Effect of oxygen species on the positive flat-band voltage shift in Al2O3/GaN metal-insulator-semiconductor capacitors with post-deposition annealing

The electrical characteristics of the Al2O3/GaN metal-insulator-semiconductor capacitors are investigated focusing on the effect of post-deposition annealing (PDA) in O-2 ambient. X-ray photoelectron spectroscopy analyses reveal that gallium oxynitride (GaOxNy) interfacial layer is formed at Al2O3/GaN interface even in non-annealed sample due to incorporation of the released oxygen from Al2O3. After PDA in O-2 ambient, the GaOxNy interfacial layer becomes oxygen-rich which plays a role in increasing negative effective oxide charge at the Al2O3/GaN interface and hence positively shifting the flat band voltage (V-FB) for the capacitors.