Keisuke Yazawa1,2,Daniel Drury2,John Hayden3,Jon-Paul Maria3,Susan Trolier-McKinstry3,Andriy Zakutayev1,Geoff Brennecka2
National Renewable Energy Laboratory1,Colorado School of Mines2,The Pennsylvania State University3
Keisuke Yazawa1,2,Daniel Drury2,John Hayden3,Jon-Paul Maria3,Susan Trolier-McKinstry3,Andriy Zakutayev1,Geoff Brennecka2
National Renewable Energy Laboratory1,Colorado School of Mines2,The Pennsylvania State University3
Ferroelectricity enables key integrated technologies from non-volatile memory to precision ultrasound. Wurtzite nitride ferroelectric materials such as (Al,Sc)N and (Al,B)N have recently received significant attention because of robust ferroelectricity [1,2] and the compatibility of the existing Si and III-V semiconductor processes. The mechanism and origin of the wurtzite ferroelectrics have been rigorously investigated [1,3] to control the ferroelectric properties and discover novel ferroelectric materials, but many questions remain, including in switching dynamics and the origin of wakeup behavior. Those questions are directly relevant to ferroelectric applications such as FeRAM.<br/><br/>In this presentation, we demonstrate and interpret anomalous switching dynamics in the wurtzite nitride thin film ferroelectrics Al<sub>0.7</sub>Sc<sub>0.3</sub>N and Al<sub>0.94</sub>B<sub>0.06</sub>N, which is explained with neither the conventional KAI nor NLS models [4]. 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 (<i>n</i> = 11), inspiring an extension of the KAI model that distinctly describes the nucleation rate and domain growth. This extended model explains the abrupt transition arising from significant growth prior to peak nucleation rate. <br/><br/>We also demonstrate that polarization switching to the polarity opposite of the growth polarity is critical to the observed wakeup behavior of thin film Al<sub>0.94</sub>B<sub>0.06</sub>N [5]. The polarization switching curve, is orders of magnitude slower for the transition from the growth polarity to the antiparallel polarization state than going from antiparallel state back to the growth polarity. The domain wall density and/or domain wall mobility for switching from the antiparallel state to the growth polarity gradually increases with the number of cycles, causing the measured remanent polarization to increase for electric fields just above the coercive field, resulting in the observed wakeup behavior. Reversible and irreversible Rayleigh coefficients, piezoelectric coefficients, and chemical etching results reveal the domain structure and its evolution with the number of electric field cycles. These are consistent with the domain states predicted by the nucleation time and domain wall velocity from switching kinetics studies on the same films. <br/> <br/>[1] S. Fichtner, N. Wolff, F. Lofink, L. Kienle and B. Wagner, <i>J. Appl. Phys.</i>, 2019, <b>125</b>, 114103.<br/>[2] J. Hayden, M. D. Hossain, Y. Xiong, K. Ferri, W. Zhu, M. V. Imperatore, N. Giebink, S. Trolier-Mckinstry, I. Dabo and J. P. Maria, <i>Phys. Rev. Mater.</i>, 2021, <b>5</b>, 044412.<br/>[3] K. Yazawa, J. Mangum, P. Gorai, G.L. Brennecka, A. Zakutayev, <i>J. Mater. Chem. C,</i> 2022, <b>10</b>, 17557.<br/>[4] K. Yazawa, J. Hayden, J.-P. Maria, W. Zhu, S. Trolier-McKinstry, A. Zakutayev, and G. L. Brennecka, <i>Mater. Horiz.</i>, 2023, Advanced Article.<br/>[5] K. Yazawa, D. Drury, J. Hayden, J.-P. Maria, S. Trolier-McKinstry, A. Zakutayev, and G. L. Brennecka, <i>J. Am. Ceram. Soc</i>, 2023, under reivew.