Light-Extraction Enhancement by Cavity Array-Textured N-Polar GaN Surfaces Ablated Using a KrF Laser

The creation of KOH-etched pyramidal patterns on the N-GaN surface is considered to be the most effective texturing method for improving the light-extraction efficiency of GaN LEDs. Using KrF-laser ablation, concave downward cavities are formed on the N-GaN surface. This letter demonstrates that KrF-laser-ablated cavities enhance the light-extraction efficiency of the KOH-etched pyramidal N-GaN surface by 25%. With further etching by KOH, the curved-surface sidewall of laser-ablated cavities do not form pyramids; instead, relatively large inclined facet sidewalls are formed in the laser-ablated cavities. We believe that these inclined facet sidewalls in laser-ablated cavities further enhance the light-extraction efficiency of KOH-etched pyramidal N-GaN surfaces.