Structural analysis of polarity inversion boundary in sputtered AlN films annealed under high temperatures

Abstract

The structure and stability of a polarity inversion boundary in sputtered AlN films with face-to-face annealing are investigated on the basis of scanning transmission electron microscop (STEM) and density functional theory (DFT) calculations. The high-resolution STEM observation around the AlN/sapphire interface for 200 nm sputtered AlN films with annealing at 1700 °C reveals that the polarity inversion boundary whose thickness is around 1 nm appears 10 nm above the AlN/sapphire interface. The calculated interface energies by DFT calculations also reveal that the oxide inversion boundary with Al vacancies is stabilized when the thickness of the inversion boundary is more than 1.1 nm. These results suggest that the formation of weak Al–Al bonds as well as stable Al–O bonds is crucial for the polarity inversion of AlN.