Diffusion-assisted current spreading for III-nitride light-emitting applications

LED structures based on nanowires (NWR) have recently received much attention as a potential way to increase the output power and efficiency of GaN LEDs. We introduce a diffusion-assisted carrier injection scheme for III-Nitride optoelectronic devices, which may open up new current injection methods e.g. for free-standing nanowire emitters (FSNWR) and other structures where the active region is located outside the pn junction and the conventional current path. We simulate the charge transport numerically in selected InGaN/GaN nanowire structures as well as present a simplified analytical model for the current transport. We also discuss the basic characteristics of the bipolar diffusion injection scheme and the factors that make it more sensitive to the dimensions and materials of the current-spreading layers than the conventional LED injection scheme. Our results show that bipolar diffusion enables high efficiency current injection to free-standing nanowires with no top contacts and may also be beneficial to more conventional quantum well structures.