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

The nanowires and nanotubes are being considered as the best candidates for high-speed applications. The mobility and saturation velocity are the two important parameters that control the charge transport in any conducting 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 non degenerately 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 temperature. The results obtained are applied to the modeling of a nanowire transistor.