JPH04137566A - Manufacture of ii-vi compound semiconductor single crystal and manufacture of semiconductor light emitting element - Google Patents

Abstract

PURPOSE:To improve characteristics of single crystal, by arranging polycrystal of II-VI compound semiconductor at a high temperature part of a crucible arranged in a sealed tube provided with temperature difference, forming an Li2Se atmosphere at a specified temperature in the crucible, and turning the polycrystal into single crystal by solid growth. CONSTITUTION:Polycrystal ZnSe which is an example of raw material 12 to be turned into single crystal and Li2Se which is dopant 13 for turning the original material into conductor are put in a crucible 11, which is put in a sealed tube 14 made of quartz as heat resistant material. The inside of the sealed tube is vacuumized at about 10<-6> Torr, and the top part of the tube is fused and sealed. The crucible 11 is so placed in a heating furnace that the crucible bottom part where the original material 12 and the dopant 13 for conductor are disposed is at the high temperature part, and the top part of the crucible is at the low temperature part of the heating furnace. In this state, heat treatment for, e.g. about two weeks is performed. Thereby the polycrystal line ZnSe as the raw material 12 is almost turned into single crystal.

Description

[Detailed Description of the Invention] [Object of the Invention (Industrial Application Field) The present invention provides a method for purifying a ■-■ group compound semiconductor, II-VI
This article will focus on a method for manufacturing a group compound semiconductor single crystal, particularly a method for single crystallizing a II-VI group compound semiconductor that is applied to a blue light emitting device, and a method for manufacturing a semiconductor light emitting device using this semiconductor substrate.

(Prior Art) Semiconductor light emitting devices using compound semiconductor materials and having a light emission range from red to green are being mass-produced, and development is underway to further improve brightness. However, a satisfactory manufacturing technology has not yet been provided for a blue light emitting element that emits blue light in the visible region.

In order to manufacture a blue light emitting device, it is necessary that the forbidden band width of the semiconductor material exceeds 2.6 to 3.7 eV,
Recently, 1l-VI group compound semiconductors have been attracting attention as semiconductors that satisfy this requirement, but the forbidden band width is 2.
．． Zinc sulfide (ZnS) in the range of 6-3.7 eV,
Zinc selenide (ZnSe) and these liquid crystals (Z n
SS e) is seen as promising. Hereinafter, the above materials will be collectively referred to as zinc sulfide selenide (ZnS Se , 1□: 0≦X≦1).

Zinc sulfide selenideAlthough it is seen as a promising material for blue light-emitting devices, it has not yet been put to practical use.
The reason is that it is difficult to obtain type crystals. The reason is ■-
Defects (Se, S vacancies, lattice, etc.) that are often found in group compounds are particularly strong, and even when doped with acceptor impurities,
This is thought to be because the effect of impurity doping does not appear and does not contribute to an increase in conductivity since V compensates for Se S and becomes n-type with high resistance. Therefore, a crystal with p-Virgin conductivity has not been obtained. Conventionally, the single crystal growth method includes, for example, a high-pressure melting method known as a crystal growth method under high temperature and high pressure conditions, such as the Bridgman method, the Tamman method, and the sealed tube chemical transport method 1 sublimation method. According to the diagonal method,
The crystals obtained are non-uniform in shape and characteristics, have a high concentration of impurities and lattice defects, and have extremely high resistance, which poses problems such as there are limits to the construction of light-emitting devices with these crystals.

(Problem to be solved by the invention) As described in the above conventional example, compound semiconductor crystals for light emitting devices, such as single crystals such as ZnS and Zn5e,
There were problems such as difficulty in controlling electrical resistance and conductivity type. In addition, S, Se vacancies, etc. are observed to occur within the crystal, which poses a problem of inhibiting light-emitting characteristics. This slanting effect has been a major obstacle in realizing blue light emitting devices with superior performance.

Furthermore, in the conventional method described above, since crystallization is performed while the tube is in a sealed tube, thermal distortion of the sealed tube and damage to the inner wall of the sealed tube and the Zn5e may occur.
Due to its "wettability" with the melt, single crystals contain many twin crystals and have the problem of solidifying.

