JPH05279195A - Production of group i-iii-vi 2 semiconductor single crystal - Google Patents

Abstract

PURPOSE:To obtain a group I-III-VI 2 semiconductor single crystal having high homogeneity, large size, stoichiometric composition and high luminous efficiency by forming a neck part having a specific shape in the middle of a growth tube and restricting the growing speed of the crystal. CONSTITUTION:The growth tube to be used in the subject process is composed of a gradient composition part for the control of the composition, a neck part for the selection of a single crystal nucleus and a single crystal growing part arranged in the order from under. The neck part has an inner diameter D0 of 2-10mm, a neck length L0 of 0-3cm, an opening angle to the growth-starting side thetab of 30-120 deg. and an opening angle to the growth-finishing side thetau of <=120 deg.. A polycrystalline material containing a group I element consisting of Ag, a group III element consisting of Al and/or Ga and a group VI element consisting of S and/or Se is sealed in the above growth tube in vacuum and a group I-III- VI 2 semiconductor single crystal is grown at a growing speed of 0.1-5cm/day by a temperature gradient solidification process, etc.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention is based on solidification from a melt.
The present invention relates to a method for producing a group I-III-VI2 semiconductor single crystal,
It is an object of the invention to provide a non-linear optical material, a substrate material for a light emitting diode and a laser diode, and a material for a blue light emitting element.

[0002]

2. Description of the Related Art I-III-VI2 group semiconductors have a tetragonal chalcopyrite type crystal structure, their forbidden band width corresponds to the visible light region from red to purple, and the transmission wavelength range of light is infrared. It is known that it has a very wide range from to visible region and has a large nonlinear optical constant and a large birefringence. From these characteristics, various applications such as a light emitting element and a non-linear optical element are considered, and it is expected to be applied to various devices.

FIG. 1 shows the relationship between the band gap Eg and the lattice constant a of I-III-VI2 group 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, the manufacturing method of these semiconductor single crystals is as follows.
It is roughly classified into two types: a chemical vapor transport method using iodine and a method of growing from a melt (eg, Bridgman method).

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

On the other hand, in the latter case, especially the Bridgman method is
Compared with the chemical vapor transport method using iodine, it is possible to obtain a large crystal without worrying about the contamination of iodine. However, the I-III-VI2 group 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 a crystal having a c-axis in the radial direction of the growth tube is included when the sample is cooled from the melt,
The growth tube is broken due to the difference in thermal expansion coefficient between the growth tube and the crystal, or strain or cracking occurs in the crystal due to internal stress. Therefore, as a method of solving 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 in which the growth tube is enclosed in a slightly larger quartz tube. Methods have been proposed to prevent the oxidation and contamination of the.

However, when observing the AgGaS ₂ single crystal obtained by this Bridgman method, the whole is not a single single crystal but a polycrystal in which small crystal grains are gathered,
It was extremely difficult to obtain a large-sized and good quality single crystal.
In addition, the obtained single crystal does not have a certain size, which is industrially not mass-producible, which is a serious problem.

[0008]

As a method for solving the above-mentioned problems, there is a seeds method which is free from strain or cracks, and is capable of obtaining a large quality single crystal, that is, a method using a so-called seed crystal (cited. Literature RS Feigelson and RKR
oute, “Recent developments in the growth of chalco
pyrite crystala for nonlinear infrared application
s ”, OPTICALENGINEERING, 26 (2) 113-119 (1987)).
This method attempts to grow a single crystal in a direction in which the growth direction of the single crystal is the same as the c-axis of the seed crystal, but has the following difficult problems.

First, it is necessary to cut out and prepare a single crystal in the c-axis direction as a seed crystal, which requires time and labor for production, and sometimes melts the whole seed crystal. As a result, it is necessary to prepare a relatively large seed crystal in order to fuse with the melt raw material. Furthermore, the handling and temperature control require considerable precision and skill, which is also a drawback of the seed crystal method.

