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A pioneering integration of oxide semiconductor memristors with optoelectronic features is presented, surpassing binary limitations to realize multi‐valued synaptic operations. Through Pt/Ga2O3/Pt memristors, their structural and electronic attributes via atomic force microscopy, X‐ray diffraction, and X‐ray photoelectron spectroscopy are explored. Demonstrating unipolar resistance switching with remarkable endurance and retention, the devices exhibit intricate light‐resistance correlations, yielding substantial photoelectric effects in distinct resistance states. Investigating synaptic behaviors, potentiation, and depression akin to biological synapses are unveiled, facilitating learning and memory processes. The standout achievement lies in attaining quaternary memory storage within a single device. Empirical data and simulations validate this concept, showcasing the potential for encoding and sustaining multiple memory states. This innovation heralds transformative possibilities, emphasizing oxide semiconductor memristors as a gateway to quaternary memory storage and enhanced synaptic functions. In essence, this work pioneers optoelectronic synaptic devices with expanded memory capabilities. [ABSTRACT FROM AUTHOR]

The increasing demand for data movement and energy consumption in physically separate von Neumann architectures, where the processor and memory are distinct entities, highlights the severity of the memory‐wall problem. Thus, memristor‐based logic‐in‐memory (LiM) has garnered significant interest as it is a paradigm that enables both logic and memory functionalities to be performed within a single device. Ferroelectric tunnel junctions (FTJs) have the advantages of low energy consumption and high scalability; thus, they are particularly appropriate for use as analog memristors in LiMs. Precise and accurate programming of the analog resistance states in FTJs is essential to achieve an efficient memristor‐based LiM design. However, existing switching models for FTJs cannot completely consider the ferroelectric domain switching, which challenges multi‐bit LiM operations. This particularly applies in cases involving updates from one intermediate resistance state (IRS) to another IRS, such as transitioning from State 01 to 10 in 2‐bit LiM. In this study, a novel phenomenon associated with domain switching is observed in the IRS of an HZO FTJ device and applied it to an LiM implementation. These findings can contribute to the operational accuracy and update rules of not only FTJ‐based LiMs but also other FTJ applications, such as crossbar arrays. [ABSTRACT FROM AUTHOR]

Hf1−xZrxO2 (HZO) thin films are versatile materials suitable for advanced ferroelectric semiconductor devices. Previous studies have shown that the ferroelectricity of HZO thin films can be stabilized by doping them with group III elements at low concentrations. While doping with Y improves the ferroelectric properties, there has been limited research on Y-HZO thin films fabricated using atomic layer deposition (ALD). In this study, we investigated the effects of Y-doping cycles on the ferroelectric and electrical properties of as-deposited Y-HZO thin films with varying compositions fabricated through ALD. The Y-HZO thin films were stably crystallized without the need for post-thermal treatment and exhibited transition behavior depending on the Y-doping cycle and initial composition ratio of the HZO thin films. These Y-HZO thin films offer several advantages, including enhanced dielectric constant, leakage current density, and improved endurance. Moreover, the optimized Y-doping cycle induced a phase transformation that resulted in Y-HZO thin films with improved ferroelectric properties, exhibiting stable behavior without fatigue for up to 1010 cycles. These as-deposited Y-HZO thin films show promise for applications in semiconductor devices that require high ferroelectric properties, excellent electrical properties, and reliable performance with a low thermal budget. [ABSTRACT FROM AUTHOR]

Owing to the 4th Industrial Revolution, the amount of unstructured data, such as voice and video data, is rapidly increasing. Brain-inspired neuromorphic computing is a new computing method that can efficiently and parallelly process rapidly increasing data. Among artificial neural networks that mimic the structure of the brain, the spiking neural network (SNN) is a network that imitates the information-processing method of biological neural networks. Recently, memristors have attracted attention as synaptic devices for neuromorphic computing systems. Among them, the ferroelectric doped-HfO2-based ferroelectric tunnel junction (FTJ) is considered as a strong candidate for synaptic devices due to its advantages, such as complementary metal–oxide–semiconductor device/process compatibility, a simple two-terminal structure, and low power consumption. However, research on the spiking operations of FTJ devices for SNN applications is lacking. In this study, the implementation of long-term depression and potentiation as the spike timing-dependent plasticity (STDP) rule in the FTJ device was successful. Based on the measured data, a CrossSim simulator was used to simulate the classification of handwriting images. With a high accuracy of 95.79% for the Mixed National Institute of Standards and Technology (MNIST) dataset, the simulation results demonstrate that our device is capable of differentiating between handwritten images. This suggests that our FTJ device can be used as a synaptic device for implementing an SNN. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]