Design of a binary metal micron grating and its application in near-infrared hot-electron photodetectors

Metal plasmonic nano-gratings possess a high absorption ability and exhibit potential applications in sensing, hot-electron photodetection, metasurfaces, etc. However, the fabrication techniques of high-quality nano-gratings are challenging. In this article, a binary metal micron grating for near-infrared hot-electron photodetectors (HEPDs) is designed in which the surface plasmons are excited by high-diffraction-order modes. The high-diffraction-order micron grating can be fabricated by conventional lithography and has a significantly higher tolerance in the grating parameters than a nano-grating. The range of absorption greater than 70% is ∼3 times that of a nano-grating. Moreover, an interesting relationship between the resonant wavelength and the grating duty cycle is found. When the high-diffraction-order micron grating is applied in metal-insulator-metal HEPDs, a high zero-biased responsivity of 0.533 mA/W is achieved.