1. Department of Electrical and Computer Engineering, University of Virginia, 351 McCormick Road, PO Box 400743, Charlottesville, VA 22904, USA
2. Virginia Diodes, Inc., 321 West Main Street, Charlottesville, VA 22903, USA
3. Electronics Division, US Army Research Office, PO Box 12211, Research Triangle Park, NC 27709-2211, USA