Tight-binding calculation of ZnSe/Ge superlattices: Electronic structure and optical property

Abstract

The results of a detailed tight-binding calculation of the electronic structure and optical properties of (ZnSe)n/(Ge2)m (110) superlattices are presented for a wide range of n,m≤20. It is found that the fundamental energy gap increases with decreasing superlattice period due to spatial quantum confinement effects. For all reasonable values (ranging from 0.2 to 2.0 eV) of the valence band discontinuity used in the calculation, no interface states are found in the thermal gap of the (ZnSe)n/(Ge2)m (110) (n,m≤20) system. An indirect–direct band gap transition is found to be driven by increasing valence band offset. The optical properties of the superlattices are investigated by calculating the absorption coefficient. The results are analyzed according to the calculated electronic structure and compared with those of the corresponding bulk materials.