Noise properties of single electron transistors

We have measured the low frequency (5 mHz < f < 30 Hz) noise in current bia sed aluminium single electron tunneling (SET) transistors. A refined high f requency (HF) shielding allows us to maintain and study a given background charge configuration for many hours at T < 100 mK. At frequencies below 10 Hz the noise is mainly due to charge traps, and the noise pattern superimpo sed on the V(V-g)-curve strongly depends on the particular background charg e configuration resulting from the cooling sequence and the applied RF irra diation, including thermal radiation from the 4.2 K environment. The noise spectra, which show both 1/f and 1/f(1/2) dependencies and saturate at f < 100 mHz can be fitted by two-level fluctuators (TLF) with Debye-Lorentz spe ctra and relaxation times on the order of seconds. (C) 1999 Elsevier Scienc e Ltd. All rights reserved.