Improved Efficiency of GaN-Based Green LED by a Nano-Micro Complex Patterned Sapphire Substrate

We demonstrate the enhancement of light extraction efficiency (LEE) of gallium-nitride (GaN)-based green light-emitting diode (LED) through a nano-micro complex patterned sapphire substrate (NMCPSS). The NMCPSS was prepared by inductively coupled plasma etching conventional microscale PSS with nickel nano-particles as the mask. The effect of NMCPSS on light output power of GaN-based green LED was investigated experimentally and numerically. The light output power at 20 mA of the LED grown on NMCPSS is 28.6% higher than that of LED grown on PSS. This is close to the value of 33.3% predicted by simulation. The results show that nano-micro complex PSS can further promote the LEE of GaN-based green LED compared with conventional PSS.