Tailored Polarization with an Invariant Coercive Field in Al_0.7Sc_0.3N Thin Films via Deposition Pressure Engineering

Ferroelectric Al_1-x Sc _x N thin films are considered promising materials for ferroelectric field-effect transistors, as their exceptionally high coercive field (3-5 MV/cm) enables a sufficiently wide memory window. However, their notably large remanent polarization (∼100 μC/cm²) can degrade retention characteristics, necessitating effective modulation. Herein, we demonstrate a decoupling strategy that gradually reduces the remanent polarization while preserving the coercive field by employing a bilayer Al_0.7Sc_0.3N structure composed of layers deposited at 6.8 and 30 mTorr. As the fraction of the film deposited at 6.8 mTorr decreases from 100% to 50%, the remanent polarization decreases from approximately 97 to 54 μC/cm², whereas the coercive field remains nearly unchanged at around 3.9 MV/cm. In addition, despite the reduction in polarization, the characteristic switching time and its homogeneity were maintained. This study demonstrates an effective pathway for achieving the decoupling of remnant polarization and coercive field in Al_1-x Sc _x N thin films, offering significant potential for ferroelectric field-effect transistors.