Study of droop phenomena in InGaN-based blue and green light-emitting diodes by temperature-dependent electroluminescence

InGaN-based blue and green light-emitting diodes are studied by temperature-dependent electroluminescence (EL) from 300 to 50 K to elucidate the effects of carrier overflow and the saturation in radiative recombination rate on the efficiency droop. Severe efficiency droop at cryogenic temperatures is attributed to the carrier overflow, which is confirmed by the EL spectra. The degree of overflow is thought to be related to the reduced effective active volume and the subsequent saturation in radiative recombination rate. Carrier transport and indium clustering in the active region are discussed in relation to the reduced effective active volume.