1. Air Force Research Laboratory, Sensors Directorate, Wright-Patterson AFB, Ohio 45433, USA
2. Semiconductor Research Center, Wright State University, Dayton, Ohio 45435, USA
3. Research Laboratory of Electronics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
4. School of Applied and Engineering Physics, Cornell University, Ithaca, New York 14853, USA
5. KBR, Beavercreek, Ohio 45431, USA