1 Microelectronics Research Center, Department of Electrical and Computer Engineering, The University of Texas, Austin, TX, 78758, USA.
2 Department of Physics, The University of Texas, Austin, TX, 78712, USA.
3 LAETA, Engineering Physics Department, Engineering Faculty, University of Porto, R. Dr. Roberto Frias s/n, 4200-465, Porto, Portugal.
4 Microelectronics Research Center, Department of Electrical and Computer Engineering, The University of Texas, Austin, TX, 78758, USA. deji@ece.utexas.edu.