Search query: Ferroelectric tunnel junction

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abstract: Hafnia ferroelectric materials have gained prominence as promising materials for advanced memory applications due to their high scalability and full complementary metal oxide semiconductor compatibility. In this paper, we present a comprehensive study on the electrical properties of Pt/Hf0.5Zr0.5O2/TiN asymmetric ferroelectric tunnel junction (FTJ) devices. The ferroelectric behavior of 4 and 5 nm Hf0.5Zr0.5O2 (HZO) thin films was confirmed by using piezoresponse force microscopy and conductive atomic force microscopy. The typical current voltage characteristics of the FTJ devices with two resistance states due to the tunneling electroresistance (TER) effect have been analyzed using a direct tunneling model based on the Wentzel Kramers Brillouin approximation. Further, we have proposed a method to extract the effective mass of the HZO thin film by numerical analysis using the MOS leakage current model. Finally, a dependence of the TER on the HZO thickness is analyzed to realize a high TER ratio.Hafnia ferroelectric materials have gained prominence as promising materials for advanced memory applications due to their high scalability and full complementary metal oxide semiconductor compatibility. In this paper, we present a comprehensive study on the electrical properties of Pt/Hf0.5Zr0.5O2/TiN asymmetric ferroelectric tunnel junction (FTJ) devices. The ferroelectric behavior of 4 and 5 nm Hf0.5Zr0.5O2 (HZO) thin films was confirmed by using piezoresponse force microscopy and conductive atomic force microscopy. The typical current voltage characteristics of the FTJ devices with two resistance states due to the tunneling electroresistance (TER) effect have been analyzed using a direct tunneling model based on the Wentzel Kramers Brillouin approximation. Further, we have proposed a method to extract the effective mass of the HZO thin film by numerical analysis using the MOS leakage current model. Finally, a dependence of the TER on the HZO thickness is analyzed to realize a high TER ratio.
author_names: Jung Ho Yoon

Seung Hoon Hong

Yong Won Song

Ji-Hoon Ahn

Seung-Eon Ahn
title: Understanding tunneling electroresistance effect through potential profile in Pt/Hf0.5Zr0.5O2/TiN ferroelectric tunnel junction memory
venue: Applied Physics Letters
year: 2019

abstract: This paper presents a unique opportunity of HZO ferroelectric tunnel junction (FTJ) for in memory computing. The device operates at an extremely low sub nA current while simultaneously achieving 50 ns fast switching, 107 cycling endurance, 10 yr retention, minimal variability, and analog state modulation. We analyze an FTJ based deep binary neural network. It achieves better accuracy and remarkable 702, 101, and 7x104 times improvements in power, area, and energy area product efficiency compared with those using NVMs with a typical mA cell current designed for fast memory access.
author_names: Tzu-Yun Wu

Tian-Sheuan Chang

Heng-Yuan Lee

Shyh-Shyuan Sheu

Wei-Chung Lo

Tuo-Hung Hou

Hsin-Hui Huang

Yueh-Hua Chu

Chih-Cheng Chang

Ming-Hung Wu

Chien-Hua Hsu

Chien Ting Wu

Min-Ci Wu

Wen-Wei Wu
title: Sub nA Low Current HZO Ferroelectric Tunnel Junction for High Performance and Accurate Deep Learning Acceleration
venue: 2019 IEEE International Electron Devices Meeting (IEDM)
year: 2019

abstract: Ferroelectric tunnel junctions (FTJs) composed by sandwiching a thin ferroelectric layer between two leads have attracted great interest for their potential applications in nonvolatile memories due to the tunnel electroresistance (TER) effect. So far, almost all FTJs studied focus on adopting three dimensional (3D) ferroelectric materials as the tunnel barrier. Recently, many two dimensional (2D) ferroelectric materials with in plane or out of plane spontaneous polarization have been theoretically proposed or even fabricated, providing a new type of candidate as the tunnel barrier in FTJs. However, very little has been known about whether such 2D ferroelectric materials may lead to an excellent TER effect. In this work, using first principles calculations, we demonstrate that a giant TER effect of around 623% which is comparable to 3D FTJs, can be realized through the ferroelectric tunnel junction constructed with the 2D ferroelectric materials BiP and B/N doped graphene. The analysis of the effective potential and electronic structure indicates that the large TER ratio arises from the unsymmetrical screening effects of the B/N doped vertical van der Waals graphene/BiP leads. Our findings demonstrate the great potential of novel application of 2D ferroelectric BiP in FTJs.
author_names: Lili Kang

