I ₂ , CdCl ₂ , CdI _{2 and the} like can be mentioned. The present invention also relates to a ternary system II-VI such as ZnSSe.
It can be effectively applied to the growth of group III compound semiconductor crystals.

[0013] In the present invention, II placed in the reservoir
By placing the halide of the group element at the lowest temperature part in the reservoir and providing a sootherotropic zone at this lowest temperature part,
The reproducibility of crystal growth can be further improved. In the case of ZnSe crystal growth, the temperature of the crystal growth part is preferably about 950 to 1150 ° C.

In the present invention, it is desirable that the junction between the growth chamber and the reservoir has a smaller inner diameter than the inner diameters of the growth chamber and the reservoir. The inner diameter of the thin tube is preferably about 10% of the inner diameter of the growth chamber, and the cross-sectional area is preferably about 1% of the growth chamber. Generally, since the heating temperature of the reservoir is set lower than that of the growth chamber, there is a possibility that the source polycrystal leaks into the reservoir and precipitates. A large amount of leakage to the reservoir side is prevented, and the polycrystalline raw material is prevented from condensing inside the reservoir.

FIG. 1 is a conceptual diagram showing an example of a growth apparatus for carrying out the present invention, and shows a case where a ZnSe single crystal is grown. The growth chamber and the reservoir are connected by a thin tube, and a ZnSe polycrystal is disposed on the reservoir side of the growth chamber, and the conical tip becomes a crystal growth part. ZnCl ₂ is disposed at the rear end of the reservoir. This rear end is desirably level tropical at the lowest temperature of the reservoir.

[0016]

【Example】

[Embodiment 1] Using the apparatus shown in FIG.
A quartz tube having a length of 20 cm and a length of 20 cm was used, and the tip was sharpened to form a crystal growth portion. The reservoir has an inner diameter of 12 mm and a length of 20 cm
The growth chamber and the reservoir were connected to each other using a small tube having a length of 10 cm and an inner diameter of 2 mm. Then, 10 g of a ZnSe polycrystalline material is placed on the reservoir side of the growth chamber,
About 0.1 g of ZnCl ₂ was placed at the rear end of the reservoir.

The ampoule is placed in a two-zone horizontal tubular furnace, the temperature of the crystal growth section is set to 1000 ° C., the temperature of the ZnSe polycrystalline raw material is set to 1020 ° C., and the ZnC
The heating temperature of the l ₂ was adjusted to four different temperatures shown in Table 1, Z
Reservoir temperature ± 1 ° C. around 10 cm around nCl ₂
, And a ZnSe single crystal was grown. In addition,
Table 1 shows the ZnCl ₂ vapor pressure inside the reservoir and the growth rate at each temperature. The period of crystal growth is 1
0 days.

[0018]

[Table 1]

The obtained ZnSe crystal is kept at a low temperature of 77 K, excited by irradiating He-Cd laser light having a wavelength of 325 nm, and measured by PL (photoluminescence) spectrum of light emitted at the time of downward transition. 2 is shown. FIG. 2B shows the case where the vapor pressure of ZnCl ₂ is 0.1 Torr.
r and (c) were grown at 10 Torr and (d) were grown at 100 Torr.
Light emission was observed in the vicinity. FIG. 3A shows a case where no vapor pressure is applied. This light emission is generally called SA (self-active) light emission and appears when impurities are doped. Accordingly, it can be seen that Cl doping was succeeded at a lower pressure than that of the CVT method using ZnCl ₂ disposed in the reservoir.

[Embodiment 2] In the embodiment 1, the ZnCl
₂ was replaced with ZnI ₂ , and the temperature at the rear end of the reservoir, the ZnI ₂ vapor pressure in the reservoir, and the growth rate were adjusted as shown in Table 2, except that ZnI ₂ was used.
A Se single crystal was grown. 2K of the obtained ZnSe crystal
FIG. 3 shows the result of the measurement of the PL spectrum at the time. FIG. 3B shows the case where the ZnI ₂ vapor pressure is 0.1 Torr and FIG.
Is grown at 1 Torr, and SA emission is observed at around 2.0 eV in any of the crystals, indicating that the doping of I was successful at a lower pressure than in the CVT method.
FIG. 3A shows a case where no vapor pressure is applied.

[0021]

[Table 2]

[0022]

According to the present invention, by employing the above structure, halogen is successfully doped when a II-VI compound semiconductor crystal is grown by sublimation.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram of one example of a crystal growth apparatus used in the present invention.

FIG. 2 is a graph showing the intensity of photon energy of a ZnSe crystal grown in Example 1 while changing the vapor pressure of ZnCl ₂ .

FIG. 3 is a graph showing the intensity of photon energy of a ZnSe crystal grown in Example 2 while changing the ZnI ₂ vapor pressure.

──────────────────────────────────────────────────続 き Continued on the front page (72) Katsumi Mochizuki 22-12 Yayoi-machi, Yagiyama, Taishiro-ku, Sendai City, Miyagi Prefecture (56) References JP-A-2-239179 (JP, A) JP-A-60-255693 ( JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) C30B 1/00-35/00 CA (STN) JICST file (JOIS)

Claims (2)

(57) [Claims] 1. A method for growing a group II-VI compound semiconductor crystal by a gas phase method, wherein a growth chamber for growing a crystal and a reservoir containing a halide of a group II element constituting the grown crystal are connected by a thin tube. A method for growing a group II-VI compound semiconductor crystal, comprising: placing a group II-VI compound raw material polycrystal in a growth chamber; and growing the crystal while controlling the heating temperature of the reservoir. 2. The group II-VI compound semiconductor crystal according to claim 1, wherein the halide of the group II element is arranged at a lowest temperature part of the reservoir, and the lowest temperature part is provided in a uniform tropical zone. Growth method.