Exciton dynamics and valence band mixing in tensile-strained semiconductorquantum wells

We have investigated the influence of the electronic band structure on the exciton dynamics in GaAsP tensile-strained quantum wells. We have found tha t the exciton cooling time is notably reduced when the heavy- and light-hol e excitons are degenerate. The lifetime of the heavy-hole exciton is simila r to 300 ps whereas it is similar to 500 ps for the light-hole exciton. Fur thermore, we have determined, from the initial degree of polarization of th e emission, the valence-band mixing as a function of the energy splitting b etween the heavy-hole and light-hole subbands. The degree of mixing is in q ualitative agreement with tight-binding calculations.