JP3193440B2 - Method for producing I-III-VI group 2 semiconductor single crystal - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to solidification from a melt.
A method for producing a group I-III-VI2 semiconductor single crystal,
An object of the present invention is to provide a nonlinear optical material, a substrate material for a light emitting diode and a laser diode, and a material for a blue light emitting device.

[0002]

_2. Description of the Related Art I-III-VI group II semiconductors have a tetragonal chalcopyrite type crystal structure, the bandgap corresponds to the visible light range from red to purple, and the light transmission wavelength range is red. It is known that it has a feature that it is very wide from the outside to the visible light region, and has a large nonlinear optical constant and a large birefringence. From these characteristics, various uses such as a light emitting element and a nonlinear optical element are considered, and development to various devices is expected.

FIG. 1 shows the relationship between the forbidden band width Eg and the lattice constant a of Group I-III-VI Group ₂ compounds and their solid solutions. As can be seen from the figure, by controlling the composition of the solid solution,
It is possible to manufacture a semiconductor single crystal having an arbitrary band gap.

Conventionally, these semiconductor single crystals have been manufactured by the following methods:
They are roughly classified into two types: a chemical vapor transport method using iodine and a method of growing from a melt (for example, the Bridgman method).

The former method is characterized in that it can be grown at a low temperature and a single crystal with high integrity can be obtained. However, there are problems that it is difficult to obtain a large crystal and that iodine as a transport agent is mixed into the crystal.

On the other hand, in the latter case, in particular, the Bridgman method
Compared with the chemical vapor transport method using iodine, large crystals can be obtained without concern about iodine contamination. However, the I-III-VI group ₂ semiconductors have completely different coefficients of thermal expansion between the a-axis and the c-axis of the crystal. That is, the a-axis has a positive thermal expansion coefficient and the c-axis has a negative thermal expansion coefficient. Therefore, when the sample is cooled from the melt, if crystals including the c-axis in the radial direction of the growth tube are included,
The growth tube is destroyed due to the difference in the thermal expansion coefficient between the growth tube and the crystal, or strain or crack is generated in the crystal due to internal stress. To solve this problem, a carbon film is applied to the inside of the growth tube to prevent the growth tube from being destroyed, or a single crystal grown by a double tube structure that encloses the growth tube in a slightly larger quartz tube. A method has been proposed for preventing oxidation and contamination of the material.

However, when observing the AgGaS ₂ single crystal obtained by the Bridgman method, the whole is not a single crystal but a polycrystal in which small crystal grains are gathered.
It was extremely difficult to obtain a large, high-quality single crystal.
Further, the obtained single crystal does not have a certain size, and there is a very large problem in that it is not industrially mass-producible.

[0008]

As a method of solving the above-mentioned problems, there is a method using a so-called seed crystal, which is capable of obtaining a large and high-quality single crystal without distortion or cracking, that is, a so-called seed crystal. Literature RSFeigelson and RKR
oute, “Recent developments in the growth ofchalco
pyrite crystala for nonlinear infrared application
s ", OPTICALENGINEERING, 26 (2) 113-119 (1987)).
This method attempts to grow a single crystal in the same direction as the c-axis of the seed crystal, but has the following difficult problem.

First, it is necessary to cut out and prepare a single crystal in the c-axis direction as a seed crystal, which takes time and effort to manufacture, and sometimes dissolves the entire seed crystal. It is necessary to prepare a relatively large seed crystal in order to fuse with the raw material. Furthermore, the difficulty of the seed crystal method is that considerable precision and technology are required for handling operations and temperature control.

As a second problem, in the obtained single crystal, there is a case where a considerable change in composition is observed from the growth start side to the growth end side. In such a state, the optical characteristics may be adversely affected. The change in the composition will be described taking the case of an AgGaS ₂ compound as an example. The stoichiometric composition of the AgGaS ₂ compound is Ag ₂
When the S content is 50%, the phase diagram of the quasi-binary system of Ag ₂ S—Ga ₂ S ₃ (see FIG. 2: References RSFeigelson and RKRout)
e, OPTICAL ENGINEERING, 26 (2) 113-119 (1987)). However, this composition is
It does not match the harmonic melt composition (point B) of the aS ₂ compound.
Therefore, it can be seen that a slight change in the composition occurs in the crystal grown from the stoichiometric composition (point A). Apart from this, when performing crystal growth from the harmonic melt composition,
The adjacent Ga ₂ S ₃ phase is mixed as a precipitate during the cooling process, and a homogeneous single crystal having a stoichiometric composition cannot be obtained. As a method of removing the precipitate, a solution is achieved by means of isothermal heat treatment of the obtained single crystal and Ag ₂ S. However, it is difficult to completely remove the precipitate even by performing the heat treatment by such a method.

