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

Abstract

This study examines systematic oxygen (O)-incorporation to reduce total leakage currents in sputtered wurtzite-type ferroelectric Al_0.73Sc_0.27N thin films, along with its impact on the material structure and the polarity of the as-grown films. The O in the bulk Al_0.73Sc_0.27N 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 Al_0.73Sc_0.27N. 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 Al_0.73Sc_0.27N 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 Al_0.73Sc_0.27N without incurring any significant structural degradation of the bulk thin film, thereby making ferroelectric nitrides more suitable for microelectronic applications.