JPS61270299A - Method for growing group ii-vi compound semiconductor crystal - Google Patents

Abstract

PURPOSE:To obtain a Groups II-VI compound semiconductor crystals having a high crystal growth rate with little defects, by adding an element of Group VI and Te to a solution containing polycrystal grains present therein, and adjusting the specific gravity. CONSTITUTION:A heat sink 1 consisting of carbon free of residual impurities is put in a quartz tube 6, and a substrate 2 is placed on the heat sink 1 to secure the substrate 2 with a quartz tube 3. After evacuation, the quartz tubes 6 and 3 are fused at a fusing part 8. An element of Group VI, Te 5 and polycrystal grains 4 are put into the tube 6 to adjust the specific gravity of the resultant solution to a higher value than that of the aimed Groups II-VI compound. The mouth of the tube 6 is then vacuum-sealed. The heat sink part 1 is turned upward, and melting is carried out. The sealed part of the tube 6 is turned upward with the side of the heat sink part 1 down to provide a temperature gradient and grow the aimed Groups II-VI compound semiconductor crystals on the substrate 2 by the epitaxial method.

Description

[Detailed description of the invention] And Tudou 1 The present invention relates to an n-VI group compound semiconductor crystal growth method,
In particular, the specific gravity of the solvent and the polycrystalline particles suspended in the solvent is set to 11, so that the polycrystalline particles do not inhibit crystal growth.

Traditionally, when single crystal or epitaxial crystal growth is performed in a quartz ampoule, polycrystalline particles as a source are placed in a solvent and sealed in an amplifier, and the target crystal is grown by controlling the temperature. Methods are being taken to encourage growth. In this case, due to the specific gravity relationship between the polycrystalline particles and the solvent,
Polycrystalline particles may float on a solvent, may settle, or be somewhere in between.

For example, FIGS. 1 and 2 show an example of growing a Zn5e single crystal (13), in which a solvent (12° 15) and a source (11) are vacuum sealed in a quartz tube.

When growing n-VI group compound crystals, Te is used as a solvent because of its low vapor pressure and high solubility for solutes.
(12) is generally used, but in the case of Zn5e, 5e(15) may also be used. In FIG. 1(a), before starting growth, set the temperature to the temperature at which growth can start (for example, 900~
1100℃), Z as a solute in the solvent.
A solution for liquid phase growth containing n5e is obtained. In the TefJ solution, polycrystalline Zn5e particles (11) have a lower specific gravity), so these particles are suspended at the top of the solution, and by lowering the temperature at a constant rate, e.g. 10°C/hour, Zn5e particles with large dalein Crystals (13) can be grown. On the other hand, in Figure 2, since the Zn5e polycrystalline particles (II) are heavier than the Se solution (15), an angled stopper (16) is installed to prevent these particles from settling and inhibiting crystal growth. It is necessary to place the Zn5e polycrystalline particles (11) thereon. Crystal growth can be performed at the bottom of the ampoule by lowering the temperature at a constant rate, as in the case of FIG.

An example of the epitaxial growth method of Zn5e is shown in FIGS. 3 and 4. In order to prevent the substrate (18) from dissolving, the substrate is initially placed on top so that the substrate does not come into contact with the solution. Place the ampoule (when starting growth, invert the ampoule to bring the substrate into contact with the solution.

After that, the epitaxial crystal layer (17) is grown by controlling the temperature as in the case of single crystal.

In such conventional methods, when a Te fJ solution is used, a trace amount of Te is mixed into the growing Zn5e <0.05~
(approximately 0.2%), distortion occurs in the crystal due to the large ionic radius of Te, resulting in poor optical properties, and photoluminescence at room temperature (approximately 300°K) has a forbidden band with a wide half-width. A deep energy level is created.

Furthermore, when Zn5e is grown using a Se solution, the optical properties are improved, but since the solubility of Se solution in Zn5e is low and the specific gravity is lighter than polycrystalline Zn5e particles, those Zn5e particles tend to grow in the crystal growth area. Falling is unavoidable, making it difficult to obtain a Zn5e grown crystal with a good quality and uniform surface condition. Furthermore, since the vapor pressure of Ss is high, it is difficult to grow it in a quartz ampoule at temperatures above 1000°C.