An object of the present invention is to solve the above-mentioned problems from a systematic experiment and to use a simple method that does not rely on a seed crystal method or an isothermal heat treatment to obtain a large and high-quality I-III-VI.
_An object of the present invention is to provide a manufacturing method for obtaining a Group ₂ semiconductor single crystal.

[Means for Solving the Problems]

The present invention, I-III-VI ₂ group semiconductor (I Group is A
g, III-group is one or one or more elements of Al and Ga, and VI ₂ group in the case of producing a single crystal by solidifying the one or one or more elements) of S and Se from melt A method of manufacturing a semiconductor single crystal, characterized in that a growth tube is divided into a “single crystal growth portion” and a “composition gradient portion”, a constriction is provided therebetween, and composition control is further performed. Among a plurality of crystal nuclei naturally formed in the “composition gradient portion”, only crystal nuclei having an orientation close to the c-axis are selected in the “constriction” provided in the middle of the growth tube. The greatest aim of the present invention is to preferentially grow large crystals in the “single crystal growth part”.
In other words, a “neck” having an arbitrary size and shape in the growth tube
In this case, a single crystal can be produced without using a seed crystal.

Further, I-III-VI group ₂ semiconductors (I-group is Ag,
Group III is one or more elements of Al and Ga, and Group VI ₂ is one or more elements of S and Se)
Has the property that during the crystal growth, the composition changes from a non-stoichiometric composition to a stoichiometric composition from the start side to the end side of the growth, but the composition is just the stoichiometric composition. It was considered that a single crystal free of precipitates could be obtained by providing a "neck" at the position where the transition to.

The present invention, I group elements Ag, III group elements Al and Ga either one or one or more, and VI ₂
In the case of manufacturing a group I-III-VI group ₂ semiconductor single crystal in which the group III element is one or more elements of S and Se, in the middle of the composition gradient part of the growth tube and the single crystal growth part. At the position where the composition just transitions to the stoichiometric composition,
A "neck" having an inner diameter of 2 mm or more and 10 mm or less, a length of 0 cm or more and 3 cm or less, an opening angle to the growth start end side of 30 ° or more and 120 ° or less, and an opening angle to the growth end end side of 120 ° or less is provided. A method for producing a group I-III-VI group ₂ semiconductor single crystal, characterized in that the growth rate is 0.1 cm / day to 5 cm / day.

Further, the present invention provides a method for manufacturing an AgGaS ₂ semiconductor single crystal, which is located between a composition gradient portion and a single crystal growth portion of a growth tube and at a position where the composition shifts to a stoichiometric composition. The inner diameter is 2 mm or more and 10 mm or less, the length is 0 cm or more and 3 cm or less, and the opening angle to the growth start end is 30 ° or more and 120 ° or more.
Provide a “constriction” of お よ び or less and the opening angle to the growth end side is 120 ゜ or less, and the growth rate is 0.4 cm / day to 2 cm.
/ Day, a method for producing an AgGaS ₂ semiconductor single crystal.

In short, according to the above-mentioned means, it is a simple method not found in a method such as a seed crystal or heat treatment, and a very large and high-quality I-III-VI group ₂ semiconductor single crystal can be produced very easily. It became possible.

