Improved light extraction efficiency of GaN-based LEDs with patterned sapphire substrate and patterned ITO

To improve the light extraction efficiency of GaN-based light-emitting diodes (LEDs), periodic semisphere patterns with 3.5 μm width, 1.2 μm height, and 0.8 μm spacing were formed on sapphire substrate by dry etching using BCl3/Cl2 gas chemistry. The indium tin oxide (ITO) transparent conductive layer was patterned by wet etching to reduce the total internal reflection existing along between p-GaN, ITO, and air. At 350 mA injection current, the high power LED by integrating patterned sapphire substrate with patterned ITO technology exhibited a 36.9% higher light output power than the conventional LEDs.

►The optical power of LEDs can be enhanced 36.7% by integrating PSS and patterned ITO. ► A thermally reflowed photoresist and dry etching method was used to fabricate PSS. ► Periodic and non-periodic hexagonal patterns were transferred to ITO by aqua regia etchant.