Semiclassical and Quantum Electronic Transport in Nanometer-Scale Structures: Empirical Pseudopotential Band Structure, Monte Carlo Simulations and Pauli Master Equation

Abstract

The study of electronic transport in nanometer-scale devices requires an accurate knowledge of the excitation spectrum (i.e., the band structure) of the systems and, for short devices, a formulation of transport which transcends the semiclassical Boltzmann formulation. Here we show that the use of ‘judiciously’ chosen empirical pseudopotentials, coupled to the supercell method, can provide a sufficiently accurate description of the band structure of thin semiconductor films, hetero-structures, nanowires, and carbon-based structures such as graphene, graphene nanoribbons, and nanotubes. We discuss semiclassical Monte Carlo simulations employing the supercell-pseudopotential band structure, considering transport in thin Si bodies. This example illustrates the importance of the full-band approach since in this case it yields the low value of the saturated high-field electron drift velocity, observed experimentally but never predicted when employing effective-mass band structures. Finally, we discuss a mixed envelope-supercell approach to deal with open systems within the full-band supercell scheme and review the Master-equation approach to quantum transport. Finally, we present some results of fully dissipative quantum transport using, for now, the effective mass approximation, emphasizing the role of impurity scattering in determining the ‘quantum access resistance’ in thin-body devices.