Deep Impurity Band Silicon for Subbandgap Photodetection

摘要

We performed experiments to test the hypothesis that partial counter- doping of sulfur-hyperdoped silicon would create a partially filled intermediate band, which could be used for sub-bandgap photodetection. We fabricated counter-doped Si:S:B of well-controlled crystal quality and dopant concentration-depth profile, and we made three independent measurements of photoconductivity: one with contacts, and two without contacts. These measurements were per-formed in collaboration with the Persans group at RPI, the Buonassisi group at MIT, and the Warrender group at Ben t Labs. In all cases, the sub-bandgap photoresponse is negligibly small. We conclude from these results that the lifetime of photo-excited carriers is very small-- less than about 10 ns. Sub-bandgap photodetection using counter-doped silicon does not appear to be promising. The optoelectronic response appears to be less desirable than those of certain deep-level transition metals in Si, which appear much more promising for future investigation.