Appropriate fabrication procedure for InAlN metal-oxide-semiconductor structures with atomic-layer-deposited Al2O3

Abstract

The fabrication-procedure dependence of the electrical properties of the InAlN metal-oxide-semiconductor (MOS) structure with Al2O3 formed by atomic layer deposition (ALD) was investigated. When the ALD Al2O3/InAlN interface was formed after ohmic-contact annealing in nitrogen without the use of a cap layer, the electrical characteristics were poor with a small capacitance change in the capacitance-voltage (C-V) curve. X-ray photoelectron spectroscopy (XPS) study indicated that the bare InAlN surface was oxidized during capless annealing presumably owing to the trace contamination in the furnace. High-temperature ohmic-contact annealing after Al2O3/InAlN interface formation, using the Al2O3 layer as a cap layer for surface protection, did not improve the interface properties, resulting in the interface state density Dit in the range of 1013 cm-2eV-1; this was highly likely related to the crystallization of Al2O3. When a SiNx layer was used as the cap layer during ohmic-contact annealing prior to ALD, greatly improved characteristics of the MOS diode were achieved, indicating that Dit was suppressed to be in the range of 1012 cm-2eV-1 near the conduction band. The obtained results indicate that an appropriate fabrication procedure leads to an improvement of the Al2O3/InAlN interface properties. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.