Furthermore, single crystals produced by the vertical Bridgman method contain many twin crystals and have low purity.

The present invention has been made in view of the above-mentioned conventional problems, and improves control of conductivity type and single crystallization of ■-■ group compound semiconductors in order to manufacture low-resistance p-type 1l-VI group compound semiconductor crystals. The present invention aims to provide a method for manufacturing a light emitting device using this semiconductor crystal substrate.

[Structure of the Invention] (Means for Solving the Problems) The present invention provides a method for controlling conductivity of a ■-■ group compound semiconductor, II-
This article describes a method for manufacturing a group VII compound semiconductor type single crystal, a semiconductor light emitting device using the semiconductor single crystal substrate manufactured using the method, and a method for manufacturing it. That is, using a sealed tube, forming a high temperature part and a low temperature part in this sealed tube, and specifying the surrounding air inside the sealed tube by using a compound semiconductor device in at least one of these parts.
Impurity treatment and single crystallization are performed using the temperature difference.

First, the first invention is to provide a II-VI=group compound semiconductor device in a high-temperature part of a rubber placed in a sealed tube with a temperature difference in order to obtain p-type thick conductivity of a compound semiconductor using a sealed tube. This method consists in making the ①-③ group compound semiconductor into a p-type single crystal by creating an atmosphere of Li236 inside.

The second invention is Li2Se as the atmosphere of the first invention.
There is a method that specifies the amount of

The third invention is based on Li2 used as the atmosphere in the first invention.
Since Se reacts with conventional quartz sealed tubes, making it difficult to control the conductivity type, there is a method for obtaining p-type by constructing the container with a material that is difficult to attack.

The fourth invention provides a high temperature section in a sealed tube with a temperature difference.
A polycrystalline body of a Group VI compound semiconductor is placed inside this sealed tube with Li2
Single crystal growth is performed in a Se atmosphere to form a ■-■ group compound semiconductor table-type single crystal substrate, and an epitaxial layer of the same type as this is laminated on this p-type vehicle crystal substrate, and this epitaxial layer is used to emit light. A method for manufacturing a semiconductor light emitting device as a layer.

A fifth invention resides in the method for manufacturing a semiconductor light emitting device according to the invention as set forth in claim 4, characterized in that the light emitting layer is formed by metal organic vapor phase epitaxy.

A sixth invention resides in the method of manufacturing a semiconductor light emitting device according to claim 4, characterized in that the light emitting layer is formed by liquid phase growth using at least one of its constituent elements.

(Function) The present invention is applied to the manufacture of a II-VII group compound semiconductor type single crystal used in a blue light emitting device, in order to control the conductivity, the sealed tube is provided with a temperature difference and a luho is placed inside the sealed tube in the high temperature part. II
Single crystallization of a group VI compound semiconductor polycrystal is achieved by solid phase growth using Li2Se as the inner atmosphere and PBN as the crucible.

Next, a crystal layer of the same type is laminated on the crystal substrate manufactured based on the above, and a light emitting junction is formed using this crystal layer as a light emitting layer, thereby obtaining current-voltage characteristics with good device characteristics. .

(Example) Hereinafter, details of the present invention will be explained with reference to illustrated embodiments.

FIG. 1 shows a sectional view of a sealed tube used in an embodiment of the present invention and its internal arrangement. As shown in FIG. 1, polycrystalline Z, an example of a raw material 12 that is made into a single crystal, is placed inside a crucible made of a heat-resistant material such as pyrolytic boron nitride.
n5e and Li2Se, which is a dopant 13 that forms the atmosphere inside the crucible and makes the raw material conductive.
The crucible is placed in a sealed tube 14 made of quartz, which is a heat-resistant material, and the top of the sealed tube 14 is evacuated to about 10''-6 Torr. The bottom part where the raw material 12 and the conductive dopant 13 are placed is placed in the high temperature part of the heating furnace, and the top part is placed in the low temperature part of the heating furnace, and heat treatment is performed in this state for about two weeks, for example. This heat treatment is carried out in a heating furnace with the temperature gradient shown in Figure 2.
Apply at °C.

