Mutable Polarization Switching Characteristics in Wurtzite Al1- xScxN Ferroelectric Films Enabled by Sc-Doping.

Abstract

Wurtzite ferroelectric aluminum scandium nitrides (Al1- xScxN) are highly appealing for their large remanent polarization, steep hysteresis, and easy integration with multiple mainstream semiconductor platforms. However, their applications are constrained by the inherently high coercive field (Ec), desperately needing comprehensive research of polarization switching for potentially lowering Ec. In particular, the correlations between polarization switching mechanisms and Sc doping levels remain underexplored. Here, the polarization switching kinetics in wurtzite ferroelectric Al1- xScxN (x = 0.25-0.3) subjected to varied voltage amplitudes and pulse durations are investigated, revealing a mutable polarization switching. The Al0.75Sc0.25N sample displays uniform switching behavior described by the Kolmogorov-Avrami-Ishibashi (KAI) model, while the intermediate composition Al0.725Sc0.275N exhibits an ambiguous switching mechanism, more aligned with KAI model-based on mathematical fitting validation. Especially, Al0.7Sc0.3N with obviously reduced coercive and activation fields, exhibits a nucleation-limited-switching (NLS) mechanism. It is found that higher-level Sc doping generates more nucleation sites, reducing energy barriers and accelerating nucleation switching, driving the transition from KAI to NLS. Energetic analysis further elucidates the doping-induced crossover of switching mechanisms. These results provide new insight into the fundamental understanding of polarization switching in wurtzite ferroelectric nitrides, which is critical for realizing their optimal and reliable applications.