Low-frequency noise in Cr—SiO 2 —N-Si tunnel diodes

Low-frequency noise of Cr-SiO 2 -n-Si tunnel diodes with about 30-A-thick oxides is investigated as function of bias, frequency, and temperature. Measurements of 1/f noise are explained by a theory employing the two step tunneling model of Sah. Electrons from the Si conduction band are trapped by states at the Si-SiO 2 interface and then tunnel into bound states of the oxide located close to the interface. The oxide states of density N 00 can be represented by a frequency dependent parallel admittance exhibiting frequency-dependent thermal noise that modulates the dc current I tunneling through the oxide barrier. This generates flicker noise at the device terminals proportional to I^{2}N_{00} and inversely proportional to frequency f and tunneling area A . The value A = 5 . 10 -3 A 0 , determined by fitting theoretical and experimental curves at low frequency, is only a small fraction of the gate area A 0 , since tunneling preferentially occurs through the thinnest parts of the oxide. The current I also exhibits full shot noise at high frequency and low current. Qualitative agreement between theoretical and measured noise is found over 9 decades. Measurements at low temperature show additional noise of generation-recombination centers at larger frequencies and currents.