Electronic band structures of the strained (ZnSe)_m(CdSe) _n(001) superlattices

The electronic band structures of (ZnSe)_m(CdSe)_n(001) superlattices (SLs) versus slab thicknesses (m, n) monolayers, bi-axial strain (substrate), and valence-band offsets (VBO) are investigated. The calculations are based on the sp³s* tight-binding models with inclusion of spin-orbit interactions. The results show that the electron is always localized within the CdSe slabs, whereas the behavior of the hole is dependent on the interface specific effects and specifically on the VBO, which is controlled mainly by the bi-axial strain (substrate composition). For instance: (i) for VBO < -0.1 eV, the hole is localized within ZnSe slabs and the SL is of type-II; (ii) for -0.1 eV < VBO < +0.1 eV, the hole is localized at the interface; and (iii) for VBO > 0.1 eV, the hole is confined within the CdSe layers and the SL is of type-I. The comparison of our theoretical results with the photoluminescence data of single and multiple quantum wells yields valuable information about the structural and optical qualities of the experimental samples.