AlGaN/GaN high-electron mobility transistors (HEMTs) structures regrown by metalorganic vapour phase epitaxy (MOVPE) on semi-insulating (SI) GaN templates, after exposure to air, results in the presence of parasitic conducting channels at regrowth interface. Air contamination of the SI GaN templates generates this parallel conduction. The parasitic conducting channel involves poor pinch-off characteristics (I-leakage similar to 0.1 mA at bias gate-source voltage above pinch off voltage) and poor inter-device isolation (I-leakage similar to 0.001-0.1 mA). To overcome this, we developed a method of local Fe doping used in GaN templates for inhibiting regrowth interface pollution and proved to be efficient. Using this annihilation method permits to reduce 4-5 orders of magnitude buffer leakage current (I-leakage similar to nA). Such HEMTs structures, with perfect charge control, have exhibited two-dimensional electron gas (2DEGs) with 300 K mobilities above 2000 cm(2)V(-1)s(-1) at carrier densities 9 x 10(12) cm(-2). (c) 2006 Elsevier B.V. All rights reserved.