JP2574123B2 - Crystal growth method for II-VI compound semiconductor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to crystal growth of compound semiconductors, and more particularly to II-VI using a group VI element as a solvent.
The present invention relates to a method for growing a group III compound semiconductor crystal.

[0002] II-VI compound semiconductors are used for light-emitting devices,
In particular, use as a blue light emitting element is expected.

[0003]

2. Description of the Related Art FIG. 2 shows a conventional apparatus for growing a compound semiconductor in a liquid phase. A heat sink 11 made of a material having good heat conductivity such as a solid rod of graphite or quartz is fixed to the bottom of a quartz crystal growth container 10 having an appropriate diameter (8 to 12 mmφ).

[0004] A seed crystal 12 is arranged on a heat sink 11, and is fixed on the heat sink 11 by a substrate stopper 13. The substrate stopper 13 is formed of quartz or carbon, and has a cylindrical shape having an appropriate length (5 to 15 mm).

Further, a group VI element is mainly contained in the container 10.
The solvent 14 is accommodated, and the source crystal 15 is arranged on the substrate stopper 13. Then, a weight 16 made of a solid rod such as quartz is fixed on the source crystal 15 for fixing the source crystal. The inside of the container 10 of the crystal growth apparatus having such a configuration is sealed by evacuating to a pressure of 1 × 10 ⁻⁶ torr or less.

The above crystal growth apparatus is arranged in a temperature gradient as shown in the right side of FIG. 2 to dissolve a source crystal 15 in a high temperature part in a solvent 14 and transport the source crystal 15 in the temperature gradient to form a seed. A crystal is grown on the crystal 12.

[0007]

In the above-described crystal growth apparatus, since the group VI element including the element constituting the grown crystal is used as a main solvent, the stoichiometric composition of the grown crystal is inevitable. It becomes Group VI rich and produces deviations from the stoichiometric composition. Therefore, the stoichiometric composition cannot be properly controlled, and it has been difficult to obtain crystals having desired characteristics.

It is an object of the present invention to provide a method for growing a II-VI compound semiconductor crystal using a group VI element as a solvent, wherein the stoichiometric composition of the grown crystal can be appropriately controlled. It is.

[0009]

According to the present invention, there is provided a method of growing a II-VI compound semiconductor crystal in a liquid phase using a solvent containing a group VI element as a main component, wherein the II-VI compound is used for growing the crystal. Heat-treating the source crystal of the group II-VI compound semiconductor under the vapor pressure of the group II constituent element of the semiconductor crystal ;
VI structure of II-VI compound semiconductor crystal to be grown
A method of growing a II-VI compound semiconductor crystal in a liquid phase by using a solvent containing a synthetic element and another group VI element as a main component.

[0010]

Before the source crystal is used for the liquid phase growth, the source crystal is first prepared.
By performing the heat treatment under the vapor pressure of the group II constituent element of the group I-VI compound semiconductor crystal, the composition of the source crystal itself is controlled to be group II rich.

Thereafter, when the source crystal subjected to the heat treatment is used to grow a crystal using a group VI element solvent, the deviation of the grown crystal from the stoichiometric composition can be controlled.

[0012]

1A and 1B show an apparatus for growing a II-VI group compound semiconductor crystal used in a method according to an embodiment of the present invention. As an example of a group II-VI compound semiconductor grown using a group VI element as a main solvent, ZnSe will be described below as an example.

In this embodiment, a first step of heat treatment for controlling the stoichiometric composition of the source crystal shown in FIG. 1A and a second step of liquid phase growth of the crystal shown in FIG. Process. FIG. 1A shows a configuration of a heat treatment apparatus used in the first step. The crystal II to be grown is formed at the bottom of the quartz container 20 which has an appropriate diameter at both ends, is effectively connected at the middle with a small cross-sectional area, and is sufficiently cleaned and etched inside.
A Zn material 21 that is a group constituent element is disposed as a composition control material. The Zn material 21 as a composition control material is one that has been sufficiently cleaned and etched.

Above the quartz container 20, a ZnSe source crystal 22 to be subjected to a heat treatment is arranged. The source crystal 22 is made of a ZnSe polycrystal synthesized at a temperature lower than the growth temperature of the liquid phase growth in the second step.

