Oxygen Doping in Ferroelectric Wurtzite‐type Al0.73Sc0.27N: Improved Leakage and Polarity Control

This study examines systematic oxygen (O)‐incorporation to reduce total leakage currents in sputtered wurtzite‐type ferroelectric Al0.73Sc0.27N thin films, along with its impact on the material structure and the polarity of the as‐grown films. The O in the bulk Al0.73Sc0.27N was introduced through an external gas source during the reactive sputter process. In comparison to samples without doping, O‐doped films showed almost a fourfold reduction of the overall leakage current near the coercive field. In addition, doping resulted in the reduction of the steady‐state leakage currents by roughly one order of magnitude at sub‐coercive fields. The microstructure analysis through X‐ray diffraction (XRD) and scanning transmission electron microscopy (STEM) indicated no notable structural degradation in the bulk Al0.73Sc0.27N. The maximum O‐doped film exhibited a c‐axis out‐of‐plane texture increase of only 20%, rising from 1.8°, while chemical mapping indicated a consistent distribution of O throughout the bulk. Our results further demonstrate the ability to control the as‐deposited polarity of Al0.73Sc0.27N via the O‐concentration, changing from nitrogen (N)‐ to metal (M)‐polar orientation. Thus, this article presents a promising approach to mitigate the leakage current in wurtzite‐type Al0.73Sc0.27N without incurring any significant structural degradation of the bulk thin film, thereby making ferroelectric nitrides more suitable for microelectronic applications.