[0017]

FIG. 3 shows the shape of a growth tube having a "neck" according to the present invention. That is, the growth tube is composed of, from the bottom, a “composition gradient” for controlling the composition, a “neck” for selecting a single crystal nucleus, and a “single crystal growth part”. In the figure, Lb and Lu are the lengths from the bottom of the “constriction” to the growth start end (the length of the “composition gradient”) and the tops of the “constriction” to the growth end end, respectively, sandwiching the “constriction”. The length (the length of the “single crystal growth portion”) is shown. Db and Du
Indicates the inner diameters of the “composition gradient portion” and the “single crystal growth portion”, respectively. Do and Lo indicate the inner diameter and length of the "neck", respectively. Further, θb indicates the opening angle from “constriction” to the lower “composition gradient portion”, and θu indicates the opening angle from “constriction” to the upper “single crystal growth portion”. A single crystal was grown from the melt using a growth tube having such a shape, and a large single crystal having a homogeneous stoichiometric composition could be obtained from the "neck" on the crystal growth end side.

The optimum conditions for producing these single crystals have been found through various experiments to be limited to the following ranges. Length Lb from the bottom of "constriction" to the start of growth
Is limited as a relative value with respect to the volume of the raw material. To obtain a large single crystal of good quality, the volume of the Lb region must be
Must be at least 85%. The inner diameter Do of the "constriction" depends on the size of Db and Du, but 2 mm or more and 10 mm
The following ranges are optimal. The length Lo of the "neck" depends on the mixing ratio of the raw materials, but is preferably 3 cm or less. The opening angle θb from “constriction” to “composition gradient” is 30 ° or more12
0 ° or less, opening angle θu from “constriction” to “single crystal growth part” is 120 ° or less, and growth rate is 0.1 cm / day or more and 5 cm / day.
Days or less is appropriate, especially for AgGaS2, 0.4 cm /
More than one day and less than 2 cm / day was optimal.

Next, basic concepts important in establishing the technology of the present invention will be described with reference to FIGS. As can be seen from FIG. 2, the region in which the AgGaS ₂ compound is present has a high temperature (about 720 ° C.).
℃ or more), the stoichiometric composition (Ag ₂ S content 50%,
(Ga ₂ S ₃ content 50%) to the Ga ₂ S ₃ side by about 2% at the maximum. The harmonic melting point of the AgGaS ₂ compound corresponds to point B (Ga ₂ S ₃ content 51%), and the melting point of the stoichiometric composition on the liquidus corresponds to point A (Ga ₂ S ₃ content 50%). I have. That is, a state diagram in which a part of FIG.
), The harmonic melt composition (Point B) of the AgGaS ₂ compound is different from the stoichiometric composition (Point A). Therefore, when the melt of AgGaS ₂ is cooled from the stoichiometric composition, first, at point A, the liquid phase (L) and the two phases of AgGaS ₂ coexist, and AgGaS ₂ crystallizes slightly in the liquid phase. Therefore, the composition of the solid phase at this temperature does not become a stoichiometric composition as can be seen from the figure, but becomes a harmonic melt composition at point B.

Next, the content of Ga ₂ S ₃ from 50% melt to 51%
When the solid phase is crystallized, the composition of the remaining melt naturally shifts slightly from the point A to the Ag ₂ S side (A ₁ −B ₁ ).
Will do. When the composition of the melt shifts to the Ag ₂ S side, the melting point slightly lowers. When the melting point decreases, the composition of the solid phase to be crystallized shifts slightly to the Ag ₂ S side from the point B (A ₂ −B ₂ ). By repeating this, the composition of the melt is further shifted from the point A to the Ag ₂ S side, and the composition to be crystallized also changes from B to B ₁ , B ₂ , B along the curve between BC.
It was considered to slide into shifted to C through B _3. FIG. 5 shows how this change corresponds to actual crystal growth.
The sketch is as shown in (a). The obtained single crystal is moved from the growth start side (point B) to the end side (C
A slight change in composition toward (point) is observed. The problem here is that the AgGaS ₂ solid phase having the composition of the crystallized B point and the composition between the B point and the C point is a coexisting phase of AgGaS ₂ and Ag ₂ Ga ₂₀ S ₃₁ due to a decrease in temperature. Phase transition. That is, A in the AgGaS ₂ matrix
is that g ₂ Ga ₂₀ S ₃₁ are mixed as a precipitate, the precipitate scatter light, and significantly impairs causes the transmittance of the single crystal. Therefore, when observing the obtained single crystal, the closer to the growth start side (the region B to B _{2 in} FIG.
Crystals become cloudy due to the large amount of ₂ Ga ₂₀ S ₃₁ precipitates,
Yuki becomes less as the deposit closer to the end side, increasing gradually transparency (B ₂ .about.B ₃ regions in FIG. 5 (A)). Further, in the portion reaching the point C near the end portion, that is, when the ratio of the composition gradient portion to the total raw material volume becomes 85%,
Completely transparent without any precipitates. The regions C to D, that is, the transparent portions having the stoichiometric composition,
A constant volume (about 15
%) Could be demonstrated by many experimental results. Judging from this, it is possible to increase the volume of the stoichiometric composition as the length in the growth direction becomes longer, and it will be possible to produce a high-quality single crystal of any size. Thought. However, as a result of the experiment I-III-
For VI ₂ group semiconductor crystal, or by increasing the pipe diameter of the growth tubes, or simply by increasing the length is not grow large single crystal nucleus, also has also been found that it is impossible to make a large single crystal.

