Spatially direct and indirect optical transitions in shallow etched GaAs/AlGaAs quantum wires

Electrons and photoexcited holes are separated into adjacent quantum wires in remote doped GaAs/AlGaAs quantum wells, using a shallow etching technique. This spatial separation results in a drastic change of the photoluminescence lineshape and an additional, broad feature shifted up to 30 meV below the luminescence energy of the unstructured sample. The two relevant recombination processes are shown to be due to spatially direct and indirect transitions, respectively. A variation of the temperature indicates, that both plasma-like and exciton-like recombinations contribute to the spatially direct luminescence.