Reproducible fluctuations of carrier concentration in Si - MOSFET below 1K

Novel reproducible fluctuations of the voltage between the potential leads of Si-MOSFETS(s) were observed in the temperature range from 100mK to 4.2K as a response to the gate voltage modulated by a weak ac signal. We interpret them as a consequence of the macroscopic fluctuations of the carrier concentration accompanying the charging of inversion and depletion layers at the Si - SiO2 interface. The surface roughness and the inhomogeneous distribution of impurities close to the interface are assumed to be a source of inhomogeneity of the concentration of carriers.