Hot Wall Epitaxy(HWE)법에 의한 BaIn2S4 단결정 박막 성장과 광학적 특성

Abstract

A stoichiometric mixture of evaporating materials for BaIn2S4 single crystal thin films was prepared from horizontal electric furnace. To obtain the single crystal thin films, BaIn2S4 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 ℃ and 420 ℃, 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 BaIn2S4 single crystal thin films measured from Hall effect by van der Pauw method are 6.13×1017cm-3 and 222cm2/V․sec at 293K, respectively. The temperature dependence of the energy band gap of the BaIn2S4 obtained from the absorption spectra was well described by the Varshni's relation Eg(T) = Eg(0) - αT2 / (T+β) in Eg(0) is 3.0581 eV, α is 3.9511×10-3 eV/K and β is 536 K. As a result of calculations for the Eg(T) = 3.0581 eV - (3.9511×10-3 eV/K)T2 / (T + 536 K). In order to explore the applicability as a photoconductive cell, we measured the sensitivity(γ), maximum allowable power dissipation (MAPD), the ratio of photocurrent to darkcurrent(pc/dc) and response time. The results indicated that the photoconductive characteristic were the best for the samples annealed in S vapour compare with in Ba, In, air and in vacuum vapour. Then we obtained the sensitivity of 0.90, the value of ratio of photocurrent to darkcurrent of 1.10×107, the MAPD of 317 mW, and the rise and decay time of 13.5 ms and 11.8 ms, respectively.