  Monte Carlo Simulations of the Spatial Transport of Excitons in a Quantum
Well Structure Yutaka Takahashi (Dep. of Electrical and Information Eng.,
Yamagata University) 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 whose diffusion
coefficient varies 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.
