All-Silicon Broadband Infrared Photodetectors With In-Plane Photon Trapping Structures

Silicon (Si) photonics has been widely explored for many various applications, including optical communication, optoelectronic computing, spectroscopy, and image sensing. As a key component for optoelectronic signal conversion in these applications, Si-based infrared photodetectors have attracted extensive attention. However, achieving all-Si on-chip photodetection in the very long-wavelength infrared (VLWIR) range remains challenging, with broadband enhancement and improved operating temperature being pressing issues that need to be addressed. An all-Si photodetector design is presented using in-plane photon trapping structures (IPTS) to enhance detection efficiency and improve the operating temperature of the photodetector at the VLWIR range. The photodetector achieves a broadband enhancement of 285-575% (across 12-19 µm) and a 31% reduction in dark current. Additionally, it exhibits an impressive peak specific detectivity of 1.9 × 10¹⁰ cm Hz^1/2 W^-1 at 15 µm, operating at a temperature of 40 K. This study introduces a novel all-Si optoelectronic device architecture that offers a promising solution for improving the operating temperature and sensitivity of broadband VLWIR devices, making the whole system more compact and cost-effective.