Polarization-Insensitive Metal-Semiconductor-Metal Nanoplasmonic Structures for Ultrafast Ultraviolet Detectors

We propose a theoretical design principle of polarization-insensitive metal-semiconductor-metal (MSM) structure for ultraviolet photodetectors based on one-dimensional nanogratings. Because the Fabry-Pérot cavity modes supported by a 100-nm-thick ZnO layer with nanostructures for transverse electric and transverse magnetic polarized incidence overlap with each other, a polarization-insensitive absorption enhancement for the ZnO layer at UV wavelengths is achieved, which can be implemented as a nano-interdigitated electrode to address a long-existing limitation between the speed and the responsivity for conventional MSM photodetectors.