Gan-Based Leds Grown on Cone-Shaped Patterned Sapphire Substrates with Peripheral Air Voids by Lateral Etching 
  Advanced Materials Research (Volume 422)
 Pages 542-546 
  Nan Ming Lin, Shih Chang Shei, Shoou Jinn Chang, Wei Chih Lai, Yang Ya Yu, Wun Cin Lin, Lo Hsin Ming