Being capable of sensing broadband infrared (IR) light is vitally important for wide-ranging applications from fundamental science to industrial purposes. Two-dimensional (2D) topological semimetals are being extensively explored for broadband IR detection due to their gapless electronic structure and the linear energy dispersion relation. However, the low charge separation efficiency, high noise level, and on-chip integration difficulty of these semimetals significantly hinder their further technological applications. Here, we demonstrate a facile thermal-assisted tellurization route for the van der Waals (vdW) growth of wafer-scale phase-controlled 2D MoTe₂ layers. Importantly, the type-II Weyl semimetal 1T′-MoTe₂ features a unique orthorhombic lattice structure with a broken inversion symmetry, which ensures efficient carrier transportation and thus reduces the carrier recombination. This characteristic is a key merit for the well-designed 1T′-MoTe₂/Si vertical Schottky junction photodetector to achieve excellent performance with an ultrabroadband detection range of up to 10.6 µm and a large room temperature specific detectivity of over 10⁸ Jones in the mid-infrared (MIR) range. Moreover, the large-area synthesis of 2D MoTe₂ layers enables the demonstration of high-resolution uncooled MIR imaging capability by using an integrated device array. This work provides a new approach to assembling uncooled IR photodetectors based on 2D materials.

The high-performance broadband photodetectors have attracted intensive scientific interests due to their potential applications in optoelectronic devices. Despite great achievements have been achieved in two-dimensional (2D) materials based photodetectors such as graphene and black phosphorus, obvious disadvantages such as low optical absorbance and instability preclude their usage for the broadband photodetectors with the desired performance. An alternative approach is to find promising 2D materials and fabricate heterojunction structures for multifunctional hybrid photodetectors. In this work, 2D WS₂/Si heterojunction with a type-II band alignment is formed in-situ. This heterojunction device produced a high I_on/I_off ratio over 10⁶, responsivity of 224 mA/W, specific detectivity of 1.5×10¹² Jones, high polarization sensitivity and broadband response up to 3044 nm. Furthermore, a 4×4 device array of WS₂/Si heterojunction device is demonstrated with high stability and reproducibility. The results suggest that the WS₂/Si type-II heterojunction is an ideal photodetector in broadband detection and integrated optoelectronic system.