Impact of ion implantation and laser processing parameters on carrier lifetimes in gold-hyperdoped silicon

In recent years, infrared photodetectors using silicon hyperdoped with deep-level dopants started to demonstrate extended light detection beyond the silicon’s absorption edge. The reported responsivities or external quantum efficiencies, however, are typically low. Focusing on gold-hyperdoped silicon and using time-resolved terahertz spectroscopy, a non-contact photoconductivity measurement, we investigated how hyperdoping parameters affect charge carrier lifetimes. Correlating the observed lifetime characteristics with dopant distribution profiles, we identify factors that impact carrier lifetime most significantly. Specifically, the charge carrier lifetime reduces with increasing gold concentrations, increasing ion implantation energies, and increasing pulsed-laser melting fluences. Both ion implantation energy and laser fluence affect the dopant incorporation depths. The total gold dose implanted and laser fluence affect the carrier distribution profile, particularly the concentration spike toward the surface. Oxide passivation and the number of laser pulses do not impact the carrier lifetime significantly. Our findings benefit future device developments.