Contactless microwave measurements of photoconductivity in silicon hyperdoped with chalcogens

Abstract

Photoconductivity in silicon hyperdoped with sulfur and selenium above the insulator-to-metal transition was measured via photoinduced changes in the microwave reflectivity of hyperdoped layers formed on p-type silicon. Despite these materials' strong subgap optical absorption, exposing them to 1310 and 1550nm light results in a change in conductivity per photon 10,000 times smaller than what is observed in untreated silicon exposed to 980nm light. A similar bound applies for 405nm light, which is absorbed entirely in the hyperdoped layer. We use these results to deduce that the photocarrier lifetime in the hyperdoped material is ≤100 ns. © 2012 The Japan Society of Applied Physics.