Silicon-based photodetectors are widely used due to their cost-effectiveness and CMOS compatibility, but their performance is hindered by high dark current, charge recombination, and limited UV sensitivity. To address these challenges, this study integrates silica nanoparticles (SiO₂ NPs) and poly (methyl methacrylate) (PMMA) as a hybrid passivation layer to enhance device performance. This study explores how silica morphology, PMMA integration, and spin-coating speed influence the structural, optical, and optoelectronic performance of the device. All electrical measurements were conducted at a saturation voltage of 3V~4V, ensuring stable photocurrent evaluation.
SEM and XRD analyses confirmed the successful integration of silica nanoparticles within the PMMA matrix, contributing to improved film uniformity. FTIR analysis confirmed the successful formation of silica nanoparticles with a well-defined siloxane (Si-O-Si) network and surface-bound hydroxyl (-OH) groups, ensuring strong chemical bonding and potential for further functionalization.
Optical characterization demonstrated that silica nanoparticles exhibit strong absorption at 342 nm, while PMMA, with its wide bandgap (4.26 eV), acts as a transparent insulating layer. Photoluminescence spectroscopy showed that PMMA reduces defect-related emissions, leading to improved charge carrier transport and lower recombination losses.
Optoelectronic measurements at 4V showed that PMMA significantly reduces dark current, improving device stability and photodetection sensitivity. The two-step silica deposition cycle/PMMA photodetector at 4000 rpm exhibited the best performance, achieving a responsivity of 0.0037 A/W, detectivity of 5.50 × 1010 Jones, and an external quantum efficiency (EQE) of 1.02% at 450 nm. Meanwhile, the 3000 rpm two-step deposition cycle device recorded the highest on/off ratio (766.76), indicating optimized light-switching behavior.
Overall, this study highlights the importance of material engineering and processing conditions in optimizing silicon-based photodetectors. The findings provide a promising pathway for developing high-performance, cost-effective photodetectors for optical sensing applications.

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