Band Bending-Driven Photo Gain in CVD-Grown Au–ZnO NWs via Schottky Barrier Tuning

Nanowire (NW)-based photodetectors (PDs) exhibit fast response speeds and high gain because of their high aspect ratio, superior signal-to-noise ratio, and greater sensitivity. The excitonic energy of zinc oxide is 60 meV, and the band gap of 3.37 eV makes it a potential capacity contender for optoelectronic devices. In this work, we grew vertically aligned Au-catalyzed ZnO NWs on a SiO2/Si substrate by thermal CVD and fabricated a high-performance ultraviolet (UV) PD. The structural and optical characterization confirms the growth of highly crystalline NWs with pronounced narrow NBE emission and defect-tailored through intense DLE bands associated with oxygen vacancies (Vo). The device exhibits nonlinear I–V characteristics with a substantial increase in photocurrent attributed to surface band bending and depletion modulation at the Au–ZnO interface. Under 365 nm illumination (0.01 mW cm–2), the device shows a responsivity of 360.9 A/W, a detectivity of 15.24 × 1012 Jones, and an EQE of 1.22 × 105. Theoretical simulations support the experimental results, elucidate the interplay of defect chemistry and interface energetics in ZnO NW-based UV PDs, and provide a robust strategy for optimizing responsivity, speed, and operational stability in next-generation optoelectronic devices.