1. Department of Nano Systems Engineering, Center for Nano Manufacturing, Inje University, Gimhae, Gyungnam 621-749, Republic of Korea
2. School of Nano Engineering, Inje University, Gimhae, Gyungnam 621-749, Republic of Korea
3. Epi R&D team, Samsung LED Co. Ltd., Suwon, Gyeonggi-do 443-373, Republic of Korea
4. Research Center of Advanced Materials Development (RCAMD), Division of Advanced Materials Engineering, Chonbuk National University, Jeonju, Chonbuk 561-756, Republic of Korea
5. Department of Physics, Yeungnam University, Gyeongsan, Gyeongsangbuk-do 712-749, Republic of Korea