Enhancing the Light Extraction Efficiency of Blue Semipolar (10\bar1\bar1) Nitride-Based Light Emitting Diodes through Surface Patterning

To enhance light extraction from a blue semipolar (1011) multiple-quantum-well light emitting diode (LED), surface patterning was performed on the backside of a GaN substrate on which LED epitaxial layers had previously been grown. After circular photoresist etching masks were defined, the surface was patterned with conical features by inductively-coupled plasma (ICP) etching. A substantial increase (100% before packaging and 33% after) in output power was observed in comparison with a reference sample which had a smooth backside at a drive current of 20 mA. Since ICP etching is a non-equilibrium process, this technique can potentially be applied to LEDs grown on nonpolar m- or a-plane GaN substrates.