1. Department
of Materials Science and Engineering, National Tsing Hua University, Hsinchu 30013, Taiwan
2. Department
of Chemistry and Biochemistry, University of California, Los Angeles, California 90095, United States
3. Department of Photonics & Institute of Electro-Optical Engineering, National Chiao Tung University, Hsinchu 30010, Taiwan
4. Institute
of Electronic Engineering, National Tsing Hua University, Hsinchu 30013, Taiwan
5. State
Key Laboratory for Superlattices and Microstructures, Institute of
Semiconductors, Chinese Academy of Sciences, Beijing 100083, China