The present inventors have conducted a number of experiments to overcome these drawbacks. As a result, a method of providing a "neck" in the middle of a growth tube as a method for preferentially growing a single nucleus is extremely promising. Was found. However, it has also been found that the growth of a uniform and large single crystal depends on where the "constriction" is provided in the growth tube, that is, how much Lb is taken and how much the raw material is introduced into the growth tube. For example, as shown in FIG. 5A, in the case where a “constriction” is provided near the growth start end (the length Lb of the “composition-graded portion” is small), even if a large single crystal is taken, the composition changes in the single crystal. Occurs, and precipitates are mixed, cracks are easily formed, and even a satisfactory single crystal cannot be obtained. Note that the hatched portions in FIGS. 5A and 5C are stoichiometric compositions, and the lower portions have different compositions.

In short, it has been found that not only "constriction" but also Lb is an important factor. FIG. 5 (c) shows that it is effective to provide a "neck" at an optimum position Lb where the composition shifts from the harmonic melt composition to the stoichiometric composition during the crystal growth. According to this method, a homogeneous single crystal having a stoichiometric composition without a precipitate was obtained on the growth termination end side (C to D) of the “neck”.

A first important point of the present invention is that the single crystal plays a role of separating a high-quality portion containing no precipitate and an opaque portion containing a precipitate in the above-described “constriction”. Moreover, this is a very effective means for obtaining a large single crystal.

Next, the relationship between the "neck" and the stoichiometric composition and the shape of the "neck" will be described. FIG.
(A) to (d) show the relationship between "constriction" and the stoichiometric composition (shaded portion). In the figure, AB indicates the boundary between the stoichiometric composition and the non-stoichiometric composition in which the composition changes.

Now, it is not easy to accurately set the position of the "constriction" as shown in FIG. 6A, and it is extremely difficult due to subtle differences in the amount, composition, and growth conditions of the raw materials. For example, as shown in FIG. 6 (a), when the transition position to the stoichiometric composition (the lower limit position AB of the oblique line) is above the "constriction", a single crystal is formed due to a composition change. Nuclear growth becomes difficult. This problem can be solved by providing a "constriction" sufficiently above the position expected to shift to the stoichiometric composition as shown in FIG. However, if the transition position is too low, the volume of the necessary portion above the “constriction” becomes small, and the problem of a low yield of the single crystal occurs. As can be seen from these descriptions, it is technically extremely difficult to match the position of the “constriction” to the composition transition position. Therefore, in order to solve this problem, as shown in FIG.
It has been found that a method of giving a suitable "length" Lo is effective. In this case, the error of the position at which the transition from the non-stoichiometric composition to the stoichiometric composition is ± 1.5 cm, and L
It is sufficient that o is 0 cm or more and 3 cm or less. Within this range, the crystal growth is not impaired, but if it is 3 cm or more, it may be a factor for inducing new crystal nuclei or deteriorating the single crystal yield. By introducing this method, even when there is a slight change in conditions, the transition from the non-stoichiometric composition to the stoichiometric composition can be reliably and easily stored in the middle of the "neck". Another feature of the present invention is that a single crystal nucleus can be grown.

In the case where a single crystal nucleus is selected from among the polycrystals of the "composition-graded portion" by utilizing the "constriction" from the "composition-graded portion", the "composition-graded portion" Opening angle θb must be optimal.

