EXCITON-POLARITON RELAXATION IN ZNSE SINGLE-CRYSTALS

We report the temperature dependence of the 1s-exciton energy and damping in a ZnSe single crystal. The measurement has been performed using a two-photon, frequency-resolved, nonlinear technique that provides accurate data and avoids complications due to spatial dispersion effects and high excitation levels. From the fit of the experimental data it is possible to determine the contribution to the relaxation due to various exciton-phonon interactions and due to impurities. The measured damping rates are compared with theoretical values reported in the literature. Finally the exciton-energy shift with temperature is analyzed: It is found to be mainly due to exciton-phonon interactions since thermal expansion only accounts for a few percent of the observed variation.