Uncooled infrared photodetectors have evoked widespread interest in basic research and military manufacturing because of their low‐cost, compact detection systems. However, existing uncooled infrared photodetectors utilize the photothermoelectric effect of infrared radiation operating at 8–12 µm, with a slow response time in the millisecond range. Hence, the exploration of new uncooled mid‐wavelength infrared (MWIR) heterostructures is conducive to the development of ultrafast and high‐performance nano‐optoelectronics. This study explores a van der Waals heterojunction on epitaxial HgCdTe (vdWs‐on‐MCT) as an uncooled MWIR photodetector, which achieves fast response as well as high detectivity for spectral blackbody detection. Specifically, the vdWs‐on‐MCT photodetector has a fast response time of 13 ns (77 MHz), which is approximately an order of magnitude faster than commercial uncooled MCT photovoltaic photodetectors. Importantly, the device exhibits a photoresponsivity of 2.5 A W‐1, quantum efficiency as high as 85%, peak detectivity of 2 × 1010 cm Hz1/2 W‐1 under blackbody radiation at room temperature, and peak detectivity of up to 1011 cm Hz1/2 W‐1 at 77 K. Thereby, this work facilitates the effective design of high‐speed and high‐performance heterojunction uncooled MWIR photodetectors.

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The preparation of surface passivation layers on InSb is essential in the process of device fabrication. An Al2O3 passivation film was deposited on the surface of medium wave InSb film by atomic layer deposition (ALD). A series of variable area photodiode devices with different P/A ratios were fabricated. The performance of the device is characterized at 77K. The effects of ALD Al2O3 and anodic oxidation on the leakage current of diode devices were investigated. The surface leakage current of the passivated photodetectors was reduced by an order of magnitude over the anode sulfidation passivated photodetectors. Moreover, the metal-insulator-semiconductor (MIS) device were developed respectively, and the effects of different films as a dielectric layer on the interfacial characteristics were investigated.