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 Al 2 O 3 /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 (GaO x N y ) interfacial layer is formed at Al 2 O 3 /GaN interface even in non-annealed sample due to incorporation of the released oxygen from Al 2 O 3 . After PDA in O 2 ambient, the GaO x N y interfacial layer becomes oxygen-rich which plays a role in increasing negative effective oxide charge at the Al 2 O 3 /GaN interface and hence positively shifting the flat band voltage ( V FB ) for the capacitors.