Leakage current induced anomalies in the photoluminescence of GaAs coupled quantum wells

We have performed photoluminescence experiments on GaAs/AlGaAs coupled quantum wells as a function of bias voltage and photoexcitation intensity. Spatially indirect recombination appears at higher electric fields for weak photoexcitation instead of the spatially direct one which is dominant at zero bias voltage. However, for strong photoexcitation with photon energy larger than the band gap of the barrier layers, the spatially direct recombination remains dominant over a wide range of bias voltage. Under this condition, the exciton ring emission is observed in the PL image at positive biases for which a large leakage current flows through the device. These results suggest that the 2DEGs induced by the large leakage current is important for interpreting the behavior of the ring emission. (C) 2004 WILEY-VCH Verlag GmbH & Co. KGaA. Weinheim.