NEGF simulations of a junctionless Si gate-all-around nanowire transistor with discrete dopants

We have carried out 3D Non-Equilibrium Green Function simulations of ajunctionlessgate-all-around n-type silicon nanowiretransistor of 4.2 × 4.2 nm2 cross-section. We model the dopants in a fully atomistic way. The dopant distributions are randomly generated following an average doping concentration of 1020 cm−3. Elastic and inelastic phonon scattering is considered in our simulation. Considering the dopants in adiscrete way is the first step in the simulation of random dopant variability in junctionlesstransistors in a fully quantum mechanical way. Our results show that, for devices with an “unlucky” dopants configuration, where there is a starvation of donors under the gate, the threshold voltage can increase by a few hundred mV relative to devices with a more homogeneous distribution of dopants. For the first time we have used a quantum transport model with dissipation to evaluate the change in threshold voltage and subthreshold slope due to the discrete random donors in the channel of ajunctionlessnanowire nMOS transistor. These calculations require a robust convergence scheme between the quantum transport equation and the Poisson equation in order to achieve convergence in the dopant-induced resonance regime