1. Department of Electrical and Electronics Engineering Department of Physics UNAM – Institute of Materials Science and Nanotechnology Bilkent University Ankara 06800 Turkey
2. Department of Materials Science and Nanotechnology Abdullah Gül University Kayseri TR‐38080 Turkey
3. LUMINOUS! Centre of Excellence for Semiconductor Lighting and Displays Centre of Optical Fiber Technology The Photonics Institute School of Electrical and Electronic Engineering School of Physical and Mathematical Sciences Nanyang Technological University 50 Nanyang Avenue Singapore 639798 Singapore