WO₃-NP-activated WS₂ layered heterostructures for efficient broadband (254 nm-940 nm) photodetection

Broadband photodetection including deep UV using Si is technically challenging due to its negligible optical absorption at 254 nm and the requirement of heterogeneous integration with very high bandgap photoactive materials. However, monolithic integration of high-bandgap semiconductors on Si is not possible due to CMOS fabrication incompatibility. Comprehensive experimental studies to achieve broadband photodetection including deep UV on Si are lacking in the literature. Here for the first time we have investigated 2D/0D heterojunctions of WS₂/WO₃ on a Si platform both experimentally and theoretically and established the charge transfer mechanism between them. Transient photocarrier decay experiments demonstrate effective quenching of excited photocarriers generated in WO₃/WS₂, signifying its utility in facilitating carrier transport, which is further evidenced by charge density calculation from DFT simulation. Our designed vertically aligned p-Si/WS₂/WO₃ heterojunction-based photodetector exhibits an excellent photosensitivity performance with a broad spectral response ranging from deep ultraviolet (254 nm) to near infrared (940 nm) wavelengths, and it not only provides a peak responsivity of 251 A W^-1 and a specific detectivity of 1.89 × 0¹⁴ Jones, but also possesses a rapid response speed with a rise/fall time of 0.64/0.48 s at 365 nm with a bias of 2 volt.