1. Advanced Devices and Sustainable Energy Laboratory (ADSEL), Bradley Department of Electrical and Computer Engineering, Virginia Tech, Blacksburg, Virginia 24061, USA
2. Electrical Engineering, The Pennsylvania State University, University Park, Pennsylvania 16802, USA
3. Electrical Engineering, University of Notre Dame, Notre Dame, Indiana 46556, USA
4. Department of Physics, Virginia Tech, Blacksburg, Virginia 24061, USA