We observe an insulator-to-metal (I-M) transition in crystalline silicon doped with sulfur to non- equilibrium concentrations using ion implantation followed by pulsed laser melting and rapid resolidification. This I-M transition is due to a dopant known to produce only deep levels at equilibrium concentrations. Temperature-dependent conductivity and Hall effect measurements for temperatures T > 1.7 K both indicate that a transition from insulating to metallic conduction occurs at a sulfur concentration between 1.8 and 4.3 x 10^20 cm-3. Conduction in insulating samples is consistent with variable range hopping with a Coulomb gap. The capacity for deep states to effect metallic conduction by delocalization is the only known route to bulk intermediate band photovoltaics in silicon.
@article{arxiv.1103.0609,
title = {Insulator-to-metal transition in sulfur-doped silicon},
author = {Mark T. Winkler and Daniel Recht and Meng-Ju Sher and Aurore J. Said and Eric Mazur and Michael J. Aziz},
journal= {arXiv preprint arXiv:1103.0609},
year = {2015}
}