Rapid thermal annealing and performance of Al2O3/GaN metal-oxide-semiconductor structures

In this paper we investigate growth of Al2O3 and performance of Al2O3/GaN MOS structures using O2, Ar and NH3 pre-treatment of GaN surface. Rapid thermal annealing (RTA) after the growth is also tested. Current-voltage (I-V) and thermal activation energy measurements were used for characterization of MOS and reference Ni/GaN Schottky contact structures. From the I-V characteristics, reduction of the leakage current was observed in MOS structures compared with the Schottky contacts for all types of processing, from three to five orders of magnitude in the reverse bias. Barrier height at the semiconductor-insulator interface (PhiS-1), which is responsible for the reduction of the forward bias leakage was extracted from the thermal I-V measurements. Values of PhiS-1 was found to be ~1.6eV for O2 and ~2.5eV for Ar treated samples and these samples show substantial leakage reduction in both senses. On the other hand I-V performance of the MOS structures with the NH3 pretreatment resemble Schottky contact diode-like characteristic