Transparent compound semiconductor and production method therefor

Abstract

The present invention relates to a transparent compound semiconductor and to a production method therefor, and is adapted to provide a transparent compound semiconductor of high stability and charge mobility while being transparent. The transparent compound semiconductor according to the present invention has a composition of Ba.sub.1XLa.sub.XSnO.sub.3 (0<x<0.1) and has a charge mobility of at least 10 cm.sup.2/V.Math.sec.

Claims

1. A transparent compound semiconductor fabricated by reacting a Ba compound, an La compound, and an Sn compound, the transparent compound semiconductor comprising: a composition of Ba.sub.1XLa.sub.XSnO.sub.3 (0<x<0.1), wherein a composition ratio of the Ba.sub.1XLa.sub.XSnO.sub.3 is (Ba+La):Sn=1:1, the thickness of the Ba.sub.1XLa.sub.XSnO.sub.3 is in the range of 0.4 nm to 400 nm, and the Ba.sub.1XLa.sub.XSnO.sub.3 has a charge mobility of at least 10 cm.sup.2/V.Math.sec or more at room temperature.

2. The transparent compound semiconductor of claim 1, wherein, when 0.01x0.07, the Ba.sub.1XLa.sub.XSnO.sub.3 has the charge mobility of 10 to 80 cm.sup.2/V.Math.sec at room temperature.

3. The transparent compound semiconductor of claim 1, wherein, when 0.04x0.07, the Ba.sub.1XLa.sub.XSnO.sub.3 has the charge mobility of 50 to 80 cm.sup.2/V.Math.sec at room temperature.

4. The transparent compound semiconductor of claim 3, wherein the Ba.sub.1XLa.sub.XSnO.sub.3 has an optical transmittance of at least 90% in the visible light band.

5. The transparent compound semiconductor of claim 3, wherein the amount of change in resistance of the Ba.sub.1XLa.sub.XSnO.sub.3 is less than about 2% when the temperature is elevated and lowered between the room temperature and 530 C. in an air atmosphere.

6. The transparent compound semiconductor of claim 1, wherein the Ba.sub.1XLa.sub.XSnO.sub.3 is in the form of a single crystal or an epitaxial film.

7. A transparent compound semiconductor fabricated by reacting a Ba compound, an La compound, and an Sn compound, the transparent compound semiconductor comprising: a composition of Ba.sub.1XLa.sub.XSnO.sub.3 (0<x<0.1), wherein a composition ratio of the Ba.sub.1XLa.sub.XSnO.sub.3 is (Ba+La):Sn=1:1, the Ba.sub.1XLa.sub.XSnO.sub.3 is in the form of a single crystal or an epitaxial film, and the Ba.sub.1XLa.sub.XSnO.sub.3 has a charge mobility of at least 10 cm.sup.2/V.Math.sec or more at room temperature.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a graph showing an optical transmission spectrum of Ba.sub.1XLa.sub.XSnO.sub.3 (0<x<0.1) according to an embodiment of the present invention.

(2) FIG. 2 shows graphs of thermal resistance levels of Ba.sub.1XLa.sub.XSnO.sub.3 (0<x<0.1) according to an embodiment of the present invention.

(3) FIG. 3 is a graph showing the charge density, resistance, and charge mobility of Ba.sub.1XLa.sub.XSnO.sub.3 (0<x<0.1) according to an embodiment of the present invention.

MODES FOR CARRYING OUT THE INVENTION

(4) The objects, features, and advantages of the present invention will be more clearly understood from the following detailed descriptions of embodiments taken in conjunction with the accompanying drawings. In the following description, detailed descriptions of related known functions or elements that may unnecessarily make the gist of the present invention obscure will be omitted.

(5) The terms and words used in the specification and claims should not be construed with common or dictionary meanings, but should be construed as meanings and conception coinciding with the spirit of the invention based on a principle that the inventors can appropriately define the concept of the terms to explain the invention in the optimum method. Therefore, embodiments described in the specification and the configurations shown in the drawings are not more than the most preferred embodiments of the present invention and do not fully cover the spirit of the present invention. Accordingly, it should be understood that there may be various equivalents and modifications that can replace those when this application is filed.