In the present invention, as a result of various studies, it has been found that a single crystal nucleus can be efficiently selected under the condition that the opening angle θb toward the growth start end is 30 ° or more and 120 ° or less. That is, when θb is 30 ° or less, it is very difficult to select a single crystal nucleus from the polycrystal. When θb is 120 ° or more, the volume of the “graded composition portion” Lb becomes large, and the yield of the single crystal deteriorates.

In the course of single crystal growth, new crystal nuclei may be generated. However, the degree of smoothness of the inner wall and the opening angle θu from “constriction” to “single crystal growth portion” are also important. Is a factor.

In the present invention, as a result of various studies, θu
Is less than 120 mm. Where θ
When u is 0 °, a single crystal is naturally obtained. However, considering that a large single crystal is to be obtained, the efficiency is poor, and thus the object of the present invention is deviated. When θu is 120 ° or more, it is very convenient to obtain a large single crystal.However, since a new crystal nucleus is generated from the inner wall, it is impossible to obtain a large single crystal as in the case where θu is 0 °. Quite difficult. In the present invention, the growth rate needs to be 0.1 cm / day to 5 cm / day.

Therefore, according to the present invention, there is no failure, excellent reproducibility, high yield, and inexpensive I-III-VI
_{Since a} Group ₂ semiconductor can be provided, it is industrially advantageous.

In the above description, the effect of the "neck" promotes the growth of a single crystal nucleus. Strictly speaking, it is explained in FIG. 7 that there is an optimum condition for the thickness of the "neck". I do. When the inner diameter Do of the “constriction” is too large (FIG. 7)
(A)) The priority of single crystal nucleus generation is impaired, which promotes polycrystallization and does not grow into a large single crystal. On the other hand, if the inner diameter Do is too small (FIG. 7 (a)), the melt is pulled up and down by the surface tension, creating a space in the "constricted" portion. Therefore, for Do, it is important to employ the optimal Do (FIG. 7 (c)) for growing only a single nucleus. The optimal Do is the result of the experiment, 2
It was found that it was not less than 10 mm and not more than 10 mm.

In short, the following three points are important for obtaining a large and high-quality single crystal. To increase the region of the stoichiometric composition obtained at the growth end side. To provide a "neck" at a position where the composition changes to the desired stoichiometric composition. At the same time, the growth and growth of single crystals should be facilitated by precisely defining the shape and dimensions of the "neck".

From the above point of view, various conditions such as the configuration, shape and dimensions of the growth tube include increasing the length and thickness of the “single crystal growth portion” in the growth tube, and the length Lb of the “gradient composition”. Should be at least 85% of the total raw material,
And the inner diameter Do and the length Lo of the "constriction" are each 2 mm.
It should be at least 10 mm and preferably at most 3 cm. Furthermore, the opening angle θb from “constriction” to “compositional gradient portion” takes an appropriate value of 30 ° or more and 120 ° or less, and the opening angle θu from “constriction” to “single crystal growth portion” takes an appropriate value of 120 ° or less. It is also necessary.

As a result, the result obtained by the technique of the present invention is:
High-quality I-III-VI group ₂ semiconductor single crystals that do not contain precipitates
It has been found that it has good optical properties. Therefore, the technique such as “constriction” related to the present invention is particularly suitable for I-III-
VI is an original method for solving the problems that have conventionally been difficult in producing Group ₂ semiconductor single crystals.

Next, the reasons for limiting the numerical values relating to the production method of the present invention will be described below. As the length Lb: Lb of the "composition gradient" is sufficiently long, high quality and large crystal nuclei grow, so that subsequent single crystal growth becomes easy. However, this Lb is not an absolute value, but is limited as a relative value to the volume of the raw material. As a relative value, when the ratio of the volume of the composition gradient portion to the volume of the total amount of the raw material melt is 85% or more, no precipitate enters the single crystal, and a high-quality large single crystal is obtained. However, when the proportion is 85% or less, even if a large single crystal is formed, a precipitate is formed and becomes opaque, which is out of the object of the present invention. The ratio of the volume of the composition gradient portion to the volume of the total amount of the raw material melt is preferably 85% or more and 95% or less in terms of experiments.

