Study of individual phonon scattering mechanisms and the validity of Matthiessen's rule in a gate-all-around silicon nanowire transistor

Abstract

In this paper, we investigate the impact of different phonon scattering mechanisms on the performance of a small silicon gate-all-around nanowire field effect transistor. The Non-equilibrium Green's function (NEGF) framework in the effective mass approximation is used to describe the carrier transport in a wide range of bias conditions. For all gate bias conditions, acoustic phonons are found to be the most important scattering mechanism. At low drain bias, the total impact of the phonons increases monotonically with the gate bias as all the contributions from different phonons increase, but at high drain bias the drain current reduction remains almost constant. At high gate bias conditions, the calculations show a different behaviour for acoustic phonons at low and high drain bias, which substantially influences the total impact of phonon scattering at high gate biases. The drain current reduction, including all phonons, is in agreement with previous simulations using a tight-binding/NEGF approach [M. Luisier and G. Klimeck, Phys. Rev. B 80, 155430 (2009)]. We find a violation of Matthiessen's rule of 13%. A value of 16% is obtained through the use of a Green-Kubo formula, which includes a self-consistent calculation of the retarded Green's function. However, an overestimation of 23% is found if a semi-classical Kubo expression is used.