Mutable Polarization Switching Characteristics in Wurtzite Al ScN Ferroelectric Films Enabled by Sc-Doping.

Wurtzite ferroelectric aluminum scandium nitrides (Al ScN) 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 (E), desperately needing comprehensive research of polarization switching for potentially lowering E. In particular, the correlations between polarization switching mechanisms and Sc doping levels remain underexplored. Here, the polarization switching kinetics in wurtzite ferroelectric Al ScN (x = 0.25-0.3) subjected to varied voltage amplitudes and pulse durations are investigated, revealing a mutable polarization switching. The AlScN sample displays uniform switching behavior described by the Kolmogorov-Avrami-Ishibashi (KAI) model, while the intermediate composition AlScN exhibits an ambiguous switching mechanism, more aligned with KAI model-based on mathematical fitting validation. Especially, AlScN 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.