Abstract: The type-II semimetal 1T′-MoTe₂ is considered a promising candidate for advanced optoelectronic devices due to its unique electronic band structure and distorted lattice configuration. However, its polarization-dependent optical properties have not yet been fully elucidated, and the high dark current due to its semimetal nature inhibits device performance enhancement. This work reports a band-engineered 1T′-MoTe₂/MoSe₂ van der Waals heterojunction capable of self-powered, broadband, and polarization-sensitive photodetection. Leveraging the asymmetric Schottky contact at the 1T′-MoTe₂/MoSe₂ interface, the device achieves efficient separation of photogenerated carriers, delivering a pronounced photoresponse spanning ultraviolet to near-infrared wavelengths. Under zero bias, it exhibits excellent optoelectronic performance, yielding a responsivity of up to 72.9 mA W^-1 and a specific detectivity of up to 3.69 × 10⁸ Jones. Concurrently, the in-plane optical anisotropy of the 1T′-MoTe₂ endows the detector with significant polarization sensitivity, achieving a polarization extinction ratio of up to 2.0 under 785 nm. This multifunctionality enables the device to show great potential for applications in polarization-resolved infrared imaging and coded optical communications. Beyond a high-performance photodetector, this work pioneers a strategy for next-generation optoelectronic design by synergizing band engineering with crystal anisotropy in 2D materials.

Key words: Semimetal, 1T′-MoTe₂/MoSe₂, Polarization-sensitive, Spectroscopic ellipsometry, Photodetector