Impurity potential induced resonances in doped Si nanowire: A NEGF approach

We study the coherent transport of electrons through a uniformly doped Silicon quantum wire in the presence of one impurity in the channel at room temperature using fully 3D Non-Equilibrium Green´s Functions technique. The potential of the single impurity, assumed to be attractive (a donor), is self-consistently calculated via Poisson equation coupled with Schro¿dinger equation in the effective mass approximation. The electron effective masses are re-normalised for the confinement. The effects of the screening on the donor and of the polarization at the Si/SiO2 interface are included in a non-perturbative way (in the Hartree´s approximation). The transmission shows different types of resonances (Breit-Wigner and Fano types) from the quasi-bound states of the impurity when compared to the impurity free wire. We found that the type of resonance is a direct consequence of the shape of the self-consistent potential. The study has significant relevance to mesoscopic wires and nanowire transistors with cross sections of few nanometers where the electron wavelength and confinement play an important role.