Ultra-compact silicon waveguide-integrated Schottky photodetectors using perfect absorption from tapered metal nanobrick arrays.

We propose and numerically analyze an integrated metal-semiconductor Schottky photodetector consisting of a tapered metal nanoblock chain on a silicon ridge waveguide. The metal-semiconductor junctions allow broadband sub-bandgap photodetection through the internal photoemission effects. The tapered array structures with different block widths can gradually tailor the cut-off frequencies and group velocities of the tightly confined plasmonic modes for enhanced light absorption and suppressed reflection of the photonic mode in the silicon waveguide. As a result, according to our simulations, six metal nanobricks with a total device length of 830 nm can almost perfectly absorb the incident sub-bandgap light and subsequently generate photocurrents with a peak responsivity value of 0.125 A/W at 1550 nm. We believe that the proposed design can provide a simple and viable solution for broadband and compact photodetection in the integrated silicon photonics platform.