Ultra-sensitive UV photodetectors enabled by built-in electric fields in hierarchical NP-type porous silicon

High-performance ultraviolet (UV) photodetectors (PDs) with rapid response and high responsivity are crucial for environmental monitoring and optoelectronic applications. However, traditional N-type porous silicon (N-PSi) PDs often suffer from limited carrier separation efficiency and significant recombination losses. Here, we report an ultra-sensitive UV-PD based on a novel NP-type (NP-PSi) thin film architecture, demonstrated for the first time. By implementing a hydrogen peroxide (H₂O₂)-assisted electrochemical anodization technique, a hierarchical and uniform PSi nanostructure was successfully engineered on an N-type crystalline silicon P-Si layered template. The integrated NP-junction provides a robust built-in electric field that effectively facilitates the spatial separation of photogenerated electron-hole pairs while suppressing recombination. Under optimized conditions, the NP-PSi-based PD exhibits a sensitivity of 67 808.33%, which is approximately 28-fold higher than that of conventional N-PSi counterparts. Furthermore, the device achieves a superior responsivity of 38.60 A/W and an ultra-fast response time (rise/fall times of 0.03 s). These results underscore the synergistic effect of built-in field assistance and refined nanostructured engineering, offering a promising strategy for developing next-generation, high-gain silicon-based UV sensing technologies.