Abstract
단결정 성장을 위한 <TEX>$MgGa_2Se_4$</TEX> 다결정은 수평 전기로에서 합성하였으며, 결정구조는 rhombohedral이고 격자상수 <TEX>$a_0$</TEX>는 3.953 <TEX>${\AA}$</TEX>, <TEX>$c_0$</TEX>는 38.890 <TEX>${\AA}$</TEX>였다. <TEX>$MgGa_2Se_4$</TEX> 단결정박막은 HWE(Hot Wall Epitaxy) 방법으로 반절연성 GaAs(100)기판에 성장시켰다. 단결정박막의 성장 조건은 증발원의 온도 <TEX>$610^{\circ}C$</TEX>, 기판의 온도 <TEX>$400^{\circ}C$</TEX>에서 진행되었으며 성장 속도는 0.5 <TEX>${\mu}m/h$</TEX>였다. 단결정박막의 결정성은 이중 결정 x-선 회절곡선의 반폭치와 X-선 회절무늬의 <TEX>${\omega}-2{\theta}$</TEX>로부터 구하여 최적 성장 조건을 알 수 있었다. Hall 효과는 van der Pauw 방법에 의해 측정되었으며, 온도에 의존하는 운반자 농도와 이동도는 293 K에서 각각 <TEX>$6.21{\times}10^{18}/cm^3$</TEX>, 248 <TEX>$cm^2/v{\cdot}s$</TEX>였다. <TEX>$MgGa_2Se_4$</TEX>/SI(Semi-Insulated) GaAs(100) 단결정 박막의 광흡수 스펙트럼을 10 K에서 293 K까지 측정하였다. 광흡수 스펙트럼으로부터 구한 에너지 갭 <TEX>$E_g(T)$</TEX>는 varshni 공식 <TEX>$E_g(T)=E_g(0)=({\alpha}T^2/T+{\beta})$</TEX>을 잘 만족함을 알 수 있었다. 여기서 <TEX>$E_g(0)=2.34\;eV$</TEX>, <TEX>${\alpha}=8.81{\times}10^{-4}\;eV/K$</TEX>, <TEX>${\beta}=251\;K$</TEX>였다. A stoichiometric mixture of evaporating materials for <TEX>$MgGa_2Se_4$</TEX> single crystal thin films was prepared from horizontal electric furnace. The crystal structure of these compounds has a rhombohedral structure with lattice constants <TEX>$a_0=3.953\;{\AA}$</TEX>, <TEX>$c_0=38.890\;{\AA}$</TEX>. To obtain the single crystal thin films, <TEX>$MgGa_2Se_4$</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>$610^{\circ}C$</TEX> and <TEX>$400^{\circ}C$</TEX>, respectively. The crystalline structure of the single crystal thin films was investigated by the double crystal X-ray rocking curve and X-ray diffraction <TEX>${\omega}-2{\theta}$</TEX> scans. The carrier density and mobility of <TEX>$MgGa_2Se_4$</TEX> single crystal thin films measured from Hall effect by van der Pauw method were <TEX>$6.21{\times}10^{18}\;cm^{-3}$</TEX> and 248 <TEX>$cm^2/v{\cdot}s$</TEX> at 293 K, respectively. The optical absorption of <TEX>$MgGa_2Se_4$</TEX> single crystal thin films was investigated in the temperature range from 10 K to 293 K. The temperature dependence of the optical energy gap of the <TEX>$MgGa_2Se_4$</TEX> obtained from the absorption spectra was well described by the Varshni's equation, <TEX>$E_g(T)=E_g(0)-({\alpha}T^2/T+{\beta})$</TEX>. The constants of Varshni's equation had the values of <TEX>$E_g(0)=2.34\;eV$</TEX>, <TEX>${\alpha}=8.81{\times}10^{-4}\;eV/K$</TEX> and <TEX>${\beta}=251\;K$</TEX>, respectively.
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