Improvement of the carrier distribution with GaN/InGaN/AlGaN/InGaN/ GaN composition-graded barrier for InGaN-based blue light-emitting diode

InGaN light-emitting diodes (LEDs) with GaN/InGaN/AlGaN/InGaN/GaN composition-graded barriers are proposed to replace the sixth and the middle five GaN barriers under the condition of removing the electron blocking layer (EBL) and studied numerically in this paper. Simulation results show that the specially designed barrier in the sixth barrier is able to modulate the distributions of the holes and electrons in quantum well which is adjacent to the specially designed barrier. Concretely speaking, the new barrier could enhance both the electron and hole concentration remarkably in the previous well and reduce the hole concentration for the latter one to some extent along the growth direction. What is more, a phenomenon, i.e., a better carrier distribution in all the wells, just appears with the adoption of the new barriers in the middle five barriers, resulting in a much higher light output power and a lower efficiency droop than those in a conventional LED structure.