Carpentieri Luca, Mikolajick Thomas, Slesazeck Stefan
NaMLab gGmbH, 01187 Dresden, Germany.
Chair of Nanoelectronics, TU Dresden, 01187 Dresden, Germany.
ACS Appl Electron Mater. 2025 May 26;7(11):5008-5017. doi: 10.1021/acsaelm.5c00469. eCollection 2025 Jun 10.
This study investigates the effects of ferroelectric thickness scaling in a bilayer-structured ferroelectric tunnel junction. It was found that both the remnant polarization and the transport mechanisms exhibit a correlation with the thickness of the ferroelectric film. While variations in ferroelectric thickness influence the tunneling current in the Off state, the magnitude of the remnant polarization significantly affects the current during the On state. Considering that the On-Off ratio serves as an important figure of merit, an analysis of the optimal memory window is provided, accounting for the impact of reading voltage and cycling conditions. Moreover, investigation of the polarization decay observed at different delay times after the writing reveals the direct correlation between the depolarization field and thickness scaling. Retention studies further indicate that tunneling current decay induced greater vulnerability to the On state, primarily attributed to the asymmetry of the stack structure, which results in imperfect screening of polarization charges. Our investigation into the scaling of ferroelectric thickness emphasizes its critical importance by examining both ferroelectric properties and device performance. These findings indicate that the optimization of FTJ for low operation voltage, long data retention, and high on-current density necessitates a coordinated optimization of the layer stack structure, establishing a direct relationship crucial for the future development of hafnia-based FTJ devices.
本研究调查了双层结构铁电隧道结中铁电层厚度缩放的影响。研究发现，剩余极化和传输机制均与铁电薄膜的厚度相关。虽然铁电层厚度的变化会影响关态下的隧穿电流，但剩余极化的大小对开态下的电流有显著影响。鉴于开-关比是一个重要的品质因数，本文考虑了读取电压和循环条件的影响，提供了对最佳存储窗口的分析。此外，对写入后不同延迟时间观察到的极化衰减的研究揭示了去极化场与厚度缩放之间的直接相关性。保持性研究进一步表明，隧穿电流衰减导致开态更容易受到影响，这主要归因于堆叠结构的不对称性，导致极化电荷的屏蔽不完善。我们对铁电层厚度缩放的研究通过考察铁电性能和器件性能，强调了其至关重要性。这些发现表明，为了实现低工作电压、长数据保持时间和高开电流密度，对铁电隧道结进行优化需要对层堆叠结构进行协同优化，这对于基于氧化铪的铁电隧道结器件的未来发展建立了至关重要的直接关系。
