Author(s) Ryu, H.; Wu, H.; Rao, F.; Zhu, W.
Journal Sci Rep
Date Published 2019 Dec 31

Ferroelectric tunneling junctions (FTJs) with tunable tunneling electroresistance (TER) are promising for many emerging applications, including non-volatile memories and neurosynaptic computing. One of the key challenges in FTJs is the balance between the polarization value and the tunneling current. In order to achieve a sizable on-current, the thickness of the ferroelectric layer needs to be scaled down below 5 nm. However, the polarization in these ultra-thin ferroelectric layers is very small, which leads to a low tunneling electroresistance (TER) ratio. In this paper, we propose and demonstrate a new type of FTJ based on metal/AlO/Zr-doped HfO/Si structure. The interfacial AlO layer and silicon substrate enable sizable TERs even when the thickness of Zr-doped HfO (HZO) is above 10 nm. We found that F-N tunneling dominates at read voltages and that the polarization switching in HZO can alter the effective tunneling barrier height and tune the tunneling resistance. The FTJ synapses based on AlO/HZO stacks show symmetric potentiation/depression characteristics and widely tunable conductance. We also show that spike-timing-dependent plasticity (STDP) can be harnessed from HZO based FTJs. These novel FTJs will have high potential in non-volatile memories and neural network applications.

DOI 10.1038/s41598-019-56816-x
ISSN 2045-2322
Citation Sci Rep. 2019;9(1):20383.

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