Green Function Simulation Study of Non Self-Averaging Scattering Processes in Atomistic Semiconductor Devices

The breakdown of the Kohn-Luttinger ansatz for self-averaging of impurity scattering is shown to occur in small finite semiconductor device structures when less than 1000 impurities are in the device volume. As a consequence the standard non-equilibrium Green function formalism for quantum transport is invalid. Instead, a non-self-averaged propagator formalism is proposed based on a T-matrix model for non-asymptotic finite-cluster scattering. The formalism is illustrated by a study of the charge density and current density profiles resulting from coherent flow through a finite atomistic device containing a small number of impurities. The flow typically separates into open streamlines and a set of blocking vortices.