Effect of Defects on Formation of Inversion Domain Boundaries in AlScN and Their Structural/Electronic Properties Improvement

Abstract

Wurtzite AlScN, a promising material for high-power electronics 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 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 ratio of Sc to Al at grain boundaries would promote abnormally oriented grain (AOG) boundaries as well as IDB. Strategies such as controlling oxygen contamination, and applying strain are identified to mitigate these issues. In addition, AlScN generally receives compressive strain from the other substrate wurtzite nitrides acting as substrates (i.e. AlN, AlGaN and GaN) that have smaller unit cell areas than AlScN. The interfacial compressive strain inevitably reduces piezoelectricity of AlScN. From the results, applying surface tensile strain to the substrates would increase the piezoelectric properties of AlScN as well as suppressing IDB. These findings provide insights into improving AlScN-based materials for advanced applications in high-power electronic devices and piezoelectric technology.