Effects of saturation of nonradiative recombination centers on internal quantum efficiency in InGaN light-emitting diodes

The internal quantum efficiency (IQE) of InGaN near-UV light-emitting diodes with different threading dislocation densities (TDDs) was studied by using excitation power density and temperature-dependent photoluminescence spectroscopy. The IQE was evaluated as functions of excitation density and temperature under band-to-band and selective excitation of the InGaN active layers. The IQE curves under weak excitation densities were analyzed with a rate equation model of radiative and nonradiative recombination of excitons, in which the exciton localization and the filling of nonradiative recombination centers (NRCs) were considered. Based on the analysis, we discussed the effects of filling NRCs on the IQE as functions of TDD and temperature and we clarified that the increase in the IQE at lower excitation densities was caused by filling NRCs. The analysis also indicated whether the maximum IQE value reached 100% at low temperatures. (C) 2018 The Japan Society of Applied Physics