The second problem is that in the obtained single crystal, the composition changes considerably from the growth start side to the growth end side. In such a state, the optical characteristics may be adversely affected. This change in composition will be described by taking the case of an AgGaS ₂ compound as an example. The stoichiometric composition of the AgGaS ₂ compound is Ag ₂
A phase diagram of Ag ₂ S-Ga ₂ S ₃ quasi-binary system with S content of 50% (see Fig. 2: Cited reference RS Feigelson and RKRout
e, OPTICAL ENGINEERING, 26 (2) 113-119 (1987)). However, this composition is AgGa
It does not match the composition of the harmony melt of the S ₂ compound (point B). Therefore, it is understood that a slight change in composition occurs in the crystal grown from the stoichiometric composition (point A). When crystal growth from a harmonic melt composition is performed separately from this, the adjacent Ga ₂ S ₃ -side phase mixes in as precipitates during the cooling process, and a homogeneous single crystal with a stoichiometric composition is obtained. I can't. As a method for removing this precipitate, a solution is attempted 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 if the heat treatment is performed by such a method.

The object of the present invention is to solve the above-mentioned problems from systematic experiments, and by using a simple method that does not rely on a seed crystal method, isothermal heat treatment, etc., a large and high-quality I-III-VI is obtained.
It is to provide a manufacturing method for obtaining a Group 2 semiconductor single crystal.

[Means for Solving the Problems]

The present invention relates to a group I-III-VI2 semiconductor (group I is A
g, group III is one or more elements of Al and Ga, and group VI is one or more elements of S and Se) is solidified from a melt to produce a single crystal, A method for producing a semiconductor single crystal is characterized in that the growth tube is divided into a "single crystal growth portion", a "constriction" and a "component gradient portion", and the composition is controlled. Among the plurality of crystal nuclei naturally formed in the “component inclined portion”, only the crystal nuclei having an orientation close to the c-axis are selected in the “constriction” provided in the middle of the growth tube, and the crystal nuclei are further selected. The greatest aim of the present invention is to preferentially grow the "single crystal growth portion" to obtain a large crystal. That is, by introducing a “constriction” having an arbitrary size and shape into the growth tube, it is possible to manufacture a single crystal without using a seed crystal.

A group I-III-VI2 semiconductor (group I is Ag,
Group III is one or more elements of Al and Ga, and Group VI is one or more element of S and Se) It has the property of causing a composition change that changes from a stoichiometric composition to a stoichiometric composition, but by forming a "constriction" in the region where the composition just begins to become stoichiometric, precipitates are included. It was thought that a single crystal that does not exist could be obtained.

According to the above-mentioned required means, it is a simple method which is not found in the method of seed crystal or heat treatment,
Moreover, it has become possible to very easily manufacture a large-sized and high-quality I-III-VI2 semiconductor single crystal.

[0015]

FIG. 3 shows the shape of a growth tube having a "constriction" according to the present invention. That is, the growth tube is composed of a “composition-graded portion” for controlling composition, a “constriction” for selecting single crystal nuclei, and a “single crystal growth portion” from below. In the figure, Lb and Lu are the length from the bottom of the "constriction" to the growth start end (the length of the "composition slope") and from the top of the "constriction" to the growth end end across the "constriction". The length (the length of the “single crystal growth portion”) is shown. Db and Du
Indicate the inner diameters of the “composition-graded portion” and the “single crystal growth portion”, respectively. Do and Lo indicate the inner diameter and length of the "constriction", respectively. Further, θb represents the opening angle from the “constriction” to the lower “composition-graded portion”, and θu represents the opening angle from the “constriction” to the upper “single crystal growth portion”. A single crystal was grown from the melt using a growth tube of such a shape, and a large single crystal having a homogeneous stoichiometric composition from the "constriction" to the crystal growth end side could be obtained.

