Atomic Structure and Electronic Properties of Pristine and O-Doped Basal-Plane Inversion Domain Boundaries in AlN

Revealing atomic and electronic structures and elemental doping behavior of basal-plane inversion domain boundaries (b-IDBs) is crucial for a deep understanding of polarization reversal mechanisms in ferroelectric wurtzites. Here, the atomic and electronic structures of pristine and O-doped b-IDBs in AlN thin films have been comparatively investigated by combining aberration-corrected transmission electron microscopy and first-principles calculations. It is found that the polarization reverses from the N-polar to Al-polar orientation across the pristine AlN b-IDB through the formation of a monolayer of hexagonal AlN in which Al and N atoms locate in the same atomic plane. The pristine b-IDB exhibits two-dimensional hole conductivity due to the increasing coordination number of Al atoms and the decreasing coordination number of N atoms. The O-doped b-IDB has a higher structural stability compared with the pristine one. The main driving force for O segregation of oxanes is the charge compensation at the b-IDB. These findings can not only help to unveil the atomic origin for the polarization switching in wurtzite ferroelectrics but also shed light on strategies for tailoring the physical properties of domain boundaries.