Planar, narrowband, and tunable photodetection in the near-infrared with Au/TiO2 nanodiodes based on Tamm plasmons

There is increasing interest in hot-electron photodetection due to the extended photoresponse well below the semiconductor band edge. However, the photoresponsivity is extremely low and the metallic nanostructures used to excite surface plasmons (SPs) for improved quantum yield are too complex for practical applications. Here, we show that by exciting Tamm plasmons (TPs), a planar device consisting of a thin metal film of 30 nm on a distributed Bragg reflector (DBR) can absorb similar to 93% of the incident light, resulting in a high hot-electron generation that is over 34-fold enhanced compared to that of the reference without the DBR. Besides, the electric field increases with the light penetration depth in the metal, leading to hot-electron generation that is strongly concentrated near the Schottky interface. As a result, the photoresponsivity can be over 30 (6) times larger than that of the reference (conventional grating system). Moreover, the planar device exhibits an easily tunable working wavelength from the visible to the near-infrared, sustained performance under oblique incidences, and a multiband photodetection functionality. The proposed strategy avoids the complicated fabrication of the metallic nanostructures, facilitating the compact, large-area, and low-cost photodetection, biosensing, and photocatalysis applications.