As a result of numerous experiments, it was found that the optimum conditions for producing these single crystals can be narrowed down to the following range. Length Lb from "constriction" to the start of growth
Is limited as a relative value with respect to the volume of the raw material, and in order to obtain a good quality large single crystal, the volume of the region of Lb is
It must be 85% or more. The inner diameter Do of the "constriction" depends on the sizes of Db and Du, but it is 2 mm or more and 10 mm.
The following range is optimal. The length “L” of the “constriction” is 3 cm or less, though it depends on the mixing ratio of the raw materials. The opening angle θb from the “constriction” to the “composition slope” is 30 ° or more 12
0 ° or less, the opening angle θu from the “constriction” to the “single crystal growth part” is 120 ° or less, and the growth rate is 0.1 cm / day or more and 5 cm /
Less than a day is appropriate, especially for AgGaS2 0.4 cm /
The optimum value is not less than 2 cm / day and not more than one day.

Next, a basic concept important for establishing the technique of the present invention will be described with reference to FIGS. 2 to 6. As can be seen from FIG. 2, the existence region of the AgGaS ₂ compound is at a high temperature (about 720
Above 50 ° C, stoichiometric composition (Ag ₂ S amount 50%,
It extends about 2% up from Ga ₂ S ₃ content 50%) in the Ga ₂ S ₃ side. The harmonic melting point of AgGaS ₂ compound corresponds to point B (Ga ₂ S ₃ amount 51%), and the melting point of the stoichiometric composition on the liquidus line corresponds to point A (Ga ₂ S ₃ amount 50%). There is. That is, a state diagram in which a part of FIG. 2 is enlarged (see FIG.
Reference), the harmonized melt composition (point B) of the AgGaS ₂ compound differs from the stoichiometric composition (point A). Therefore, when the melt of AgGaS ₂ is cooled from the stoichiometric composition, first, at the point A, two phases of the liquid phase (L) and AgGaS ₂ coexist, and AgGaS ₂ slightly crystallizes 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 it becomes a harmonic melt composition at point B.

Next, from the melt containing 50% of Ga ₂ S ₃ to 51%
When the solid phase is crystallized, naturally the composition of the remaining melt slightly shifts from the point A to the Ag ₂ S side (A ₁ -B ₁ ).
Will be done. When the composition of the melt shifts to the Ag ₂ S side, the melting point becomes slightly lower. When the melting point becomes lower, the composition of the solid phase that crystallizes out shifts slightly from the point B to the Ag ₂ S side (A ₂ -B ₂ ). When this is repeated, the composition of the melt further shifts from the point A to the Ag ₂ S side, and the composition that crystallizes also follows the curve between BC from B to B ₁ , B ₂ ,
I thought that I would shift to C after going through B ₃ . If the state of this change is made to correspond to the actual crystal growth, FIG.
The sketch is as shown in (a). The obtained single crystal is from the crystal growth start side (point B) to the end side (C
A slight compositional change is observed toward the point. The problem here is that the solid phase of AgGaS ₂ having the composition of the crystallized B point and the composition between the B point and the C point is the coexisting phase of AgGaS ₂ and Ag ₂ Ga ₂₀ S ₃₁ due to the temperature drop. It means that the phase transitions to. That is, A in the GaGaS ₂ matrix
This is because g ₂ Ga ₂₀ S ₃₁ is mixed in as a precipitate, and this precipitate scatters light and causes the transmittance of the single crystal to be significantly impaired. Therefore, when observing the obtained single crystal, Ag was found to be closer to the growth start side (B to B ₂ region in FIG. 5A).
_A large amount of ₂ Ga ₂₀ S ₃₁ precipitates were included and the crystals became cloudy.
The closer to the end side, the less the precipitates, and the more the transparency gradually increases (B _{2 to} B ₃ region in FIG. 5A). Further, in the portion reaching the point C closer to the terminal portion, that is, at the time when the ratio to the total melt amount (raw material) is 85%, no precipitate is contained at all, and it becomes completely transparent. It has been proved by many experimental results that the region of C to D, that is, the transparent portion having the stoichiometric composition, is always occupied by a fixed volume (about 15%) with respect to the total amount of melt. did it. Judging from this, the longer the growth direction, the larger the volume of the stoichiometric composition,
We thought that it would be possible to produce good quality single crystals of arbitrary size. However, in the case of group I-III-VI2 semiconductor crystals, the single crystal nuclei did not grow significantly if the diameter of the growth tube was increased or the length was increased.
It was also found that a large single crystal could not be produced.

