Type-I interband transition in undoped ZnSe/BeTe type-II quantum wells under high excitation density

Abstract

A spatially direct photoluminescence (PL) spectrum associated with type-I interband transition of a ZnSe layer in undoped ZnSe/BeTe type-II quantum structures was investigated by varying the photo-excitation density. For a sample with a narrower ZnSe layer both PL intensity and linewidth of the trion show a superlinear increase with increasing excitation density in comparison to that with a wider ZnSe layer. The results are explained by the effective increase of the electron concentration and an enhanced dephasing rate of the trion resulting from the electron-trion scattering. The effective increase of the electron concentration in the ZnSe layer is considered to be originating from both the greater transfer rate of the hole into the BeTe layer due to the narrower ZnSe layer and the efficient spatially indirect transition PL of the complex states through the interface. With decreasing excitation density, no indication of any shift in peak energy density was observed indicating that the studied structures are of excellent quality.