Oxide has been grown on 4H-SiC samples using a high pressure oxidation system at temperature as low as 400 and 450 degrees C using water vapor. Effect of post oxidation annealing (POA) in various ambient on electrical and structural properties of this oxide has been systematically investigated. X-ray photoelectron spectroscopy with sputter depth profile has been carried out to study the incorporation of nitrogen in the oxide. Significant nitrogen incorporation has been observed at the SiO2/SiC interface with POA in O-2+N-2 ambient resulting in effective passivation of the SiO2/SiC interface. This is reflected in the low interface state density and leakage current as well as high breakdown field strength for the samples with POA in O-2+N-2 compared to those for the sample with POA in N-2. A very small hysteresis window (<10 mV) also indicates low charge trapping and a good SiO2/SiC interface for the samples with POA in O-2+N-2. (C) 2012 Elsevier B. V. All rights reserved.