As a result of numerous experiments conducted by the present inventors in order to overcome these drawbacks, a method of providing a “constriction” in the middle of the growth tube is very promising as a method of preferentially growing a single nucleus to a large size. I found that. However, it has also been clarified that the growth of a homogeneous and large single crystal is influenced by the position of the "constriction" in the growth tube, that is, how much Lb is taken and how much the raw material is put in the growth tube. For example, as shown in FIG. 5 (a), when a "constriction" is provided near the growth start end (the length Lb of the "composition-graded portion" is small), even if the single crystal is large, the composition changes in the single crystal. Occurs, which leads to the inclusion of precipitates and cracks are likely to occur, so that even a satisfactory single crystal cannot be obtained. The hatched portions in FIGS. 5A and 5C indicate the stoichiometric composition, and the composition changes in the lower portion.

In short, it was found that not only the "constriction" but also Lb is an important factor. FIG. 5C shows that it is effective to provide a "constriction" at the optimum position Lb where the composition of the harmonious melt changes to the stoichiometric composition during crystal growth. By this method, a homogeneous single crystal having a stoichiometric composition was obtained without containing precipitates on the growth end side (CD) of the "constriction".

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

Next, the relationship between the "constriction" and the stoichiometric composition and the shape of the "constriction" will be described. Figure 6
(A) to (d) show the relationship between the "constriction" and the stoichiometric composition (hatched portion). In the figure, AB indicates the boundary line between the stoichiometric composition and the non-stoichiometric composition in which the composition changes.

It is not easy to accurately set the position of the "neck" as shown in FIG. 6 (a), and it is extremely difficult due to subtle differences in the amount, composition and growth conditions of raw materials. For example, when the transition position to the stoichiometric composition (the lower limit position AB of the diagonal line) is above the "constriction" as shown in FIG. Nuclear growth becomes difficult. This problem can be solved by providing a “constriction” well above the position where it is expected to shift to the stoichiometric composition, as shown in FIG. However, if this transition position is too low, the volume of a necessary portion above the “constriction” becomes small, and the yield of single crystals deteriorates. As can be seen from these explanations, it is technically extremely difficult to match the position of the "neck" with the composition transition position. Therefore, in order to solve this problem, as shown in FIG.
It has been found that the method of giving a proper "length" Lo to the is effective. In this case, the error in the position of transition from the non-stoichiometric composition to the stoichiometric composition is ± 1.5 cm.
It is sufficient that o is within 3 cm. Within this range, crystal growth is not impaired, but when it is 3 cm or more, it becomes a factor of inducing new crystal nuclei and deteriorating the single crystal yield. By introducing this method, even if there are some changes in conditions, the place where the non-stoichiometric composition shifts to the stoichiometric composition can be securely and easily placed in the middle of the "constriction". The fact that single crystal nuclei can be grown is also a major feature of the present invention.

When a single crystal nucleus is selected from the polycrystals of the "composition-graded portion" by utilizing the "composition-graded portion" to "constriction", the "constriction" to the "composition-graded portion" is selected. The opening angle θb should be optimal.

In the present invention, as a result of various studies, θb
It was found that a single crystal nucleus can be efficiently selected under a condition of 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 within the polycrystal. On the other hand, when θb is 120 ° or more, the volume of the “composition-graded portion” Lb becomes large and the yield of single crystal deteriorates.

Although new crystal nuclei are sometimes generated in the process of single crystal growth, the degree of smoothness of the inner wall and the opening angle θu from the “constriction” to the “single crystal growth part” are also important. Is a factor.

