Research progress in the preparation of patterened sapphire substrates for high-efficiency and high-power GaN-based LEDs

Patterned substrate sapphire has attracted much interest in recent years due to its outstanding properties in improve GaN epitaxial crystal quality and light output powers of the LEDs. The fabrication methods of patterned substrate sapphire are reviewed, including dry etch, wet etch and epitaxial growth method. The relationship between the mechanism of improve epitaxial crystal quality and morphology of the patterned substrate sapphire (grooves, micron hole, micron columnar, micron hemispherical, nano-hole and nano-columnar) is also discussed.