Hot Wall Epitaxy(HWE)법에 의한 BaIn2Se4에피레어 성장과 가전자대 갈라짐에 대한 광전류 연구

Abstract

A stoichiometric mixture of evaporating materials for BaIn2Se4 epilayers was prepared from horizontal electric furnace. To obtain the single crystal thin films, BaIn2Se4 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 620 o C and 400 o C, respectively. The crystalline structure of the epilayers was investigated by the photoluminescence and double crystal X-ray diffraction (DCXD). The carrier density and mobility of BaIn2Se4 epilayers measured from Hall effect by van der Pauw method are 8.94×10 17 cm -3 and 343 cm 2 /vs at 293 K, respectively. The temperature dependence of the energy band gap of the BaIn2Se4 obtained from the absorption spectra was well described by the Varshni's relation, Eg(T)=2.6261 eV-(4.9825×10 -3 eV/K)T 2 /(T+558 K). The crystal field and the spin-orbit splitting energies for the valence band of the BaIn2Se4 have been estimated to be 116 meV and 175.9 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 states of the valence band of the BaIn2Se4/ GaAs epilayer. The three photocurrent peaks observed at 10 K are ascribed to the A1-, B1-exciton for n = 1 and C21-exciton peaks for n=21.