High-Performance HfS₂-HfO_X-WSe₂ P-i-N Photodetector Based on Self-Oxidized HfS₂

2D transition metal dichalcogenides (TMDs) have attracted considerable interest for next-generation optoelectronics owing to their layer-tunable bandgap and strong light-matter interaction. Indeed, 2D TMDs-based photodetectors are facing an intrinsic trade-off between responsivity and response speed, as well as the unexpectedly large dark current. Particularly, customizing P-i-N structures through incorporating an insulating interlayer between p-type and n-type semiconductors simultaneously suppresses dark current and enables faster response. Nevertheless, preparing insulating layer typically requires complex epitaxial growth techniques that exhibit poor compatibility with 2D TMDs materials. Although the P-i-N structure also can be achieved more readily by dry- or wet-transfer, yet leaving contaminants and defects at the interface. Here, we report an innovative strategy for realizing high-performance HfS₂-HfO_X-WSe₂ P-i-N photodetectors through controlled self-limiting surface oxidation to form an insulating interlayer HfO_X. The introduction of HfO_X effectively reduces dark current through the high potential barrier, while transfers the carrier transport mechanism to tunneling. Consequently, the HfS₂-HfO_X-WSe₂ photodetector exhibits markedly enhanced performance, with the light switching ratio increasing from 22 to 10⁵ and the responsivity rising from 0.034 A/W to 0.245A/W. Our study offers a novel and exceptionally simple route to 2D P-i-N photodetectors that is compatible with 2D semiconductor technology.