Sensitive and fast mid-wave infrared graphene/HgCdTe van der Waals heterojunction empowered by interface engineering

The development of new-generation infrared technology has raised the requirements for mid-wave infrared (MWIR) photodetectors capable of operating at room temperature. Conventional infrared photodetectors such as mercury cadmium telluride (MCT, HgCdTe), struggle to meet the demands of room-temperature infrared detection due to high dark current caused by thermal excitation in narrow bandgap and defects induced by lattice mismatch. Homojunctions formed by ion implantation are hard to prevent the diffusion of hot carriers. However, heterojunctions formed by van der Waals integration are promising platforms to overcome these limitations. In this work, we demonstrate a high-sensitivity MWIR photodetector operating at room temperature, based on a nitric acid (HNO ₃ )-doped graphene/HgCdTe van der Waals heterojunction. Chemical doping with HNO ₃ effectively tunes the carrier density and work function of graphene, increasing the built-in potential ( V _bi ) and heterojunction barrier height ( Φ _B ) at the interface. This interface engineering method suppresses dark current while improving the efficiency of photogenerated carrier separation and collection, thereby enabling high performance without external cooling. The device achieves a responsivity of 0.9 A/W and high detectivity of 5.44×10 ¹⁰ cm Hz ^1/2 W ^− 1 at room temperature. The results provide a feasible strategy for developing high-performance and low-cost room-temperature MWIR photodetectors.