Bias and temperature dependence of the noise in a single electron transistor

A single electron transistor based on Al-AlOx-Nb tunnel junctions was fabri cated by shadow evaporation and in situ barrier formation. Its output curre nt noise was measured, using a transimpedance amplifier setup, as a functio n of bias voltage, gain, and temperature, in the frequency range (1-300) Hz . The spot noise at 10 Hz is dominated by a gain dependent component, indic ating that the main noise contribution comes from fluctuations at the input of the transistor. Deviations from ideal input charge noise behaviour are found in the form of a bias dependence of the differential charge equivalen t noise, i. e. the derivative of current noise with respect to gain. The te mperature dependence of this effect could indicate that heating is activati ng the noise sources; and that they are located inside or in the near vicin ity of the junctions.