Perturbative vs non-perturbative impurity scattering in a narrow Si nanowire GAA transistor: A NEGF study

In this paper we study the effect of impurity scattering on the performance of a Si gate-all-around nanowire transistors. The non-equilibrium Green function formalism is used in order to describe the carrier transport. Impurity scattering is introduced using two different formalisms, one that considers the impurity potential as a small perturbation by introducing self energies and the other in which the impurity potential is described exactly by included the impurity potential through the Poisson equation. The non-perturbative method does not use a fitting parameter but the perturbative one uses a phenomenological constant that can be calibrated to match the result of the non-perturbative method. We confirm Ohms-law-type behaviour by using the perturbative approach for larger channel lengths.