Enhanced Light Output of Vertical-Structured GaN-Based Light-Emitting Diodes with TiO2/SiO2 Reflector and Roughened GaOx Surface Film

GaN-based thin-film vertical-structured light-emitting diodes (VLEDs) with a GaOx film atop an n-GaN layer roughened via KrF laser irradiation and a TiO2/SiO2 distributed Bragg reflector (DBR) are proposed and investigated. As compared with regular VLEDs with an Al reflector and without a roughened GaOx film, the proposed VLEDs with a chip size of 1 mm2 show a typical increase in light output power by 68% at 350 mA and by 51% at 750 mA, which is attributed to the enhanced reflectivity and current blocking capability of the DBR layer, the surface roughening with circular GaN protrusions, and the formation of a surface GaOx film by KrF laser irradiation.