An Ultrasensitive and Broad-Spectrum MoS 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 MoS photodetectors respond only to visible light with limited absorption, resulting in a narrow spectral response and low sensitivity. Here, a surrounding homojunction MoS photodetector featuring localized p-type nitrogen plasma doping on the surface of n-type MoS 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 × 10 A W and specific detectivity is 1.21 × 10 Jones @ 638 nm, with an optimal light on/off ratio of ≈10 at V = -27 V. Notably, the introduction of additional bands within MoS bandgap through nitrogen doping leads to an extrinsic broadband response to short-wave infrared. The device exhibits a photoresponsivity of 34 A W and a specific detectivity of up to 5.92 × 10 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.