JPH04325499A - Manufacture of potassium sulfide added cadmium-zinc mixed crystal thin film - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a potassium-added cadmium-zinc sulfide mixed crystal thin film. In particular, the present invention provides a method for producing a potassium-doped cadmium-zinc sulfide mixed-crystal thin film that exhibits p-type conductivity, which is essential for the production of p-n junction light-emitting devices, in cadmium-zinc sulfide mixed-crystal semiconductors useful for light-emitting devices in the visible short wavelength range. It is related to.

0002

[Prior Art] It is generally said that it is difficult to control the conductivity type of II-VI group compound semiconductors. A method of doping with phosphorus has been used.

0003

[Problems to be Solved by the Invention] However, in the conventional method as described above, when lithium or sodium, which is a Group I element, is used as a dopant, the size of the dopant atom is smaller than that of cadmium or zinc to be replaced. ,
The problem was that it easily moved within the semiconductor due to heat or electrical energy, making it difficult to obtain stable characteristics.

[0004] Furthermore, when nitrogen, arsenic, or phosphorus, which are group V elements, are used as a dopant, there is a problem that the activation rate as an acceptor is low and a semiconductor exhibiting low resistance p-type conduction cannot be obtained. In view of this, the present invention has been developed to create a cadmium-zinc sulfide mixed crystal thin film exhibiting p-type conductivity by efficiently adding potassium, which has a size that does not easily move around in the cadmium-zinc sulfide mixed crystal and has high chemical activity. The purpose is to provide a method for manufacturing.

[0005]

[Means for Solving the Problems] In order to achieve the above object, the method for producing a potassium-added cadmium-zinc sulfide mixed crystal thin film of the present invention provides a method for producing a potassium-added cadmium-zinc sulfide mixed crystal thin film, in which sulfur molecular beams, cadmium molecular beams, and zinc molecular beams are formed on the surface of a substrate in vacuum. When manufacturing a cadmium-zinc sulfide mixed crystal thin film using the molecular beam epitaxy method using irradiation with ions, the method is characterized in that potassium is added to the mixed crystal thin film by simultaneously irradiating a molecular beam of heated and evaporated potassium sulfide.

In the above configuration, the sulfur molecular beam heats and evaporates sulfur, or heats and decomposes at least one sulfur compound selected from the group consisting of hydrogen sulfide, dimethyl sulfur, diethyl sulfur, methyl mercaptan, and ethyl mercaptan. A sulfur molecular beam obtained by heating and vaporizing metal cadmium, or by thermally decomposing the vapor of at least one cadmium compound selected from the group consisting of dimethyl cadmium and diethyl cadmium. The zinc molecular beam is preferably a molecular beam obtained by heating and evaporating metallic zinc or thermally decomposing the vapor of at least one zinc compound selected from the group consisting of dimethylzinc and diethylzinc.

Further, in the above structure, it is preferable that the substrate is a single crystal of gallium arsenide, gallium phosphide, or indium phosphide. Further, in the above configuration, it is further preferable that the substrate temperature is 200° C. or more and 500° C. or less.

[0008]

[Operation] The present invention uses heated and evaporated potassium sulfide when producing a cadmium zinc sulfide mixed crystal thin film by the molecular beam epitaxy method in which the surface of a substrate is irradiated with a sulfur molecular beam, a cadmium molecular beam, and a zinc molecular beam in a vacuum. Potassium sulfide containing sulfur, which is a constituent element of cadmium zinc sulfide, is used as an impurity source by adding potassium to the mixed crystal thin film by simultaneous irradiation with molecular beams. The molecules obtained by heating and evaporating potassium sulfide have an atomic arrangement similar to that of II-VI group compound semiconductor crystals, and contain group II elements (cadmium, zinc).
The potassium atom that should enter the position is exactly adjacent to the sulfur atom, which is a group VI element, and potassium easily settles in the group II element position, so that it is efficiently taken in as an acceptor.

[0009] In addition, sulfur molecular beams can be used to thermally evaporate sulfur or to thermally decompose at least one sulfur compound selected from the group consisting of hydrogen sulfide, dimethyl sulfur, diethyl sulfur, methyl mercaptan, and ethyl mercaptan. It is a sulfur molecular beam, and the cadmium molecular beam is a molecular beam obtained by heating and vaporizing metal cadmium or thermally decomposing the vapor of at least one cadmium compound selected from the group consisting of dimethyl cadmium and diethyl cadmium, According to a preferred embodiment of the present invention, the zinc molecular beam is obtained by heating and evaporating metallic zinc or thermally decomposing the vapor of at least one zinc compound selected from the group consisting of dimethylzinc and diethylzinc. This is preferable because unnecessary impurity components incorporated into the cadmium zinc sulfide mixed crystal thin film do not adversely affect the properties of the obtained thin film.

