Influence of trapping on the exciton dynamics of AlxGa1−xAs films

We present a systematic study on the exciton relaxation in high-purity AlGaAs epilayers. The time for the excitonic photoluminescence to reach its maximum intensity, defined as tmax, shows a nonmonotonic dependence on excitation density which is attributed to a competition between exciton localization and carrier–carrier scattering. A phenomenological four level model fully describes the influence of exciton localization on tmax. This localization effect is enhanced by the increase of the Al content in the alloy and disappears when localization is hindered by rising the lattice temperature above the exciton trapping energy.