Plasmonic MSM Photodetektor

We propose to study the interplay of plasmonic field enhancement and semiconductor absorption in planar metallic photonic crystals, and to use it in a novel class of fast photodetectors. The photonic crystal structures consist of periodically patterned gold or silver deposited on a semiconductor material. They perform two tasks: First, surface plasmon polaritons improve the light transmission through the metal layer, and the local field enhancement associated with these excitations increases the optical absorption in the semiconductor. Second, optically generated electrons and holes are rapidly extracted into the metallic electrodes like in conventional metal-semiconductor-metal (MSM) photodiodes. The structures will be fabricated by a novel technique based on a combination of interference lithography and double oblique evaporation. Using this technique, the gaps between features of the metallic structures can be adjusted very precisely down to a few nanometers, such that a good control over the surface-plasmon polaritons is possible. This work might lead to ultrafast photodetectors with a high quantum efficiency, due to the combination of a very strong absorption, small RC-times and very short carrier transit times.