Interaction of excitons with carriers accelerated by the electric field of a surface acoustic wave in type-II GaAs/AlAs superlattices

The influence of the lateral electric field of the surface acoustic wave (SAW) on the kinetics of the exciton photoluminescence (PL) in the X sub(Z) and X sub(XY) type-II GaAs/AlAs superlattices has been studied in the present work. It has been found that the application of the SAW electric field leads first to the enhancement of the PL intensity of free excitons and then to the acceleration of the PL kinetics of all types of exciton transitions. It has been shown that both effects result from the interaction of the carriers ejected by the SAW from the shallow states formed by the quantum well width fluctuations with each other and excitons. In the first case the ejected carriers form an appreciable amount of excitons that leads to the increase in their PL intensity. In the second case the collision of these carriers with the excitons described by Townsend-Shockley law results in the delocalization of the excitons with their subsequent capture by the nonradiative centers, which leads to the acceleration of the kinetics of the excitonic PL.