1. Guangdong Engineering Research Center of Optoelectronic Functional Materials and Devices, Institute of Semiconductors, South China Normal University, Guangzhou 510631, People's Republic of China
2. Key Laboratory of Submillimeter Astrophysics, Department of Physics, Shanghai Normal University, Shanghai 200234, People's Republic of China
3. Physics Department, University of Kotli Azad Kashmir Pakistan, Azad Kashmir 11100, Pakistan