Peng Jiang

Ning Cao

Hua Hao

Xiaohong Zheng

Lei Zhang

Zhi Zeng
title: Realizing giant tunneling electroresistance in two dimensional graphene/BiP ferroelectric tunnel junction.
venue: Nanoscale
year: 2019

abstract: Abstract This paper proposes a device incorporating ferroelectric tunnel junction which analyzes the concept of tunneling across a silicon doped hafnium oxide ferroelectric. Variation of electrical parameters with ferroelectric thickness has been examined. Subthreshold swing (SS) of 40 mV/dec has been achieved with ferroelectric thickness of 2 nm. An increasing trend in the ION/IOFF ratio is observed with the increase in ferroelectric thickness. Moreover, the impact of temperature (300 K 500 K) on drain current as well as various RF parameter performance such as gate capacitance (CGG) transconductance (gm) output conductance (gd) intrinsic delay, intrinsic gain (gm/gd) cut off frequency (ft) and transconductance frequency product (TFP) has been studied.
author_names: Pujarini Ghosh

Rupam Goswami

Brinda Bhowmick
title: Optimization of ferroelectric tunnel junction TFET in presence of temperature and its RF analysis
venue: Microelectron. J.
year: 2019

abstract: Abstract The ferroelectric tunnel junction represents a memory concept that allows a nondestructive readout by utilizing a very thin ferroelectric film between two metal electrodes. Application of an electric field across the thin ferroelectric changes the polarization orientation and an accompanying modulation of the barrier height of the stack, which alters the tunneling current. For a long time, this concept was neglected due to the expected difficulties using common perovskite ferroelectrics and epitaxy for depositing such a thin layer while maintaining high ferroelectric properties. The discovery of ferroelectricity in the hafnium oxide system represents a game changer. In this chapter, the crucial design parameters are discussed that have to be considered for controlling the current transport, reducing the depolarization field, and finally optimizing the tunneling electroresistance effect.
author_names: Shosuke Fujii

Masumi Saitoh
title: Ferroelectric Tunnel Junction
year: 2019

abstract: Ferroelectric tunnel junction (FTJ) is a promising low power nonvolatile memory for beyond CMOS applications. In this paper, Co/BaTiO3/SrRuO3 FTJs are fabricated, simulated, and their electrical characteristics are measured by capacitance voltage {C} {V} current voltage {I} {V} and high frequency S parameter measurements. Ferroelectricity of the ultrathin BaTiO3 ~3.2 nm) film is first verified by a butterfly shaped hysteresis {C} {V} profile, from which saturation polarizations are calculated in the ON state and OFF state as {P}_{ \mathrm{ON} {20}\mu {C} \text{cm} {2} and {P}_{ \mathrm{OFF} {25}\mu {C}\text{cm} {2} respectively. The numerical simulation of the FTJ device is performed using experimental electronic band parameters of the heterostructure. The device structure was optimized for ON/OFF ratio, {I}_{ \mathrm{ON} {I}_{ \mathrm{OFF} {75} for a depolarization field, {E}_{{dpol} The calculated tunnel currents of {250}{nm}\times {250}{nm} FTJ in ON state {I}_{ \mathrm{ON} {250}\times {250} {250}{A} and OFF state {I}_{{OFF}{1.75}\times {250} 9}{A} match with experimental values. From the S parameters of RF measurements, the high frequency small signal device model of the FTJ in ON state {C}_{ \mathrm{ON} {250}{fF}{R}_{ \mathrm{ON}{0.8}{M}\Omega$ and OFF state {C}_{ \mathrm{OFF} {250}{fF}{R}_{ \mathrm{OFF} {250}{M}\Omega$ is developed for a frequency range from 50 MHz to 5 GHz. The extracted capacitor model of Co/BaTiO3/SrRuO3 FTJ is useful for high frequency simulation of benchmark FTJ circuits.
author_names: Mohammad Abuwasib

