Importance of ballistic carriers for the dynamic response in sub-100 nm MOSFETs

Monte-Carlo simulations of the metal-oxide semiconductor field-effect transistor (MOSFET) switch-off characteristics are used to verify that ballistic carriers change the electric-field distribution along the MOSFET channel below 100 nm channel length. The field change has two main aspects: increase of field magnitude and shift of zero-field position from channel middle to source side. The shift of the zero-field position forces more carriers to flow to drain during switch-off. This results in a changed charge-partitioning ratio Q(s) (source) / Q(d) (drain) for sub-100 nm MOSFETs from 60/40 (long channel) to 40/60 at 40 nm and a slower emptying of the channel during switch-off than expected from the channel length reduction.