Abstract
The transport and synaptic characteristics of the two-terminal Au/Ti/ amorphous Indium-Gallium-Zinc-Oxide (a-IGZO)/thin SiO2/p+-Si memristors based on the modulation of the Schottky barrier (SB) between the resistive switching (RS) oxide layer and the metal electrodes are investigated by modulating the oxygen content in the a-IGZO film with the emphasis on the mechanism that determines the boundary of the abrupt/gradual RS. It is found that a bimodal distribution of the effective SB height (ΦB) results from further reducing the top electrode voltage (VTE)-dependent Fermi-level (EF) followed by the generation of ionized oxygen vacancies (VO2+s). Based on the proposed model, the influences of the readout voltage, the oxygen content, the number of consecutive VTE sweeps on ΦB, and the memristor current are explained. In particular, the process of VO2+ generation followed by the ΦB lowering is gradual because increasing the VTE-dependent EF lowering followed by the VO2+ generation is self-limited by increasing the electron concentration-dependent EF heightening. Furthermore, we propose three operation regimes: the readout, the potentiation in gradual RS, and the abrupt RS. Our results prove that the Au/Ti/a-IGZO/SiO2/p+-Si memristors are promising for the monolithic integration of neuromorphic computing systems because the boundary between the gradual and abrupt RS can be controlled by modulating the SiO2 thickness and IGZO work function.
Highlights
The electronic computing systems developed so far have been structured on the von Neumann architecture in which the memory, the processor, and the controller exist separately, and the sequential processing among them embodies specific functions within the programmed software
Our results prove that the Au/Ti/amorphous Indium-Gallium-Zinc-Oxide (a-IGZO)/SiO2 /p+ -Si memristors are promising for the monolithic integration of neuromorphic computing systems because the boundary between the gradual and abrupt resistive switching (RS) can be controlled by modulating the SiO2 thickness and IGZO
Most of the digital and analog circuits included in the memory and processing units are composed of complementary metal-oxide-semiconductor (CMOS) devices that have made a significant contribution to the semiconductor industry
Summary
The electronic computing systems developed so far have been structured on the von Neumann architecture in which the memory, the processor, and the controller exist separately, and the sequential processing among them embodies specific functions within the programmed software. The two-terminal binary metal-oxide-based resistive switching (RS) devices, such as HfOx , AlOx , WOx , TaOx , and TiOx , have been widely studied as memristor devices that play the role of synapses in the crossbar arrays because the underlying metal–insulator–metal structure is simple, compact, CMOS-compatible, and highly scalable Their energy consumptions per synaptic operation and programming currents can be made ultralow (sub-pJ energies,
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