Anisotropic Unipolar Barrier Heterostructures with Semimetal Contacts for Polarization Detection and Computational Imaging.

Unipolar barrier architectures enable sensitive detection for computational imaging by blocking majority carriers while allowing efficient minority-carrier transport. However, their performance is often constrained by contact-interface transport limitations that suppress responsivity. Here, we demonstrate an anisotropic unipolar barrier detector based on a BP/MoS2/WTe2 van der Waals heterostructure. By incorporating semimetal WTe2 as the contact layer with a BP/MoS2 quasi-unipolar heterostructure, we engineer a robust architecture that synergizes low-resistance carrier extraction with the intrinsic anisotropy of the heterostructure. Crucially, by suppressing the isotropic dark current to prevent signal dilution, this design optimizes the signal-to-noise ratio for polarization-sensitive detection. At zero bias, the detector delivers a responsivity of about 128 mA/W, a specific detectivity of 3.4 × 1010 cm Hz1/2/W, and rise/fall times of 137/170 μs under 638 nm illumination, while achieving a polarization ratio of about 7.8 at 1550 nm. Furthermore, by integrating the device with a digital micromirror device for single-pixel computational imaging, we successfully reconstruct a high-contrast 8 × 8 "H" pattern, outperforming conventional large-area photoresistors. Beyond intensity imaging, the device also enables clear polarization imaging of <0.5 mm. Our findings underscore the significance of semimetal contact engineering in realizing high-sensitivity detection, paving the way for advanced unipolar barrier detectors in computational vision.