Onset of the Efficiency Droop in GaInN Quantum Well Light-Emitting Diodes under Photoluminescence and Electroluminescence Excitation

The efficiency of Ga 0.87 In 0.13 N/GaN single and multiple quantum well (QW) light-emitting diodes is investigated under photoluminescence (PL) and electroluminescence (EL) excitation. By measuring the laser spot area (knife-edge method) and the absorbance of the GaInN QW (transmittance/reflectance measurements), the PL excitation density can be converted to an equivalent EL excitation density. The EL efficiency droop-onset occurs at an excitation density of 2.08 × 10 26 cm –3 s –1 ( J = 10 A/cm 2 ), whereas no PL efficiency droop is found for excitation densities as high as 3.11 × 10 27 cm –3 s –1 ( J = 149 A/cm 2 ). Considering Shockley–Read–Hall, radiative, and Auger recombination and including carrier leakage shows that the EL efficiency droop is consistent with a reduction of injection efficiency.