Effect of dislocation density on efficiency droop in GaInN∕GaN light-emitting diodes

Abstract

Measurements of light-output power versus current are performed for $\mathrm{Ga}\mathrm{In}\mathrm{N}∕\mathrm{Ga}\mathrm{N}$ light-emitting diodes grown on GaN-on-sapphire templates with different threading dislocation densities. Low-defect-density devices exhibit a pronounced efficiency peak followed by droop as current increases, whereas high-defect-density devices show low peak efficiencies and little droop. The experimental data are analyzed with a rate equation model to explain this effect. Analysis reveals that dislocations do not strongly impact high-current performance; instead they contribute to increased nonradiative recombination at lower currents and a suppression of peak efficiency. The characteristics of the dominant recombination mechanism at high currents are consistent with processes involving carrier leakage.