  Visible and infrared photons can be detected with a broadband response via
the internal photoeffect. By using plasmonic nanostructures, i.e. nanoantennas,
wavelength selectivity can be introduced to such detectors through
geometry-dependent resonances. Also, additional functionality, like electronic
responsivity switching and polarization detection have been realized. However,
previous devices consisted of large arrays of nanostructures to achieve
detectable photocurrents. Here we show that this concept can be scaled down to
a single antenna level, resulting in detector dimensions well below the
resonance wavelength of the device. Our design consists of a single
electrically-connected plasmonic nanoantenna covered with a wide-bandgap
semiconductor allowing broadband photodetection in the VIS/NIR via injection of
hot carriers. We demonstrate electrical switching of the color sensitivity as
well as polarization detection. Our results hold promise for the realization of
ultra small, highly integratable photodetectors with advanced functionality.
