Ultrathin Al1−xScxN for Low‐Voltage‐Driven Ferroelectric‐Based Devices. Issue 1 (12th October 2022)

• Record Type: Journal Article
• Authors: Schönweger, Georg; Islam, Md Redwanul; Wolff, Niklas; Petraru, Adrian; Kienle, Lorenz; Kohlstedt, Hermann; Fichtner, Simon
• Is Part Of: Physica status solidi. Volume 17:Issue 1(2023)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2022-10-12
• Subjects: aluminum–scandium–nitride (Al1−xScxN) -- epitaxial growth -- ferroelectrics -- gallium nitride -- ultrathin; Solid state physics -- Periodicals; 530.4105
• DOI: 10.1002/pssr.202200312
• Languages: English
• ISSNs: 1862-6254

Abstract

Abstract : Thickness scaling of ferroelectricity in Al1− x Sc x N is a determining factor for its potential application in neuromorphic computing and memory devices. In this letter, ultrathin (10 nm) Al0.72 Sc0.28 N films that are ferroelectrically switchable at room temperature are reported on. All‐epitaxial Al0.72 Sc0.28 N/Pt heterostructures are grown by magnetron sputtering onto GaN/sapphire substrates followed by an in situ Pt capping approach to avoid oxidation of the Al0.72 Sc0.28 N film surface. Structural characterization by X‐Ray diffraction and transmission electron microscopy reveals the established epitaxy. The thus‐obtained high‐quality films in combination with in situ capping facilitate ferroelectric switching of Al1− x Sc x N in the ultrathin regime. The analysis of the relative permittivity and coercive field dependence on Al0.72 Sc0.28 N film thicknesses in the range from 100 nm down to 10 nm indicates only moderate scaling effects, suggesting that the critical thickness for ferroelectricity is not yet approached. Furthermore, the deposited layer stack demonstrates the possibility of including ultrathin ferroelectric Al1− x Sc x N into all‐epitaxial GaN‐based devices using sputter deposition techniques. Thus, the integration and scaling potential of all‐epitaxial ultrathin Al1− x Sc x N offering high storage density paired with low‐voltage operation desired for state‐of‐the‐art ferroelectric memory devices are highlighted. Abstract : The scalability of ferroelectric wurtzite‐type thin films down to 10 nm thickness is confirmed, based on epitaxial Al0.72 Sc0.28 N. The absence of major scaling effects in coercive field and permittivity promises the possibility of further miniaturization. This is an important step toward the utilization of the material class in highly integrated microelectronic devices.