RELAXATION DYNAMICS OF ELECTRON-HOLE PAIRS STUDIED BY SPATIOTEMPORAL PUMP AND PROBE EXPERIMENTS

The temporal evolution of the ambipolar diffusivity of optically excit ed electron-hole pairs is investigated for a strained quantum well str ucture by temporally and spatially resolved pump and probe experiments . Dependent on the excitation conditions the diffusivity transients re flect the cooling and heating processes of excitons as well as the for mation dynamics of excitons out of free electron-hole pairs within les s than 10 ps. Diffusivity transients obtained by Monte Carlo simulatio ns of a simplified excitonic Boltzmann equation display all features o f the experimental curves and support our interpretation of the latera l propagation dynamics in terms of formation, cooling and heating of e xcitons.