1. UNAM Institute of Materials Science and Nanotechnology Bilkent University Ankara 06800 Turkey
2. LUMINOUS! Center of Excellence for Semiconductor Lighting and Displays School of Electrical and Electronic Engineering Nanyang Technological University 50 Nanyang Avenue Singapore 639798 Singapore
3. Division of Physics and Applied Physics School of Physical and Mathematical Sciences Nanyang Technological University 21 Nanyang Link Singapore 639798 Singapore
4. Department of Electrical and Electronics Engineering Department of Physics Bilkent University Ankara 06800 Turkey
5. Department of Mechanical Engineering Bilkent University Ankara 06800 Turkey