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

The efficiency of Ga0.87In0.13N/GaN single and multiple quantum well (QW) light-emitting diodes is investigated under photoluminescence (PL) and electro-luminescence (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 x 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 X 10(27) cm(-3) s(-1) (j = 149 A/cm(2)). Considering Shockley Read Hall, radiative, and Auger rcombination and including carrier leakage shows that the EL efficiency droop is consistent with a reduction of injection efficiency.