Exciton pattern generation in GaAs/AlxGa1-xAs multiple quantum wells

Exciton photoluminescence pattern generation is investigated in multiple quantum wells. High-contrast outer rings and localized bright spots are generated using efficient field-assisted upconversion of laser light whose photon energy lies below the energy of the luminescing quantum well transition. Time-resolved images of the bright spots reveal unexpected dynamics that are not explained by two-dimensional rate equations for generation and diffusion. This behavior can be understood as a result of three-dimensional transport in the vertically extended samples.