In gratings, incident light can couple strongly to plasmons propagating through periodicallyspaced slits in a metal film, resulting in a strong, resonant absorption whose frequency isdetermined by the nanostructure periodicity. When a grating is patterned on a silicon substrate,the absorption response can be combined with plasmon-induced hot electron photocurrentgeneration. This yields a photodetector with a strongly resonant, narrowbandphotocurrent response in the infrared, limited at low frequencies by the Schottky barrier, notthe bandgap of silicon. Here we report a grating-based hot electron device with significantlylarger photocurrent responsivity than previously reported antenna-based geometries. Thegrating geometry also enables more than three times narrower spectral response thanobserved for nanoantenna-based devices. This approach opens up the possibility of plasmonicsensors with direct electrical readout, such as an on-chip surface plasmon resonancedetector driven at a single wavelength.
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