On the strong coupling of polarization and charge trapping in HfO2/Si-based ferroelectric field-effect transistors: overview of device operation and reliability

Abstract

Ferroelectric field-effect transistors (FeFETs) have become an attractive technology for memory and emerging applications on a silicon electronic platform after the discovery of the ferroelectric phase in silicon-friendly hafnium oxide insulators. In this tutorial, we review one nonideal physical phenomenon that determines the device operation of practical FeFETs based on ferroelectric hafnium oxide (FE-HfO2) insulators and silicon channels: polarization-induced electron trapping. The ferroelectric polarization in FE-HfO2 induces an enormous amount of trapped electron density of an order of 1014 cm−2 near the interface between the FE-HfO2 and interfacial layer, which in turn screens the electric flux from polarization. We examine how electron trapping affects the device operation particularly the polarization switching mechanism, retention characteristics, endurance characteristics, and read-after-write delay. The asymmetric behavior of electron and hole trapping in FeFETs and its impact on the device operation are also discussed. We review several approaches based on different operations, device structure modification, and material engineering to mitigate anomalous electron trapping and improve the device characteristics of FeFETs.