1. Department of Engineering Sciences, Solid State Electronics, Ångström Solar Center, Box 534, 751 21 Uppsala, Sweden
2. LCP-A2MC, Institut Jean Barriol, University of Lorraine, ICPM, 1 Bd Arago, Metz F-57078, France
3. Materials Science and Engineering, University of Utah, Salt Lake City, Utah 84112, USA
4. Electrical and Computer Engineering, University of Utah, Salt Lake City, Utah 84112, USA