Auger recombination-induced neutralization and stretched exponential recharging in an InAs quantum dot

We investigate the charging dynamics in epitaxially grown InAs quantum dots (QDs) under resonant excitation with and without additional low-power above-band excitation. Time-resolved resonance fluorescence from a charged exciton (trion) transition is recorded as the above-band excitation is modulated on and off. The fluorescence intensity varies as the QD changes from charged to neutral and back due to the influence of the above-band excitation. We fit the transients of the decay of the time-resolved resonance fluorescence after the above-band excitation turns off with a model that represents the neutralization process. The time dependence of the transients indicate that Auger recombination of resonantly excited trions is largely responsible for neutralization of the charged state when the above-band excitation is off. Additionally, a stretched exponential component of the transient of the fluorescence decay indicates the QD is supplied with charges via carrier migration through a stochastic collection of weakly-binding sites, resulting in sub-diffusion-like dynamics.