By tilting it upward, polycrystalline Z, which is the raw material 12,
n5e achieves almost single crystallization. Further, by doping with Li, a p-type crystal was obtained.

In this heat treatment, 11 has a diameter of 20 mm and a length of 50 mm, and 10 g of polycrystalline Zn5e12 as a raw material and 1001 of Li 2 S e 13 (0) impurities and 4 electric bodies are added to this.
00l11,1 mol %) were placed in sealed tubes 14 with a diameter of 30 mm and a length of 7011111, and the temperature difference was set at 850° C. in the high temperature part and 840° C. in the low temperature part.

After the above-mentioned heat treatment, the crystal was sliced into 1-inch thick slices, surface-treated with 30% NaOH, and an electrode was placed on the surface to perform hole measurement. Furthermore, heat treatment was performed with various changes in the impurity doping material Li2Se2,
By comparing the electrical characteristics, the results shown in FIG. 3 were obtained.

As seen in Fig. 3, the acceptor degree is correlated with the amount of doped Li2Se, and in order to obtain the required concentration of 1017 cm-3 to 1018 cm-3, L
The amount of i2Se added may be 0.01 to 0.5 mol%, and the electrical resistance value may also be within this range.By diffusing and growing Ll as an impurity into the Zn5e crystal, these It is possible to reduce the electrical resistance value of the crystal.

Next, an embodiment of the third invention will be described with reference to FIG. FIG. 4 shows a sectional view of the sealed tube used in one embodiment and its internal arrangement. As shown in FIG. 4, an atmosphere in the sealed tube is formed with polycrystalline Zn5e, which is an example of the raw material 12, which is monocrystallined at the bottom of the sealed tube 24 made of a heat-resistant material such as quartz, and the raw material is made conductive. dopant 1
3 of Li2Se are placed respectively. Then, the bottom of this sealed tube 21 is connected to the high temperature section 12 of the heating furnace. The top portions are respectively placed in the low temperature section of the heating furnace and kept in this state for about two weeks, for example. This crystal growth is performed in a heating furnace having the temperature distribution shown in FIG. 2 at a temperature of 850° C. in the high temperature portion and 840° C. in the low temperature portion.

The seal 21 in the above embodiment has a diameter of 20 mm and a length of 50 mm.
Using the one formed in III11, the raw material polycrystalline Z
The semiconductor crystal is manufactured by placing n5e at Log, Li2Se at 100111 at the bottom, and evacuating the inside of the sealed tube to about 10'' Torr.

In the tube that was heat-treated in this way, the inner wall of the quartz tube that was the sealed tube was devitrified, and the polycrystalline Zn5e that was the raw material remained as it was and had not become a single crystal. Similar results were obtained even when a small amount of Li2Se was added, indicating that quartz is a material that is easily attacked by Li.

Next, a sealed tube vacuum-sealed in the same manner as in the first embodiment, the melt tube to be charged at this time being made of Al2203, and the other parts being the same, was placed in an electric furnace with the temperature distribution shown in FIG. 2. , and was subjected to the same heat treatment as in the first example.

The ZnSe polycrystalline body treated in the diagonal manner either achieved single crystallization as in the first example, or did not have electrical conductivity and had high resistance. Even if the added Li25effi was changed, low resistance could not be obtained.

According to the above embodiments, by using pyrolytic boron nitride (PBN) as the crucible material, (1) impurities can be stably doped.

(2) Low resistance can be obtained.

(3) It is possible to align defects on the surface in one direction, and there are advantages such as improving the characteristics of the single crystal.

Next, a fourth embodiment shown in FIG. 5 shows a blue light emitting element. In the figure, 51 is a p-type Zn5e substrate crystal obtained by an atmospheric heat treatment method using the raw material obtained in the present invention,
On top of this, MOCVD using dimethylzinc (DMZ) and dimethylselenium (DMSe) as raw materials
A p-type Zn5e crystal layer 52. N-type Zn5e crystal layers 53 were sequentially stacked to form a pn junction type light emitting device.

