Variation of bandgap with composition in (ZnTe)x(CdSe)1-x single crystals

摘要

Band gaps of vapor phase grown (ZnTe)$-x$/(CdSe)$-1$MIN@x$/ single crystals in the entire range of composition x are obtained by photoconductivity spectral response and diffuse reflectance spectral analysis. The band gap varies nonlinearly with composition and passes through a minimum around x $EQ 0.3. A least-square fitting of energy gap values to a quadratic equation gives a bowing parameter of 0.724 eV. The bowing parameter calculated using Hill and Richardson's equation is also found to be 0.724. However, Chandrasekharam et al. reported a value of 1.088 eV for (ZnSe)$-x$/(CdTe)$-1$MIN@x$/ single crystals. Pseudopotential and dielectric models are generally used to estimate the bowing parameter of similar miscible crystal structures. However, the systems involved in the present study are divergent with wurtzite and zinc blend structures. It is shown that the pseudopotential model fails to account for the observed bowing due to the presence of structural transition in the present system.