CONDUCTANCE FLUCTUATIONS AND NOISE IN BARELY CONDUCTING N+ WIRES

Conduction in narrow n+-GaAs wires prepared by reactive ion etching of epitaxial layers has been studied at low temperatures. Applications of high electric fields for short periods or exposure to low intensity visible light enables the number of carriers in the samples to be decreased or increased. Photocurrent noise is found to be anomalously large for samples with closely spaced voltage probes. When samples are allowed to relax after the introduction of a non-equilibrium carrier concentration, steps are observed in the conductance which we ascribe to single electrons interacting with traps. From the magnitude of these steps, we estimate the coherence length in these samples to be of the order of the wire width, and postulate that the electron coherence is limited by trapping events occurring at the wire edges. © 1991.