1. Department of Electrical and Electronics Engineering and Department of Physics, 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, School of Physical and Materials Sciences, Nanyang Technological University, 639798 Singapore
3. Department of Physics, Abant Izzet Baysal University, Bolu 14280, Turkey