The space for accommodating the composition control material Zn21 and the space for accommodating the source crystal 22 are connected to each other by a space having a small cross section at a certain distance. Quartz container 2 having the above configuration
0 is evacuated and sealed.

Next, the quartz container 20 is placed in an electric furnace having a temperature gradient as shown on the left of FIG.
In the temperature gradient, T ₁ is the temperature of the high temperature part where the source crystal 22 is disposed, and T ₂ is the temperature of the low temperature part where the Zn material 21 for controlling the composition is disposed.

The amount of the composition controlling Zn material 21 is not less than the saturated molar amount in the container at the temperature T ₂ . By this heat treatment, Z at the temperature T ₂ is added to the source crystal 22.
The saturated vapor pressure of n is added, and changes the stoichiometric composition of ZnSe as the source crystal.

The temperature T of the high temperature part during this heat treatment is
_{For 1} , it is effective that the temperature is higher than the liquid phase growth temperature Tg of the crystal, and it is preferable to keep the temperature of each part constant during the heat treatment. The heat treatment time is preferably 100 hours or more.

Next, the liquid phase crystal growth in the second step will be described. FIG. 1B shows the configuration of a liquid crystal growth apparatus. A quartz crystal growth vessel 30 having an appropriate diameter (8 to 12 mmφ) and having a portion with an enlarged inner diameter at the top is prepared, and subjected to hydrofluoric acid etching, washing and vacuum baking. At the bottom of the quartz container 30, a heat sink 31 made of a material having good thermal conductivity such as graphite is stored.
Fix it. A seed crystal 32 of ZnSe single crystal is arranged on a heat sink 31.

The seed crystal 32 preferably has a (111) plane, but may have a (100) plane. The seed crystal 32 is sufficiently cleaned and etched before being housed in the container 30.

The seed crystal 32 is tightly fixed on the heat sink 31 by stopping the seed. As a seed stop,
A cylindrical member formed of a material such as quartz or carbon and having an appropriate length (5 to 15 mm) can be used. However, the seed stopper may not be used. The seed crystal 32 may be fixed by making the wall of the quartz container 30 concave.

Further, Se or Se /
A Te crystal 34 is accommodated, and a polycrystalline ZnSe source crystal 35 subjected to the heat treatment described with reference to FIG.

VI which is a constituent element of ZnSe as a solvent
When only the group element Se is used, the possibility of Te incorporation can be reduced, but the saturation solubility of ZnSe in Se is low. When Se / Te in which Se and Te are mixed is used as the solvent, the saturation solubility increases. Source crystal 35 whose composition is controlled by heat treatment
A weight made of a solid quartz rod or the like may be placed on the solid support to fix the weight.

The inside of the vessel 30 of the crystal growth apparatus having such a structure is evacuated to 1 × 10 ⁻⁶ torr or less and sealed. Next, the container 30 prepared as described above is
(B) The liquid crystal is grown in a growth furnace having a temperature gradient, as shown on the left side, by a temperature difference. In the temperature gradient, Ts is the temperature of the high temperature portion where the source crystal 35 is disposed, and Tg is the temperature of the low temperature portion where the seed crystal 32 is disposed and crystal growth occurs thereon.

In the above-described first stage heat treatment, the source crystal 35 has a temperature higher than Tg (Tg <T ₁ ) and
Heat treatment is performed under elemental vapor pressure, and the composition changes from the stoichiometric composition to a Zn-rich composition. By using this source crystal, Z in Se or Se / Te solvent 34
controlled composition of nSe (solute), yet since Tg <T _1, it is possible to control the stoichiometry of the stable crystal growth.

Next, in order to confirm the effect of the above method,
Optical of ZnSe crystals grown under different conditions, crystallography
The properties were measured. 3 and 4 show the results. The sample crystal was grown by changing the heat treatment conditions in the first step.

Heat treatment temperature of source crystal T ₁ = 1050
C., a treatment time of 100 hours, and a crystal growth temperature of 950.degree. C. under constant conditions, and heat treatment was performed under four different Zn pressure conditions using the vapor pressure P (Zn) of the composition control Zn material as a change parameter.

FIG. 3 shows the Zn pressure P (Z
The intensity of the emission peak in the blue region of photoluminescence at room temperature for n) is shown. That is, the Zn pressure dependency of the crystallinity that contributes to light emission.

