The Suppression of Random Telegraph Noise in a Point Contact

Abstract

The conductance of a one-dimensional (1D) constriction in a two-dimensional electron gas (2DEG) can be quantized in steps of 2e2/h as a function of the width of the constriction, corresponding to the depopulation of 1D subbands, provided the constriction is short enough so that backscattering from impurities is improbable. Generally, impurities or disorder have a deleterious effect on the quantization of the conductance of a one-dimensional constriction, but not always. We demonstrate that scattering from a defect can be suppressed in a modulation doped, 1D constriction through an examination of discrete changes in the conductance of the wire which resemble a random telegraph signal (RTS). The discrete changes in the conductance develop from time-dependent fluctuations in the scattering potential of a single defect in close proximity to the 2DEG. We show that the switching associated with RTS is quenched whenever an integral number of 1D subbands are occupied, but reappears near the threshold for the occupation of a subband. The suppression of the switching is attributed to the quenching of small angle impurity scattering in a one-dimensional wire.