In the present invention, as a result of various studies, θu
It is essential that the angle is 120 ° or less. However, θ
When u is 0 °, naturally a single crystal can be obtained, but on the other hand, considering the fact that a large single crystal is obtained, the efficiency is low, and this is outside the scope of the present invention. Further, if θu is 120 ° or more, it is very convenient to obtain a large single crystal, but since new crystal nuclei are generated from the inner wall, it is not possible to obtain a large single crystal as in the case where θu is 0 °. Quite difficult. Therefore, according to the present invention, it is possible to provide a group I-III-VI2 semiconductor which has no failures, is excellent in reproducibility, has a high yield, and is inexpensive, which is industrially advantageous.

In the above description, the effect of the "constriction" is said to promote the growth of single crystal nuclei, but strictly speaking, there is an optimum condition in the thickness of the "constriction", which is explained in FIG. To do. If the inner diameter Do of the "constriction" is too large (Fig. 7
(A)), the priority of single crystal nucleation is impaired, polycrystallization is promoted, and a large single crystal does not grow. Further, when the inner diameter Do is too small (FIG. 7 (A)), the melt is pulled up and down by the surface tension to create a space in the "constricted" portion. Therefore, regarding Do, it is important to adopt the optimum Do (FIG. 7C) for growing only a single nucleus. The optimum Do is the result of the experiment, 2
It was found to be between mm and 10 mm.

In summary, the following three points are important for obtaining a large and high quality single crystal. To increase the area of stoichiometric composition obtained on the growth end side. Providing a "constriction" at the position where the composition changes to the desired stoichiometric composition. At the same time, to facilitate the growth of single crystals by precisely defining the shape and dimensions of the "constriction".

From the above viewpoint, various conditions such as the structure, shape and size of the growth tube are as follows: the length and thickness of the “single crystal growth portion” in the growth tube are increased, and the length Lb of the “composition-graded portion” is Lb. To be 85% or more of the total raw materials,
And the inner diameter Do and the length Lo of the "constriction" are each 2 mm.
It should be 10 mm or less, preferably 3 cm or less. Further, the opening angle θb from the “constriction” to the “composition-graded portion” should be 30 ° or more and 120 ° or less, and the opening angle θu from the “constriction” to the “single crystal growth portion” should be 120 ° or less. It is also necessary.

As a result, obtained by the technique of the present invention,
A high quality I-III-VI2 semiconductor single crystal without deposits
It became clear that it has an optically good characteristic. Therefore, the technology such as "constriction" related to the present invention is particularly effective in I-III-
It is an original method to solve the problems that were difficult in the past when producing Group VI2 semiconductor single crystals.

Next, the reasons for limiting the numerical values relating to the manufacturing method of the present invention will be described below. If the length Lb: Lb of the “composition-graded portion” is sufficiently long, a good 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 this relative value, L for the volume of the total melt amount
When the ratio of b is 85% or more, precipitates do not enter into the single crystal, and a large single crystal with good quality can be obtained. However, if the ratio is 85% or less, even if a large single crystal is formed, a precipitate is generated and becomes opaque, which is outside the scope of the present invention.

Inner diameter Do of constriction Do: Do is 2 mm or more 10
When 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-graded portion”. However, when Do is 2 mm or less, it becomes impossible to guide the crystal orientation of the “composition-graded portion” to the “single crystal growth portion” because a cavity is formed in the middle of the “constriction”. When Do is 10 mm or more, a plurality of crystal nuclei enter into the “single crystal growth part” from the polycrystal of the “composition-graded part”, impairing the priority of single crystal nucleation and obtaining a large single crystal. It is not suitable for

When the length "Loss" L0: L0 is within 3 cm, the transition from the non-stoichiometric composition to the stoichiometric composition is sure and easy, and the growth of single crystal nuclei is facilitated. It will be possible. However, when Lo is 3 cm or more, not only the induction of new crystal nuclei is feared but also the yield of the single crystal is deteriorated, which is out of the object of the present invention. Therefore, Lo is limited to 3 cm or less.

When the opening angle θb from the “constriction” to the “composition-graded portion”: 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 it is larger than 120 °, a single crystal nucleus cannot be obtained. Therefore θb is
Limited to 30 ° or more and 120 ° or less.

