Self-Powered Broad-Spectrum UV–vis–NIR Photodetector Based on p-Si/Zn–Sn–Al–O Heterojunction

Broad-spectrum photodetectors capable of UV–vis-NIR detection are highly desirable for advanced optical sensing and imaging applications; however, conventional silicon-based photodetectors exhibit inadequate UV responsivity due to limited absorption and surface interference, whereas alternative broadband strategies commonly suffer from complex fabrication, instability, and integration challenges. This study addresses these issues by developing a self-powered broadband heterojunction photodetector, leveraging plasma-enhanced atomic layer deposition to deposit indium-free n-type Zn–Sn–Al–O (ZTAO) films onto p-Si substrates. The p-Si/ZTAO photodetector achieves panchromatic detection across 365–905 nm, harnessing the UV responsivity of ZTAO and the compatibility of p-Si with established fabrication processes. Characterization reveals rectifying I–V behavior and stable photoswitching, with peak performance at 905 nm (0 V, 5 mW cm–2) yielding a responsivity of 6.09 mA W1– and detectivity of 2.31 × 1010 Jones. Transient photocurrent analyses demonstrate millisecond-scale responses, with a near-linear photocurrent-intensity relationship (α = 0.98) at 365 nm. By carefully applying minimal forward biases, reversible binary photoresponse functionality is also demonstrated, enabling controllable switching between photocurrent and dark current directions. Long-term stability testing demonstrates robust device performance under continuous illumination. Energy band analysis through ultraviolet photoelectron spectroscopy confirms a favorable type-II alignment at the p-Si/ZTAO interface, enhancing carrier separation efficiency and suppressing dark current. Collectively, this research not only offers a viable strategy to realize stable, self-powered, broad-spectrum photodetection but also provides a significant pathway toward the integration of indium-free amorphous oxide semiconductors with established silicon-based technologies, facilitating scalable development of next-generation broadband optoelectronic devices.