The inner diameter Do of the "neck": Do not less than 2 mm 10
When the crystal growth is performed in the range of mm or less, it becomes easy to select a single crystal nucleus from the polycrystals of the “composition gradient”. However, when Do is 2 mm or less, a cavity is formed in the middle of the "constriction", so that it is impossible to guide the crystal orientation of the "composition gradient portion" to the "single crystal growth portion". If Do is 10 mm or more, a plurality of crystal nuclei from the polycrystal in the "compositionally graded portion" enter the "single crystal growth portion", and the priority of single crystal nucleus generation is impaired, and a large single crystal is obtained. This is because it is inappropriate.

When the length Lo of the "neck" is less than 3 cm, the transition from the non-stoichiometric composition to the stoichiometric composition is assured and easy, and the growth of single crystal nuclei is facilitated. It becomes possible. However, if Lo is more than 3cm or Lo is 0cm,
In addition to fear of induction of new crystal nuclei, the yield of single crystals is deteriorated, and this is excluded from the object of the present invention. Therefore, the length Lo of the neck is 0 cm or more and 3
cm or less (however, Lo does not include 0 cm).

When the opening angle θb from the “constriction” to the “composition gradient”: θb is 30 ° or more and 120 ° or less, it is suitable for forming a single crystal nucleus. However, when θb is smaller than 30 °, many crystal nuclei are generated, and when θb is larger than 120 °, a single crystal nucleus cannot be obtained. Therefore, θb is
Limited to 30 to 120 mm.

It is preferable that the opening angle θu from the “constriction” to the “single crystal growth portion”: θu be 120 ° or less, since single crystal nuclei promote single crystal growth. However, when θu is negative, single crystal growth is hindered, and when θu is larger than 120 °, new crystal nuclei are generated during crystal growth, which is not preferable. Therefore, θu is limited to 120 ° or less.

Growth rate V: When V is in the range of 0.1 cm / day to 5 cm / day, crystal growth is good. But V is 5cm /
This is because a single crystal does not grow over a day or more, and a single crystal nucleus is not formed at a time of 0.1 cm / day or less, which may hinder crystal growth in a “single crystal growth portion”. Therefore, the growth rate is limited to 0.1 cm / day to 5 cm / day.

[0041]

Next, a method for producing AgGaS ₂ and AgAlSe ₂ single crystals will be described below.

Example 1 : Production of AgGaS ₂ semiconductor single crystal-1 Raw materials used in the experiment were Ag, G having a purity of 99.9999% or more.
a and S. In order to produce an AgGaS ₂ single crystal, first, the raw materials are mixed at a predetermined mixing ratio (Ag = 25 at%, Ga =
Weigh accurately to 25 atomic% and S = 50 atomic%). After that, the raw material is vacuum-sealed in a transparent quartz tube, and 1000
It is synthesized by heating at a high temperature of at least ℃ for a long time. The synthesized yellow solid substance was analyzed by X-ray diffraction and found to have a tetragonal chalcopyrite-type crystal structure. Next, this substance was made into a powder, and 25.1 g of the whole was collected, placed in a transparent quartz tube having an inner wall coated with a carbon coating, and vacuum-sealed. Here, two types of transparent quartz tubes, one having a “constriction” and one not having the same (comparative example), were prepared, and after being sufficiently cleaned,
Used after drying. Finally, the quartz tube ampoule manufactured by the above method is placed in an electric furnace, and a temperature gradient solidification method shown in FIG. 8 (reference: for example, Takashi Kawatoda, “Semiconductor Crystal”, pp. 29-30)
(1987)). This method is a kind of the Bridgman method, in which the growth tube and the temperature gradient are fixed, and only the temperature in the furnace is changed, and since there is no rotation or vibration of the ampoule, a good quality crystal can be obtained. .