Furthermore, since the heat sink is provided outside the ampoule, the heat from the crystal growth area flows through the wall thickness of the quartz ampoule and the air layer between the heat sink and the quartz ampoule (therefore, a uniform heat flow does not occur and the overall Thermal resistance also increases, making it difficult to obtain uniformly grown crystals and slowing down the growth rate.

I-A further object of the present invention is to provide a method that avoids the drawbacks of the conventional methods described above and can provide a crystal with fewer defects than the conventional method while maintaining a high crystal growth rate.

]-Two! According to the method of the present invention, the above objectives are achieved by: 1. A method for growing a II-Vl group compound semiconductor crystal in which a group II element other than Te is present by controlling temperature from a solution in which polycrystalline particles as a source of the crystal are present. This is achieved by mixing group elements and Te in a ratio such that the specific gravity is greater than that of the -Vl group compound and using the mixture as a solvent.

As a specific example of the present invention, a case in which Zn5e epitaxial growth is carried out will be described below with reference to FIGS. 5 to 9.

First, high-purity carbon is used as a heat sink. After processing it into a size of 8φ x 5Qmm, it is baked in a vacuum at 1000℃ for 3 hours to remove residual impurities in the carbon. This heat sink (1) has an inner diameter of 8φ and a wall thickness. Place it in the quartz tube (6).

Next, Zn5e obtained by sintering method or liquid phase growth method
A single crystal piece of 8φ×500 μm was cut out from the bulk crystal and placed on a heat sink (1) as a substrate (2). The board is (110) and has an inner diameter of 6φ and an outer diameter of 8φ as a 6th order board stop with twin crystals.

A quartz tube (3) with a length of 8H is placed on the substrate and evacuated using an oil-free ion pump, and then the quartz ampoule (6) and the quartz tube (3) fixed to the substrate are heated with a gas burner. Weld (8) to fix the substrate and heat sink (2).

Next, fill the quartz ampoule with nitrogen gas, return it to atmospheric pressure, and then Se: 3211vt, Te: 5395
+w (5) and Zn5e polycrystalline particles 3984■ (4) were added, and the vacuum was again drawn to 1 to 2 x 10-7 Torr using an ion pump. After melting the 5e-Te (5), the quartz tube was heated. The mouth was vacuum sealed. At this time, the distance from the top of the solution to the bottom of the solution was 50 m5. For Se and Te solution (5), the specific gravity is heavier than Zn5e, and the solubility of Zn5e is higher. , good thermal conductivity, high quality grown crystals, and low vapor pressure are required.

In Zn5e growth, Z
It is ideal to use an n5e solution, but with a Zn solution, Se vacancies are likely to form in the growing crystal, and due to the difference in thermal expansion coefficient with quartz, there is a problem of ampoule breakage when the temperature is raised or lowered.
Furthermore, when Se solution is used, since the specific gravity is lighter than Zn5e, Zn5e polycrystals fall onto the substrate and hinder growth. Also, the vapor pressure of both Zn and Se is high <%.The solubility of ZnSe is 0.02mol% at 1000℃ for Se, and
If it is less than that, it is not suitable as a growth solvent. From the point of view of thermal conductivity, Se is about 1/20th that of Te. 1/3 of Zn
00, and increases in the order of Zn>Te>Se.

Therefore, in this example, the solubility was increased and the specific gravity was Zn5.
Se45mol%, Te55sol heavier than e
% mixture was used as a solution. It was confirmed that this solution had improved thermal conductivity compared to the Se solution, and that the crystals produced were of optically good quality Zn5e. In this example, the solute Zn5e polycrystal is added to the 5e-Te solution in an amount of 30s+ol %.

Next, the quartz ampoule after sealing was melted for 2 hours at a temperature T2 (e.g. 1000°C) higher than the growth temperature with the heat sink part facing up and the sealing part enlarged as shown in Figure 5.
(See Figure 6). At this time, the substrate and the solution are not in contact with each other, and the surface is purified by heat treatment without dissolving into the substrate.

Next, as shown in FIG. 7, place the quartz ampoule sealing portion upward and the heat sink side downward. A temperature gradient as shown in FIG. 8 is provided between the upper part of the solution shown in FIG. 7 and the substrate, and the temperature is set so that epitaxial growth is performed at a constant temperature due to a diffusion phenomenon caused by the temperature difference. In this example, T
ff960℃.

