Enhancement of light extraction from GaN-based light-emitting diodes by coating surface with Al₂O₃ powder

GaN-based light-emitting diodes (LEDs) were fabricated by coating Al ₂O₃ powder on a p-GaN and a semitransparent p-contact metal surface to increase the extraction probability of the internal reflected photons through the Al₂O₃ powder. The density of the ∼300-nm-diameter Al₂O₃ powder was about 1.9 × 10¹³ cm^-2 on both surfaces. The forward voltages of the LEDs coated with Al₂O₃ powder on the p-GaN surface and the semitransparent p-contact metal surface were 4.15 and 3.42 V at 20mA, respectively. The tight output powers of both LED structures with Al ₂O₃ powder coated on the p-GaN and semitransparent p-contact metal surfaces were increased by almost 30% compared with the conventional LED structure without Al₂O₃ powder coating.