Optical properties of ZnS_(1-x)Se_(x) alloys fabricated by plasma-induced isoelectronic substitution

摘要

Nonequilibrium growth of thin-film ternary ZnS_(1-x)Se_(x) semiconductor alloys was accomplished using physical vapor deposition with simultaneous electron cyclotron resonance H_(2)S plasma activation. Substrate temperature, gas flow, and plasma power determine the ZnS_(1-x)Se_(x) alloy composition and structure. Integrated optical transmission spectra for the ZnS_(1-x)Se_(x) semiconductor alloys as a function of H_(2)S plasma power are presented. Using the α~(2) vs hv plots for the various ZnS_(1-x)Se_(x) films, the optical band gap E_(g) is extrapolated from each curve. This methodology yields the values of the band gap as a function of stoichiometry. We observe that the plasma induced isoelectronic substitution of S into the ZnSe lattice increases the band gap. This study shows that plasma-induced isoelectronic substitution is technologically feasible and useful for fabricating ternary II-VI alloys under nonequilibrium conditions.