It is preferable that the opening angle θu: θu from the “constriction” to the “single crystal growth portion” is 120 ° or less because the single crystal growth is promoted from a single crystal nucleus. 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 becomes good. However, V is 5 cm /
This is because a single crystal does not grow when the time is longer than a day, and a single crystal nucleus is not formed when it is 0.1 cm / day or less, which may hinder the crystal growth in the “single crystal growth portion”. Therefore, the growth rate is limited to 0.1 cm / day or more and 5 cm / day or less.

[0038]

EXAMPLES 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 The raw material used in the experiment was 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 in a predetermined mixing ratio (Ag = 25 atomic%, Ga =
Accurately weigh 25 atomic% and S = 50 atomic%). Then, vacuum seal the raw material in a transparent quartz tube, and
It is synthesized by heating at a high temperature of ℃ or more for a long time. As a result of X-ray diffraction analysis, the synthesized yellow solid substance had a tetragonal chalcopyrite type crystal structure. Next, this substance was made into powder, 25.1 g of which was taken out of the total amount, placed in a transparent quartz tube having a carbon coating on its inner wall, and vacuum-sealed. Here, two types of transparent quartz tube were prepared, one having a "constriction" and the other not (comparative example), and after being sufficiently cleaned,
It was dried and used. Finally, the quartz tube ampoule produced by the above method was placed in an electric furnace, and the temperature gradient solidification method shown in FIG. 8 (reference: for example, Takashi Kawatoda “Semiconductor Crystal” p.29-30
(1987)). This method is a kind of Bridgman method, and has the characteristic that the temperature inside the furnace is changed by fixing the temperature gradient in the growth tube, and there is no rotation or vibration of the ampoule, so good quality crystals can be obtained. ..

In this system, the position of the growth tube is fixed between a and b, and the temperature in the furnace is lowered while keeping the temperature gradient between them constant during the period from time t ₁ to t _2, so that crystals can be grown. Therefore, there is a feature that polycrystallization due to shaking of the growth tube can be prevented. As a result of single crystal growth 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 yellow transparent single crystal (total length 23 mm, straight body length 13 mm, diameter A 12 mm pencil shape: Figure 9) was obtained. In addition, Table 1 shows the results when a growth tube having no "constriction" was used as a comparative example. In the comparative example, the size of the crystal obtained in this example is remarkably large as compared with the case where only a small single crystal grain is obtained, and the result of the crystal perfection and the degree of transparency is much better. Was obtained.

[0041]

[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 placed in a growth tube coated with a carbon film and vacuum-sealed. As a growth method, a temperature gradient of 11.6 ° C. per cm and 16.08 per day
The condition was a cooling rate of ° C. The size of the growth tube is as shown in Table 2. As a result, a large yellow transparent single crystal (length: 30 mm, straight body length: 20 mm, diameter: 12 mm, pencil-shaped) was obtained as in Example 1. The difference from the comparative example was the same as in Example 1.

[0043]

[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, inclusion of precipitates was not observed, and it was found that crystals with good transparency can be obtained. Figure 10 shows A
The transmission spectrum at room temperature of a sample obtained by cutting a gGaS ₂ single crystal to a thickness of about 0.75 mm and then polishing the surface is shown. Satisfactory transmission of about 60 to 70% was obtained over the wavelength range of 500 to 1000 nm. The high transmittance up to the vicinity of the forbidden band indicates that this material has excellent optical characteristics. Next, FIG. 11 shows AgGa.
The photoluminescence spectrum at 4.2 K of an S ₂ single crystal is shown. The single crystal obtained by the conventional manufacturing method (Comparative Example) showed remarkable broad emission on the low energy side, whereas the emission of the single crystal obtained by the manufacturing method of the present invention was very close to the band gap. It showed a strong and sharp spectrum at 2.687 eV, which proved to be extremely promising as a blue light emitting diode. Judging from the results of the above-mentioned optical microscope and the characteristics of the transmission spectrum and the photoluminescence spectrum, the present invention can be said to be an extremely excellent manufacturing method for obtaining a large-sized 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 the single crystal was almost the same as in Example 1. First, AgAlS was added to the growth tube coated with carbon film.
16.0 g of e ₂ polycrystal powder was charged and vacuum-sealed, and growth was performed under the same temperature gradient solidification method and conditions as in Example 2. The size of the growth tube is as shown in Table 3. As a result, the obtained crystal was yellow and was a transparent single crystal (length 10 mm, diameter 12 mm.
It was a cone). It was found that the size and completeness of the single crystal were better than those of the comparative example having no "constriction".

