Optical properties of epitaxial ZnMnTe and ZnMgTe films for a wide range of alloy compositions

Abstract

Zn 1−x Mn x Te and Zn1−xMgxTe ternary wide-gap semiconductor alloys were grown by molecular beam epitaxy on (100) GaAs substrates over a wide range of compositions (0⩽x⩽0.75 and 0⩽x⩽0.67, respectively). Values of the band gap were measured by photoluminescence at 12 K, and by optical reflectivity at room temperature. The wavelength dependence of the indices of refraction n of these ternary systems was also measured for these alloys at wavelengths below their respective energy gaps. The measurements were performed using a combination of the prism coupler method and reflectivity. Compilation of these results allows us to establish a set of empirical parameters for the two alloy families, that can be used to calculate the index of refraction for an arbitrary alloy composition and arbitrary wavelength. It is interesting that the values of n show a surprisingly linear dependence on the corresponding energy gaps for both these alloy systems.