Cycling Waveform Dependent Wake-Up and ON/OFF Ratio in Al2O3/Hf0.5Zr0.5O2 Ferroelectric Tunnel Junction Devices

Keerthana Shajil Nair; Marco Holzer; Catherine Dubourdieu; Veeresh Deshpande

doi:10.1021/acsaelm.2c01492

Cycling Waveform Dependent Wake-Up and ON/OFF Ratio in Al₂O₃/Hf_0.5Zr_0.5O₂ Ferroelectric Tunnel Junction Devices

ACS Appl Electron Mater. 2023 Mar 10;5(3):1478-1488. doi: 10.1021/acsaelm.2c01492. eCollection 2023 Mar 28.

Authors

Keerthana Shajil Nair^{1

2}, Marco Holzer^{1

2}, Catherine Dubourdieu^{1

2}, Veeresh Deshpande¹

Affiliations

¹ Helmholtz-Zentrum-Berlin für Materialien und Energie, Institute "Functional Oxides for Energy Efficient Information Technology", Hahn-Meitner Platz 1, 14109 Berlin, Germany.
² Physical Chemistry, Freie Universität Berlin, Arnimallee 22, 14195 Berlin, Germany.

Abstract

The wake-up behavior and ON/OFF current ratio of TiN-Al₂O₃-Hf_0.5Zr_0.5O₂-W ferroelectric tunnel junction (FTJ) devices were investigated for different wake-up voltage waveforms. We studied triangular and square waves, as well as square pulse trains of equal or unequal voltage amplitudes for positive and negative polarities. We find that the wake-up behavior in these FTJ stacks is highly influenced by the field cycling waveform. A square waveform is observed to provide wake-up with the lowest number of cycles, concomitantly resulting in higher remnant polarization and a higher ON/OFF ratio in the devices, compared to a triangular waveform. We further show that wake-up is dependent on the number of cycles rather than the total time of the applied electric field during cycling. We also demonstrate that different voltage magnitudes are necessary for positive and negative polarities during field cycling for efficient wake-up. Utilizing an optimized waveform with unequal magnitudes for the two polarities during field cycling, we achieve a reduction in wake-up cycles and a large enhancement of the ON/OFF ratio from ∼5 to ∼35 in our ferroelectric tunnel junctions.