Direct white noise characterization of short-channel MOSFETs

On-wafer evaluation of white thermal and shot noise in nanoscale MOSFETs is demonstrated by directly sensing the drain current under zero- and nonzsero-drain-bias (V_d) conditions for the first time, without recourse to a hot noise source, commonly needed in noise figure measurement. The dependence of white noise intensity on the drain bias clearly shows thermal noise at V_d=0 V and shot noise at V_d>0 V with its gate-bias-dependent suppression. An empirical expression for the Fano factor (shot-noise suppression factor) that is well-behaved even at V_d=0V exactly and suitable for measurement-based evaluation is proposed. The direct measurement approach could allow more accurate and predictive noise modeling of RF MOSFETs than has conventionally been possible.