Ultrafast, broadband and polarization-sensitive photodetector enabled by MoTe₂/Ta₂NiSe₅/MoTe₂ van der Waals dual heterojunction

The emergence of cutting-edge technology has spurred an urgent demand for highly efficient photodetectors, due to their crucial applications in surveillance, thermal imaging, optical communication and environmental monitoring. Yet, the simultaneous optimization of photodetector parameters including miniaturization, high quantum efficiency, and heterogenous functionality remains a challenging task. In this study, we address these limitations by leveraging the anisotropic properties of Ta₂NiSe₅ materials for polarization-sensitive photodetection and selecting suitable two-dimensional (2D) materials to enhance the performance. We present a dual van der Waals heterojunction comprising top/bottom MoTe₂ and middle Ta₂NiSe₅ layers. Thanks to the augmented light collection efficiency and two opposing built-in electric fields at the dual heterojunction interfaces, our device demonstrates not only a broad spectral response ranging from 400 to 1550 nm, but also impressive performance parameters including an external quantum efficiency of 82.9%, and a rapid response speed of 3.5/4.2 µs, which has a substantial improvement over the single junction device. Leveraging the robust in-plane anisotropy of 2D Ta₂NiSe₅ nanosheets, the double heterojunction device displays competitive polarization sensitivity with polarization ratio values of 16.3 and 8.1 under 635 and 1550 nm, respectively. This work provides a promising platform for the development of high-performce and multifunctional photodetectors, thereby pioneering new directions for advanced optoelectronic device design and applications.