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)