Black GeSn on Silicon for Enhanced Short-Wave Infrared Detection and Imaging

Abstract: Sensitive and cost-effective Group-IV short-wave infrared (SWIR) photodetectors (PDs), compatible with complementary metal-oxide semiconductor (CMOS) processes, are crucial for various emerging applications. Here, we developed a black GeSn thin-film PD on silicon, optimised for efficient SWIR photodetection and imaging. Incorporating Sn into the Ge layer effectively extended the photodetection range to 1960 nm. The blackening of the GeSn surface resulted in a substantial reduction of reflection loss across a broad spectral range of 1200-2200 nm. Furthermore, the responsivity experienced a remarkable increase of 1.45 times through reduced reflection loss and carrier multiplication by the carrier ionization. The black GeSn surface significantly boosts the detectivity, enhances the wide-angle SWIR photodetection, and improves the quality of the resultant images. This demonstration heralds a new era for CMOS-compatible, cost-effective, high-performance black GeSn PDs and imagers for a wide range of applications in the underexplored SWIR region.