Synergistic regulation of polarization intensity and coercive electric field in FeFETs: overcoming the trade-off between enhanced memory window and subthreshold swing degradation

Ferroelectric field-effect transistors (FeFETs), a type of ferroelectric memory with a transistor-based structure, have attracted significant attention from integrated circuit researchers due to their compact device architecture, non-destructive readout capability, and elimination of additional selector devices. These advantages make FeFETs highly promising for achieving higher storage density and enabling computing-in-memory applications. For their practical industrial deployment, extensive studies have been conducted on device fabrication, circuit design, and reliability. Among the key challenges, enlarging the memory window (MW) while maintaining stability is critical, as it directly affects data accuracy and retention. In this work, we experimentally investigate the modulation of the MW and interface defect density (Δ<i>N</i>_it) in Zr-doped HfO₂(HfZrO<i>_x</i>)-based FeFETs under different polarization states of the ferroelectric gate dielectric. The results demonstrate that with progressively enhanced ferroelectric polarization, the MW expands, while the interface trap density is simultaneously suppressed, suggesting that robust polarization effectively inhibits the formation of interface defects and improves subthreshold swing characteristics of the device. Furthermore, TCAD simulations were conducted to systematically investigate the impact of various ferroelectric properties, including remanent polarization (<i>P</i>_r), saturation polarization (<i>P</i>_s) and variations in coercive field (<i>E</i>_c), on the memory characteristics of HfZrO<i>_x</i>FeFETs. It was confirmed that higher polarization can alleviate the degradation caused by defects. In addition, an increase in<i>P</i>_rand<i>P</i>_s, together with a lower<i>E</i>_c, enhances the surface potential difference, charge separation, and switching efficiency, thereby improving both the MW and the stability of the device. This study provides valuable insights for the development of reliable FeFET-based memory technologies.