1. Department of Materials Science
and Engineering, KAIST, 373-1 Guseong-dong,
Yuseong-gu, Daejeon 305-701, Korea
2. School of Advanced Materials
Science and Engineering, Sungkyunkwan University, 300 Cheoncheon-dong, Jangan-gu, Suwon, Gyeonggi-do 440-746, Korea
3. R&D Institute, Samsung LED, Yongin-si 446-711, Korea