Sub-bandgap photoresponse and leakage current analysis in gold thin film-hyperdoped silicon photodiodes

We present a study of the sub-bandgap photoresponse and leakage current in gold-hyperdoped silicon photodiodes prepared using pulsed laser melting (PLM) of sub-nanometer gold films on n-type silicon substrates. Variable-temperature photo- and dark-current analysis provide insight into the role of PLM conditions on device performance. In general, we find photocurrent activation energies comparable to room temperature, suggesting a weak thermally-assisted optical photoresponse mechanism. Additionally, we establish a connection between repetitive PLM pulsing and increased device leakage current, which originates from electrically-active defects. Finally, we propose an explanation for the limited sub-bandgap external quantum efficiencies reported for hyperdoped silicon devices on the basis that the depletion layer largely does not encompass the hyperdoped layer where absorption occurs.