Ferroelectricity in AlScN: Switching, Imprint and sub-150 nm Films

TL;DR

This paper reports the discovery of ferroelectricity in AlScN, highlighting its switching behavior, imprint effects, and the ability to maintain ferroelectric properties in films thinner than 30 nm, with potential for nanoscale applications.

Contribution

It provides the first detailed study of ferroelectric switching, imprint, and thickness dependence in AlScN, a material with large coercive fields and remnant polarization.

Findings

Ferroelectricity observed in AlScN with large coercive fields and polarization.

Switching dynamics suggest domain wall motion limited process.

Ferroelectricity persists in films below 30 nm thickness.

Abstract

The discovery of ferroelectricity in AlScN allowed the first clear observation of the effect in the wurtzite crystal structure, resulting in a material with a previously unprecedented combination of very large coercive fields (2-5 MV/cm) and remnant polarizations (70-110 ${\mu}$C/cm$^2$). We obtained initial insight into the switching dynamics of AlScN, which suggests a domain wall motion limited process progressing from the electrode interfaces. Further, imprint was generally observed in AlScN films and can tentatively be traced to the alignment of charged defects with the internal and external polarization and field, respectively. Potentially crucial from the application point of view, ferroelectricity could be observed in films with thicknesses below 30 nm - as the coercive fields of AlScN were found to be largely independent of thickness between 600 nm and 27 nm.