Droop in III-nitrides: Comparison of bulk and injection contributions

We study mechanisms which are thought to contribute to efficiency droop in III-nitrides. We first observe droop in a photoluminescence (PL) experiment on bulk GaN, which confirms the existence of a bulk contribution to droop, unrelated to piezoelectric fields or alloy fluctuations. We then perform biased-PL on a series of InGaN light-emitting diodes to estimate the potential impact of carrier leakage on PL experiments. We conclude that carrier leakage is only significant at very low pump densities and does not contribute to droop, thus validating the use of PL to characterize droop. (C) 2010 American Institute of Physics. [doi:10.1063/1.3515851]