Investigation of efficiency droop for InGaN-based LEDs with carrier localization state and polarization effect

We prepared wavelength-dependent InGaN-based light emitting diodes (LEDs) with peak emissions ranging from 400 to 445 nm, and investigated their efficiency droop characteristics at injection currents of up to 1 A. We found that the emissions of the wavelength-dependent InGaN LEDs underwent blue shifts at elevated currents. In addition, although the external quantum efficiencies (EQEs) changed dramatically when the critical current was less than 350 mA, the efficiency droop of each device exhibited a similar negative slope upon increasing the current from 350 mA to 1 A. Whereas the effects of piezoelectric polarization and different localized states in the active layer of the near-UV-to-blue LEDs influenced the peak EQEs and the dramatic decays of the EQE droops at lower injection currents, they were not responsible for the EQE droops at higher current levels. In addition, the piezoelectric effect and Auger non-radiative recombination were not dominating influences determining the efficiency droops of the wavelength-dependent LEDs at higher carrier densities.