Depth profile of donor–acceptor pair transition revealing its effect on the efficiency of green LEDs

Abstract

GaInN/GaN light emitting diodes are the primary choice for efficient green light emitters, yet their performance limiting factors have yet to be identified. Here we perform a low-temperature luminescence study in depth-resolved cathodoluminescence. A series of LEDs with a combination of blue and green light emitting quantum wells exhibiting low and high electroluminescence output power were compared. In all samples, a band of donor-acceptor pair recombination was identified at 77 K. In the samples with lowest performance, such transitions located within the active region of the quantum wells had a particular strong contribution to the spectrum. In LEDs of higher performance, such luminescence was substantially suppressed within those layers. We argue that the higher performance of LEDs without such donor acceptor transition bands may be associated with the absence of corresponding dopant impurities and indicate a higher epitaxial perfection within the active quantum well region.