Uncooled Mid-Infrared Sensing Enabled by Chip-Integrated Low-Temperature-Grown 2D PdTe2 Dirac Semimetal.

Next-generation mid-infrared (MIR) imaging chips demand free-cooling capability and high-level integration. The rising two-dimensional (2D) semimetals with excellent infrared (IR) photoresponses are compliant with these requirements. However, challenges remain in scalable growth and substrate-dependence for on-chip integration. Here, we demonstrate the inch-level 2D palladium ditelluride (PdTe2) Dirac semimetal using a low-temperature self-stitched epitaxy (SSE) approach. The low formation energy between two precursors facilitates low-temperature multiple-point nucleation (∼300 °C), growing up, and merging, resulting in self-stitching of PdTe2 domains into a continuous film, which is highly compatible with back-end-of-line (BEOL) technology. The uncooled on-chip PdTe2/Si Schottky junction-based photodetector exhibits an ultrabroadband photoresponse of up to 10.6 µm with a large specific detectivity. Furthermore, the highly integrated device array demonstrates high-resolution room-temperature imaging capability, and the device can serve as an optical data receiver for IR optical communication. This study paves the way toward low-temperature growth of 2D semimetals for uncooled MIR sensing.