Built‐in bias fields for retention stabilisation in hafnia‐based ferroelectric tunnel junctions. Issue 21 (7th September 2020)

• Record Type: Journal Article
• Authors: Max, B.; Hoffmann, M.; Slesazeck, S.; Mikolajick, T.
• Is Part Of: Electronics letters. Volume 56:Issue 21(2020)
• Page Start: 1108
• Page End: 1110
• Publication Date: 2020-09-07
• Subjects: zirconium compounds -- work function -- dielectric polarisation -- hafnium compounds -- dielectric hysteresis -- tunnelling -- aluminium compounds -- dielectric depolarisation -- electric domains -- ferroelectricity; symmetric metal electrode structure -- built‐in bias fields -- retention stabilisation -- hafnia‐based ferroelectric tunnel junctions -- double‐layered ferroelectric tunnel junctions -- ferroelectric hafnium zirconium oxide -- memory layer -- dielectric aluminium oxide -- tunnelling barrier -- unscreened polarisation charges -- retention behaviour -- ferroelectric domains -- diminishing memory window -- work function -- polarisation hysteresis curve -- electric depolarisation field -- back‐switching -- titanium nitride -- on‐current -- off‐current degradation -- HfZrO -- AlO; Electronics -- Periodicals; 621.381
• DOI: 10.1049/el.2020.1529
• Languages: English
• ISSNs: 0013-5194

Abstract

Abstract : Ferroelectric tunnel junctions have recently attracted a lot of research interest, not only for memory operation but also for e.g. neuromorphic computing. Retention characteristics of these devices are of utmost importance in many applications. The authors have recently demonstrated the feasibility of double‐layered ferroelectric tunnel junctions where the ferroelectric hafnium zirconium oxide acts as the memory layer and the dielectric aluminium oxide as the tunnelling barrier. The depolarisation field from the unscreened polarisation charges that is introduced by this structure causes serious limitations on the retention behaviour due to the unintentional back‐switching of ferroelectric domains. This leads to a diminishing memory window over time. By using a built‐in bias field from different work function metal electrodes, in this case platinum and titanium nitride with 0.85 eV difference, one can shift the polarisation hysteresis curve and counteract the electric depolarisation field. This leads to a more stable on‐current over time while only marginally increasing the off‐current degradation. Extrapolation to ten years shows a much larger memory window compared to the symmetric metal electrode structure.