Electric Field Reduced Charging Energies and Two-Electron Bound Excited States of Single Donors in Silicon
Date of this Version9-15-2011
Phys. Rev. B 84, 115428 (2011)
We present atomistic simulations of the D0 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.
Nanoscience and Nanotechnology