In this method, the crystal can be grown by fixing the position of the growth tube between a and b and lowering the furnace temperature while keeping the temperature gradient between the times t ₁ and t ₂ constant. Therefore, there is a feature that polycrystallization accompanying the fluctuation of the growth tube can be prevented. As a result of growing a single crystal under the conditions of a temperature gradient of 7.7 ° C. per cm and a cooling rate of 11.5 ° C. per day, a large transparent single crystal of yellow color (length: 23 mm, straight body length: 13 mm, diameter: 12 mm pencil shape: FIG. 9) was obtained. Table 1 shows the results of a comparative example in which a growth tube without “neck” was used. In the comparative example, as compared with the case where only a small single crystal grain is obtained, the crystal obtained in this example is much larger in size, and several times better results are obtained with respect to the degree of crystal perfection and transparency. Obtained.

[0044]

[Table 1]

Example 2 : Production of AgGaS ₂ semiconductor single crystal-2 The raw materials and growth tubes used were the same as in Example 1. The single crystal was grown in the same manner as in Example 1. First, 21.21 g of AgGaS ₂ polycrystalline powder was put into a growth tube provided with a carbon coating, followed by vacuum sealing. As a growth method, a temperature gradient of 11.6 ° C./cm and 16.08 / day
C. Cooling rate conditions. The size and the like of the growth tube are as shown in Table 2. As a result, a large transparent single crystal (30 mm in total length, 20 mm in length of a straight body portion, and 12 mm in diameter) was obtained as in Example 1. The difference from the comparative example was the same as in Example 1.

[0046]

[Table 2]

Next, the optical evaluation of the crystals obtained in Examples 1 and 2 will be described below. According to the production method of the present invention, as a result of microscopic observation, no inclusion of a precipitate was observed, and it was found that crystals having good transparency were obtained. FIG. 10 shows A
The transmission spectrum at room temperature of a sample obtained by cutting a gGaS ₂ single crystal into a thickness of about 0.75 mm and polishing the surface is shown. Satisfactory transmission of about 60 to 70% was obtained over the wavelength range from 500 to 1000 nm. The material exhibits high transmittance up to the vicinity of the forbidden band width, indicating that the optical properties of the material are excellent. Next, FIG.
4 shows a photoluminescence spectrum at 4.2 K of an S ₂ single crystal. The single crystal obtained by the conventional manufacturing method (Comparative Example) showed remarkable broad light emission on the low energy side, whereas the single crystal light emission by the manufacturing method of the present invention was very close to the forbidden band width. It showed a strong and sharp spectrum at 2.687 eV, which proved to be extremely promising as a blue light emitting diode. Also, judging from the results of the above-mentioned optical microscope and the characteristics of the transmission spectrum and the photoluminescence spectrum, it can be said that the present invention is an extremely excellent manufacturing method for obtaining a large and high-quality single crystal.

Example 3 Production of AgAlSe ₂ Semiconductor Single Crystal Ag, Al and Se having a purity of 99.9999% or more were used as raw materials. The method for producing a single crystal was almost the same as in Example 1. First, AgAlS was added to the growth tube with carbon coating.
vacuum sealed put e ₂ polycrystalline powders 16.0 g, was grown at the same temperature gradient solidification method and conditions as in Example 2. The size and the like of the growth tube are as shown in Table 3. As a result, the resulting crystals are yellow, transparent single crystals (length 10 mm, diameter 12 mm
Cone). It was found that the size and the integrity of the single crystal were better than those of the comparative example where there was no “neck”.

[0049]

[Table 3]

As described above, when Examples 1, 2, and 3 are summarized, a polycrystal composed of small grains was observed in the "composition-graded portion" after growth, but one single crystal was observed in the "single-crystal growth portion". (See FIG. 9). In the first embodiment, the total length is 23
A pencil-shaped single crystal having a diameter of 13 mm and a diameter of 12 mm was obtained. In Example 2, a pencil-shaped single crystal having a total length of 30 mm, a length of a straight body of 20 mm, and a diameter of 12 mm was obtained. In Example 3, a conical single crystal having a length of 10 mm and a diameter of 12 mm was obtained. Tables 1, 2, and 3 summarize the growth conditions, the dimensions of the obtained single crystals, and the evaluation of the crystals in each example.