Hyungwoo Lee

Jung-Woo Lee

C B Eom

Alexei Gruverman

Uttam Singisetti
title: Characterization and Modeling of Co/BaTiO3/SrRuO3 Ferroelectric Tunnel Junction Memory by Capacitance Voltage {C} {V} Current Voltage {I} {V} and High Frequency Measurements
venue: IEEE Transactions on Electron Devices
year: 2019

abstract: Resistive switching (RS) devices have attracted increasing attention for artificial synapse applications in neural networks because of their nonvolatile and analogue resistance changes. Among the neural networks, a spiking neural network (SNN) based on spike timing dependent plasticity (STDP) is highly energy efficient. To implement STDP in resistive switching devices, several types of voltage spikes have been proposed to date, but there have been few reports on the relationship between the STDP characteristics and spike types. Here, we report the STDP characteristics implemented in ferroelectric tunnel junctions (FTJs) by several types of spikes. Based on simulated time evolutions of superimposed spikes and taking the nonlinear current voltage (I V) characteristics of FTJs into account, we propose equations for simulating the STDP curve parameters of a magnitude of the conductance change (DG max) and a time window (tC) from the spike parameters of a peak amplitude (V peak) and time durations (t p and t d) for three spike types: triangle triangle, rectangular triangle, and rectangular rectangular. The power consumption experiments of the STDP revealed that the power consumption under the inactive synapse condition (spike timing |Dt| tC) was as large as 50 82% of that under the active synapse condition |Dt| tC) This finding indicates that the power consumption under the inactive synapse condition should be reduced to minimize the total power consumption of an SNN implemented by using FTJs as synapses.
author_names: P Stoliar

H Yamada

Yoshikiyo Toyosaki

Akihito Sawa
title: Spike shape dependence of the spike timing dependent synaptic plasticity in ferroelectric tunnel junction synapses
venue: Scientific Reports
year: 2019

abstract: Ferroelectric tunnel junction (FTJ) is a promising low power nonvolatile memory for beyond CMOS applications. In this paper, Co/BaTiO<sub>3</sub>/SrRuO<sub>3</sub> FTJs are fabricated, simulated, and their electrical characteristics are measured by capacitance voltage <inline formula> <tex math notation="LaTeX"{C} /tex math>/inline formula> <inline formula> <tex math notation="LaTeX"{V} /tex math>/inline formula> current voltage <inline formula> <tex math notation="LaTeX"{I} /tex math>/inline formula> <inline formula> <tex math notation="LaTeX"{V} /tex math>/inline formula> and high frequency S parameter measurements. Ferroelectricity of the ultrathin BaTiO<sub>3</sub> ~3.2 nm) film is first verified by a butterfly shaped hysteresis <inline formula> <tex math notation="LaTeX"{C} /tex math>/inline formula> <inline formula> <tex math notation="LaTeX"{V} /tex math>/inline formula> profile, from which saturation polarizations are calculated in the ON state and OFF state as <inline formula> <tex math notation="LaTeX"{P}_{ \mathrm{ON} {20}\mu {C} \text{cm} {2} /tex math>/inline formula> and <inline formula> <tex math notation="LaTeX"{P}_{ \mathrm{OFF} {25}\mu {C}\text{cm} {2} /tex math>/inline formula> respectively. The numerical simulation of the FTJ device is performed using experimental electronic band parameters of the heterostructure. The device structure was optimized for ON/OFF ratio, <inline formula> <tex math notation="LaTeX"{I}_{ \mathrm{ON} {I}_{ \mathrm{OFF} {75} /tex math>/inline formula> for a depolarization field, <inline formula> <tex math notation="LaTeX"{E}_{{dpol} {10} {6}{V} \text{cm} /tex math>/inline formula> The calculated tunnel currents of <inline formula> <tex math notation="LaTeX" {250}{nm}\times {250}{nm} /tex math>/inline formula> FTJ in ON state <inline formula> <tex math notation="LaTeX"{I}_{ \mathrm{ON} {250}\times {250} {250}{A} /tex math>/inline formula> and OFF state <inline formula> <tex math notation="LaTeX"{I}_{{OFF}{1.75}\times {250} 9}{A} /tex math>/inline formula> match with experimental values. From the S parameters of RF measurements, the high frequency small signal device model of the FTJ in ON state <inline formula> <tex math notation="LaTeX"{C}_{ \mathrm{ON} {250}{fF}{R}_{ \mathrm{ON}{0.8}{M}\Omega$ /tex math>/inline formula> and OFF state <inline formula> <tex math notation="LaTeX"{C}_{ \mathrm{OFF} {250}{fF}{R}_{ \mathrm{OFF} {250}{M}\Omega$ /tex math>/inline formula> is developed for a frequency range from 50 MHz to 5 GHz. The extracted capacitor model of Co/BaTiO<sub>3</sub>/SrRuO<sub>3</sub> FTJ is useful for high frequency simulation of benchmark FTJ circuits.
author_names: Mohammad Abuwasib

