"Picosecond carrier recombination dynamics in chalcogen-hyperdoped silicon"

Meng-Ju Sher: Christie B. Simmons, Jacob J. Krich, Austin J. Akey, Mark T. Winkler, Daniel Recht, Tonio Buonassisi, Michael J. Aziz and Aaron M. Lindenberg; Appl. Phys., 08/07/14.

Additional Authors: Christie B. Simmons, Jacob J. Krich, Austin J. Akey, Mark T. Winkler, Daniel Recht, Tonio Buonassisi, Michael J. Aziz and Aaron M. Lindenberg

Abstract:

Intermediate-band materials have the potential to be highly efficient solar cells and can be fabricated by incorporating ultrahigh concentrations of deep-level dopants. Direct measurements of the ultrafast carrier recombination processes under supersaturated dopant concentrations have not been previously conducted. Here, we use optical-pump/terahertz-probe measurements to study carrier recombination dynamics of chalcogen-hyperdoped silicon with sub-picosecond resolution. The recombination dynamics is described by two exponential decay time scales: a fast decay time scale ranges between 1 and 200 ps followed by a slow decay on the order of 1‚ÄČns. In contrast to the prior theoretical predictions, we find that the carrier lifetime decreases with increasing dopant concentration up to and above the insulator-to-metal transition. Evaluating the material’s figure of merit reveals an optimum doping concentration for maximizing performance.