Hyperdoping SiGe with S using ion implantation and pulsed laser melting for infrared absorption and detection

Abstract

Hyperdoping of Si has been demonstrated to induce sub-bandgap absorption through the formation of intermediate bands (IBs). In this work, a p-type SiGe film with 16% Ge grown on Si was hyperdoped with S. Optical absorption measurements show that the SiGe:S material has significant absorption below the bandgap of Si or the SiGe film, and spreading resistance profiling indicates that the S-hyperdoped region is n-type, thereby forming a p–n junction in the SiGe layer. A prototype photodetector was fabricated, and the external quantum efficiency (EQE) spectrum of the detector shows only limited enhancement of the EQE in the region near the Si bandgap. This may be due to the formation of an IB in SiGe:S that crosses the conduction band, thereby leading to intra-conduction band absorption that does not result in additional photoconductivity, similar to previous results from Si hyperdoped with-. Additionally, the SiGe layer is thin and contains extended defects that limit the lifetime and lower the EQE. Although the sub-bandgap enhancement in EQE was small, this nevertheless demonstrates the possibility of using ion implantation followed by pulsed laser melting for hyperdoping of SiGe alloys.