Temperature-independent switching rates for a random telegraph signal in a silicon metal–oxide–semiconductor field-effect transistor at low temperatures

We have observed discrete random telegraph signals (RTSs) in the drain voltages of three, nominally 1.25 μm×1.25 μm, enhancement-mode p-channel metal–oxide–semiconductor transistors operated in strong inversion in their linear regimes with constant drain-current and gate-voltage bias, for temperatures ranging from 4.2 to 300 K. The switching rates for all RTSs observed above 30 K were thermally activated. The switching rate for the only RTS observed below 30 K was thermally activated above 30 K but temperature independent below 10 K. This response is consistent with a crossover from thermal activation to tunneling at low temperatures. Implications are discussed for models of change exchange between the Si and the near-interfacial SiO2.