We have demonstrated significant improvement on the performance of a self-powered (zero power consumption) GaN ultraviolet photodetector (GaN-UVPD) under a 254-nm UV light exposure through the application of nickel nanoparticles (NiNPs). Indeed, the detectivity of the device increased from 2.81 x 10(13) to 7.19 x 10(13) cm Hz(1/2) W-1 at 0 V, which is the highest reported detectivity of the self-powered UV photodetectors, with the application of 5-mu l Ni nanoparticle solution to the device surface under UV exposure. Furthermore, the GaN-UVPD revealed very high sensitivity values at zero bias as 5.04 x 10(6) and 6.67 x 10(6) before and after the application of the Ni nanoparticle solution, respectively. The preeminent improvement in detectivity and sensitivity from the Ni nanoparticles is likely due to localized surface plasmons leading to a strong light absorption around the Ni nanoparticles resulting an increase in number of photocarriers. Thus, this work will contribute towards developing high-performance self-powered UV photodetectors that can potentially replace traditional high-energy-consuming UV detection and secure ultraviolet communication devices.