Enhancement mode HEMT using fluorine implantation below the channel Saleem Hamady, Frédéric Morancho, Bilal Beydoun, Patrick Austin and Mathieu Gavelle Eur. Phys. J. Appl. Phys., 70 3 (2015) 30102 Published online: 24 June 2015 DOI: 10.1051/epjap/2015150062