At this time, the main p-type impurity of the p-type Zn5e crystal layer 52 is Ll, and the main n-type impurity of the n-type Zn5e crystal layer 53 is C1. An AuZn electrode 54 is formed as a p sub-electrode on the back surface of the Zn5e substrate 51, and an n-type Zn5e
InGa 55 is formed on the surface of the layer 53 as an n-type electrode.

The light-emitting device thus obtained exhibits good blue light emission and exhibits excellent light-emitting characteristics.

This invention was achieved by the conventional p-type substrate which was difficult to crystallize.1]-V
p-type of Group I compound semiconductor materials can be achieved extremely easily;
Conductivity can be controlled. Furthermore, according to the present invention, it has become possible to obtain a large p-type Zn5e crystal.

Furthermore, by using this p-type wheel crystal as a substrate crystal, a semiconductor light emitting device exhibiting good blue light emission characteristics can be obtained, and mass productivity and uniformity of light emission characteristics can be achieved.

Although Zn5e was explained in the above embodiment, it goes without saying that similar effects can be applied to II-VI group compound semiconductor materials such as ZnS, CdS, and CdSe.

Furthermore, the method for growing the II-VI group compound semiconductor layer is not limited to the MOCVD method, but other vapor phase growth, MBE method, or liquid $11 growth method may be used.

In addition, the present invention can be implemented with various modifications without departing from the spirit thereof.

[Effects of the invention] According to the present invention, II-V, which was conventionally difficult to convert into P-type.
It is extremely easy to convert a Group I compound semiconductor material into a p-type material, and its conductivity can be controlled. A semiconductor layer of a light-emitting layer is formed on the p-type crystal substrate thus obtained by MOCVD or the like, and the light-emitting efficiency is determined.

It is possible to obtain a blue light-emitting element with excellent light-emitting characteristics.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view showing a sealed tube used in an embodiment of the first invention, a crucible housed inside the tube, and the arrangement of raw materials, etc.;
Fig. 2 is a diagram showing the heat treatment conditions for the sealed tube used in the example of the present invention, Fig. 3 is a diagram showing the amount of addition and electrical characteristics of the Li3Se doped product according to the invention, and Fig. 4 5 is a sectional view showing the state of the sealed tube after heat treatment used in the embodiment of the third invention, and FIG. be. 11... Crucible, 12... Raw material 13... Dopant, 14.24... Sealed tube 51 =
・P-type Zn5e substrate 52...p-type Zn5e crystal layer 53...n-type Zn5e crystal layer 54---A u Z n electrode 55-1 n Ga electrode

Claims (6)

[Claims] (1) When producing a compound semiconductor single crystal using a sealed tube, the high-temperature part of the crucible is placed inside the sealed tube with a temperature difference.
II-VI characterized in that a polycrystalline body of a group II-VI compound semiconductor is arranged, the interior of the crucible is made into an Li_2Se atmosphere, the temperature is raised to a predetermined temperature, and the polycrystalline body is turned into a single crystal by solid phase growth. A method for producing a group compound semiconductor single crystal. (2) Li_2Se used as the atmosphere in the crucible
2. The method for producing a II-VI group compound semiconductor single crystal according to claim 1, wherein the range of is 0.01 to 0.5 mol%. (3) The crucible according to claim 1, wherein the material is pyrolytic boron nitride (PBN).
A method for producing a II-VI group compound semiconductor single crystal. (4) A polycrystal of a II-VI group compound semiconductor is placed in the high-temperature part of a crucible placed in a sealed tube with a temperature difference, and a single crystal is grown in the Li_2Se atmosphere inside the crucible to produce a II-VI group compound semiconductor. A method for manufacturing a semiconductor light emitting device, in which a single crystal substrate is formed, an epitaxial layer of the same type as the single crystal substrate is laminated on the single crystal substrate, and the epitaxial layer is used as a light emitting layer. (5) The method for manufacturing a semiconductor light emitting device according to claim 4, wherein the light emitting layer is formed by metal organic vapor phase epitaxy. (6) Claim 4 characterized in that the light emitting layer is formed by liquid phase growth using at least one of its constituent elements.
The method for manufacturing the semiconductor light emitting device described above.