Scattering of charged impurities in Si nanowires

Impurity scattering is expected to be one of the most serious limiting factor of the performances of devices based on Si nanowires. Dopants are a very special class of impurities, because they are introduced on purpose to design devices with the desired properties and thus are the ultimate source of carrier scattering. By definition, at device operation temperatures, a dopant is ionized. Nevertheless, all the transport calculations based on first-principles methods reported to date by-pass this important point and restrict to neutral defects. We propose a method to calculate efficiently the resistance associated to charged impurity within a first-principles formalism. It is shown that taking into account the proper charge state in the calculation of the conductance lead to large deviation from the neutral impurity results and we find that the minority scattering is increased by a factor of 1000.