At T4980°C, the solution had a temperature gradient of 4°C/cIl. After growing in this state for 104 hours, the substrate was separated from the solution by inverting the quartz ampoule again.

As shown in FIG. 9, the grown crystal was a flat Zn5e pitaxial layer with a thickness of about 250 μm.

In the above embodiments, crystal growth without conduction type impurities was described, but it is of course possible to grow crystals according to the present invention with conduction type impurities added.

It goes without saying that not only three elements but also three or four elements such as ZnS+-xse can be grown by the method of the present invention.

1”L■JL! The effects obtained by the present invention and their possible reasons are listed below.

i) When a vertical ampoule is used, by making the specific gravity of the solution higher than the specific gravity of the ■-■ group compound to be grown, it is possible to prevent, for example, crystal particles from settling in the crystal growth area. Figures 10 and 11 show Zn5e and CdSe.
, ZnS, CdS specific gravity, Se/Te, S/Te
The relationship between the specific gravity of is shown for the ratio of Se and Te and the ratio of S and Te. This graph can be used to determine the minimum content of Te, which can be used as a solution for crystal growth according to the invention.

1i) Most Vl group elements have high vapor pressures, but Te has a vapor pressure that is three orders of magnitude lower than S and two orders of magnitude lower than Se, so by mixing Te and S or Te and Ss, the vapor pressure can be lowered. (e.g., 1000° C., Se-Se-5O%Te: about 300 torr, Se-only special about 3000 torr), therefore, growth in a quartz ampoule vacuum enclosure is possible.

1ii) The thermal conductivity of Se is 0.0007 to 0.00
183 Cul / +IJQ / ad / sec
/ "C Compared to that, the thermal conductivity of Te is 0.014C
ul/cs/ad/sec/'C (25°C), which is very large. Therefore, by using a mixed solution, heat flows easily through the heat sink, increasing the growth rate.

1v) The solubility of n-VI group compounds in Se and S is small.The solubility of Zn5e in Se is approximately 0 at 1000°C.
．． Although it is only 0:2wol%, Se -50mo
About 0.1 mo at 1000°C by changing to l%Te
increase to l%. In this way, by using a mixed solution of Te and other group Ⅰ elements as a solvent, the solubility increases and crystal growth becomes possible.

■) When the content of Te in the solution increases, the grown n-VI group compound becomes a crystal with many optical defects [
As an example, Fig. 12 shows the cathodoluminescence (CC,L,) of Zn5e crystal grown only in Te solution and Se solution.
respectively shown in Figure 13], but for Te with respect to other group Ⅰ elements,
At least the minimum content mentioned in item i) above (in the case of ZnSe,
By setting Te/Ss+Te to 38 mol% or more and 65 mol% or less, high-quality crystal growth is possible.As an example, Figure 14 shows the cathode luminescence of the ZaSe surface when epitaxially grown at 5e55 mol%. shows.

vi) High-purity carbon with high thermal conductivity is usually used for the heat sink, but BN, SiC, etc. may also be used.

By directly contacting the substrate on this heat sink, heat from the crystal precipitation area flows without intervening quartz or an air layer.This makes it possible to increase the growth rate and lower the growth temperature, resulting in fewer defects. Crystals are obtained.

As described above, the present invention has the advantage that it can be widely applied to the production of visible light emitting devices using Group II-VI compounds, photoelectric conversion devices using Group II-VI compounds, and the like.

[Brief explanation of the drawing]