Further, according to a preferred embodiment of the present invention in which a single crystal of gallium arsenide, gallium phosphide, or indium phosphide is used as the substrate, the lattice constant of these substrates is lower than that of the potassium-doped cadmium zinc sulfide mixture formed on the substrate. Since the lattice constant is similar to that of crystals, pure single crystals can be easily produced. Furthermore, the substrate temperature should be increased to 200°C or higher and 500°C.
According to the preferred embodiments of the present invention described below, the atoms constituting the produced thin film are sufficiently migrated, and each atom is stably arranged at a precise lattice position. Further, since the defect of atomic vacancies caused by excessive re-evaporation of atoms is suppressed, it is easier to obtain more perfect crystals.

[0011]

[Examples] The present invention will be explained in detail below with reference to Examples. FIG. 1 is a schematic diagram showing the structure of a molecular beam epitaxial apparatus (MBE apparatus) used in an embodiment of the manufacturing method of the present invention. In the figure, 6a, 7a, 8a, and 9a are metal cadmium, metal zinc, sulfur, and potassium sulfide, respectively, placed in a normal evaporation crucible, and heated and evaporated to form a cadmium molecular beam 6c, a zinc molecular beam 7c, and a sulfur molecular beam 8c. , a potassium sulfide molecular beam 9c is obtained.

[0012] Actual thin film growth is performed according to the following procedure. First, the substrate 4 whose surface has been cleaned is mounted on a substrate holder 13 made of, for example, molybdenum. In this example, a gallium arsenide single crystal having a lattice constant close to that of cadmium zinc sulfide was used as the substrate material. Next, the vacuum container 1 is evacuated to an ultra-high vacuum of about 10 -9 Torr or less by the ultra-high vacuum exhaust device 2 . In FIG. 1, the position of the ultra-high vacuum evacuation device 2 is only shown, and the details are omitted. After that, for example, 12 crucibles 6a, 7a, 8a
Heat to around 0°C, 240°C, and 100°C, 1x each.
Cadmium molecular beams 6c, zinc molecular beams 7c, and sulfur molecular beams 8c having appropriate strengths of about 10<-6 >Torr are obtained. Further, the potassium sulfide 9a is heated, for example, in a crucible to about 200 DEG C. so that a potassium sulfide molecular beam 9c having an appropriate strength of about 1.times.10@-7 Torr can be obtained.

Next, the substrate 4 is heated to about 600° C. to remove the surface oxide film. The substrate is then lowered to a temperature suitable for crystal growth. In this example, the temperature was 300°C. Thereafter, the shutters 6b, 7b, 8b, and 9b were simultaneously opened, and the substrate was irradiated with molecular beams of cadmium, zinc, sulfur, and potassium sulfide to grow crystals. In the potassium-doped cadmium zinc sulfide mixed crystal thin film formed by the method described above, by using potassium sulfide as a dopant, potassium was efficiently incorporated into the film, and as a result of photoluminescence characteristics measurement, the results are shown in Figure 2. As shown in FIG. It could be confirmed.

[0014] This sample was also heated in vacuum (400°C
・Even after 1 hour), no change was observed in the photoluminescence properties, indicating stable properties. In addition, in the above-mentioned example, a sulfur molecular beam obtained by heating and vaporizing elemental sulfur was used, but hydrogen sulfide, dimethyl sulfur, diethyl sulfur, or methyl mercaptan (CH3 SH
) or ethyl mercaptan (C2 H5 SH), a similar effect was observed using a sulfur molecular beam obtained by thermally decomposing at least one of them.

Although a cadmium molecular beam obtained by heating and vaporizing metallic cadmium was used as the cadmium molecular beam, a similar effect can also be obtained by using a cadmium molecular beam obtained by thermally decomposing dimethyl cadmium or diethyl cadmium vapor. It was seen. In addition, although the zinc molecular beam obtained by heating and vaporizing metallic zinc was used, the same effect could also be obtained by using a zinc molecular beam obtained by thermally decomposing dimethylzinc or diethylzinc vapor. .

[0016] Furthermore, the substrate temperature during thin film formation is such that the migration of atoms constituting the formed thin film is sufficiently carried out.
Each atom is easily arranged stably at a precise lattice position,
In addition, by suppressing the defect of atomic vacancies caused by excessive re-evaporation of atoms,
A preferable temperature range was 0° C. or lower because it was easier to obtain more perfect crystals.

In addition to gallium arsenide, single crystals of gallium phosphorus and indium phosphorus, whose lattice constants are similar to those of the potassium-added cadmium zinc sulfide mixed crystal formed on the substrate, may also be used as the substrate material. Almost similar results were obtained. The degree of vacuum varies depending on the distance between the molecular beam source and the substrate and the type of molecular beam source used, but the vacuum is such that the distance between the molecular beam source and the substrate is within the mean free path of the molecular beam. It is preferable to do so, and the higher the vacuum, the higher the vacuum is usually 10 −5 Torr or less.

