Switching it Up: New Mechanisms Revealed in Wurtzite-type Ferroelectrics

Wurtzite-type ferroelectrics have drawn increasing attention due to the promise of better performance and integration than traditional oxide ferroelectrics with semiconductors such as Si, SiC, and III-V compounds. However, wurtzite-type ferroelectrics generally require enormous electric fields, approaching breakdown, to reverse their polarization. The underlying switching mechanism(s), especially for multinary compounds and alloys, remains elusive. Here, we examine the switching behaviors in (Al,Sc)N alloys and new wurtzite-type multinary candidate compounds we recently computationally identified. We find that switching in these tetrahedrally-coordinated materials proceeds via a variety of non-polar intermediate structures and that switching barriers are dominated by the more electronegative of the cations. For (Al,Sc)N alloys, we find that the switching pathway changes from a collective mechanism to a lower-barrier mechanism enabled by inversion of individual tetrahedra with increased Sc composition. Our findings provide insights for future engineering and realization of wurtzite-type materials and open a door to understanding domain motion.