Enhanced light extraction of nonpolar a-plane (11-20) GaN light emitting diodes on sapphire substrates by photo-enhanced chemical wet etching

The extraction efficiency of nonpolar a-plane (11-20) GaN LEDs on sapphire substrates has been enhanced by selectively etching the mesa sidewall faces and the n-type GaN surfaces with photoenhanced chemical wet etching. Submicron-sized trigonal prisms having prismatic planes of {1-100} were clearly displayed on the n-type GaN surfaces as well as the sidewall face after 5 min etching at 60 degrees C. The radiation patterns have shown that more light is extracted in all directions and the output powers of surface textured a-plane GaN LEDs have increased by 25% compared with control samples. PEC wet etching produced unique feature of etching morphology on the mesa sidewall faces and the n-type GaN surface.