FINITE-TEMPERATURE FERMI-EDGE SINGULARITY IN TUNNELING STUDIED USING RANDOM TELEGRAPH SIGNALS

We show that random telegraph signals in metal-oxide-silicon transisto rs at millikelvin temperatures provide a powerful means of investigati ng tunneling between a two-dimensional electron gas and a single defec t state. The tunneling rate shows a peak when the defect level lines u p with the Fermi energy, in excellent agreement with theory of the Fer mi-edge singularity at Finite temperature, This theory also indicates that defect levels are the origin of the dissipative two-state systems observed previously in similar devices.