Gold-nanoparticles-enhanced photoconductive gains and optical generation of GaN epilayer.

We demonstrate gallium nitride (GaN) photodetectors with high photoconductive gains enhanced by gold nanoparticles (AuNPs) self-assembled on a thin n+-GaN epilayer. Under 370-nm ultraviolet (UV) illumination, the AuNP-decorated device exhibits a 2.4× enhancement in photocurrent (Iph), responsivity (R), and external quantum efficiency (EQE) compared with the pristine device. At 0.45 mW/cm2, the R reaches 3.7 × 105 A/W, and the EQE reaches 1.2 × 108%. Transfer length method (TLM) analysis further shows that AuNP decoration reduces the sheet resistance (Rsh) and increases the photogenerated carrier concentration and optical generation rate. The enhancement is attributed to two cooperative effects: hot-electron injection from AuNPs into the n+-GaN epilayer and AuNP-induced interfacial band bending, which confines photogenerated holes and prolongs the lifetime. This approach provides an effective route toward highly sensitive GaN UV photodetectors.