Mixed-dimensional WS2/WSe2/Si unipolar barrier heterostructure for high-performance photodetection

The use of unipolar barrier structures that can selectively block dark current but allow photocurrent to flow unimpededly has emerged as an effective strategy for constructing high-performance photodetectors. In particular, two-dimensional (2D) materials with tunable band structures and self-passivated surfaces not only satisfy band-matching requirements but also avoid interface defects and lattice mismatches, which are attractive for designing unipolar barriers. Here, we demonstrate a mixed-dimensional WS2/WSe2/p-Si unipolar barrier photodetector, in which 2D WS2 acts as the photon absorber, atomically thin WSe2 as the unipolar barrier, and 3D p-Si as the photogenerated carrier collector. The intercalated WSe2 not only mitigates detrimental substrate effects but also forms a high-conduction band barrier to filter out several dark current components with the photocurrent flowing unimpededly. Driven by tunneling and carrier multiplication effects, the WS2/WSe2/p-Si device exhibits a high light on/off ratio above 105, a high detectivity of 2.39 × 1012 Jones, and a fast rise/decay time of 8.47/7.98 ms. These figures of merit are significantly improved over the conventional WS2/p-Si device, opening up an effective scheme for designing high-performance optoelectronic devices.