| Summary: | The effects of post-deposition annealing (PDA) on the formation of polarization-charge inversion at ultrathin Al<sub>2</sub>O<sub>3</sub>/Ga-polar GaN interfaces are assessed by the analysis of energy band bending and measurement of electrical conduction. The PDA-induced positive interface charges form downward energy band bending at the Al<sub>2</sub>O<sub>3</sub>/GaN interfaces with polarization-charge inversion, which is analyzed using X-ray photoelectron spectroscopy. Net charge and interface charge densities at the Al<sub>2</sub>O<sub>3</sub>/GaN interfaces are estimated after PDA at 500 °C, 700 °C, and 900 °C. The PDA temperatures affect the formation of charge densities. That is, the charge density increases up to 700 °C and then decreases at 900 °C. Electrical characteristics of GaN Schottky diodes with ultrathin Al<sub>2</sub>O<sub>3</sub> layers exhibit the passivation ability of the Al<sub>2</sub>O<sub>3</sub> surface layer and the effects of polarization-charge inversion through PDA. This result can be applied to improvement in GaN-based electronic devices where surface states and process temperature work important role in device performance.
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