Pushing Photodetection Beyond the Limit of Silicon PIN Junctions Through In Situ Integration of Randomly Interlinked Gold Nanoparticles and Black Silicon.

High-responsivity and broad-spectrum photodetectors are indispensable for advanced photoelectric applications. While silicon PIN junctions offer several advantages, such as mature manufacturing processes, stable performance, and cost-effectiveness, their near-infrared detection capabilities are fundamentally constrained by the intrinsic properties of silicon. In this study, we propose a device structure that advances photodetection beyond the limitation of silicon PIN junctions by in situ integrating randomly interlinked gold nanoparticles and black silicon (RIL-AuNPs/B-Si). The localized surface plasmon resonance effect (LSPR) of the gold nanoparticles induces strongly coupled and enhanced electric fields on the black silicon surface, significantly improving light absorption and boosting device responsivity. Furthermore, when exposed to photons with energies below the silicon bandgap, hot electrons generated within the gold nanoparticles are efficiently transferred into the black silicon, extending the spectral response range. Experimental results reveal that the RIL-AuNPs/B-Si PD achieves a responsivity of 0.62 A/W at 1064 nm, while also maintaining responsivities of 42.8 mA/W at 1310 nm and 23.8 mA/W at 1550 nm, where conventional planar silicon PDs exhibit no photoelectric response. This work not only establishes RIL-AuNPs/B-Si PDs as high-performance broadband photodetectors but also provides a promising strategy for designing next-generation optoelectronic devices.