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.