(6) Hereinafter, various embodiments will now be described more fully with reference to the accompanying drawings.

(7) A transparent compound semiconductor according to an embodiment of the present invention is an n-type transparent compound semiconductor having a composition of Ba.sub.1XLa.sub.XSnO.sub.3 (0<x<0.1). The Ba.sub.1XLa.sub.XSnO.sub.3 satisfies a composition ratio of (Ba+La):Sn=1:1.

(8) Here, the composition ratio of Ba.sub.1XLa.sub.XSnO.sub.3 is 0<x<0.1 so as to have semiconductor characteristics. Since BaSnO.sub.3 is an insulating material (in the case that x=0, that is, La=0), the composition ratio of La needs to be greater than zero. In addition, since Ba.sub.0.9La.sub.0.1SnO.sub.3 is a metal (in the case that La is doped at 0.1), the composition ratio of La needs to be less than 0.1. Accordingly, the Ba.sub.1XLa.sub.XSnO.sub.3 has a composition ratio of 0<x<0.1 to have semiconductor characteristics.

(9) The Ba.sub.1XLa.sub.XSnO.sub.3 may preferably have a thickness of 0.4 nm to 400 nm in order to have good transparency and stability, and to have a charge mobility of at least 10 cm.sup.2/V.Math.sec. The Ba.sub.1XLa.sub.XSnO.sub.3 needs to have such a thickness for the following reasons. First, the thickness of Ba.sub.1XLa.sub.XSnO.sub.3 may not be less than 0.4 nm since 0.4 nm corresponds to the thickness of a single atomic layer. In addition, when the thickness of Ba.sub.1XLa.sub.XSnO.sub.3 is greater than 400 nm, transparency may be degraded.

(10) In addition, the Ba.sub.1XLa.sub.XSnO.sub.3 may be fabricated in the form of a single crystal or an epitaxial film.

(11) Ba.sub.1XLa.sub.XSnO.sub.3 used as a transparent compound semiconductor according to an embodiment of the present invention may be formed as follows.

(12) First, Ba.sub.1XLa.sub.XSnO.sub.3 may be formed by doping undoped BaSnO.sub.3 with La. BaSnO.sub.3 is an insulating material having a lattice constant of 0.41 nm, a bandgap greater than 3 eV, and a transparent property.

(13) Here, the BaSnO.sub.3 is used as a base material of Ba.sub.1XLa.sub.XSnO.sub.3 for the following reasons. First, it is difficult to expect in terms of a basic science that a material formed by doping an insulating material having a bandgap of about 4 eV with a metal material in a concentration of 10.sup.20/cm.sup.3 or less, has a high charge mobility. However, in this embodiment of the present invention, it is discovered that a high charge mobility can be implemented through A-site doping in a perovskite metal oxide having an ABO.sub.3 structure, such as BaSnO.sub.3. That is, although a perovskite metal oxide has a higher crystallization temperature than other metal compounds having different structures, the perovskite metal oxide has an advantage of providing two cationic sites which can be doped with other material. In particular, BaSnO.sub.3, a perovskite metal oxide having a high bandgap of 3 eV may used as the base material of Ba.sub.1XLa.sub.XSnO.sub.3 in this embodiment of the present invention.

(14) The bandgap of BaSnO.sub.3 is greater than 3 eV, which means that BaSnO.sub.3 has high transparency. In addition, Ba.sub.1XLa.sub.XSnO.sub.3 formed using BaSnO.sub.3 having such high transparency has several advantages in terms of transparency, compared to silicon with a bandgap of about 1.2 eV or GaAs with a bandgap of about 1.5 eV.

