Observation of giant oscillations in the phonon-induced conductivity of a GaAs quantum wire

We have made phonon measurements of the electron-phonon interaction in a long quantum wire using the phonoconductivity technique. The wire was formed in a GaAs/${\mathrm{Al}}_{\mathrm{x}}$${\mathrm{Ga}}_{1\mathrm{-}\mathrm{x}}$As heterojunction using the split-gate method. It was subjected to a pulsed beam of nonequilibrium phonons generated by a heater on the opposite side of the substrate. The incident phonon pulses caused a transient increase in the device conductance. The strength of the detected signal displayed giant oscillations as the wire was narrowed by increasing the negative bias on the gate. We give a qualitative account of these observations in terms of phonon-induced delocalization of weakly localized electron states in the wire.