  Donor states in Si nanodevices can be strongly modified by nearby insulating
barriers and metallic gates. We report here experimental results indicating a
strong reduction in the charging energy of isolated As dopants in Si FinFETs
relative to the bulk value. By studying the problem of two electrons bound to a
shallow donor within the effective mass approach, we find that the measured
small charging energy may be due to a combined effect of the insulator
screening and the proximity of metallic gates.

Mesoscale and Nanoscale Physics