Digital and Analog Switching Characteristics of InGaZnO Memristor Depending on Top Electrode Material for Neuromorphic System

Abstract

In this study, we demonstrate both of digital and analog memory operations in InGaZnO (IGZO) memristor devices by controlling the electrode materials for neuromorphic application. The switching properties of the devices are determined by the initial energy barrier characteristics between the metal electrodes and the IGZO switching layer. Digital switching characteristics are obtained after the forming process when Schottky junction occurs at both of top and bottom electrodes. On the other hands, analog resistive switching is achieved when Schottky and Ohmic junctions exist at each side because the applied voltage modulates the Schottky barrier height through the Ohmic contact. In addition, the weightupdate properties of the devices are verified depending on identical and incremental pulse schemes. The incremental pulse trains improve the linearity and variation of weight modulation, leading to the stable learning characteristics of neuromorphic system in terms of pattern recognition with MNIST handwritten digit images.

Effect of the Gate Dielectric Layer of Flexible InGaZnO Synaptic Thin-Film Transistors on Learning Behavior

“…Here, the network is trained with the gradient descent algorithm assuming on-chip learning with the measured learning characteristics in Figure b,c. How large each weight should be updated (Δ W ) is determined by the weight-update model developed with the relation between the amount of weight change and current weight value . First, the nonlinear weight modulation with the pulse condition A significantly degrades the recognition rate (dotted lines) no matter which kind of device is used as a synaptic transistor.…”

“…How large each weight should be updated (ΔW) is determined by the weight-update model developed with the relation between the amount of weight change and current weight value. 52 First, the nonlinear weight modulation with the pulse condition A significantly degrades the recognition rate (dotted lines) no matter which kind of device is used as a synaptic transistor. Especially, the accuracy is not saturated at all after enough number of epochs with the pulse condition A.…”

Effect of Post-Annealing on Barrier Modulations in Pd/IGZO/SiO2/p+-Si Memristors

“…Oxidation and reduction reactions occur inside IGZO depending on the external bias, which changes the resistance of IGZO; thus, IGZO is used as a memory device by utilizing these characteristics [ 42 , 43 ]. In fact, there have already been studies on various memory devices using IGZO [ 44 , 45 , 46 , 47 , 48 , 49 ]. In particular, the p + Si-based IGZO memristors introduced in this paper show high retention and endurance characteristics.…”

Compact SPICE Model of Memristor with Barrier Modulated Considering Short- and Long-Term Memory Characteristics by IGZO Oxygen Content

“…Memristor can be a building block in neuromorphic systems by controlling conductance [ 7 , 8 , 9 , 10 , 11 , 12 , 13 ]. Various resistive switching behaviors are observed in a lot of materials, such as oxides, nitrides and other materials [ 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 ]. Among them, the indium gallium zinc oxide (IGZO)-based memristor is very promising for memory applications because of its interface-type switching and good compatibility with conventional Si processing [ 14 , 15 , 16 , 17 , 18 , 19 ].…”