Hot Wall Epitaxy(HWE)법에 의한 AgGaS2 단결정 성장과 열처리 효과

Abstract

A stoichiometric mixture of evaporating materials for AgGaS2 single crystal thin films was prepared from horizontal electric furnace. To obtain the single crystal thin films, AgGaS2 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 590oC and 440oC, respectively. The temperature dependence of the energy band gap of the AgGaS2 obtained from the absorption spectra was well described by the Varshni’s relation, Eg(T) = 2.7284 eV . (8.695×10.4 eV/K)T2/(T + 332 K).After the as-grown AgGaS2 single crystal thin films was annealed in Ag-, S-, and Ga-atmospheres, the origin of point defects of AgGaS2 single crystal thin films has been investigated by the photoluminescence (PL) at 10 K. The native defects of VAg, VS, Agint, and Sint obtained by PL measurements were classified as a donors or acceptors type. And we concluded that the heat-treatment in the Ag-atmosphere converted AgGaS2 single crystal thin films to an optical n-type. Also, we confirmed that Ga in AgGaS2/GaAs crystal thin films did not form the native defects because Ga in AgGaS2 single crystal thin films existed in the form of stable bonds.