Study of Discrete Doping-Induced Variability in Junctionless Nanowire MOSFETs Using Dissipative Quantum Transport Simulations

The impact of discrete doping in junctionless gate all-around n-type silicon nanowire transistors is studied using 3-D nonequilibrium Green´s functions simulations. The studied devices have a 20 nm long gate and cross sections of 4.2 × 4.2 and 6.2 × 6.2 nm². The average doping concentration is 10²⁰ cm^-3. The dopant distributions are randomly generated and modeled in a fully atomistic way. Phonon scattering, elastic and inelastic, is also included in the simulations. We show that junctionless nanowire transistors have a much higher subthreshold variability than their inversion mode counterparts for the equivalent geometry and doping level.