On the thermal oxidation of AlInN/AlN/GaN heterostructures

In this work, we report on the thermal oxidation of AlInN/AlN/GaN heterostructures. A 'nearly-native' Al2O3 oxide was formed during this procedure, which can be used as a gate oxide and thus enables the fabrication of MIS-HFET. 2DEG density and, in particular, carrier mobility are strongly affected by the thermal treatment in O-2 atmosphere. Hence, only a narrow processing window for successful thermal oxidation was identified, covering annealing temperatures between 700 degrees C and 800 degrees C and annealing durations of few minutes. Oxide thicknesses estimated to be in the range of 0.6 nm and 2.6 nm were fabricated, enabling a suppression of reverse leakage currents of MIS large-area gate diodes by up to three orders of magnitude. The resulting oxide thickness scales well with the square root of oxidation time, indicating a diffusion of oxygen atoms into the barrier. (C) 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim