A New F(ast)-CMS Algorithm for Efficient Three-Dimensional NEGF Simulations of Arbitrarily Shaped Silicon Nanowire MUGFETs

We present here 3D quantum simulations based on non-equilibrium Green's function (NEGF) formalism using the Comsol Multiphysicstrade software and on the implementation of a new fast coupled mode-space (FCMS) approach. The FCMS algorithm allows one to simulate transport in nanostructures presenting discontinuities, as the normal coupled mode-space (CMS) algorithm does, but with the speed of a fast uncoupled-mode space (FUMS) algorithm (a faster algorithm that cannot handle discontinuities). Using our simulator, we also show that energy barriers resulting from cross-section variations at the gate edge of a nanowire can be optimized to improve the on/off current ratio. A subthreshold slope steeper than the kT/q.log(10) limit of classical transistors together with symmetrical source-drain operation is demonstrated for the first time using this new variable barrier tunnel transistor (VBT) concept.