The high-field drift velocity in degenerately-doped silicon nanowires

Abstract

The charge transport in nanowires suitable for high-speed applications depends on charge carrier's mobility and saturation velocity in the conducting channel. It is shown that the high mobility does not always lead to higher carrier drift velocity. The ultimate drift velocity (the intrinsic velocity) due to the high-electric-field streaming is based on the asymmetrical distribution function that converts randomness in zero-field to a streamlined one in a very high electric field. The saturation velocity limited to the intrinsic velocity is an appropriate thermal velocity for a non-degenerately doped nanowire, increasing with the temperature, but independent of carrier concentration. However, this saturation velocity is the appropriate Fermi velocity for a degenerately doped silicon nanowire, increasing with carrier concentration but independent of temperature. The results obtained are applied to the modelling of a silicon nanowire transistor.