Experimental separation of injection and radiative efficiencies in InGaN/GaN light emitting diodes

The carrier injection efficiency (CIE) and the radiative efficiency (RE) are experimentally determined in order to clarify the origin of the efficiency droop in blue-emitting GaN light emitting diodes. The difference in the shape of RE curves and the external quantum efficiency (EQE) curves shows the CIE is a function of the injection current, while the RE curves show the droop behavior to a certain degree. The experimentally determined CIE is significantly lower than unity and decreases with the current density, indicating that imperfect carrier injection has strong effects on the efficiency droop. Through our analysis, we conclude that both an intrinsic component, such as Auger recombination, and current leakage component exist and make notable contributions to the total EQE droop. These two components can be quantitatively separated through our proposed method. In addition, the result above is also comparatively investigated with the result of time-resolved electroluminescence (TREL) spectroscopies. The obtained CIE and RE consistently explain the behavior of TREL at various current density levels.