Interface-controlled broadband photodetection in Si₃N₄/n-Si hybrid devices

In this study, Si₃N₄/n-Si hybrid photodiodes with distinct interfacial layer configurations (Si₃N₄-1, Si₃N₄-2, and Si₃N₄-3) were constructed and comprehensively examined to evaluate the influence of interface engineering on their optical performance. Measurements of current-voltage (I-V) under dark and illuminated settings show that the ideality factor (n) declines with increasing illumination intensity. However, the barrier height (Φ_B) shows structure-dependent variation, indicating enhanced carrier transport and interface modulation. To assess device performance under varying light intensities, responsivity (R), photosensitivity (K), noise specific detectivity (D*) and equivalent power (NEP) were determined. The Si₃N₄-3/n-Si structure had the highest photosensitivity, while the Si₃N₄-2/n-Si device showed superior overall performance with enhanced responsivity, higher detectivity, and lower NEP, indicating an optimal balance between photocarrier generation and transport. Spectral investigation confirmed a broadband response with higher external quantum efficiency (EQE) in the UV-Vis-NIR region. The linear relationship between log(I_ph) and log(P) features indicates a dominating photoconduction mechanism impacted by trap states within the mobility gap. The results show that precisely controlling the Si₃N₄ interfacial layer improves photodiode performance by minimizing recombination losses and improving carrier dynamics. These findings show that Si₃N₄-based interface engineering is a promising method for producing high-performance, broadband silicon photodetectors for advanced optoelectronic applications.