(15) Alternatively, Ba.sub.1XLa.sub.XSnO.sub.3 may be formed by reacting a Ba compound, an La compound, and an Sn compound. Here, BaCO.sub.3 or BaO may be used as the Ba compound, La.sub.2O.sub.3 may be used as the La compound, and SnO.sub.2 may be used as the Sn compound. For example, the Ba.sub.1XLa.sub.XSnO.sub.3 may be fabricated by mixing the Ba compound, the La compound, and the Sn compound to have the composition of Ba.sub.1XLa.sub.XSnO.sub.3 (0<x<0.1) and reacting the mixed compounds at a temperature of 500 C. to 1500 C.

(16) Here, the reaction is performed at the temperature of 500 C. to 1500 C. because, when the temperature is lower than 500 C., a crystal structure of Ba.sub.1XLa.sub.XSnO.sub.3 may not be formed, and when the temperature is higher than 1500 C., the crystal structure of Ba.sub.1XLa.sub.XSnO.sub.3 may be broken or characteristics as a transparent compound semiconductor may be deteriorated.

(17) The Ba.sub.1XLa.sub.XSnO.sub.3 may be formed on a base substrate by providing the base substrate using a physical or chemical method while reacting the Ba compound, the La compound, and the Sn compound. As the base substrate, a perovskite metal oxide having an ABO.sub.3 structure similar to BaSnO.sub.3 having a lattice constant of 0.41 nm may be used. For example, SrTiO.sub.3, LaAlO.sub.3, SrZrO.sub.3, BaNbO.sub.3, or the like having a lattice constant of 0.37 nm to 0.45 nm may be used as the base substrate, but the inventive concept is not limited thereto.

(18) In addition, the Ba.sub.1XLa.sub.XSnO.sub.3 formed by reacting the Ba compound, the La compound, and the Sn compound has a charge mobility of 10 cm.sup.2/V.Math.sec or more. In particular, the Ba.sub.1XLa.sub.XSnO.sub.3 has a charge mobility of 10 cm.sup.2/V.Math.sec or more at room temperature.

(19) Through the graphs of FIGS. 1 to 3, it may be found that the Ba.sub.1XLa.sub.XSnO.sub.3 according to the embodiment of the present invention has good transparency, stability, and charge mobility.

(20) FIG. 1 is a graph showing an optical transmission spectrum of Ba.sub.1XLa.sub.XSnO.sub.3 (0<x<0.1) according to an embodiment of the present invention.

(21) Referring to FIG. 1, optical transmission spectrums of undoped BaSnO.sub.3 and Ba.sub.1XLa.sub.XSnO.sub.3 according to the embodiment of the present invention are shown. Here, (a) shows a transmittance spectrum of undoped BaSnO.sub.3 and transmittance spectrums of doped BaSnO.sub.3 (Ba.sub.1XLa.sub.XSnO.sub.3 according to an embodiment of the present invention), and (b) shows absorption coefficients () as a function of photon energy of undoped BaSnO.sub.3 and doped BaSnO.sub.3.

(22) The absorption coefficients () of the undoped BaSnO.sub.3 and the doped BaSnO.sub.3 were extracted by measuring transmission coefficients of the same samples with different thicknesses. Optical bandgaps of the undoped BaSnO.sub.3 and the doped BaSnO.sub.3 (n=2.3910.sup.20 cm.sup.3) derived from the relationship between a and photon energy were respectively 3.03 eV and 3.01 eV.

(23) That is, it is found that the Ba.sub.1XLa.sub.XSnO.sub.3 according to the embodiment of the present invention has an optical transmittance of 90% or more in a thin film having a normal thickness.

(24) FIG. 2 shows graphs of thermal resistance levels of Ba.sub.1XLa.sub.XSnO.sub.3 (0<x<0.1) according to an embodiment of the present invention.

(25) Referring to FIG. 2, thermal resistance levels of a Ba.sub.0.966La.sub.0.04SnO.sub.3 thin film according to the embodiment of the present invention were measured in O.sub.2, Ar, and air atmospheres. That is, the thermal resistance levels of the Ba.sub.0.96La.sub.0.04SnO.sub.3 thin film were measured after elevating and lowering a temperature between the room temperature and 530 C. in the O.sub.2, Ar, and air atmospheres. The Ba.sub.0.96La.sub.0.04SnO.sub.3 thin film may be an epitaxial film.

