Cu-ion-actuated three-terminal neuromorphic synaptic devices based on binary metal-oxide electrolyte and channel

Abstract

An analogous change in lateral channel current from source to drain in three-terminal synaptic devices actuated by mobile ions vertically provided from a gate can enhance neuromorphic computing performances. We demonstrate a gradually tuned channel current in a fully complementary metal–oxide–semiconductor compatible HfOx/WOx stack with Cu ions. By examining each layer in the three-terminal device, such as the channel, electrolyte, and mobile ion supplier, we identify which device structure can modulate the channel current effectively using mobile ions. Our findings reveal that the gate-tunable channel current response can be solely achieved when the Cu ions are not locally formed but migrate throughout the HfOx electrolyte. The linear dependence of the analog current operation on the channel width further proves the area-switching mechanism. The importance of ion movement can be indirectly verified from the uncontrollable channel currents using either Ag ions with faster mobility than Cu ions or a local path is created because of the thinned HfOx electrolyte.

Ion-Driven Electrochemical Random-Access Memory-Based Synaptic Devices for Neuromorphic Computing Systems: A Mini-Review

“…Recently, analog switching was demonstrated in a fully CMOS-compatible stack with a Cu gate electrode/HfO x electrolyte/WO x channel structure [ 19 ], as shown in Figure 8 . It is believed that the valence change of the W atom at the channel with respect to Cu ions as a dopant was involved.…”

“… Synaptic responses of ( a ) classical RRAM [ 12 ], ( b ) analog RRAM [ 12 ], and ( c ) ECRAM [ 19 ]. The first row shows the schematic diagram of each device.…”

“…The uniformly increased channel current can be achieved by the stoichiometry of the channel material. The magnitude of the current increase is adjusted by the gate voltage amplitude [ 19 ]. Copyright AIP, 2021.…”

“… Area-scalable synaptic response. As the width of the channel is expanded, the channel current becomes proportionally larger [ 19 ]. Copyright AIP, 2021.…”

“…Li-ion-incorporating channel and electrolyte materials, such as lithium phosphorus oxynitride (LiPON), were used. However, considering CMOS compatibility, new mobile ions, such as oxygen ions (or vacancies) [ 18 ] and Cu ions [ 19 ], have been studied. Considering recent advancements of the ECRAM, in this study, the progress and prospect of each type of ECRAM classified according to the use of mobile ions were discussed.…”