Structure stability and carrier localization in $\mathrm{Cd}X(X=\mathrm{S},\mathrm{}\mathrm{S}\mathrm{e},\mathrm{}\mathrm{Te})$ semiconductors

We studied systematically the structural and electronic properties of binary $\mathrm{Cd}X$ $(X=\mathrm{S},$ Se, and Te) semiconductors in both zinc-blende (ZB) and wurtzite (WZ) structures, the band alignment on the ZB/WZ interfaces, and carrier localization induced by the band offsets. We show, by first-principles band-structure calculation that at low temperature, CdS is stable in the wurtzite structure, while CdSe and CdTe are stable in the zinc-blende structure. However, coherent substrate strain can change CdTe to be more stable in the wurtzite form. We find that $\mathrm{Cd}X$ in the wurtzite structure has a larger band gap than the one in the zinc-blende structure. The band alignment on the ZB/WZ interface is found to be type II with holes localized on the wurtzite side and electrons on the zinc-blende side.