Monte Carlo simulations of the spatial transport of excitons in a quantum well structure

The in-plane spatial transport of nonequilibrium excitons in a GaAs quantum well structure has been simulated with the ensemble Monte Carlo method. The simulation has been performed for excitons in the presence of residual heavy holes including the interparticle Coulomb scatterings, LA-phonon scatterings, and exciton/carrier-interface roughness scatterings. It has been found that, in contrast to the free electrons/holes system in which the carrier-carrier scattering is significant, the interface roughness scattering is the dominant process for excitons because of the relatively small scattering rate of exciton-carrier and exciton-exciton scatterings. This strongly affects both the spatial motion and the energy relaxation of excitons. The spatial and momentum distributions of excitons have been simulated up to 500 ps at several exciton temperatures and interface roughness parameters. We have found that the exciton transport can be regarded as a diffusive motion, with its diffusion coefficient varying with time. The diffusivity varies because the average velocity of excitons change through the energy transfer between the excitons and the residual heavy-hole/lattice system. © 1996 The American Physical Society.