Unveiling Ferroelectric HZO Cryogenic Performance (4–300 K): Kinetic Barrier Engineering and Underlying Mechanism

In this work, we perform comprehensive and in-depth investigation of the cryogenic characteristics of ferroelectric (FE) hafnium zirconium oxide (HZO) thin films with varying thicknesses (3/5/7/10 nm) across a broad temperature range (<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$4\sim 300$ </tex-math></inline-formula> K), assisted by the extensive material and electrical characterizations. We discover: 1) 3 and 5 nm HZO films exhibit distinct temperature dependence in remnant polarization (<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${P} _{\text {r}}$ </tex-math></inline-formula>) and coercive field (<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${E} _{\text {c}}$ </tex-math></inline-formula>) as compared with 7 and 10 nm ones owing to different phase transition mechanisms and 2) the concentration and location of oxygen vacancies act as pivotal factors influencing the pinning effect as well as the trap-assisted-tunneling process, thereby affecting the temperature-dependent behaviors of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${P} _{\text {r}}$ </tex-math></inline-formula> and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${E} _{\text {c}}$ </tex-math></inline-formula>. Building upon these insights, we propose and experimentally demonstrate an innovative cryogenic barrier engineering approach for <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${P}_{\text {r}}$ </tex-math></inline-formula> enhancement, particularly valuable for ultra-thin HZO films.