By the method of the present invention, it has become possible to easily produce a cadmium zinc sulfide mixed crystal thin film that has stable characteristics against heat and electrical energy and exhibits p-type conductivity. A light-emitting device in the visible short wavelength range can be expected from a pn junction with cadmium zinc sulfide that exhibits n-type conductivity, which can be produced at present, and its practical effects are significant.

[0019]

As explained above, according to the method of the present invention, potassium can be incorporated into a film by molecular beam epitaxy using potassium sulfide, which has a similar atomic arrangement to cadmium zinc sulfide, as an impurity source. It becomes possible to easily produce a cadmium zinc sulfide mixed crystal thin film exhibiting p-type conductivity and exhibiting stable characteristics without easily diffusing potassium even by heat or electrical energy.

[0020] Furthermore, the sulfur molecular beam is obtained by heating and evaporating sulfur or by thermally decomposing at least one sulfur compound selected from the group consisting of hydrogen sulfide, dimethyl sulfur, diethyl sulfur, methyl mercaptan, and ethyl mercaptan. It is a sulfur molecular beam, and the cadmium molecular beam is a molecular beam obtained by heating and vaporizing metal cadmium or thermally decomposing the vapor of at least one cadmium compound selected from the group consisting of dimethyl cadmium and diethyl cadmium, According to a preferred embodiment of the present invention, the zinc molecular beam is obtained by heating and evaporating metallic zinc or thermally decomposing the vapor of at least one zinc compound selected from the group consisting of dimethylzinc and diethylzinc. , unnecessary impurity components incorporated into the cadmium-zinc sulfide mixed crystal thin film do not adversely affect the properties of the thin film.

Further, according to a preferred embodiment of the present invention in which a single crystal of gallium arsenide, gallium phosphide, or indium phosphide is used as the substrate, the lattice constant of these substrates is lower than that of the potassium-doped cadmium zinc sulfide mixture formed on the substrate. Since the lattice constant is similar to that of crystals, pure single crystals can be easily produced. Furthermore, the substrate temperature should be increased to 200°C or higher and 500°C.
According to the preferred embodiments of the present invention described below, the atoms constituting the produced thin film are sufficiently migrated, and each atom is stably arranged at a precise lattice position. Further, since the defect of atomic vacancies caused by excessive re-evaporation of atoms is suppressed, it is easier to obtain more perfect crystals.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing the structure of a molecular beam epitaxial apparatus for producing a potassium-added cadmium-zinc sulfide mixed crystal thin film in one embodiment of the present invention.

FIG. 2 is a diagram showing a photoluminescence spectrum of a potassium-added cadmium-zinc sulfide mixed crystal thin film at a temperature of 12K in an example of the present invention.

[Explanation of symbols]

1 Vacuum container 2 Ultra-high vacuum evacuation device 3 Substrate holder 4 Substrate 5 Cadmium-zinc sulfide mixed crystal thin film 6a Metal cadmium in the crucible 6b Shutter 6c Cadmium molecular beam 7a Metal zinc in the crucible 7b Shutter 7c Zinc molecular beam 8a In the crucible Sulfur entered 8b Shutter 8c Sulfur molecular beam 9a Potassium sulfide 9b entered the crucible Shutter 9c Potassium sulfide molecular beam

Claims (4)

[Claims] Claim 1: When producing a cadmium zinc sulfide mixed crystal thin film using a molecular beam epitaxy method in which the substrate surface is irradiated with a sulfur molecular beam, a cadmium molecular beam, and a zinc molecular beam in a vacuum, potassium sulfide molecules are heated and evaporated. A method for producing a potassium-added cadmium-zinc sulfide mixed crystal thin film, characterized in that potassium is added to the mixed crystal thin film by simultaneously irradiating the same with radiation. [Claim 2] The sulfur molecular beam is obtained by thermally evaporating sulfur or by thermally decomposing at least one sulfur compound selected from the group consisting of hydrogen sulfide, dimethyl sulfur, diethyl sulfur, methyl mercaptan, and ethyl mercaptan. It is a sulfur molecular beam, and the cadmium molecular beam is a molecular beam obtained by heating and vaporizing metal cadmium or thermally decomposing the vapor of at least one cadmium compound selected from the group consisting of dimethyl cadmium and diethyl cadmium, The potassium addition according to claim 1, wherein the zinc molecular beam is a molecular beam obtained by heating and evaporating metallic zinc or thermally decomposing the vapor of at least one zinc compound selected from the group consisting of dimethylzinc and diethylzinc. A method for producing a cadmium zinc sulfide mixed crystal thin film. 3. The method for producing a potassium-doped cadmium zinc sulfide mixed crystal thin film according to claim 1, wherein the substrate is a single crystal of gallium arsenide, gallium phosphorus, or indium phosphorus. 4. The method for producing a potassium-added cadmium zinc sulfide mixed crystal thin film according to claim 1, wherein the substrate temperature is 200° C. or higher and 500° C. or lower.