Type-I Band Engineering of van der Waals InSe/TiS₃ Heterostructures for Broadband and Polarization-Sensitive Photodetection with a Large Dichroic Ratio

van der Waals (vdW) heterostructures formed from two-dimensional (2D) layered materials have opened promising avenues in broadband photodetection, particularly in polarization-sensitive applications. Previous research indicates that type-I heterostructures hold considerable potential for broadband polarization photodetector development; however, achieving high polarization sensitivity in these vdW heterostructures has remained insufficiently explored. In this work, we systematically present combined theoretical and experimental studies on designing and fabricating a high-performance photodetector based on the InSe/TiS₃ vdW heterostructure exhibiting type-I band alignment. Theoretical studies supported by experimental verification confirmed the presence of a type-I band alignment between InSe and TiS₃. Leveraging this favorable band alignment, the fabricated device demonstrated broadband photodetection spanning the deep ultraviolet to near-infrared spectral range along with pronounced polarization sensitivity. The photodetector exhibited superior performance metrics, including a high responsivity of 55 A/W^-1, detectivity of 1.80 × 10¹³ Jones, an external quantum efficiency reaching 15,633%, and a rapid response time of approximately 23.6 μs. Additionally, significant polarization sensitivity was observed, characterized by a notable dichroic ratio of approximately 5, emphasizing the device's potential for advanced optoelectronic applications. This study provides valuable insights and a practical reference for the development of high-performance polarized photodetectors across a broad spectral range.