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

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 alpha(2) vs h nu plots for the various ZnS1-xSex 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. (C) 2000 American Institute of Physics. [S0021-8979(00)02412-9].