Diffusion and inter-valley noise in (100) n-channel Si-MOSFETs from T = 4.2 to 295 K

Abstract

Noise in the drain current of (100) n-channel Si-MOSFETs was investigated as a function of both source-drain voltage and gate voltage, from T = 4.2 to 295 K. The frequency range covered was from 1 to 250 kHz. Three contributions to the noise could be distinguished: 1/ f-noise, generation-recombination noise and white noise. This paper deals mainly with the white noise component. The current-voltage characteristics at T = 295 K can be described by simple MOSFET-theory, but at T = 4.2 K hot carrier effects and field-induced transitions occur, and the theory has to be amended accordingly. The white noise that was measured at room temperature is diffusion noise. At T = 4.2 K however we observed extra white noise over and above diffusion noise. We also observed extra white noise at intermediate temperatures but it was less pronounced. We have developed a model which interprets this extra noise as the frequency-independent part of generation-recombination noise caused by inter-valley transitions between three groups of valleys. There is good agreement between the model and our experimental results.