Modeling nonuniform doping in subthreshold MOSFETs

For subthreshold MOSFETs, there can be large variations in depletion region width relative to above threshold operation. This work investigates the significance of nonuniform doping effects in subthreshold conduction through numerical calculations based on measured dopant profiles. The ultimate goal of the simulations is improving the accuracy of compact MOSFET models for subthreshold circuit simulation. To this end, a semi-empirical expression suitable for inclusion in a public domain MOSFET model [the EPFL model by Enz, Krummenacher, and Vittoz (1995)] is also proposed.