Specific features in the temperature dependence of photoluminescence from CdTe/ZnTe size-quantized islands and ultrathin quantum wells

Abstract

A study has been carried out of the temperature dependences of luminescence spectra on a large number of CdTe/ZnTe structures differing in average thickness, 〈L z〉=0.25–4 monolayers (ML), and CdTe layer geometry (continuous, island type). The influence of geometric features in the structure of ultrathin layers on linewidth, the extent of lateral localization of excitons, their binding energy, and exciton-phonon coupling is discussed. It is shown that in island structures there is practically no lateral exciton migration. The exciton-phonon coupling constant in a submonolayer structure has been determined, Γph=53 meV, and it is shown that in structures with larger average thicknesses Γph is considerably smaller. Substantial lateral exciton migration was observed to occur in a quantum well with 〈L z〉=4 ML, and interaction with acoustic phonons was found to play a noticeable part in transport processes. It has been established that the depth of the exciton level in a quantum well and structural features of an ultrathin layer significantly affect the temperature dependences of integrated photoluminescence intensity.