A pyramidal pattern was produced on a c-plane sapphire substrate by a mask-free etching process. Photoluminescence (PL) results show that a GaN-based light-emitting diode (LED) epilayer grown on the pyramidally patterned sapphire substrate has higher epitaxial quality than that grown on a standard flat c-plane sapphire substrate. When the input current is 350 mA, the average light output power of LED chips on the pyramidally patterned sapphire substrate is 37% larger than that of LED chips on a standard c-plane sapphire substrate. (C) 2010 The Japan Society of Applied Physics
