Determining the low-frequency noise source in cryogenic operation of short-channel bulk MOSFETs.

For the first time, we clarified the low-frequency noise source of short-channel bulk MOSFETs at cryogenic temperature. We experimentally revealed that, with decreasing temperature, noise sources transition from inner-oxide traps to interface traps and then to band-edge localized states that have energy levels within a few tenths of meV from the conduction band-edge. This transition occurs because the Fermi level at the interface shifts to near the conduction band, resulting in charge traps responsible for the noise being filled and shallower energy traps contributing to the noise. Determining the noise sources is a critical step in increasing the coherence time of qubits and realizing practical quantum computers with silicon.