Temperature dependence of photoluminescence bands in Zn1-xCdxSe/ZnSe quantum wells with planar CdSe islands -: art. no. 085308

We have studied the temperature dependence of the photoluminescence (PL) spectra of molecular beam epitaxy grown ultrathin Zn1-xCdxSe/ZnSe quantum wells with random and inhomogeneous Cd distributions over cation sublattice within the temperature interval 2-300 K. Depending on the Cd concentration, the PL band maximum position E-max(PL)(T) follows either a "normal" or an "anomalous" (known as "S-shaped") temperature dependence. We have analyzed both dependences in detail for a model of an island ensemble which can be characterized by a single-mode distribution of the most important parameters governing the optical properties of the quantum well. We demonstrate that the anomalous behavior arises due to the strong temperature dependence of the lifetimes of a family of metastable states participating in formation of the PL band at low temperatures. The metastablility of some island states is ascribed to a complex topological structure of the islands. The mechanism of the exciton-phonon interaction responsible for the fast decrease of the lifetime of these states with the increase of temperature has the same origin as the mechanism leading to the vanishing of narrow lines in mu-PL. We also present results of time-resolved experiments which yield the shift of the PL band for hot excitons cooling in a cold lattice.