Orientational Dependence of Charge Transport in Disordered Silicon Nanowires

We report on a theoretical study of surface roughness effects on charge transport in silicon nanowires with three different crystalline orientations, [100], [110] and [111]. Using an atomistic tight-binding model, key transport features such as mean-free paths, charge mobilities, and conductance scaling are investigated with the complementary Kubo-Greenwood and Landauer-Büttiker approaches. The anisotropy of the band structure of bulk silicon results in a strong orientation dependence of the transport properties of the nanowires. The best orientations for electron and hole transport are found to be the [110] and [111] directions, respectively.