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 (I_ph), 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 (R_sh) 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.