Annealing-induced Modifications of Carrier Dynamics and Plasmon-phonon Coupling in Low-temperature-grown GaAs

The annealing temperature dependence of the carrier dynamics was studied for a GaAs layer grown at 290 degrees C by using molecular beam epitaxy. The modified carrier lifetime is interpreted to be a result of the increased defect-to-defect distance caused by the aggregation process of As-related point defects. The disappearance of the plasmon-phonon coupling and the carrier-induced phonon dephasing, which are observed in coherent phonon experiments for the layer annealed at 400 degrees C, is consistent with the instantaneous trapping of photoexcited carriers as, observed in pump-probe measurements.