  Ferroelectric polarization switching is one common example of a process that
occurs via nucleation and growth, and understanding switching kinetics is
crucial for applications such as ferroelectric memory. Here we describe and
interpret anomalous switching dynamics in the wurtzite nitride thin film
ferroelectrics Al0.7Sc0.3N and Al0.94B0.06N using a general model that can be
directly applied to other abrupt transitions that proceed via nucleation and
growth. When substantial growth and impingement occur while nucleation rate is
increasing, such as in these wurtzite ferroelectrics under high electric
fields, abrupt polarization reversal leads to very large Avrami coefficients
(e.g., n = 11), inspiring an extension of the KAI (Kolmogorov-Avrami-Ishibashi)
model. We apply this extended model to two related but distinct scenarios that
crossover between (typical) behavior described by sequential nucleation and
growth and a more abrupt transition arising from significant growth prior to
peak nucleation rate. This work therefore provides more complete description of
general nucleation and growth kinetics applicable to any system while
specifically addressing both the anomalously abrupt polarization reversal
behavior in new wurtzite ferroelectrics.
