Temperature dependence of low-frequency noise in Al–Al2O3–Al single-electron transistors

We have measured the temperature dependence of the charge noise power spectral density Sq in two-junction Al–Al2O3–Al single-electron transistors at temperatures from 85 mK to 4 K. Although individual Lorentzians are often visible, the noise spectra are dominated by excess low-frequency noise with a power-law dependence on frequency f where Sq∝1/fβ and β≃1. Below about 0.5 K, Sq is weakly dependent on the temperature T. Above 1 K, the charge noise Sq increases with T, and at 4 K Sq≈10−4 e2/Hz at 1 Hz, about a factor of 100 greater than at 85 mK.