1. Singapore University of Technology and Design (SUTD), 8 Somapah Road, 487372 Singapore
2. Department of Materials Science & Engineering, National University of Singapore, 9 Engineering Drive 1, 117575 Singapore
3. Optoelectronics Research Centre, University of Southampton, Southampton SO17 1BJ, United Kingdom
4. Institute of Materials Research and Engineering (IMRE), Agency for Science Technology and Research (A*STAR), 2 Fusionopolis Way, Innovis 138634, Singapore