Aluminium Single Electron Transistors with Islands Isolated from the Substrate

AbstractThe low-frequency noise figures of single-electron transistors(electrometers) of traditional planar and new stacked geometrywere compared. We observed a correlation between the chargenoise and the contact area of the transistor island with adielectric substrate in the set of Al transistors located onthe same chip and having almost similar electric parameters.We have found that the smaller the contact area the lower thenoise level of the transistor. The lowest noise value (δQx=(8±2)×10−6e/ $$\sqrt {Hz}$$ at 10Hz)has been measured in a stacked transistor with an island which wascompletely isolated from a substrate. Our measurements haveunambiguously indicated that the dominant source of thebackground charge fluctuations is associated with a dielectricsubstrate.