(26) Here, the graph (a) shows variations in temperature and gas atmosphere, and the graph (b) shows variations in resistance according to the temperature and gas atmosphere. The Ba.sub.0.96La.sub.0.04SnO.sub.3 thin film having a thickness of 100 nm was maintained at a temperature of 530 C. for 5 hours.

(27) (b) shows a relationship between the resistance level and the temperature, and the resistance level was changed by 1.7% in the air atmosphere, lowered by 8% in the Ar atmosphere, and raised by 8% in the O.sub.2 atmosphere at the temperature of 530 C. for 5 hours.

(28) In this way, it was found that the Ba.sub.1XLa.sub.XSnO.sub.3 according to the embodiment of the present invention has high stability such that the variation in resistance level is small even when the temperature is elevated and lowered between the room temperature and 530 C. in the O.sub.2, Ar, and air atmospheres. In particular, the Ba.sub.1XLa.sub.XSnO.sub.3 according to the embodiment of the present invention has high stability such that the variation in resistance level is less than 2% when the temperature is elevated and lowered between the room temperature and 530 C. in the air atmosphere.

(29) FIG. 3 is a graph showing the charge density, resistance, and charge mobility of Ba.sub.1XLa.sub.XSnO.sub.3 (0<x<0.1) according to an embodiment of the present invention.

(30) Referring to FIG. 3, changes in a charge density n, a resistance , and a charge mobility of a Ba.sub.1XLa.sub.XSnO.sub.3 thin-film according to an embodiment of the present invention, are shown according to a change in the temperature of the Ba.sub.1XLa.sub.XSnO.sub.3 thin-film. The charge density n, the resistance , and the charge mobility are coefficients affected by the temperature. Here, (b, d, and f) respectively represent the charge density n, resistance , and charge mobility of the Ba.sub.1XLa.sub.XSnO.sub.3 thin-film.

(31) It is discovered that the Ba.sub.1XLa.sub.XSnO.sub.3 according to the embodiment of the present invention has a charge mobility of 10 cm.sup.2/V.Math.sec or more. That is, the Ba.sub.1XLa.sub.XSnO.sub.3 has a charge mobility of 10 cm.sup.2/V.Math.sec or more at room temperature. Further, when the x value is 0.04 and 0.07, the Ba.sub.1XLa.sub.XSnO.sub.3 has a charge mobility of 50 cm.sup.2/V.Math.sec or more.

(32) Thus, Ba.sub.1XLa.sub.XSnO.sub.3 according to the embodiment of the present invention may be transparent and, at the same time, has high stability and high charge mobility. That is, the Ba.sub.1XLa.sub.XSnO.sub.3 has excellent characteristics of a transparent compound semiconductor. For example, the Ba.sub.1XLa.sub.XSnO.sub.3 has high transparency such that optical transmittance is 90% or more in the visible light bandwidth, high stability such that variation of the resistance is less than 2% when the temperature is elevated and lowered between the room temperature and 530 C. in the air atmosphere, and high charge mobility of 50 cm.sup.2/V.Math.sec or more (in a doping level of about 10.sup.20/cm.sup.3 at room temperature)

(33) In addition, since the Ba.sub.1XLa.sub.XSnO.sub.3 according to the embodiment of the present invention has good transparency, stability, and charge mobility, the Ba.sub.1XLa.sub.XSnO.sub.3 may be used in a variety of industrial fields, such as an electronic industry and a communication equipment industry. In particular, since the Ba.sub.1XLa.sub.XSnO.sub.3 according to the embodiment of the present invention is an oxide having high stability and a wide bandgap, the Ba.sub.1XLa.sub.XSnO.sub.3 may be used at a high temperature, less influenced by radiation, and applied to aerospace industry or military industry which consumes large electric energy.

(34) Although a few embodiments have been described, it will be apparent to those skilled in the art that various modifications can be made to the above-described exemplary embodiments of the present invention without departing from the spirit or scope of the invention.