A comprehensive study of velocity overshoot effects in double gate silicon on insulator transistors

A comprehensive study of velocity overshoot in double gate silicon on insulator (DGSOI) transistors has been undertaken. Monte Carlo simulations were performed to clarify the dependence of velocity overshoot effects on the low field mobility, channel inversion charge and silicon layer thickness. The relationships and dependences between the energy- and momentum-relaxation times were also investigated. In general, two opposite effects influence electron transport in DGSOI inversion layers as the silicon thickness is reduced: a reduction in the conduction effective mass and a phonon scattering increase. However, we show that electron mobility is mainly determined by the increase in the phonon scattering rate as the silicon thickness is reduced, i.e., the lower the silicon thickness the lower the electron mobility, while the velocity overshoot effects for ultrathin DGSOI inversion layers are dominated by the reduction of the average conduction effective mass, i.e., the lower the silicon thickness the higher the velocity overshoot peak.