1. Department of Electrical and Computer Engineering, University of California Santa Barbara, Santa Barbara, CA 93106, USA
2. Materials Department, University of California Santa Barbara, Santa Barbara, CA 93106, USA
3. IQE, Inc., Greensboro, NC 27409, USA
4. NAsPIII–V GmbH, 35032 Marburg, Germany
5. RF SUNY Polytechnic Institute, Albany, NY 12203, USA