Abstract
This work demonstrates the synaptic properties of the alloy-type resistive random-access memory (RRAM). We fabricated the HfAlOx-based RRAM for a synaptic device in a neuromorphic system. The deposition of the HfAlOx film on the silicon substrate was verified by X-ray photoelectron spectroscopy (XPS) analysis. It was found that both abrupt and gradual resistive switching could be implemented, depending on the reset stop voltage. In the reset process, the current gradually decreased at weak voltage, and at strong voltage, it tended to decrease rapidly by Joule heating. The type of switching determined by the first reset process was subsequently demonstrated to be stable switching by successive set and reset processes. A gradual switching type has a much smaller on/off window than abrupt switching. In addition, retention maintained stability up to 2000 s in both switching cases. Next, the multiple current states were tested in the gradual switching case by identical pulses. Finally, we demonstrated the potentiation and depression of the Cu/HfAlOx/Si device as a synapse in an artificial neural network and confirmed that gradual resistive switching was suitable for artificial synapses, using neuromorphic system simulation.
Highlights
In the rapidly increasing number of server computers and Internet of Things (IoT) era, there is a demand for the development of higher capacity and faster memory than the conventional memory, such as flash memory [1]
Low-resistance state (LRS) and high-resistance state (HRS) can be converted according to the applied voltage, and the state, once stored, has a nonvolatile characteristic that is maintained over time [4,5,6,7]
The reset process occurs by Joule heating and it is accompanied by high current
Summary
In the rapidly increasing number of server computers and Internet of Things (IoT) era, there is a demand for the development of higher capacity and faster memory than the conventional memory, such as flash memory [1]. The conductivity changes as the oxygen increases or decreases for the intrinsic switching in the oxide In this case, a non-active metal is used for the top and bottom electrodes. The resistive switching occurs by the creation and rupture of a metallic filament when using the metal electrodes with high diffusion ability to the dielectric. These electrochemical metallization effects are commonly observed when using Cu and Ag electrodes [16]. This kind of resistive memory has a fast switching speed but shows low endurance. A bidirectional selector element is needed for each memory cell in a crossbar array to reduce the sneak current path [28]
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