Mesoscopic charge mapping by conductance fluctuations

We present a new technique for studying changes in the microscopic configuration of charged scatterers in doped semiconductors. The technique is based on Universal Conductance Fluctuations (UCF). To illustrate the process we describe experiments on Si-doped GaAs wires fabricated using electron-beam lithography. By pulsing an infra-red LED we are able to depopulate meta-stable charge traps in the wire. We also investigate changes in the scattering configuration due to thermal cycling.