Strain-induced band-mixing effects in ZnS/CdS (001) superlattices

摘要

The electronic properties of ZnS/CdS (001) superlattices (SLs) are investigated using the sp(3)S* tight-binding method versus substrate composition and valence-band offset (VBO). The results show that the electron is always confined within the CdS slabs; and also show a more striking feature due to the prominent localization of the top hole state near the interface region independently from the substrate composition (strain state). Theoretically, we have varied the VBO and inspected its effect on the interface state, and found that this latter persists to exist for VBO values within the interval [-1.4 eV, 0.6 eV]. This interface state is a manifestation of strong band mixing effects induced by the biaxial strain, and is expected to enhance the radiative efficiency of the SLs. The modelling of some available PL data, obtained for thin CdS quantum well embedded inside ZnS, has shown that the samples are of type-I with high energy bandgaps lying within the blue to ultraviolet spectral region.