Green function treatment of electronic transport in narrow rough semiconductor conduction channels

We explore the effect of geometrical fluctuations on the electronic transport in rough Si nanowire (NW) thermoelectric devices of diameter D < 10 nm. At this scale, the quantum nature of transport is accounted in the computation of energy dependent transmission coefficients through a recursive green function algorithm. The rough 3D NW geometry is used as a direct input to simulations through the roughness height Δ and autocovariance length L. Using a non parabolic band structure, the channel conductance above 0.1 eV is drastically reduced in such NW with high D/Δ ratio. In addition, the roughness induced resistivity is only increased by 6% on the first energy level of 10 nm Si channels with Δ = 7.7 Å, showing possible application for high thermoelectric figures of merit ZT.