title: Light interaction in sapphire/MgF2/Al triple-layer omnidirectional reflectors in AlGaN-based near ultraviolet light-emitting diodes.
abstract: This study examined systematically the mechanism of light interaction in the sapphire/MgF2/Al triple-layer omnidirectional reflectors (ODR) and its effects on the light output power in near ultraviolet light emitting diodes (NUV-LEDs) with the ODR. The light output power of NUV-LEDs with the triple-layer ODR structure increased with decreasing surface roughness of the sapphire backside in the ODR. Theoretical modeling of the roughened surface suggests that the dependence of the reflectance of the triple-layer ODR structure on the surface roughness can be attributed mainly to light absorption by the Al nano-structures and the trapping of scattered light in the MgF2 layer. Furthermore, the ray tracing simulation based upon the theoretical modeling showed good agreement with the measured reflectance of the ODR structure in diffuse mode.
authors.affiliation: Department of LED Business, LG Innotek Company, Ltd., Paju 413-901, Korea.
authors.forename: Keon Hwa
authors.initials: KH
authors.lastname: Lee
authors.affiliation: Department of LED Business, LG Innotek Company, Ltd., Paju 413-901, Korea.
authors.forename: Yong-Tae
authors.initials: YT
authors.lastname: Moon
authors.affiliation: Department of LED Business, LG Innotek Company, Ltd., Paju 413-901, Korea.
authors.forename: June-O
authors.initials: JO
authors.lastname: Song
authors.affiliation: Department of Printed Electronics Engineering, Sunchon National University, Jeonnam 540-742, Korea.
authors.forename: Joon Seop
authors.initials: JS
authors.lastname: Kwak