1. Department of Materials Science and Engineering, National Tsing Hua University, Hsinchu 30013, Taiwan
2. College of Semiconductor Research, National Tsing Hua University, Hsinchu 30013, Taiwan
3. Semiconductor Research Center, Hon Hai Research Institute, Taipei 11492, Taiwan
4. Department of Physics, National Sun Yat-Sen University, Kaohsiung 80424, Taiwan
5. Ph. D. Program in Prospective Functional Materials Industry, National Tsing Hua University, Hsinchu 30013, Taiwan
6. Department of Electrophysics, College of Science, National Yang Ming Chiao Tung University, Hsinchu 30010, Taiwan
7. Instrument Center, National Tsing Hua University, Hsinchu 30013, Taiwan
8. Department of Photonics, Institute of Electro-Optical Engineering, National Yang-Ming Chiao Tung University, Hsinchu 30010, Taiwan
9. Department of Materials Science and Engineering, Korea University, Seoul 02841, Republic of Korea