Enhanced Photoelectric and Photothermal Responses on Silicon Platform by Plasmonic Absorber and Omni-Schottky Junction

Recent progresses in plasmon-induced hot electrons open up the possibility to achieve photon harvesting beyond the fundamental limit imposed by band-to-band transitions in semiconductors. To obtain high efficiency, both the optical absorption and electron emission/collection are crucial factors that need to be addressed in the design of hot electron devices. Here, we demonstrate a photoresponse as high as 3.3mA/W at 1500nm on a silicon platform by plasmonic absorber (PA) and omni-Schottky junction integrated photodetector, reverse biased at 5V and illuminated with 10mW. The PA fabricated on silicon consists of a monolayer of random Au nanoparticles (NPs), a wide-band gap semiconductor (TiO2) and an optically thick Au electrode, resulting in broadband near-infrared (NIR) absorption and efficient hot-electron transfer via an all-around Schottky emission path. Meanwhile, time and spectral-resolved photoresponse measurements reveal that embedded NPs with superior absorption resembling plasmonic local heating sources can transfer their energy to electricity via the photothermal mechanism, which until now has not been adequately assessed or rigorously differentiated from the photoelectric process in plasmon-mediated photon harvesting nano-systems.