Numerical demonstration of low-dark-current photodetector using phoxonic crystal waveguide for midwave infrared (MWIR) sensing

Abstract

While currently used silicon-germanium (SiGe) and germanium-on-insulator (Ge-OI) waveguide photodetectors offer CMOS-compatible alternatives, but their performance is often hindered by high dark currents and limited responsivity. These photodetectors have always been suffering from high-dark currents due to significant photon-phonon scattering losses. This study presents a numerical demonstration of novel waveguide photodetector which has been designed to suppress the photon-phonon interactions using phoxonic crystal-based Ge/SiGe waveguide to enhance MWIR detection performance. By suppressing unwanted lattice vibrations, the proposed PxC waveguide achieves ultra-low dark currents (0.06–0.15 nA) and high responsivity (0.28–0.4 A/W) at a low bias (-1V). Compared to conventional Ge-OI and SiGe rib waveguides, which exhibit dark currents ranging from 35 nA to 416μA, the proposed PxC photodetector demonstrates a 3–4 orders of magnitude reduction in dark current. The PxC-based structure also achieves a responsivity enhancement of up to 33 % over Ge/SiGe-on-insulator rib waveguides, while maintaining a broad operational wavelength range of 3–5 µm, making it highly suitable for low-noise MWIR sensing.