An Ultrasensitive and Broad-Spectrum MoS₂ Photodetector with Extrinsic Response Using Surrounding Homojunction

As unique building blocks for advancing optoelectronics, 2D semiconducting transition metal dichalcogenides have garnered significant attention. However, most previously reported MoS₂ photodetectors respond only to visible light with limited absorption, resulting in a narrow spectral response and low sensitivity. Here, a surrounding homojunction MoS₂ photodetector featuring localized p-type nitrogen plasma doping on the surface of n-type MoS₂ while preserving a high-mobility underlying channel for rapid carrier transport is engineered. The establishment of p-n homojunction facilitates the efficient separation of photogenerated carriers, thereby boosting the device's intrinsic detection performance. The resulting photoresponsivity is 6.94 × 10⁴ A W^-1 and specific detectivity is 1.21 × 10¹⁴ Jones @ 638 nm, with an optimal light on/off ratio of ≈10⁷ at V_GS = -27 V. Notably, the introduction of additional bands within MoS₂ bandgap through nitrogen doping leads to an extrinsic broadband response to short-wave infrared. The device exhibits a photoresponsivity of 34 A W^-1 and a specific detectivity of up to 5.92 × 10¹⁰ Jones @ 1550 nm. Furthermore, the high-performance broadband response is further demonstrated through imaging and integration with waveguides, paving the way for next generation of multifunctional imaging systems and high-performance photonic chips.