Highly resistive GaN was grown by MOVPE onto sapphire with dislocation density in the range of 108 to 8 x 108/cm2, using Fe modulation doping. High mobility 2DEGs were created at AlGaN/GaN:Fe interface for moderate Al composition: 2200cm2/Vs with an ns value of about 7.6 x 1012/cm2. Good DC and RF small signal behaviour could be obtained in HEMTs processed on structures with less dislocated GaN:Fe template: IDSmax = 1.28 A/mm, gmmax  290mS/mm and fT  23GHz were measured for 0.2µm transistors.

Fe Doping for Making Resistive GaN Layers with Low Dislocation Density; Consequence on HEMTs. Z.Bougrioua, M.Azize, A.Jimenez, A.F.Braña, P.Lorenzini, B.Beaumont, E.Muñoz, P.Gibart: Physica Status Solidi C, 2005, 2[7], 2424-8