High-performance light-emitting diodes using hierarchical m-plane GaN nano-prism light extractors

Abstract

We demonstrated high-performance GaN-based light-emitting diodes (LEDs) with hierarchical m-plane nano-prism light extractors on the n-GaN mesa sidewalls by using a tetramethylammonium hydroxide (TMAH)-based crystallographic etching technique. The crystallographic etching method leads to a chemically stable formation of hierarchical m-plane nano-prism structures as light extractors, increased p-carriers near the p-GaN surface, and the effective removal of the native oxides on the p-GaN surface. These results lead to considerable improvement of the p-ohmic contact properties between the p-GaN layer and the ITO electrode, remarkable device-performance characteristics, an improved efficiency droop, and a longer device lifetime. Based on the device-performance and the p-ohmic contact data, the hierarchical m-plane nano-prism structure acts as a multifunctional factor exhibiting high-efficiency photon-extraction, strong packaging effects, strong suppression of the leakage current along the sidewalls from the p-GaN to the n-GaN, and/or a partial release of the piezoelectric field across the quantum well region.