The kinetics of charge transport in quantum point contacts has been studied by low-frequency noise spectroscopy. Temperature and frequency (Lorentzian and 1/f) dependences of the noise spectral density are found to vary strongly from device to device, but the low-T conductance dependence universally exhibits a strong quantum size effect. Based on the direct observation in the time domain of spontaneous resistance switching, the noise is identified to be due to trapping processes which affect the local electrostatic potential. A model is presented which explains the main experimental observations.

• Received 9 October 1990

DOI:https://doi.org/10.1103/PhysRevLett.66.2148