Surface-acoustic-wave-induced carrier transport in quantum wires

The ambipolar transport of photogenerated electron-hole pairs by surface acoustic waves (SAWs) in coupled GaAs quantum wells (QWs) and quantum wires (QWR's) is investigated by spatially and time-resolved photoluminescence. Experimental configurations for SAW propagation direction parallel or perpendicular to the QWRs have been studied. In the first configuration, the QWR confinement potential inhibits lateral carrier diffusion. The carriers are then efficiently transported along the wire as well-defined charge packages with a repetition rate corresponding to the SAW frequency. In the second configuration, we demonstrate that the SAW can be used to transfer electron-hole pairs generated in the QW into the QWR. We also provide clear evidence for the extraction of carriers from the QWR into the QW, when the SAW piezoelectric field is sufficiently strong to overcome the QWR confinement potentia