Reducing the tunneling barrier thickness of bilayer ferroelectric tunnel junctions with metallic electrodes.

Ferroelectric tunnel junctions (FTJs) are non-volatile devices in which the read current is controlled by the polarisation state of a ferroelectric (FE) layer [1]. Bilayer FTJs based on hafnium zirconium oxide (HZO) and a dielectric layer (DE, here Al 2 O 3 ) on metallic electrodes show promise for embdedded Non-Volatile Memory and BEOL integration [2], [3]. However, the DE thickness impacts both the FTJ properties [4] and stability of the FE state [5]. Previous research indicated an optimal DE thickness of 2-3 nm [4], but this leads to a deleterious rapid polarisation loss [6]. Here, electrode work function (WF) engineering is presented as a suitable measure to reduce the tunneling barrier height, thus improving the current density of bilayer FTJs [7]. DE scaling is also proposed to retain high TER and $J_{on}-J_{off}$ at reduced operating voltages.