The effects of field cycling of Al0.78Sc0.22N capacitors to ferroelectric poperties are investigated. In the first hundreds of switching cycles, the reduction in the switching voltage was observed, possibly due to the formation of nitrogen vacancy to facilitate the atom displacements. With futher switching cycles, fatigue effect was observed, especially for domains with low switching voltage. The leakage current analysis indicates continuous downward band bending with the number of switching cycles, effectively reducing the Schottky barrier heigh for electron. The breakdown of Al0.78Sc0.22N films is triggered by the Joule heat due to excessive leakage current. The mechanism is in contrast to conventional ferroelectric materials, where breakdown is triggred by local conductive filametns.

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Leakage current analysis on 50 nm thick ferroelectric Al0.78Sc0.22N films with TiN electrodes has been performed. The electron conduction followed Schottky emission with an initial Schottky barrier height (ϕ B) of 0.46 eV. During the initial switching, a gradual shift in the leakage current was observed, changing the ϕ B to 0.36 eV, and stayed constant for further switching cycles. From the extracted Richardson constant, the change in the ϕ B can be interpreted as the formation of a tunneling barrier due to the formation of nitrogen vacancies at the metal interface.

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