Hai Son Nguyen, Gregory Sallen, Marco Abbarchi, Robson Ferreira, Christophe Voisin, Philippe Roussignol, Guillaume Cassabois, Carole Diederichs
We investigate experimentally and theoretically the resonant emission of single InAs/GaAs quantum dots in a planar microcavity. Due to the presence of at least one residual charge in the quantum dots, the resonant excitation of the neutral exciton is blocked. The influence of the residual doping on the initial quantum dots charge state is analyzed, and the resonant emission quenching is interpreted as a Coulomb blockade effect. The use of an additional non-resonant laser in a specific low power regime leads to the quantum dots neutralization and allows an efficient optical gating of the exciton resonant emission. A detailed population evolution model, developed to describe the quantum dot neutralization and the optical gate effect, perfectly fits the experimental results in the steady state and dynamical regimes of the optical gate with a single set of parameters. We deduce that ultra-slow Auger- and phonon-assisted capture processes govern the quantum dot neutralization with relaxation times in the 1-100 microsecond range. We conclude that the optical gate acts as a very sensitive probe of the quantum dot population relaxation in an unprecedented slow-capture regime.
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http://arxiv.org/abs/1212.3212
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