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Hot Wall Epitaxy(HWE)법에 의한 BaAl2Se4 단결정 박막 성장과 광전도 특성
정준우 ( Junwoo Jeong ),이기정 ( Kijung Lee ),홍광준 ( Kwangjoon Hong ) 한국센서학회 2015 센서학회지 Vol.24 No.6
A stoichiometric mixture of evaporating materials for BaAl2Se4 single crystal thin films was prepared from horizontal electric furnace. To obtain the single crystal thin films, BaAl2Se4 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 610 oC and 410 oC, respectively. The crystalline structure of the single crystal thin films was investigated by the photoluminescence and double crystal X-ray diffraction (DCXD). The carrier density and mobility of BaAl2Se4 single crystal thin films measured from Hall effect by van der Pauw method are 8.29 ×10-16 cm-3 and 278 cm2/vs at 293 K, respectively. The temperature dependence of the energy band gap of the BaAl2Se4 obtained from the absorption spectra was well described by the Varshni``s relation, Eg(T) = 3.4205 eV-(4.3112 × 10-4 eV/K)T2/(T + 232 K). The crystal field and the spin-orbit splitting energies for the valence band of the BaAl2Se4 have been estimated to be 249.4 meV and 263.4 meV, respectively, by means of the photocurrent spectra and the Hopfield quasicubic model. These results indicate that the splitting of the Δso definitely exists in the 5 states of the valence band of the BaAl2Se4/GaAs epilayer. The three photocurrent peaks observed at 10 K are ascribed to the A1-, B1-exciton for n =1 and C31-exciton peaks for n=31.