We present atomistic simulations of the $D^0$ to $D^{-}$ charging energies of a gated donor in silicon as a function of applied fields and donor depths and find good agreement with experimental measurements. A self-consistent field large-scale tight-binding method is used to compute the $D^{-}$ binding energies with a domain of over 1.4 million atoms, taking into account the full band structure of the host, applied fields, and interfaces. An applied field pulls the loosely bound $D^{-}$ electron toward the interface and reduces the charging energy significantly below the bulk values. This enables formation of bound excited $D^{-}$ states in these gated donors, in contrast to bulk donors. A detailed quantitative comparison of the charging energies with transport spectroscopy measurements with multiple samples of arsenic donors in ultrascaled metal-oxide-semiconductor transistors validates the model results and provides physical insights. We also report measured $D^{-}$ data showing the presence of bound $D^{-}$ excited states under applied fields.

• Received 28 June 2011

DOI:https://doi.org/10.1103/PhysRevB.84.115428