High coupling efficiency two-color quantum well infrared photodetectors based on dual micro-cavities

This paper proposes a kind of high coupling efficiency dual-color quantum well infrared photodetectors (QWIPs) based on dual micro-cavities. By stacking two metal-insulator-metal (MIM) micro-cavities with multiple quantum wells operating at 12.4μm and 15.3μm respectively, the photodetectors can achieve dual-color detection in the long and very long infrared wavelengths. The MIM micro-cavity can excite micro-cavity modes and surface plasmon (SP) modes. By controlling the inner and outer radii of the upper micro-cavity's metallic ring and the side length of the lower micro-cavity's square metallic plate, the operation wavelengths of the two micro-cavities can be independently regulated to match the inherent wavelengths of the dual-color quantum wells. Based on the combined effects of micro-cavity modes and SP modes, the coupling efficiency of the device at peak response wavelengths can hit 587% and 4558%, respectively. In addition, the total absorptions reach 0.76 and 0.9. Compared with the traditional coupling structure, the design of dual micro-cavities QWIPs has a more significant enhancement, which will provide a potential scheme to fabricate high-performance dual-color QWIPs.