Growth of GaN Layer and Characterization of Light-Emitting Diode Using Random-Cone Patterned Sapphire Substrate

GaN was grown on a random-cone patterned sapphire substrate (RC-PSS) fabricated by natural lithography via metalorganic vapor phase epitaxy. Scanning and transmission electron microscopies were performed to investigate the growth mode of the GaN layer on the RC-PSS. Some dislocations generated at the GaN/sapphire interface were bent and annihilated by lateral overgrowth and selective area growth. Dislocation density decreased with increasing cone density. The external quantum efficiency of the light-emitting diode on the RC-PSS was 49.5% at a current injection of 20 mA. An improvement in output power was indicated by increases in light extraction efficiency and crystalline quality owing to the use of the RC-PSS. The light extraction efficiency of the LED on the RC-PSS was estimated to be 86.8%.