Exciton cooling in short period GaAsAlGaAs superlattices

An experimental and theoretical study of the cooling of excitons in short period GaAs Al x Ga 1−x As superlattices (SLs) is presented. The time resolved luminescence results show that the exciton cooling rate is higher in a superlattice than in 3D GaAs and depends on the periodicity of the SL. The experimental data can quantitatively be explained by a model which relies on a generalization of a 3D exciton cooling model, the SL being treated as a 3D anisotropic material. This model which takes into account the deformation potential and piezoelectric exciton-acoustic phonon interaction shows that the exciton energy loss rate increases when the SL miniband dispersion decreases.