1. Institute of Materials Science and Nanotechnology – UNAM, Bilkent University, Ankara 06800, Turkey
2. Department of Physics, Bilkent University, Ankara 06800, Turkey
3. Department of Electrical and Electronics Engineering, Bilkent University, Ankara 06800, Turkey
4. LUMINOUS! Centre of Excellence for Semiconductor Lighting and Displays, The Photonics Institute, School of Electrical and Electronic Engineering, School of Physical and Mathematical Sciences, School of Materials Science and Engineering Nanyang Technological University, Singapore 639798, Singapore