1. Department of Electrical and Electronics Engineering Eskisehir Technical University Eskisehir 26555 Turkey
2. Department of Electrical and Electronics Engineering Department of Physics UNAM‐Institute of Materials Science and Nanotechnology Bilkent University Ankara 06800 Turkey
3. Luminous! Centre of Excellence for Semiconductor Lighting and Displays School of Electrical and Electronic Engineering School of Physical and Mathematical Sciences School of Materials Science and Engineering Nanyang Technological University Singapore 639798 Singapore