1. Center for Power Electronics Systems, Virginia Polytechnic Institute and State University, Blacksburg, Virginia 24061, USA
2. The Bradley Department of Electrical and Computer Engineering, Virginia Polytechnic Institute and State University, Blacksburg, Virginia 24061, USA
3. Ming Hsieh Department of Electrical and Computer Engineering, University of Southern California, Los Angeles, California 90086, USA
4. Enkris Semiconductor Inc., Suzhou 215123, China
5. Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37830, USA