Optical properties of ZnS1−xSex alloys fabricated by plasma-induced isoelectronic substitution

Abstract

Nonequilibrium growth of thin-film ternary ZnS1−xSex semiconductor alloys was accomplished using physical vapor deposition with simultaneous electron cyclotron resonance H2S plasma activation. Substrate temperature, gas flow, and plasma power determine the ZnS1−xSex alloy composition and structure. Integrated optical transmission spectra for the ZnS1−xSex semiconductor alloys as a function of H2S plasma power are presented. Using the α2 vs hν plots for the various ZnS1−xSex films, the optical band gap Eg 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.