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 mu mx1.25 mu m, 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. (C) 2000 American Institute of Physics. [S0003-6951(00)01822-2].