Revisiting Dopant Deactivation In Silicon Nanostructures

The successful activation (ionization) of dopants is essential for the operation of virtually all semiconductor devices to obtain the required doping polarity and charge carrier density. On the nanoscale, however, the established effects of quantum confinement and dielectric mismatch impede dopant activation. Here, the ionization energies of dopant atoms in ultrathin silicon films embedded in different dielectric environments are calculated. We demonstrate that a stack of interfacial SiO2 combined with a thin high‐k HfO2 gate dielectric provides for a significantly reduced dopant deactivation by dielectric mismatch. Moreover, beyond the established dopant deactivation mechanisms, this study incorporates the impact of the Nanoscale Electronic Structure Shift Induced by Anions at Surfaces (NESSIAS) as a phenomenon that has previously not been considered in this context. The analysis models the NESSIAS as an additional interface potential that decays exponentially from the Si/SiO2 interface on length scales of only 1.5 nm. Nevertheless, a reduced dopant ionization energy, especially in the center of the Si films, is observed even for 13 nm Si thickness. These findings highlight the critical role of NESSIAS as an interface effect that fundamentally alters the spatial dependence of the dopant ionization energy and thereby impacts the dopant properties in nanoscale Si‐devices.