The graphene intercalation in realizing giant tunneling electroresistance in HfO2 ferroelectric tunnel junctions

Abstract

Hafnia-based ferroelectric tunnel junctions (FTJs) have recently aroused significant interest due to their compatibility with complementary metal-oxide-semiconductor processes, as well as their potential applications in non-volatile memory and neuromorphic computing. However, the application of HfO2 FTJs is limited by its low tunnel electroresistance (TER) ratio and low ON-state current. In this work, we propose to embed a single layer graphene between the ferroelectric (FE) HfO2 and metal electrode to improve the device performance. Graphene has a low quantum capacitance and is beneficial for modulating metal-induced gap states at the metal–FE interface. Density functional theory calculations show that graphene can greatly change the interfacial charge distribution and inhabit the Fermi pinning effect. Therefore, the tunneling barrier height can be effectively modulated by the ferroelectric switching in FTJs with a graphene intermediate layer. First-principles quantum transport calculations show that the TERs are significantly improved and exceed 106% in FTJs with 3.5 nm Hf-terminated HfO2. At the same time, ON-state current is increased by 104 times due to the reduced tunneling barrier.