MEASUREMENT OF PHONON-ASSISTED MIGRATION OF LOCALIZED EXCITONS IN GAAS/ALGAAS MULTIPLE-QUANTUM-WELL STRUCTURES

We report high-resolution nonlinear-laser-spectroscopy measurements of relaxation of lowest-energy heavy-hole excitons in GaAs multiple-quantum-well structures. We show that excitons below the absorption line center are spatially localized, and migrate among localization sites with a time scale of order 100 ps. The measurements give the resultant quasiequilibrium energy distribution of the scattered excitons and, based on the temperature dependence of the migration rate, confirm the theoretical model for phonon-assisted migration. © 1990 The American Physical Society.