Transformation of charge polarity at HfO₂/GaN interfaces through post-deposition annealing

The transformation of charge polarity at HfO₂/GaN interfaces was investigated through the post-deposition annealing (PDA) at 500 °C, 700 °C and 900 °C for 3 min. The change in surface property of atomic-layer deposition HfO₂/GaN with the PDA conditions was estimated by a contact angle measurement. The PDA improved surface adhesion and thus decreased the contact angle of HfO₂, which was shown with the PDA up to 700 °C. The increased contact angle with the PDA at 900 °C was presumably due to the transformation of crystallinity of HfO₂ film from amorphous to polycrystalline. The charge polarity at the HfO₂/GaN interfaces was changed from negative to positive with the elevated PDA temperature. The energy band bending at the HfO₂/GaN interfaces was described based on the elemental binding energy obtained by X-ray photoelectron spectroscopy. The charge polarity at the HfO₂/GaN interface was converted at the 700 °C PDA with increased net charge density. The PDA affected the interface property of HfO₂/GaN and determined the interface polarity and charge density.