Construction of mixed-dimensional WS2/Si heterojunctions for high-performance infrared photodetection and imaging applications

Recently, high-quality large-area two-dimensional (2D) layered materials are highly desired for integrated optoelectronic devices and systems due to their unique optoelectrical properties. In this work, large size 2D WS2 films are synthesized by a simple and general sulfuration process. By virtue of excellent flexibility, a high-performance mixed-dimensional WS2/Si heterojunction with a type-II band alignment is readily fabricated for infrared detection. The as-assembled device exhibits a broad response of up to 3 mu m due to the interlayer transition in the type-II heterostructure. Further optoelectronic analysis reveals a large responsivity, a high specific detectivity, and a fast response speed of the detector which are acquired upon 980 nm light illumination at zero bias. Significantly, our detector can serve as a single-pixel sensing system, displaying excellent imaging capability with a high resolution and contrast ratio. In view of these remarkable advantages, the as-fabricated WS2/Si heterojunction device has displayed great potential for applications in broadband photodetection and infrared imaging.