Efficiency droop behavior of direct current aged GaN-based blue light-emitting diodes

By direct current (dc) stressing, GaN-based blue light-emitting diodes (LEDs) with different density of nonradiative recombination centers in the active region of InGaN/GaN multiple quantum wells were obtained and studied for injection-current-induced efficiency droop. It is found that with increasing stressing time, the overall quantum efficiency of the aged LEDs drops while the peak-efficiency-current shifts toward higher magnitude. At selected injection current levels, the electroluminescence spectra of the aged LEDs show little change in peak position and shape. The shift in peak-efficiency-current, which follows the same trend as the degree of luminescence decay, is explained by a rate-equation model in which the newly created defects by dc stressing enlarge the dominant low-current region of nonradiative recombinations.