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

Abstract

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 nm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> . The average doping concentration is 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">20</sup> cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-3</sup> . 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.