Light output enhancement of GaN-based flip-chip light-emitting diodes fabricated with SiO₂ / TiO₂ distributed Bragg reflector coated on mesa sidewall

We report on the enhanced light output of GaN-based flip-chip light-emitting diodes (LEDs) fabricated with SiO₂ / TiO₂ distributed Bragg reflector (DBR) on mesa sidewall. At the wavelength of 400 nm, five pairs of SiO₂ / TiO₂ DBR coats on the GaN layer showed a normal-incidence reflectivity as high as 99.1%, along with an excellent angle-dependent reflectivity. As compared to the reference LED, the LED fabricated with the DBR-coated mesa sidewall showed an increased output power by a factor of 1.32 and 1.12 before and after lamp packaging, respectively. This could be attributed to an efficient reflection of the laterally guided mode at the highly reflective mesa sidewall, enhancing the subsequent extraction of light through the sapphire substrate.