Exciton transport and nonradiative decay in semiconductor nanostructures

Abstract

A phenomenological theory describing the exciton photoluminescence (PL) kinetics in type-II superlattices is proposed herein, which takes into account both the intrinsic exciton radiative decay and nonradiative decay due to exciton trapping by interfacial defects surrounding a ``disordered'' interface. We have thus investigated the effect of system dimensionality on details of these nonradiative-decay kinetics. For effectively three-dimensional and two-dimensional structures, the theory predicts a transition from strongly nonexponential to nearly exponential decay kinetics as the temperature is increased. Contrastingly, for one-dimensional structures the decay kinetics is predicted to be nonexponential at all temperatures. Using these predictions, we have applied this model to explain our observed time-resolved PL on specific short-period type-II GaAs/AlAs superlattices. These PL decays are thus explained both over a wide range of temperatures (2--30 K) and over an observed crossover from nonexponential to exponential behavior. The model allows us to extract a nonradiative-defect density and an average radiative-decay rate from the experimental data.