<i>Ab initio</i>pseudopotential calculations of the band lineups at strained ZnS/ZnSe interfaces: Including the 3<i>d</i>electrons of Zn as valence states

Abstract

A first-principles pseudopotential approach has been used to calculate the valence-band offset (${\mathrm{\ensuremath{\Lambda}}}_{\mathit{v}}$) at strained ZnS/ZnSe (001) interfaces, and the structural and electronic structure properties of ZnS and ZnSe. In these calculations the semicore 3d electrons of Zn are included as relaxed valence states. Three strain configurations, corresponding to growth on ${\mathrm{ZnS}}_{\mathit{x}}$${\mathrm{Se}}_{1\mathrm{\ensuremath{-}}\mathit{x}}$ (001) (with x=0, 0.5, and 1) substrates were considered. We found that ${\mathrm{\ensuremath{\Lambda}}}_{\mathit{v}}$ varies almost linearly between 0.43 and 0.78 eV in the above strain range, with the state at the top of the valence band in ZnSe being higher in energy. The averages of ${\mathrm{\ensuremath{\Lambda}}}_{\mathit{v}}$ and the conduction-band offset are found to be independent of the strain state and with values of 0.50 and 0.23 eV, respectively. These results and that of the other studied properties are found to be in excellent agreement with experiment and all-electron calculations. The charge density associated with the d bands shows some deviations from being spherically symmetric around the Zn ions and has appreciable magnitude in the anions regions, which suggests that the dp hybridization is quite strong.