Ferroelectric aluminum−scandium nitride by plasma-enhanced atomic layer deposition under ultrahigh purity conditions

Wurtzite aluminum–scandium nitride thin films hold strong potential for future electronic and sensing technologies. However, achieving precise control and uniform coverage across complex three-dimensional architectures remains challenging. Here, we demonstrate aluminum–scandium nitride growth by plasma-enhanced atomic layer deposition, a layer-by-layer technique that provides atomic-scale control over film thickness, composition and structure. Films grown on {111}-oriented platinum exhibit clear ferroelectric switching, with coercive fields as low as ±3.3 MV cm⁻¹. They align exclusively along the c-axis, indicating high structural order even on the sidewalls of three-dimensional features. When deposited on single-crystal gallium nitride, the films adopt a highly ordered arrangement both in and out of the surface plane, consistent with epitaxial growth. Imaging of films deposited over narrow trenches further confirms uniform, conformal coating of three-dimensional structures. Together, these results demonstrate that this growth method yields high-quality aluminum–scandium nitride films suitable for advanced three-dimensional electronic and sensing applications.