An improved carrier rate model to evaluate internal quantum efficiency and analyze efficiency droop origin of InGaN based light-emitting diodes

A carrier rate model taking carrier delocalization into account is presented to analyze current dependent internal quantum efficiency of InGaN based light-emitting diodes (LEDs). By fitting normalized experimental internal quantum efficiency-current curves, both injection efficiency and radiative recombination efficiency depending on current can be obtained. Based on the fitting results from two LED samples with and without the InGaN interlayer beneath the active regions of 5 InGaN quantum wells (QWs), carrier delocalization and carrier leakage are believed to lead to the efficiency droop effect under considerable and even larger injection, respectively. By investigating two LED samples with 8 and 10 QWs, it is found that the 8-QWs LED has the highest radiative recombination efficiency over 80% and the 10-QWs one has the highest injection efficiency over 50% under 120 A/cm2. This means that increasing QW number is an effective method to suppress droop effect.