Hot Wall Epitaxy(HWE)법에 의한 BaIn<sub>2</sub>S<sub>4</sub> 단결정 박막 성장과 광전도 특성

Abstract

A stoichiometric mixture of evaporating materials for <TEX>$BaIn_2S_4$</TEX> single crystal thin films was prepared from horizontal electric furnace. To obtain the single crystal thin films, <TEX>$BaIn_2S_4$</TEX> mixed crystal was deposited on thoroughly etched semi-insulating GaAs(100) substrate by the Hot Wall Epitaxy (HWE) system. The source and substrate temperatures were <TEX>$620^{\circ}C$</TEX> and <TEX>$420^{\circ}C$</TEX>, respectively. The crystalline structure of the single crystal thin films was investigated by double crystal X-ray diffraction (DCXD). The carrier density and mobility of <TEX>$BaIn_2S_4$</TEX> single crystal thin films measured from Hall effect by van der Pauw method are <TEX>$6.13{\times}10^{17}cm^{-3}$</TEX> and <TEX>$222cm^2/v{\cdot}s$</TEX> at 293 K, respectively. The temperature dependence of the energy band gap of the <TEX>$BaIn_2S_4$</TEX> obtained from the absorption spectra was well described by the Varshni's relation, <TEX>$E_g(T)=3.0581eV-(3.9511{\times}10^{-3}eV/K)T^2/(T+536K)$</TEX>. The crystal field and the spin-orbit splitting energies for the valence band of the <TEX>$BaIn_2S_4$</TEX> have been estimated to be 182.7 meV and 42.6 meV, respectively, by means of the photocurrent spectra and the Hopfield quasicubic model. These results indicate that the splitting of the <TEX>${\Delta}so$</TEX> definitely exists in the <TEX>${\Gamma}_5$</TEX> states of the valence band of the <TEX>$BaIn_2S_4/GaAs$</TEX> epilayer. The three photocurrent peaks observed at 10 K are ascribed to the <TEX>$A_1$</TEX>-, <TEX>$B_1$</TEX>-exciton for n = 1 and <TEX>$C_{24}$</TEX>-exciton peaks for n = 24. A stoichiometric mixture of evaporating materials for <TEX>$BaIn_2S_4$</TEX> single crystal thin films was prepared from horizontal electric furnace. To obtain the single crystal thin films, <TEX>$BaIn_2S_4$</TEX> mixed crystal was deposited on thoroughly etched semi-insulating GaAs(100) substrate by the Hot Wall Epitaxy (HWE) system. The source and substrate temperatures were <TEX>$620^{\circ}C$</TEX> and <TEX>$420^{\circ}C$</TEX>, respectively. The crystalline structure of the single crystal thin films was investigated by double crystal X-ray diffraction (DCXD). The carrier density and mobility of <TEX>$BaIn_2S_4$</TEX> single crystal thin films measured from Hall effect by van der Pauw method are <TEX>$6.13{\times}10^{17}cm^{-3}$</TEX> and <TEX>$222cm^2/v{\cdot}s$</TEX> at 293 K, respectively. The temperature dependence of the energy band gap of the <TEX>$BaIn_2S_4$</TEX> obtained from the absorption spectra was well described by the Varshni's relation, <TEX>$E_g(T)=3.0581eV-(3.9511{\times}10^{-3}eV/K)T^2/(T+536K)$</TEX>. The crystal field and the spin-orbit splitting energies for the valence band of the <TEX>$BaIn_2S_4$</TEX> have been estimated to be 182.7 meV and 42.6 meV, respectively, by means of the photocurrent spectra and the Hopfield quasicubic model. These results indicate that the splitting of the <TEX>${\Delta}so$</TEX> definitely exists in the <TEX>${\Gamma}_5$</TEX> states of the valence band of the <TEX>$BaIn_2S_4/GaAs$</TEX> epilayer. The three photocurrent peaks observed at 10 K are ascribed to the <TEX>$A_1$</TEX>-, <TEX>$B_1$</TEX>-exciton for n = 1 and <TEX>$C_{24}$</TEX>-exciton peaks for n = 24.