Nanostructure light emitting arrays, with the mitigated quantum confined stark effect, provide a different angle to investigate the efficiency decrease in the GaN based LEDs. In this paper, the external quantum efficiency and the electroluminescent spectra of GaN based nanorod LEDs are characterized through experiments and simulations. The strains in the InGaN/GaNnanorods are varied with the choice of nanorod sidewall passivation materials. Our results indicate that Auger recombination dominates at low-level currents. However, even though the effect of Auger accounts fora higher percentage weighting, the increase number of leakage carriers out of quantum wells is responsible for the efficiency drop at high current levels.