Spatially resolved study of quantum efficiency droop in InGaN light-emitting diodes

We investigate the spatial variation of the external quantum efficiency (EQE) of InGaN light-emitting diodes. Two different types of EQE droop are examined in one single device, offering unambiguous analyses on the underlying material physics without the complications of the processing variation. The interplays of microscopic defects, extended defects, and energy fluctuation dictate the mechanisms of the droop, which represents a common theme in various optoelectronic devices. The two droop types correspond to the two extreme situations of energy fluctuation that affects the carrier diffusion and recombination. The finding suggests ways for improving the device performance, depending on operation conditions.