Reduced coercive field in epitaxial thin film of ferroelectric wurtzite Al0.7Sc0.3N

Abstract

Epitaxial ferroelectric wurtzite films exhibiting clear polarization-electric field hysteresis behavior are presented. The coercive field of this epitaxial Al0.7Sc0.3N film on the W/c-sapphire substrate is 0.4 ± 0.3 MV cm−1 (8%) smaller than that of a conventional fiber textured film on a Pt/TiOx/SiO2/Si substrate, attributed to the 0.01 ± 0.007 Å smaller c-axis lattice parameter in the epitaxial film. The strain and decrease in the coercive field most likely originate from epitaxial strain rather than the mismatch in the thermal coefficient of expansion. These results provide insight for further coercive field reduction of wurtzite ferroelectrics using epitaxial mismatch strain.

High-Temperature Ferroelectric Behavior of Al0.7Sc0.3N

“…While this high E c is problematic for integration with low−voltage devices, it can be valuable for retention characteristics as temperatures increase [8]. The E c of AlScN can be tuned through various modifications such as composition [14][15][16], stress [17], epitaxial alignment [18], and temperature [19][20][21][22]. In addition to thickness scaling, these trends are important for integrating AlScN into a high−temperature chip to reduce the operating voltages.…”

Synthesis of LaWN 3 nitride perovskite with polar symmetry

“…S10, E to H), but the results were inconclusive, suggesting the presence of defects at this larger scale. We also attempted macroscale electrical measurements for the samples with a narrow composition gradient and 100-μm-radius contacts ( 21 ), a process benchmarked by ferroelectric Al 1– x Sc x N thin films synthesized and characterized in our laboratory ( 23 ). We deposited these (111)-oriented perovskite films (fig.…”

“…Nitride perovskites may offer additional integration advantages compared with oxide perovskites on wurtzite nitrides. High-quality epitaxial layers of thermodynamically stable nitride perovskites (similar to oxide perovskites) would be easier to synthesize at high temperature than the recently reported metastable (Al,Sc)N wurtzite alloys with high (>30%) Sc content ( 23 , 25 ). Also, compared with oxide perovskites, nitride perovskites would be easier to integrate with GaN, similar to other nitride wurtzites.…”

Effect of Substrate-RF on Sub-200 nm Al0.7Sc0.3N Thin Films

“…While a few works addressed the latter issue [16,17], several groups demonstrated how it is possible to reduce the coercive field by acting on either the AlScN structure or on the experimental set-up. A higher Sc-content [10], higher crystallinity [18], the use of different substrates [19], and testing-temperature [20] have been proven to reduce the voltage needed to switch, while still maintaining large polarization values. Another effective tuning parameter is represented by the residual bulk stress on the film, which can be controlled though different process parameters, such as pressure, N 2 /Ar ratio, or substrate bias [21][22][23].…”