Epitaxial lateral overgrowth of GaN-based light emitting diodes on SiO ₂ nanorod-array patterned sapphire substrates by MOCVD

High efficiency GaN-based light-emitting diodes (LEDs) are demonstrated by a nanoscale epitaxial lateral overgrowth (NELO) method on a SiO ₂ nanorod-array patterned sapphire substrate (NAPSS). The SiO ₂ NAPSS was fabricated by a self-assembled Ni nano clusters and reactive ion etching. The average diameter and density of the formed SiO ₂ nanorod-array was about 100 to 150 nm and 3 × 10 ⁹ cm ^-2 . The transmission electron microscopy images suggest that the voids between SiO ₂ nanorods and the stacking faults introduced during the NELO of GaN can effectively suppress the threading dislocation density. The output power and external quantum efficiency of the fabricated LED by NELO method on NAPSS were enhanced by 52% and 56% respectively, compared to those of a conventional LED. The improvements originated from both the enhanced light extraction assisted by the NAPSS, and the reduced dislocation densities using the NELO method.