Toward Broadband Photodetection: Band Alignment and Interlayer Charge Transfer in 2D Transition Metal...

Recently, various transition metal dichalcogenides (TMDs)/Ga₂O₃ heterostructures have emerged as excellent candidates for the development of broadband photodetection, exhibiting various merits such as broadband optical absorption, efficient interlayer carrier transfer, a relatively simple fabrication process, and potential for flexibility. In this work, vertically stacked MoSe₂/Ga₂O₃, WS₂/Ga₂O₃, and WSe₂/Ga₂O₃ heterostructures were experimentally synthesized, all exhibiting broadband light absorption, spanning at least from 200 to 800 nm. The absorption coefficients of these TMDs/Ga₂O₃ heterostructures are significantly improved compared to those of individual Ga₂O₃ films. The superior performance can be attributed to the type-I band alignment and efficient interlayer carrier transfer, which result from various band offsets along with the different doping conditions of the TMD layers, leading to distinct photoluminescence (PL) emission properties. Through a detailed analysis of the excitation-power-dependent PL spectra, we offer an in-depth discussion of the interlayer carrier transfer mechanism in the TMDs/Ga₂O₃ heterostructures. Regarding interlayer coupling effects, the shift of the E_F of TMD layers plays a crucial role in modulating their trion emission properties. These findings suggest that these three TMDs/Ga₂O₃ heterostructures have great potential in broadband photodetection, and our in-depth physical mechanism analysis lays a solid foundation for a new device design.