Suppression of gap plasmon resonance for high-responsivity metal–insulator–metal near-infrared hot-electron photodetectors

Binary metal layers composed of a grating and a thin film are designed for high-responsivity metal-insulator-metal (MIM) near-infrared hot-electron photodetectors (HEPDs). The binary metal grating structure HEPDs demonstrate a strong asymmetrical optical absorption and result in a high current responsivity. In our devices, the top and bottom absorption ratio is as high as 76:1, much higher than that in the traditional grating structure HEPDs. The maximum zero-biased responsivity is 0.585 mA/W at 1550 nm by employing a five-step electrical model, which is 3.42 times that of the traditional silver grating structure devices. Simply changing the grating period enables spectrally selective photodetection covering a wide range of 500 nm at the near-infrared band with net absorption higher than 0.95 and linewidths narrower than 0.7 meV.