Hyungwoo Lee

Jung-Woo Lee

C B Eom

Alexei Gruverman

Uttam Singisetti
title: Characterization and Modeling of Co/BaTiO3/SrRuO3 Ferroelectric Tunnel Junction Memory by Capacitance Voltage {C} {V} Current
venue: IEEE Transactions on Electron Devices
year: 2019

abstract: Abstract We report successful synthesis of superconducting Bi Sr Ca Cu2 OX (BSCCO) target for fabrication of heterostructure thin films. For the first time, we have grown LSMO (50 nm)/PZT (5 nm)/BSCCO (100 nm)/LAO (100) heterostructure by pulsed laser deposition technique to understand the tunneling effect and role of the superconducting electrode on transport and magnetic properties. The bulk superconductor Bi Sr Ca Cu2 OX (BSCCO) and heterostructure shows superconducting phase transition near 92 K and 110 K, respectively. Magnetic susceptibility data indicate large negative susceptibility below 110 K which confirms the superconducting nature of heterostructure bottom electrode. A large hysteresis in current voltage data has been obtained at 78 K below the superconducting state of bottom electrode. These results suggest that the ferromagnetic/ferroelectric/superconductor tunnel structure may provide four distinct resistance states depending on the direction of ferroelectric polarization.
author_names: V N Ojha

Ashok Kumar
title: Fabrication of ferroelectric tunnel junction using superconducting and magnetic electrodes
year: 2019

abstract: Brain inspired neuromorphic computing has shown great promise beyond the conventional Boolean logic. Nanoscale electronic synapses, which have stringent demands for integration density, dynamic range, energy consumption, etc. are key computational elements of the brain inspired neuromorphic system. Ferroelectric tunneling junctions have been shown to be ideal candidates to realize the functions of electronic synapses due to their ultra low energy consumption and the nature of ferroelectric tunneling. Here, we report a new electronic synapse based on a three dimensional vertical Hf0.5Zr0.5O2 based ferroelectric tunneling junction that meets the full functions of biological synapses. The fabricated three dimensional vertical ferroelectric tunneling junction synapse (FTJS) exhibits high integration density and excellent performances, such as analog like conductance transition under a training scheme, low energy consumption of synaptic weight update (1.8 pJ per spike) and good repeatability >103 cycles) In addition, the implementation of pattern training in hardware with strong tolerance to input faults and variations is also illustrated in the 3D vertical FTJS array. Furthermore, pattern classification and recognition are achieved, and these results demonstrate that the Hf0.5Zr0.5O2 based FTJS has high potential to be an ideal electronic component for neuromorphic system applications.
author_names: Lin Chen

Tian-Yu Wang

Ya-Wei Dai

Ming-Yang Cha

Hao Zhu

Qingqing Sun

S J Ding

Peng Zhou

Leon Ong Chua

David-Wei Zhang
title: Ultra low power Hf0.5Zr0.5O2 based ferroelectric tunnel junction synapses for hardware neural network applications.
venue: Nanoscale
year: 2018