Multilevel Nonvolatile Ferroelectric Diode Employing HfZrO _<i>x</i> and Metal Oxynitride Semiconductor for Neuromorphic Computing

Metal oxide semiconductors (OSs) are now facing a new paradigm across wide research communities beyond the display industry. Despite the literature on ferroelectric thin-film transistors (FeTFTs) using fluorite-structured materials, the wide-bandgap nature and oxygen vacancy (VO) of OSs are challenges to realize high-performance FeTFTs. In this paper, a metal oxynitride semiconductor (ONS) featuring a narrow bandgap and VO tolerance was integrated with a HfZrOx (HZO) thin film. A two-terminal (2T) ferroelectric diode (FD) which does not require thin HZO and selector was fabricated, showing anticlockwise hysteresis with an on/off ratio of ∼5 × 104 and excellent uniformity. An HZO/ZnON FD exhibited polarization-dependent resistive switching, and multilevel nonvolatile characteristics were utilized for neuromorphic computing. This study investigates an HZO/ZnON ferroelectric device and its operation as an artificial synapse, which has rarely been reported so far.