Investigation of wavelength-dependent efficiency droop in InGaN light-emitting diodes

The physical mechanisms leading to the effi- ciency droop of InGaN/GaN light-emitting diodes (LEDs) are theoretically investigated. We first discuss the effect of Auger recombination loss on efficiency droop by taking dif- ferent Auger coefficients into account. It is found that the Auger recombination process plays a significant nonradia- tive part for carriers at typical LED operation currents when the Auger coefficient is on the order of 10 −30 cm 6 s −1 . Fur- thermore, the InGaN/GaN multiple-quantum-well (MQW) LEDs with varied indium compositions in InGaN quan- tum wells are studied to analyze the wavelength-dependent efficiency droop. The simulation results show that the wavelength-dependent efficiency droop is caused by sev- eral different effects including non-uniform carrier distrib- ution, electron overflow, built-in electrostatic field induced by spontaneous and piezoelectric polarization, and Auger recombination loss. These internal physical mechanisms are the critical factors resulting in the wavelength-dependent ef- ficiency droop in InGaN/GaN MQW LEDs.