Amorphous Semiconducting 3As2Se3·2Sb2Se3 Films. I. Optical Properties

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Abstract
Transmittance and absorption studies have been made in the 0.7–16-μ range on 60% As2Se3·40% Sb2Se3 evaporated films of amorphous composition to provide information about the optical properties and the energy-band structure. The refractive index shows a sharp increase near the interband transition, and the films do not exhibit free-carrier absorption. The static relative dielectric constant obtained is ε=n2=5.11 The relaxation time for free carriers is τ=1.63×10−15 sec, and the mobility calculated from τ is less than 5 cm2/V sec. The relation α2∼hv near the absorption edge is proposed to be due to the transitions between the localized states in the valence band edge and the nonlocalized states in the conduction band. The thermal coefficient of energy is found to be dEopt/dT=−5.3×10−4 eV/°K, with Eopt (absorption edge extrapolated to α=0)=1.442 eV.