Reduction of reverse-leakage current in selective-area-grown GaN-based core-shell nanostructure LEDs using AlGaN layers

We report a simple method to improve the p-type doping efficiency and eliminate the diode leakage current in selective-area-grown GaN-based core-shell nanostructure LEDs by growing an n-type AlGaN layer underneath the InGaN/GaN active region. A significant reduction in reverse-leakage current density is correlated with longer AlGaN layer growth time and higher flow rate of the aluminum precursor. A comparison of the SIMS profiles with and without the underlayer indicates a high concentration of donor-type impurities (e.g., silicon and oxygen) in the p-GaN layer in the structure with no AlGaN underlayer. Conversely, LEDs with an AlGaN underlayer exhibit enhanced magnesium incorporation and much lower silicon and oxygen impurity concentrations within the p-GaN layer. The reverse current density was also reduced by the addition of a p-type AlGaN electron blocking layer above the active region. (C) 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim