# Patent

## Title
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 Ba1−XLaXSnO3 (0<x<0.1) and has a charge mobility of at least 10 cm2/V·sec.

## Background
TECHNICAL FIELD
The present invention relates to a transparent compound semiconductor and a method of fabricating the same, and more specifically, to a transparent compound semiconductor which is transparent and, at the same time, has high stability and high charge mobility, and a method of fabricating the same.
BACKGROUND ART
A trend of the current information technology is to combine functions of electronic devices and functions of display devices. In order to combine the functions of the electronic devices and display devices, the electronic devices need to be transparent.
Therefore, studies on transparent semiconductors and transparent conductors capable of performing functions of the electronic devices while satisfying transparency, and a method of fabricating thereof are being actively conducted. For example, indium tin oxide (ITO) has been developed and used as the transparent conductor, and ZnO has been developed as the transparent semiconductor. However, since those materials have low stability, application thereof as a transparent semiconductor is severely limited.
DISCLOSURE
Technical Problem
Accordingly, the present invention is directed to a transparent compound semiconductor which is transparent and has high stability and high charge mobility, and a method of fabricating the same.
Technical Solution
According to an aspect of the present invention, there is provided a transparent compound semiconductor fabricated by reacting a Ba compound, an La compound, and an Sn compound, and having a composition of Ba1−XLaXSnO3 (0<x<0.1) and a charge mobility of at least 10 cm2/V·sec.
In some embodiments, the Ba1−XLaXSnO3 may have the charge mobility of at least 10 cm2/V·sec at room temperature.
In other embodiments, the Ba1−XLaXSnO3 may be fabricated by mixing the Ba compound, the La compound, and the Sn compound to have the composition of Ba1−XLaXSnO3 (0<x<0.1) and reacting the mixed compounds at a temperature of 500° C. to 1500° C.
In still other embodiments, the thickness of the Ba1−XLaXSnO3 may be in the range of 0.4 nm to 400 nm.
In still other embodiments, the Ba1−XLaXSnO3 may have an optical transmittance of at least 90% in the visible light band.
In still other embodiments, the amount of change in resistance of the Ba1−XLaXSnO3 may be less than about 2% when the temperature is elevated and then lowered between the room temperature and 530° C. in an air atmosphere.
In still other embodiments, the Ba1−XLaXSnO3 may be in the form of a single crystal or an epitaxial film.
According to another aspect of the present invention, there is provided a method of fabricating a transparent compound semiconductor including reacting a Ba compound, an La compound, and an Sn compound. The transparent compound semiconductor has a composition of Ba1−XLaXSnO3 (0<x<0.1) and a charge mobility of at least 10 cm2/V·sec.
In some embodiments, the Ba1−XLaXSnO3 may have the charge mobility of at least 10 cm2/V·sec at room temperature. In other embodiments, the Ba compound may be BaCO3 or BaO, the La compound may be La2O3, and the Sn compound may be SnO2.
In still other embodiments, the Ba1−XLaXSnO3 may be fabricated by mixing the Ba compound, the La compound, and the Sn compound to have the composition of Ba1−XLaXSnO3 (0<x<0.1) and reacting the mixed compounds at a temperature between 500° C. to 1500° C.
In still other embodiments, the Ba1−XLaXSnO3 may be fabricated by performing a physical or chemical deposition process on a base substrate.
In still other embodiments, the base substrate may include a perovskite metal oxide having an ABO3 structure with a lattice constant of 0.37 to 0.45 nm.
In still other embodiments, the ABO3 may be one of SrTiO3, LaAlO3, SrZrO3, and BaNbO3.
In still other embodiments, the thickness of the Ba1−XLaXSnO3 may be in the range of 0.4 nm to 400 nm.
Advantageous Effects
A transparent compound semiconductor Ba1−XLaXSnO3 (0<x<0.1) according to embodiments of the present invention is a transparent compound semiconductor doped with n-type impurities, and has high stability and high charge mobility. That is, the Ba1−XLaXSnO3 is a transparent compound semiconductor having an optical transmittance of at least 90% in the visible light band, stability such that variation in a resistance level is less than 2% when the temperature is elevated and lowered between the room temperature and 530° C. in an air atmosphere, and a charge mobility of at least 10 cm2/V·sec.
In particular, since the Ba1−XLaXSnO3 (0<x<0.1) according to the embodiments of the present invention is a transparent compound semiconductor having a high charge mobility of at least 10 cm2/V·sec, it can be applied to a variety of electronic products such as a display device.



BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a graph showing an optical transmission spectrum of Ba1−XLaXSnO3 (0<x<0.1) according to an embodiment of the present invention.
FIG. 2 shows graphs of thermal resistance levels of Ba1−XLaXSnO3 (0<x<0.1) according to an embodiment of the present invention.
FIG. 3 is a graph showing the charge density, resistance, and charge mobility of Ba1−XLaXSnO3 (0<x<0.1) according to an embodiment of the present invention.



MODES FOR CARRYING OUT THE INVENTION
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.
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.
Hereinafter, various embodiments will now be described more fully with reference to the accompanying drawings.
A transparent compound semiconductor according to an embodiment of the present invention is an n-type transparent compound semiconductor having a composition of Ba1−XLaXSnO3 (0<x<0.1). The Ba1−XLaXSnO3 satisfies a composition ratio of (Ba+La):Sn=1:1.
Here, the composition ratio of Ba1−XLaXSnO3 is 0<x<0.1 so as to have semiconductor characteristics. Since BaSnO3 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 Ba0.9La0.1SnO3 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 Ba1−XLaXSnO3 has a composition ratio of 0<x<0.1 to have semiconductor characteristics.
The Ba1−XLaXSnO3 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 cm2/V·sec. The Ba1−XLaXSnO3 needs to have such a thickness for the following reasons. First, the thickness of Ba1−XLaXSnO3 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 Ba1−XLaXSnO3 is greater than 400 nm, transparency may be degraded.
In addition, the Ba1−XLaXSnO3 may be fabricated in the form of a single crystal or an epitaxial film.
Ba1−XLaXSnO3 used as a transparent compound semiconductor according to an embodiment of the present invention may be formed as follows.
First, Ba1−XLaXSnO3 may be formed by doping undoped BaSnO3 with La. BaSnO3 is an insulating material having a lattice constant of 0.41 nm, a bandgap greater than 3 eV, and a transparent property.
Here, the BaSnO3 is used as a base material of Ba1−XLaXSnO3 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 1020/cm3 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 ABO3 structure, such as BaSnO3. 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, BaSnO3, a perovskite metal oxide having a high bandgap of 3 eV may used as the base material of Ba1−XLaXSnO3 in this embodiment of the present invention.
The bandgap of BaSnO3 is greater than 3 eV, which means that BaSnO3 has high transparency. In addition, Ba1−XLaXSnO3 formed using BaSnO3 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.
Alternatively, Ba1−XLaXSnO3 may be formed by reacting a Ba compound, an La compound, and an Sn compound. Here, BaCO3 or BaO may be used as the Ba compound, La2O3 may be used as the La compound, and SnO2 may be used as the Sn compound. For example, the Ba1−XLaXSnO3 may be fabricated by mixing the Ba compound, the La compound, and the Sn compound to have the composition of Ba1−XLaXSnO3 (0<x<0.1) and reacting the mixed compounds at a temperature of 500° C. to 1500° C.
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 Ba1−XLaXSnO3 may not be formed, and when the temperature is higher than 1500° C., the crystal structure of Ba1−XLaXSnO3 may be broken or characteristics as a transparent compound semiconductor may be deteriorated.
The Ba1−XLaXSnO3 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 ABO3 structure similar to BaSnO3 having a lattice constant of 0.41 nm may be used. For example, SrTiO3, LaAlO3, SrZrO3, BaNbO3, 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.
In addition, the Ba1−XLaXSnO3 formed by reacting the Ba compound, the La compound, and the Sn compound has a charge mobility of 10 cm2/V·sec or more. In particular, the Ba1−XLaXSnO3 has a charge mobility of 10 cm2/V·sec or more at room temperature.
Through the graphs of FIGS. 1 to 3, it may be found that the Ba1−XLaXSnO3 according to the embodiment of the present invention has good transparency, stability, and charge mobility.
FIG. 1 is a graph showing an optical transmission spectrum of Ba1−XLaXSnO3 (0<x<0.1) according to an embodiment of the present invention.
Referring to FIG. 1, optical transmission spectrums of undoped BaSnO3 and Ba1−XLaXSnO3 according to the embodiment of the present invention are shown. Here, (a) shows a transmittance spectrum of undoped BaSnO3 and transmittance spectrums of doped BaSnO3 (Ba1−XLaXSnO3 according to an embodiment of the present invention), and (b) shows absorption coefficients (α) as a function of photon energy of undoped BaSnO3 and doped BaSnO3.
The absorption coefficients (α) of the undoped BaSnO3 and the doped BaSnO3 were extracted by measuring transmission coefficients of the same samples with different thicknesses. Optical bandgaps of the undoped BaSnO3 and the doped BaSnO3 (n=2.39×1020 cm−3) derived from the relationship between a and photon energy were respectively 3.03 eV and 3.01 eV.
That is, it is found that the Ba1−XLaXSnO3 according to the embodiment of the present invention has an optical transmittance of 90% or more in a thin film having a normal thickness.
FIG. 2 shows graphs of thermal resistance levels of Ba1−XLaXSnO3 (0<x<0.1) according to an embodiment of the present invention.
Referring to FIG. 2, thermal resistance levels of a Ba0.966La0.04SnO3−δ thin film according to the embodiment of the present invention were measured in O2, Ar, and air atmospheres. That is, the thermal resistance levels of the Ba0.96La0.04SnO3−δ thin film were measured after elevating and lowering a temperature between the room temperature and 530° C. in the O2, Ar, and air atmospheres. The Ba0.96La0.04SnO3−δ thin film may be an epitaxial film.
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 Ba0.96La0.04SnO3−δ thin film having a thickness of 100 nm was maintained at a temperature of 530° C. for 5 hours.
(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 O2 atmosphere at the temperature of 530° C. for 5 hours.
In this way, it was found that the Ba1−XLaXSnO3 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 O2, Ar, and air atmospheres. In particular, the Ba1−XLaXSnO3 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.
FIG. 3 is a graph showing the charge density, resistance, and charge mobility of Ba1−XLaXSnO3 (0<x<0.1) according to an embodiment of the present invention.
Referring to FIG. 3, changes in a charge density n, a resistance ρ, and a charge mobility μ of a Ba1−XLaXSnO3 thin-film according to an embodiment of the present invention, are shown according to a change in the temperature of the Ba1−XLaXSnO3 thin-film. The charge density n, the resistance ρ, and the charge mobility μ are coefficients affected by the temperature. Here, (b, d, and f) respectively represent the charge density n, resistance ρ, and charge mobility μ of the Ba1−XLaXSnO3 thin-film.
It is discovered that the Ba1−XLaXSnO3 according to the embodiment of the present invention has a charge mobility of 10 cm2/V·sec or more. That is, the Ba1−XLaXSnO3 has a charge mobility of 10 cm2/V·sec or more at room temperature. Further, when the x value is 0.04 and 0.07, the Ba1−XLaXSnO3 has a charge mobility of 50 cm2/V·sec or more.
Thus, Ba1−XLaXSnO3 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 Ba1−XLaXSnO3 has excellent characteristics of a transparent compound semiconductor. For example, the Ba1−XLaXSnO3 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 cm2/V·sec or more (in a doping level of about 1020/cm3 at room temperature)
In addition, since the Ba1−XLaXSnO3 according to the embodiment of the present invention has good transparency, stability, and charge mobility, the Ba1−XLaXSnO3 may be used in a variety of industrial fields, such as an electronic industry and a communication equipment industry. In particular, since the Ba1−XLaXSnO3 according to the embodiment of the present invention is an oxide having high stability and a wide bandgap, the Ba1−XLaXSnO3 may be used at a high temperature, less influenced by radiation, and applied to aerospace industry or military industry which consumes large electric energy.
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.

