Carrier Relaxation Dynamics Between Localized Vertical Confinement States in GaAs/AlGaAs Quantum Rings

Abstract

We have performed time-resolved photoluminescence of dilute GaAs/AlGaAs quantum rings for increasing excitation and temperature. Although a large distance between quantum rings (200 ± 50 nm) prevents a ring-to-ring carrier transport, a decay time difference over the wide spectrum and its change became significant with increased excitation and temperature. Those results were explained in terms of an internal relaxation of the fine levels in a quantum ring structure. As carrier injection is increased, the carrier relaxation of high energy levels becomes enhanced possibly via the state-filling effect and Auger scattering. We also found that the population decay of low energy levels slows down due to a carrier feeding, but the net population of intermediate levels become nearly constant due to a balanced carrier transfer in between the high and low energy levels. For increased temperature, we observed a photoluminescence quenching at the high energy levels as a consequence of a thermal escape from the shallow potential depth.