The effect of defects on the formation of inversion domain boundaries in AlScN and their structural/electronic property improvement

Abstract

Wurtzite AlScN, a promising material for high-power electronic and piezoelectric applications, faces performance challenges due to defects such as inversion domain boundaries (IDBs) and elemental contaminations at interfaces. This study explores the mechanisms underlying the IDB formation of AlScN, using density functional theory (DFT) and density functional perturbation theory (DFPT). The results show that IDBs are influenced by Sc incorporation, oxygen contamination, and applied strains, which impact abnormal crystallinity, piezoelectricity and electronic performance. In particular, an increase in the ratio of Sc to Al at grain boundaries would promote abnormally oriented grain (AOG) boundaries as well as IDBs. Strategies such as controlling oxygen contamination and applying strain are identified to mitigate these issues. In addition, AlScN generally receives compressive/tensile strains from the other wurtzite nitrides acting as substrates (i.e. AlN, AlGaN, GaN, InAlN, InGaN and InN) that have different unit cell areas compared to AlScN. The interfacial compressive strain inevitably reduces the piezoelectricity of AlScN. However, applying surface tensile strain to the substrates would increase the piezoelectric properties of AlScN as well as suppress IDBs. These findings provide insights into improving AlScN-based materials for advanced applications in high-power electronic devices and piezoelectric technology.