Modeling short-channel effects in channel thermal noise and induced-gate noise in MOSFETs in the NQS regime

Abstract

Analytical expressions for channel thermal noise and induced-gate noise considering mobility degradation and carrier heating in the non-quasi-static regime are presented. At a given frequency, as a function of channel electric field, channel thermal noise current increases for pure carrier heating and decreases for pure mobility degradation. With both effects present, the increase in noise is much slower and under quasi-static approximation, based on the model used, the two effects cancel out. Induced-gate current noise, on the other hand, increases when both effects are present. Individual presence of either of the two short-channel effects produces similar but slower increase. A physical explanation for the above behavior is presented. An elemental analysis for long-channel devices reveals that, under device saturation, thermal voltage fluctuations precisely at a distance (5/9)L eff from the source, do NOT produce any induced-gate current noise.