Ten-Fold Enhancement of Bulk Gallium Nitride Deep Ultraviolet Photodetectors via Silver Nanoparticles

Abstract Silver nanoparticles (AgNPs) were synthesized using pulsed laser ablation in liquid (PLAL) and integrated onto bulk gallium nitride (GaN) to enhance deep-ultraviolet (DUV) photodetector (PD) performance. Structural and optical characterizations confirmed the formation of crystalline AgNPs with an average size of 8 nm. These nanoparticles exhibited a surface plasmon resonance (SPR) peak at 405 nm, which red-shifted to 415 nm upon deposition onto bulk GaN, a change attributed to nanoparticle-substrate coupling. Field-emission scanning electron microscopy and atomic force microscopy analyses revealed uniformly distributed AgNPs and increased surface roughness from 0.146 nm to 39.5 nm, thereby facilitating stronger light–matter interaction. The AgNPs/bulk GaN metal–semiconductor–metal (MSM) DUV PD exhibited a tenfold enhancement in photocurrent. At 6 V bias under 280 nm illumination, its responsivity increased from 81.9 to 829 mA/W and its external quantum efficiency rose from 36.6% to 370%, significantly outperforming the bare bulk GaN device. These results confirm that plasmonic coupling between AgNPs and bulk GaN effectively amplifies photoresponse, establishing a promising strategy for high-performance DUV PDs.