  Graphene's high mobility and Fermi velocity, combined with its constant light
absorption in the visible to far-infrared range, make it an ideal material to
fabricate high-speed and ultra-broadband photodetectors. However, the precise
mechanism of photodetection is still debated. Here, we report wavelength and
polarization dependent measurements of metal-graphene-metal photodetectors.
This allows us to quantify and control the relative contributions of both
photo-thermo- and photoelectric effects, both contributing to the overall
photoresponse. This paves the way for a more efficient photodetector design for
ultra-fast operating speeds.
