[1] Univ Texas, Microelect Res Ctr, Austin, TX 78758 USA
[2] Univ Illinois, Ctr Compound Semicond Microelect, Urbana, IL 61801 USA
[3] Univ Virginia, Dept Mat Sci & Engn, Charlottesville, VA 22906 USA
[4] Harvard Univ, Gordon McKay Lab Appl Sci, Cambridge, MA 02138 USA