It is preferable that the blue light emitting element has a high peak intensity in the blue region and does not emit light in other visible regions. When the emission intensities are compared under the same conditions, P (Zn) = 1
It becomes the maximum at 000 torr. In the case of a low Zn pressure, the light emission intensity is lower than that of a crystal grown using a source crystal that has not been heat-treated.

Further, when observing the intensity of light emitted from regions other than the blue region, the intensity becomes minimum in a crystal grown using a source crystal to which a Zn pressure of 1000 torr is applied. From these results, it can be said that a Zn pressure of about 1000 torr is the optimum Zn pressure.

FIG. 4 shows the half width of the rocking curve measured by the X-ray diffraction method (the smaller the numerical value, the better the crystallinity).
And the relationship between Zn pressure P (Zn) during heat treatment. In a good crystal having a good stoichiometric composition, the number of defects is small, so that diffracted X-ray scattering is small and the half width is narrow.

The measured half width is P (Zn) = 1000.
The minimum value is shown near torr. That is, a crystal with few defects and good crystallinity can be grown at a Zn pressure of around 1000 torr.

From these characteristic diagrams, it can be seen that the grown crystal ZnSe is
For example, when using as a blue light emitting element, the vapor pressure P (Zn) of the heat treatment of the source crystal in the first step is set to 1000 t
It is considered that the light emission characteristics are the most favorable and the crystallinity is the highest when it is near orr, and the stoichiometric composition of the grown crystal is optimal.

It is needless to say that the optimum vapor pressure P (Zn) depends on the heat treatment temperature and the crystal growth temperature, and may be appropriately selected. Furthermore, in the embodiments, ZnSe was described as an example of the type of the grown crystal, but the present invention is not limited thereto, and other II-
The present invention is also applicable to crystal growth of a group VI compound semiconductor. The solvent is not limited to Se / Te, and S, Se, Te and a mixture thereof may be used. A trace amount of impurities may be contained.

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

[0036]

As described above, according to the present invention,
In a method of growing a II-VI compound semiconductor crystal on a heat sink using a solvent containing a Group VI element as a main component, a source crystal is formed in advance of II before growing the crystal.
-Heat treatment under the vapor pressure of the group II constituent element of the group VI compound semiconductor crystal to control the composition of the source crystal itself, and to use the heat-treated source crystal to make the group VI element the main component; By growing a crystal on a substrate using the solvent thus obtained, the deviation of the grown crystal from the stoichiometric composition can be arbitrarily controlled.

[Brief description of the drawings]

FIGS. 1A and 1B are a cross-sectional view and a temperature distribution diagram of a II-VI compound semiconductor crystal growth apparatus for performing a crystal growth method according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view and a temperature distribution diagram of a liquid phase growth apparatus for explaining liquid phase growth of a semiconductor crystal according to a conventional technique.

FIG. 3 is an optical characteristic diagram of a ZnSe crystal grown under different conditions in order to verify the effect of the embodiment of the present invention.

FIG. 4 is a graph showing the measurement results of X-ray diffraction of a ZnSe crystal grown under different conditions in order to verify the effect of the embodiment of the present invention.

[Explanation of symbols]

 10, 20, 30 Quartz container 11, 31 Heat sink 12, 32 Seed crystal 14, 34 Solvent 15, 22, 35 Source crystal 21 Composition control material (Zn material)

 ──────────────────────────────────────────────────の Continuation of the front page Examiner Yoichi Gotani (56) References JP-A-4-21588 (JP, A)

Claims (2)

(57) [Claims] 1. The method of claim 1, wherein a solvent containing a Group VI element as a main component is used.
In the method of growing a group I-VI compound semiconductor crystal in a liquid phase, a step of heat-treating the source crystal of the group II-VI compound semiconductor under a vapor pressure of a group II constituent element of the group II-VI compound semiconductor crystal to be grown, Using the processed source crystal to grow a crystal II
-Group VI element and other V in group VI compound semiconductor crystal
Liquid phase growth of a II-VI compound semiconductor crystal using a solvent containing a group I element as a main component.
A method for growing a group I compound semiconductor crystal. 2. The method according to claim 1, wherein said II-VI group compound semiconductor is ZnS.
2. II-VI according to claim 1, wherein e is e, and the vapor of the group II constituent element of the II-VI compound semiconductor is Zn vapor.
A method for growing a group III compound semiconductor crystal.