High extraction efficiency light-emitting-diodes using hemispherical corrugated interface substrate

The external quantum efficiency of nitride light-emitting diodes (LEDs) grown on sapphire substrates is greatly influenced by the internal reflection of lights at the nitride-substrate interface. To improve the external quantum efficiency of nitride LEDs with an InGaN multi-quantum well (MQW) structure, we introduced various patterned structures at the interface, The output power was increased by 1.7 times by incorporating an optimized patterned structure in nitride LEDs. In this study, the corrugated interface substrate (CIS) pattern was fabricated by standard photolithography and subsequent reactive ion etching (RIE) process. When the flip-chip type LED grown on CIS was operated at a forward bias current 20mA at room temperature, emission wavelength, output power, and external quantum efficiency were 400 nm, 21 mW and 34%, respectively.