December 2, 2014
Li and Valentine demonstrate a hot electron photodetector with a near-record photoresponsivity by using a metamaterial perfect absorber. Ordinarily, the losses in plasmonic structures are considered a burden. However, the hot electrons generated in metals during light absorption can actually be extracted, although the efficiency of this process is typically very low. In this paper the authors created a patterned Si metamaterial structure coated with a thin gold film. This structure results in all the incident light being absorbed in the 15 nm gold film, which happens to be about the diffusion length of hot electrons in gold. Generating nearly perfect absorption in such a thin metal layer allows for more hot electrons to be collected.