## 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 Ba1−XLaXSnO3 (0<x<0.1),
wherein
a composition ratio of the Ba1−XLaXSnO3 is (Ba+La):Sn=1:1,
the thickness of the Ba1−XLaXSnO3 is in the range of 0.4 nm to 400 nm, and
the Ba1−XLaXSnO3 has a charge mobility of at least 10 cm2/V·sec or more at room temperature.

2. The transparent compound semiconductor of claim 1, wherein, when 0.01≦x≦0.07, the Ba1−XLaXSnO3 has the charge mobility of 10 to 80 cm2/V·sec at room temperature.

3. The transparent compound semiconductor of claim 1,
wherein, when 0.04≦x≦0.07, the Ba1−XLaXSnO3 has the charge mobility of 50 to 80 cm2/V·sec at room temperature.

4. The transparent compound semiconductor of claim 3, wherein the Ba1−XLaXSnO3 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 Ba1−XLaXSnO3 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 Ba1−XLaXSnO3 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 Ba1−XLaXSnO3 (0<x<0.1),
wherein
a composition ratio of the Ba1−XLaXSnO3 is (Ba+La):Sn=1:1,
the Ba1−XLaXSnO3 is in the form of a single crystal or an epitaxial film, and
the Ba1−XLaXSnO3 has a charge mobility of at least 10 cm2/V·sec or more at room temperature.