2D WSe2/MoS2 p-i-n Vertical Heterojunction Photodetectors by Selective Plasma Doping

Abstract

Compared to traditional pn junctions, photodetectors based on 2D materials with a p-i-n structure offer enhanced photoresponsivity by broadening the depletion region and improving response speed by reducing junction capacitance. However, due to the lack of a mature, controllable doping process, p-i-n heterostructure photodetectors based on 2D materials are rarely reported. A 2D WSe₂/MoS₂ p-i-n vertical heterojunction photodetector created through plasma selective doping is presented. This device not only retains the wide junction region of the vertical heterojunction, but in coordination with the intrinsic layer (i layer), the width of the depletion region is broadened, increasing the photoactive area, Additionally, a strong built-in electric field is formed internally, greatly accelerating the rapid separation and transport of photogenerated carriers. The p-i-n vertical heterojunction photodetector exhibits a high responsivity and an ultra-fast response time (τ_r = 7.3 µs, τ_f = 5.49 µs), achieving nearly a 100 fold improvement over the pristine WSe₂/MoS₂ heterojunction. Under self-driven conditions, the device achieves a maximum responsivity of 0.32 A W⁻¹ and a detectivity of 3.41 × 10⁹ Jones at 637 nm. Additionally, stable detection in the near-infrared (NIR) is realized due to the interband transitions. These findings are expected to advance the development and application of photoelectric detection technologies.