Investigation of the electronic properties of strained ZnSe/ZnTe(001) superlattices

The empirical sp³s* tight-binding method, which includes both spin-orbit coupling and strain effects, is employed to investigate the electronic properties of the strained ZnSe/ZnTe(001) superlattices (SLs) versus the biaxial strain, layer thicknesses and valence band offset (VBO). The results show that the conduction-band edge state is always represented by an electron localized within the ZnSe slabs; whereas the valence-band edge state (which is mostly a heavy hole (HH) related to ZnTe) can be controlled by the biaxial strain. In this respect, the results show the existence of a certain critical VBO (V_c ≃ 0.44 eV) separating two kinds of hole-confinement character (i.e. for VBO > V_c, the HH gets localized within the ZnTe layers and the SL is of type-II; whereas for VBO ≤ V_c, the HH has a tendency to localize at the hetero-interface and, as a consequence, the radiative efficiency is enhanced). Finally, our results are compared to some available photoluminescence data and conclusions about the structural and optical qualities of the experimental samples are drawn.