Enhancement of Light Extraction from GaN-Based Light-Emitting Diodes by Coating Surface with Al₂O₃ Powder

Abstract

GaN-based light-emitting diodes (LEDs) were fabricated by coating Al 2 O 3 powder on a p-GaN and a semitransparent p-contact metal surface to increase the extraction probability of the internal reflected photons through the Al 2 O 3 powder. The density of the $300-nmdiameter Al 2 O 3 powder was about 1:9 Â 10 13 cm À2 on both surfaces. The forward voltages of the LEDs coated with Al 2 O 3 powder on the p-GaN surface and the semitransparent p-contact metal surface were 4.15 and 3.42 V at 20 mA, respectively. The light output powers of both LED structures with Al 2 O 3 powder coated on the p-GaN and semitransparent p-contact metal surfaces were increased by almost 30% compared with the conventional LED structure without Al 2 O 3 powder coating. #

Study on photoluminescence of GaN-based UV-LEDs with refractive index gradient polymeric nanopatterns

“…Since the deposition of the secondary material does not harm the surface of GaN [13][14][15], it is expected not to degrade the electrical properties of GaN as possibly done by the direct patterning/roughing methods. As an effort to control the refractive index of the top layer for better light extraction efficiency, nanoporous structure is being investigated by controlling the porosity [16][17][18][19][20]. Still inorganic materials are not only difficult, but also expensive material to process; block copolymers as a representative material of a nanopatterned organic layer have very particular conditions for microphase separation [21], which makes it difficult to control the porosity and the thickness.…”