[0046]

[Table 3]

As described above, Examples 1, 2, and 3 were summarized. After the growth, a polycrystal composed of small grains was observed in the "composition-graded portion", but one single crystal was observed in the "single crystal growth portion". Had been formed (see FIG. 9). In Example 1, the total length is 23
A pencil-shaped single crystal having a diameter of 12 mm, a body length 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 straight body length of 20 mm and a diameter of 12 mm was obtained. Further, in Example 3, a conical single crystal having a length of 10 mm and a diameter of 12 mm was obtained. In addition, Table 1, Table 2 and Table 3 summarize the growth conditions in each example, the dimensions of the obtained single crystal and the evaluation of the crystal.

[0048]

In the method for producing a single crystal from the melt of the I-III-VI2 group semiconductor of the present invention, the "single crystal growth portion" is provided in the growth tube,
By providing the “constriction” and the “composition-graded portion”, a homogeneous, large-sized single crystal having a stoichiometric composition with high emission efficiency was obtained. Furthermore, the present invention contributes significantly to cost reduction and quality improvement of the I-III-VI2 group semiconductor material for next-generation optical functional devices and light emitting devices. Further, the ripple effect is extremely large in achieving single crystallization of a material having a complicated composition.

[Brief description of drawings]

1 is a group I-III-VI2 group (group I is Ag, II
Group I is any one or more elements of Al and Ga, and group VI is any one or more element of S and Se) compounds and their band gaps of solid solutions. This shows the relationship between the lattice constants.

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

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

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

FIG. 5 is an explanatory diagram for determining the optimum position of the “neck” in the method of the present invention. (A) is an explanatory view showing a state of a polycrystal obtained as a result of performing single crystal growth using a growth tube having no "constriction". (A) and (c)
It is explanatory drawing which shows the condition of the crystal obtained as a result of using the growth tube provided with the constriction.

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

FIG. 7 shows the thickness Do of the “constriction” in the method of the present invention.
FIG. 4 is an explanatory diagram for explaining that it is necessary to limit

8 (A) and 8 (B) are explanatory views for explaining the outline of the temperature gradient solidification method in the method of the present invention.

FIG. 9 is an explanatory diagram showing an outline of the position and size of a single crystal when crystal growth is performed 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 diagram, respectively, 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 diagram of an AgGaS ₂ semiconductor single crystal produced by the method of the present invention.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Katsumi Mochizuki 22-12 Yayoi-cho, Yagiyama, Taishiro-ku, Sendai City, Miyagi Prefecture

Claims (2)

[Claims] 1. A Group I element is Ag, a Group III element is any one or more of Al and Ga, and a Group VI element is S.
I-consisting of any one or more of Se and Se
In the case of producing a III-VI2 semiconductor single crystal, the inner diameter of the growth tube 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 side is 30 ° or more and 120 ° or less. A “constriction” with an opening angle to the end of growth of 120 ° or less is provided, and the growth rate is 0.1 cm / day to 5 cm.
/ Day of the group I-III-VI2 semiconductor single crystal. 2. When manufacturing an AgGaS ₂ semiconductor single crystal, the inner diameter of the growth tube 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 side is 30 ° or more and 120 ° or more. A “constriction” with an opening angle of 120 ° or less and an angle to the end of growth of 120 ° or less, and a growth rate of 0.
AgGa characterized by 4 cm / day to 2 cm / day
Method for producing S ₂ semiconductor single crystal.