Impact of single charge trapping in nano-MOSFETs-electrostatics versus transport effects

In this paper, using Monte Carlo (MC) simulations featuring ab initio Coulomb scattering, we study the impact of Coulomb scattering from a single trapped electron on the magnitude of the corresponding drain-current reduction in a series of well scaled n-channel nano-MOSFETs. Through a careful comparison with drift-diffusion (DD) simulations that only capture the electrostatic effects associated with the trapped charge, we were able to demonstrate the specific contribution of the scattering. The simulations are performed at low drain bias for MOSFETs with channel lengths of 30, 20, and 10 nm, respectively. Compared to the DD results, the MC simulations show significant additional reduction in drain current associated with the scattering from the trapped electron. The scattering related percentage reduction in the current increases with the increase of the gate voltage toward strong inversion conditions. The velocity distributions in the presence of the trapped charge at various gate conditions are carefully analyzed in order to explain the magnitude of the observed effect.