Phosphorus Deactivation and Electron Mobility Enhancement in Ultrathin Silicon Nanosheets

Ex-situ doping is used to introduce a constant dose
$(\sim 1\ \mathrm{x}\ 10^{13}\ \mathbf{cm}^{-2})$
of P atoms into Si nanosheets with thickness ranging from 70 to 6 nm. Full activation of P atoms is demonstrated in Si nanosheets with
$\mathbf{thickness\ h}\geq \boldsymbol{30}$
nm. Conversely, progressive deactivation of dopant impurities is observed when decreasing the thickness of the Si nanosheets below 30 nm. Si nanosheets with thickness
$\mathbf{h} < \boldsymbol{10}$
nm exhibit electron mobility values higher than the ones reported for bulk Si at the same doping concentration. Data provide information for the design of ultra-scaled GAAFET devices.