Channel-size dependent dopant placement in silicon nanowires

Sensitivity of Phosphorus dopant placement to the channel size of highly doped silicon nanowires is studied using a 10-band sp3 d5 s* tight-binding approach coupled to self-consistent simulations. Extending the simulation scope to realistically sized nanowires, we observed that uniform doping does not necessarily reduce the channel energy compared to surface-oriented doping when the diameter of a nanowire cross-section is smaller than 20 nm, whilst uniform doping lowers the energy, making the channel more stable at larger cross-sections. This size-dependency, firmly connected to the recent experiment, is understood well in detail by investigating channel electrostatics.