Dynamics of a Charged Fluctuator in an Al-AlO_x-Al Single-Electron Transistor

We report detailed observations of random-telegraph charge fluctuations in a two-junction Al-AlOx-Al single-electron transistor (SET). We measured the fluctuations from 85 mK to 3 K and observed that the SET switched between two states, causing charge shifts of AQo = 0.1 ± 0.025 e on the SET's island. The transition rate out of each state was periodic in the gate voltage, varied non-monotonically with the device bias voltage, and was independent of the temperature below about 0.3 K. We discuss two effects which could contribute to the behavior of the transition rates, including heating of the defect by the island conduction electrons and inelastic scattering between the defect and electrons flowing through the SET.