Retarded dopant diffusion by moderated dopant-dopant interactions in Si nanowires.

The retarded dopant diffusion in Si nanostructures is investigated using the first principles calculation. It is presented that weak dopant-dopant interaction energy (DDIE) in nanostructures is responsible for the suppressed dopant diffusion in comparison with that in bulk Si. The DDIE is significantly reduced as the diameter of the Si nanowire becomes smaller. The mechanical softening and quantum confinement found in nanostructures are the physical origin for the small interaction energy. Reduced dopant-dopant interaction slows down the diffusion process from heavily doped regions to undoped regions. Thus, we suggest that an additional annealing process is indispensable to make a desired dopant profile in the nanoscale semiconductor devices.