Figure 1 is a schematic diagram showing a conventional liquid phase crystal growth method when the source is lighter than the solvent, and Figure 2 is a schematic diagram showing the same liquid phase crystal growth method as in Figure 1 when the source is heavier than the solvent. Figure 3 is a schematic diagram showing a liquid phase epitaxial crystal growth method when the source is lighter than the solvent, and Figure 4 is a schematic diagram showing a liquid phase epitaxial crystal growth method similar to Figure 3 when the source is heavier than the solvent. 5 and 7 are schematic diagrams showing the epitaxial crystal growth method according to the present invention, and FIG. 6 shows the relationship between the temperature maintained in the apparatus of FIG. 5 and the distance in the longitudinal direction of the apparatus. FIG. 8 is a schematic diagram showing the relationship between the temperature change occurring in the device shown in FIG. 7 and the distance in the longitudinal direction of the device. FIG. 9 is a schematic diagram showing the epitaxial crystal growth layer and substrate obtained by the method of the present invention. FIG. 10 is a schematic diagram showing the state of 7. Figure 11 shows the relationship between the specific gravity of nSe*CdSe and the specific gravity of Se/Te for the ratio of Se and Te. Figure 11 shows the relationship between the specific gravity of ZnS and CdS and the specific gravity of S/Te. Figure 12 is a diagram showing the cathode mineralization at 300° for a Zn5e crystal grown only in a Te solution, and Figure 13 is a diagram showing the cathode mineralization at 300° for a Zn5e crystal grown only in a Se solution. Figure 14 shows the cathode luminescence at 300° of 5e-5
FIG. 3 is a diagram showing the cathode luminescence at 300° of a Zn5e crystal grown using a 5 mol % Te solution. 1... Heat sink, 2... Board, 3...
Substrate fixed quartz tube, 4...Zn5e e.g. crystal particles,
5,... 5e-Te solution, 6... Quartz ampoule,
7... Vacuum sealing part, 8... Welding part, 9...
Epitaxial growth layer, 10...substrate, 11...
・Z n S e M crystal particles (source), 12...
Te solvent, 13... ZaSe with large dalein, 1
4...Heat sink, 15...Se solvent, 16
... Stopper, 17... Epitaxially grown crystal layer, 18... Substrate. Figure 11 Figure 2 (Q) (b) (Q)
(b) (a) (b)
(a) (b) Figure 5 Figure 16 off view Figure 18 m:lJ3 [(σ) Figure 19 Figure 10 Figure 11 Procedural amendment (voluntary) June 20, 1986 1, Indication of case Patent application No. 60-87404 2, Title of invention: II-Vl group compound crystal growth method 4
, Agent Address: 5 Shinbashi, Minato-ku, Tokyo 105
No. 196, contents of the amendment (11 Specification, page 2, line 6, "...Relating to crystal growth methods." is corrected to "...Relating to crystal growth methods." J. 2) Change “during the amplifier” on page 2, line 10 of the specification to r
Correct 1 in the ampoule. (3) “Solvent specific gravity relationship” on page 2, line 13 of the specification
is corrected to "specific gravity relationship with the solvent." (4) Delete "first" in the third line of page 4 of the specification. (5) Change “liquid phase growth method” on page 6, line 13 of the specification cylinder to “
Correct it to growth method j. (6) Correct “Placed in...” on page 6, line 16 of the specification as ◆j (7) rZnSe solution on page 7, line 16 of the specification "of'
Zn-3e solution” is corrected. (8) "Enlarge the sealing part" on page 8, line 16 of the specification cylinder is corrected to "1 with the sealing part facing down." (9) "Into the board" on page 8, line 19 of the specification. is corrected to ``1 into the solution.'' α・ Correct ``conductive type impurity'' to ``conductive type impurity'' in lines 13 and 144 of page 9 of the specification, respectively. αD Specification page 9, line 16 r ZnS+ use J' ZnS+-xsex
Correct it with J. (2) On page 10, line 18 of the specification, "When only rSe is present" is corrected to "1 when only 'Ss" is present. Q'J "Cu1" on page 11, lines 2 and 3 of the specification
'' are respectively corrected as 'Ca1j.

Claims (3)

[Claims] (1) In a method of growing a II-VI group compound semiconductor crystal in which a group VI element other than Te is present from a solution containing polycrystalline particles as a source of the crystal by controlling the temperature, A certain group VI element and Te are added to the above II-
A crystal growth method characterized by mixing Group VI compounds in a ratio that has a higher specific gravity and using the mixture as a solvent. (2) The method according to claim (1), wherein the growth is epitaxial growth on a substrate crystal. (3) Temperature control is performed using a heat sink that is in direct contact with the side of the substrate opposite to the side that is in contact with the solution, and the heat sink, substrate, solution, and polycrystalline particles are placed inside a quartz tube. The method according to claim (2), characterized in that crystal growth is performed by enclosing the crystal in a crystal.