CMOS-Compatible Broad-Band Hot Carrier Photodetection with Cu-Silicon Nanojunctions

Plasmonic harvesting of hot carriers (HCs) in metal-semiconductor (M-S) junctions has stimulated intensive research activities for sub-bandgap photodetection, in particular the development of silicon-based infrared photodetectors. Here, a copper-silicon heterojunction was investigated both theoretically and experimentally in comparison to the commonly used gold- silicon ones. A 1-order-of-magnitude higher responsivity and a longer cutoff wavelength over 2000 nm were observed in experiments in the sub-bandgap wavelength range of silicon with a copper-silicon junction. A phenomenological model was developed to analyze the dynamic processes of HCs and attributed the advanced photodetection performance of copper-silicon devices to the relatively higher electron density of state above the Fermi level and the higher ejection probability. Such a complementary metal-oxide- semiconductor-compatible and low-cost HC photodetection platform shows promising potential in silicon-based optoelectronic applications.