Improvement of light extraction efficiency of GaN-based flip-chip light-emitting diodes by patterning the double sides of sapphire

The double-side patterned sapphire structure was proposed to improve the light extraction efficiency (LEE) of flip-chip GaN-based light-emitting diodes (LEDs). The influences of sapphire substrate thickness, pattern shapes and sizes on LEE were analyzed by Monte Carlo simulation method. Using silicon oxide as mask membrane, double-side patterned sapphires were processed by the standard lithography and the reaction-ion-etching (RIE) technology. The LEDs with patterned sapphire were packaged. The measured light outputs of LEDs verified our predicted effects.