1. Semiconductor Device Research Laboratory, Department of Electronic Science; University of Delhi South Campus; New Delhi 110021 India
2. Department of Physics, Motilal Nehru College; University of Delhi; New Delhi 110021 India
3. Department of Electrical and Electronics Engineering; Maharaja Agrasen Institute of Technology; New Delhi 110086 India
4. Department of Electronics and Communication Engineering; Maharaja Agrasen Institute of Technology; New Delhi 110086 India