Mechanisms of exciton photoluminescence quenching in the electric field of a standing surface acoustic wave

Abstract

Mechanisms of exciton photoluminescence (PL) quenching in the longitudinal electric field of a standing surface acoustic wave (SAW) have been studied by the example of type II GaAs/AlAs superlattices (SLs). Such SLs with a long lifetime of nonequilibrium carriers have allowed examining the influence of the SAW electric field on the excitonic PL both under the continuous and impulse laser excitations. It has been found that the mechanisms of the interaction of excitons and a SAW electric field depend upon the kinetic energy of excitons and carriers. As for hot excitons and carriers, the standing SAW electric field causes the impact ionization of excitons with a subsequent capture of free carriers at the nonradiative recombination centers, which results in a decrease in the steady-state exciton PL. As for cold excitons and carriers, the impact of excitons with the carriers accelerated by the SAW electric field results mainly in exciton delocalization from the levels of quantum wells formed due to interface roughness with a subsequent capture of excitons at the nonradiative recombination centers, which leads to the acceleration of the PL kinetics.