Inhibition of interface pollution in AlGaN/GaN HEMT structures regrown on semi-insulating GaN templates

Abstract

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∼0.1 mA at bias gate-source voltage above pinch off voltage) and poor inter-device isolation ( I leakage∼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∼ 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 9×10 12 cm −2.