In Situ Fabrication of 2D WS2/Si Type-II Heterojunction for Self-Powered Broadband Photodetector with Response up to Mid-Infrared

The high-performance broadband photodetectors have attracted intensive scientific interests due to their potential applications in optoelectronic systems. Despite great achievements 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 photo detectors. 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 10,(6) responsivity of 224 mA/W, specific detectivity of 1.5 x 10(12) Jones, high polarization sensitivity, and broadband response up to 3043 nm. Furthermore, a 4 x 4 device array of WS2/Si heterojunction device is demonstrated with high stability and reproducibility. These results suggest that the WS2/Si type-II heterojunction is an ideal photodetector in broadband detection and integrated optoelectronic system.