Channel length dependence of discrete dopant effects in narrow si nanowire transistors: A full 3D NEGF study

In this paper we study the variability induced by random discrete dopants in a gate-all-around silicon nanowire transistor. The electron transport is described using the Non-Equilibrium Green Function formalism. Coupled-mode-space representations are used. A silicon nanowire transistor with 4.2×4.2 nm² cross-section and two different channel lengths (6 nm and 12 nm) has been considered. The mobility associated with discrete dopants can be estimated from the averaged current voltage characteristics. The threshold voltage and subthreshold slope variability are greatly reduced in the longer channel length transistor. At the same time the on current variability associated with the resistance variability of the access regions is virtually independent of the channel length.