Analytical study of drift velocity in p-type silicon nanowires

Abstract

An analytical model that captures the essence of physical processes in a p- type silicon nanowire transistor is presented. The model covers seamlessly the whole range of transport from driftdiffusion to ballistic. The mobility and saturation velocity are the two important parameters that control the charge transport in a MOSFET channel. It is shown that the high mobility does not always lead to higher carrier velocity. The ultimate drift velocity due to the high electric-field streaming are based on the asymmetrical distribution function that converts randomness in zero-field to streamlined one in a very high electric field. The limited drift velocity is found to be appropriate thermal velocity for a nondegenerately doped sample of silicon, increasing with the temperature, but independent of carrier concentration. However, the limited drift velocity is the Fermi velocity for a degenerately doped silicon nanowire, increasing with carrier concentration but independent of the temperature.