<p>In this work, we investigate the effect of rapid thermal oxidation on the structural, optical, and electrical properties of p-Si nanowires (SiNWs)/SiO₂/n-ZnO heterojunction photodiodes. ZnO thin films were deposited via sputtering onto both planar and nanostructured silicon substrates. XRD and FTIR analyses confirmed the formation of a single-phase hexagonal wurtzite structure, while thermal oxidation led to the appearance of SiO₂-related signatures and modified the crystallographic orientation of ZnO. SEM observations revealed uniform ZnO coating on vertically aligned SiNWs, with grain sizes between 250 and 360 nm. Optical measurements highlighted the excellent light-trapping capability of SiNWs, despite a slight increase in reflectivity due to the SiO₂ layer. Electrical characterization demonstrated that oxidation at 900°C significantly enhances diode performance by reducing both series and dynamic resistances, indicating improved interface passivation. However, oxidation at 1000°C led to a moderate degradation in electrical parameters, likely due to excessive oxide growth. These results underline the potential of controlled thermal oxidation for tuning the properties and improving the performance of SiNWs-based heterojunction photodiodes for optoelectronic applications.</p>