[0051]

According to the method of the present invention for producing a single crystal from a melt of an I-III-VI Group ₂ semiconductor, a "neck" is formed between a "single crystal growth portion" and a "composition gradient portion" of a growth tube. Provided a single crystal having a stoichiometric composition which is homogeneous, large, and has high luminous efficiency. Further, the present invention greatly contributes to cost reduction and high quality of I-III-VI group ₂ semiconductor materials for next-generation optical functional devices and light-emitting devices. In addition, the ripple effect is extremely large in achieving single crystallization of a material having a complicated composition.

[Brief description of the drawings]

FIG. 1 shows a group I-III-VI ₂ (group I is Ag,
Group III either one or one or more elements of Al and Ga, and VI ₂ group is any one or one or more elements of S and Se) compounds and bandgap of their typical solid solution It shows the relationship between and the lattice constant.

FIG. 2 shows a phase diagram of a pseudo binary system of Ag ₂ S—Ga ₂ S ₃ .

FIG. 3 shows the shape of a growth tube having a “neck” according to the present invention.

4 is an enlarged view of a part of FIG. 2 and is a quasi-binary phase diagram for explaining a change in composition of a grown crystal.

FIG. 5 is an explanatory diagram for determining an optimum position of “constriction” in the method of the present invention. (A) is "constriction"
FIG. 4 is an explanatory diagram showing a state of a polycrystal obtained as a result of performing single crystal growth using a growth tube having no crystal. (A) and (C) are explanatory views showing the state of crystals obtained as a result of using a growth tube provided with a constriction.

FIG. 6 is an explanatory diagram showing the relationship between the position of “constriction” and the position of transition to stoichiometric composition in the method of the present invention.

FIG. 7 shows a method of the present invention, in which the thickness “D” of “constriction” is obtained.
FIG. 9 is an explanatory diagram for explaining that it is necessary to limit o.

FIG. 8 (A) and (B) show the method of the present invention.
It is an explanatory view for explaining an outline of a temperature gradient solidification method.

FIG. 9 is an explanatory view schematically showing the position and size of a single crystal when a crystal is grown using a growth tube having a “neck” in the method of the present invention.

FIG. 10 is a transmission spectrum characteristic and a photoluminescence spectrum characteristic of an AgGaS ₂ semiconductor single crystal produced by the method of the present invention.

FIG. 11 is a transmission spectrum characteristic and a photoluminescence spectrum characteristic of an AgGaS ₂ semiconductor single crystal manufactured by the method of the present invention.

Continuation of the front page (72) Inventor Katsumi Mochizuki 22-12, Yayoi-machi, Yagiyama, Taishiro-ku, Sendai, Miyagi Prefecture (56) References JP-A-61-261287 (JP, A) IEICE Technical Report, 79 [251], p. 79-84, (1980) (58) Fields studied (Int. Cl. ⁷ , DB name) B30B 29/46 B30B 11/00 INSPEC (DIALOG) JICST file (JOIS)

Claims (2)

(57) [Claims] A group I element is Ag, a group III element is one or more of Al and Ga, and a group VI element is S.
And I- consisting of one or more elements of Se
In the case of manufacturing a III-VI Group ₂ semiconductor single crystal, the inner diameter is 2 mm at a position between the composition gradient portion of the growth tube and the single crystal growth portion, where the composition just transitions to the stoichiometric composition.
10 mm or less and length Lo is 0 cm or more and 3 cm or less (however, Lo
Does not include 0 cm), a constriction with an opening angle to the growth start end side of 30 ° or more and 120 ° or less and an opening angle to the growth end end side of 120 ° or less is provided, and the growth rate is 0.1 cm / day. A method for producing a group I-III-VI group ₂ semiconductor single crystal, characterized in that the temperature is 5 cm / day. 2. A method for producing an AgGaS ₂ semiconductor single crystal, which is located between a composition gradient portion of a growth tube and a single crystal growth portion, at a position where the composition shifts to a stoichiometric composition, and The inner diameter is 2 mm or more and 10 mm or less, and the length Lo is 0 cm or more and 3 cm or less (however, Lo does not include 0 cm) so that the volume of the inclined portion is 85% or more of the volume of the entire raw material melt.
A constriction with an opening angle of 30 ° or more and 120 ° or less at the growth start end and 120 ° or less at the growth end end, and a growth rate of 0.4 cm / day to 2 cm / day A method for producing an AgGaS ₂ semiconductor single crystal, characterized in that: