Spintronic devices provide a promising beyond-complementary metal-oxide-semiconductor (CMOS) device option, thanks to their energy efficiency and compatibility with CMOS. To accurately capture their multiphysics dynamics, a rigorous treatment of both spin and charge and their inter-conversion is required. Here, we present physics-based device models based on $4\times4$ matrices for the spin-orbit coupling (SOC) part of the magneto-electric spin-orbit (MESO) device. Also, a more rigorous physics model of ferroelectric and magnetoelectric (ME) switching of ferromagnets, based on Landau–Lifshitz–Gilbert (LLG) and Landau–Khalatnikov (LK) equations, are presented. With the combined model implemented in a SPICE circuit simulator environment, simulation results were obtained which show feasibility of the MESO implementation and the functional operation of buffers, synchronous oscillators, and majority gates.

A constant current stress scheme is implemented for endurance study on OTS-PCM devices for the first time. It provides a feasible method to estimate the read/write endurance for cross-point PCM products, which can save testing time for chips qualification. A 256kb chip with 1E7 cycles is demonstrated that corresponds with the endurance evaluation on the doped AsGeSe OTS with doped Ge2Sb2Te5 system.

Voltage-controlled spintronic devices are considered promising candidates for low-power applications due to the nonvolatility and the elimination of the Joule heating energy. Recently, experiments have demonstrated the voltage-controlled magnetization switching in the bismuth ferrite (BFO)/CoFe heterojunction that can achieve 180 switching at room temperature. In addition, it has been demonstrated that the ferroelectric coercive voltage of the La-doped BFO can be as low as 0.2 V by tuning the doping concentration of La and choosing a thinner BFO layer. To evaluate the potential performance of the magnetoelectric magnetic random access memory (ME-MRAM) using the BFO/CoFe heterojunction, we first build a physicsbased compact model of the antiferromagnet/ferromagnet (AFM/FM) bilayer. The results from our circuit-compatible model match well with the micromagnetic simulations on the dynamics of the order parameters in both the AFM and FM layers. Next, we simulate the read and write performances of ME-MRAM using the compact model we have developed. Our results show that the write energy of the ME-MRAM can be as low as a few fJ per bit and the layout area is similar to 20 F-2, which is more energy and area efficient compared to SRAM and other spintronic memory candidates.

We present a trap limited model on OTS-PCM devices with the thickness effect to depict the conduction behavior. The forming process is well explained by using the effective thickness concept. Moreover, the dependence between leakage current and sub-threshold slope resulting in high density cross-point OTS-PCM application is discussed, and the successful readout from a 1Mb cross-point PCM ADM using half-v scheme is demonstrated accordingly.

We present a trap limited model on OTS-PCM devices with the thickness effect to depict the conduction behavior. The forming process is well explained by using the effective thickness concept. Moreover, the dependence between leakage current and sub-threshold slope resulting in high density cross-point OTS-PCM application is discussed, and the successful readout from a 1Mb cross-point PCM ADM using half-v scheme is demonstrated accordingly.

New phase-change materials (PCM) from single composite target, which is made of GST-225 and dopants “A+O (oxygen)” using special setup magnetron sputtering are systematically studied their potential for 3D crosspoint memory technology. The PCM’s stable cycling endurance characteristic is the critical criterion to guarantee tight $\mathrm{V}_{\mathrm {th}}$ distribution during write cycles. We propose a new PCM material for 3D crosspoint memory technology. The new material, with optimized concentration, integrated with high Indium doped AsSeGe selector, demonstrates a wide $\mathrm{V}_{\mathrm {tS}}/ \mathrm{V}_{\mathrm {tR}}$ memory window (~1.5V memory window), stable 1E7 chips level write cycles (using 400ns SET box pulse time) and extremely low $\mathrm{V}_{\mathrm {tS}}$ and $\mathrm{V}_{\mathrm {tR}}$ drift characteristic (~0V) at 85 °C/1 day in 256kbits (64kbits are tested) ADM memory arrays.

The negative capacitance (NC) stabilization of a ferroelectric (FE) material can potentially provide an alternative way to further reduce the power consumption in ultra-scaled devices and thus has been of great interest in technology and science in the past decade. In this article, we present a physical picture for a better understanding of the hysteresis-free charge boost effect observed experimentally in metal-ferroelectric-insulator-metal (MFIM) capacitors. By introducing the dielectric (DE) leakage and interfacial trapped charges, our simulations of the hysteresis loops are in a strong agreement with the experimental measurements, suggesting the existence of an interfacial oxide layer at the FE-metal interface in metal-ferroelectric-metal (MFM) capacitors. Based on the pulse switching measurements, we find that the charge enhancement and hysteresis are dominated by the FE domain viscosity and DE leakage, respectively. Our simulation results show that the underlying mechanisms for the observed hysteresis-free charge enhancement in MFIM may be physically different from the alleged NC stabilization and capacitance matching. Moreover, the link between Merz's law and the phenomenological kinetic coefficient is discussed, and the possible cause of the residual charges observed after pulse switching is explained by the trapped charge dynamics at the FE-DE interface. The physical interpretation presented in this work can provide important insights into the NC effect in MFIM capacitors and future studies of low-power logic devices.

The switching dynamics of a single-domain BiFeO3/CoFe heterojunction is modeled and key parameters such as interface exchange coupling coefficient are extracted from experimental results. The lower limit of the magnetic order response time of CoFe in the BiFeO3/CoFe heterojunction is theoretically quantified to be on to the order of 100 ps. Our results indicate that the switching behavior of CoFe in the BiFeO3/CoFe heterojunction is dominated by the rotation of the Neel vector in BiFeO3 rather than the unidirectional exchange bias at the interface. We also quantify the magnitude of the interface exchange coupling coefficient J_int to be 0.32 pJ/m by comparing our simulation results with the giant magnetoresistance (GMR) curves and the magnetic hysteresis loop in the experiments. To the best of our knowledge, this is the first time that J_int is extracted quantitatively from experiments. Furthermore, we demonstrate that the switching success rate and the thermal stability of the BiFeO3/CoFe heterojunction can be improved by reducing the thickness of CoFe and increasing the length to width aspect ratio of the BiFeO3/CoFe heterojunction. Our theoretical model provides a comprehensive framework to study the magnetoelectric properties and the manipulation of the magnetic order of CoFe in the BiFeO3/CoFe heterojunction.

Electric-field-driven spintronic devices are considered promising candidates for beyond CMOS logic and memory applications thanks to their potential for ultralow energy switching and nonvolatility. In this work, we have developed a comprehensive modeling framework to understand the fundamental physics of the switching mechanisms of the antiferromagnet/ferromagnet heterojunction by taking BiFeO3/CoFe heterojunctions as an example. The models are calibrated with experimental results and demonstrate that the switching of the ferromagnet in the antiferromagnet/ferromagnet heterojunction is caused by the rotation of the Neel vector in the antiferromagnet and is not driven by the unidirectional exchange bias at the interface as was previously speculated. Additionally, we demonstrate that the fundamental limit of the switching time of the ferromagnet is in the subnanosecond regime. The geometric dependence and the thermal stability of the antiferromagnet/ferromagnet heterojunction are also explored. Our simulation results provide the critical metrics for designing magnetoelectric devices.

In this article, the multidomain nature of ferroelectric (FE) polarization switching dynamics in a metal-nferroelectric-nmetal (MFM) capacitor is explored through a physics-based phase-field approach, where the 3-D time-dependent Ginzburg-nLandau (TDGL) equation and Poisson's equation are self-consistently solved with the SPICE simulator. Systematically calibrated based on the experimental measurements, the model well captures transient negative capacitance (NC) in pulse switching dynamics, with domain interaction and viscosity being the key parameters. It is found that the influence of pulse amplitudes on voltage transient behaviors can be attributed to the fact that the FE free energy profile strongly depends on how the domains interact. In addition, we extract the domain viscosity dynamics during polarization switching according to the experimental measurements. For the first time, a physics-based circuit-compatible SPICE model for multidomain phase-field simulations is established to reveal the impact of domain interaction on the NC effect and microscopic domain evolution. The findings of this article may have important implications for the charge boost induced by the stabilization of NC in an FE/dielectric (DE) stack since the so-called capacitance matching needs to be designed at a specific operating voltage or frequency.

In this paper, the multi-domain nature of ferroelectric (FE) polarization switching dynamics in a metal-ferroelectric-metal (MFM) capacitor is explored through a physics-based phase field approach, where the three-dimensional time-dependent Ginzburg-Landau (TDGL) equation and Poisson's equation are self-consistently solved with the SPICE simulator. Systematically calibrated based on the experimental measurements, the model well captures transient negative capacitance in pulse switching dynamics, with domain interaction and viscosity being the key parameters. It is found that the influence of pulse amplitudes on voltage transient behaviors can be attributed to the fact that the FE free energy profile strongly depends on how the domains are interacted. This finding has an important implication on the charge-boost induced by stabilization of negative capacitance in an FE + dielectric (DE) stack since the so-called capacitance matching needs to be designed at a specific operation voltage or frequency. In addition, we extract the domain viscosity dynamics during polarization switching according to the experimental measurements. For the first time, a physics-based circuit-compatible SPICE model for multi-domain phase field simulations is established to reveal the effect of domain interaction on the FE energy profile and microscopic domain evolution.

In this letter, we present a comprehensive performance analysis of ferroelectric (FE)-based logic gates and repeaters. In addition, we highlight the key aspects of negative capacitance FET (NCFET) characteristics, including the proper circuit initialization, the negative capacitance (NC) effect on leakage currents, and the impacts of the FE viscosity coefficient. The threshold voltage adjustment is proposed to optimize the NCFET-based devices according to the activity factor. Furthermore, we study the interconnect repeater insertions and optimize the numbers and sizes of repeaters to minimize the overall energy-delay product. The NCFET is implemented in SPICE, with FE dynamics described by the Landau-Khalatnikov equation. Our analyses with the SPICE circuit model can provide useful insights into future studies of low-power devices.