Orientador: Guillermo Gerardo Cabrera Oyarzún / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Fisica Gleb Wataghin / Made available in DSpace on 2018-08-18T12:28:58Z (GMT). No. of bitstreams: 1 Fernandes_ImaraLima_M.pdf: 9006612 bytes, checksum: accaacf2ec8bab2326612b97e18b9b16 (MD5) Previous issue date: 2011 / Resumo: Neste trabalho, apresentamos um estudo do tunelamento e do transporte quântico em sistemas mesoscópicos, particularmente em junções de tunelamento magnéticas, visando esclarecer a polarização magnética da corrente de tunelamento. Nos dispositivos de tunelamento, um filme isolante é crescido entre os eletrodos ferromagnéticos. Nesse sistema a condutância é controlada pelo coeficiente de transmissão do efeito túnel. Nos metais de transição (Fe, Co, Ni), as bandas s, p e d contribuem para a condução eletrônica, entretanto a magnetização deve-se à polarização das bandas d. Resultados experimentais mostram que essa polarização da corrente pode ser muito diferente da polarização do volume no nível de Fermi, podendo até estar invertida. Qualitativamente sabe-se que os elétrons da banda d apresentam menor probabilidade de tunelamento do que os elétrons s ou p. Os elétrons de condução do tipo s são representados por ondas planas com vetores de onda pequenos (centro da zona de Brillouin). Já os elétrons d possuem maior massa efetiva e um caráter localizado, portanto, são representados por pacotes de muitas componentes de ondas planas com vetores de onda maiores. Estudamos o tunelamento desses elétrons por barreiras de potencial que representam o material isolante entre eletrodos metálicos. Propomos um modelo simples para a corrente de tunelamento e estimamos o efeito da magnetoresitência / Abstract: This work introduces a detailed study of tunneling and quantum transport in mesoscopic systems, particularly in tunneling magnetic junctions, to understand the magnetic polarization of the tunneling current. These systems consist of two ferromagnetic metal layers separated by a thin insulating barrier layer. The conductance is controlled by the transmission coeficient of the tunnel effect. In the transition metal (Fe, Co, Ni), the bands s, p and d contribute to the electronic conduction, however, to the magnetization only the d-band contributes. Experimental results show that the current polarization may be different of the bulk polarization in the Fermi level and may be reversed. Qualitatively it is known that tunneling probability of the d-like electrons is lower than the s-like and p-like electrons. The s-electrons are represented by wave planes with small wave vector (center of the Brillouin zone). Since the d-electrons have higher effective mass and they are localized states, they are represented by wave packet with many components of wave planes with larger wave vectors. We investigate the tunneling of these electrons through potential barriers, which represent the insulating layer between the ferromagnetic electrodes. We propose a simple model for the tunneling current and estimated the effect of the magnetoresistance / Mestrado / Física da Matéria Condensada / Mestra em Física

Ce travail de thèse porte sur l'étude et la réalisation de Lasers à Emission par la Surface à Cavité Verticale pompés électriquement (EP-VCSELs) à base d'antimoniures émettant dans le moyen-infrarouge au-delà de 2 µm. Ces VCSELs proposent des caractéristiques intéressantes pour la détection de gaz tel qu'une émission monomode et une large accordabilité sans saut de mode. L'objectif de ce travail était de développer de tels composants. La première partie de ce mémoire présente les propriétés des couches qui seront empilés pour former la structure VCSEL. La seconde partie traite des différentes conditions pour obtenir une source laser monomode. La troisième partie présente les procédés de fabrication qui ont étés mis en place. Notamment de la sous-gravure sélective de la Jonction Tunnel (JT), qui est une technique de confinement originale dans le système GaSb. Celle-ci permet de réduire le diamètre de la JT jusqu'à 6 µm, ce qui est la condition pour obtenir une émission monomode.La dernière partie de ce manuscrit présente les caractérisations menées sur les structures monolithiques à JT sous-gravées. La sous-gravure sélective nous a ainsi permis d'obtenir le premier EP-VCSEL monolithique monomode. Ce composant fonctionne au-delà de la température ambiante et en régime continu. Avec des courants de seuils aussi bas que 1,9 mA et un fonctionnement jusqu'à 70°C. Le développement des structures monolithique à zone active (ZA) en cascade a également permis d'augmenter les puissances optiques en sortie de ces composants. Celles-ci sont passées de 300 µW @ 20°C à 950 µW pour la première structure citée classique et la structure à ZA en cascades respectivement. / This thesis deals with study and conception of GaSb-based electrically pumped Vertical Cavity Surface Emitting Lasers (EP-VCSELs) emitting in the mid-infrared range above 2 µm. This VCSELs exhibits suitable characteristics for gas analysis like single-mode emission and a large current tunability without mode-hopping. The objective of this work was to develop such devices. The first part of this work is about properties of the epitaxial stack layers used to form the VCSEL structure. The second parts deal with characteristics and the confinement system to design a single mode cavity. The third part presents manufacturing process which has been set up, like Tunnel Junction (TJ) under-etching, which is an innovate approach on the GaSb system. It allows reducing TJ diameter down to 6 µm, which is a necessary point to demonstrate single-mode operation.The final part of this manuscript presents the characterisations purchased on the under-etched TJ monolithic-VCSELs. Selective under-etching of the TJ allowed the first demonstration of the first single-mode monolithic EP-VCSEL. This device emits around 2.3 µm in continuous regime above room temperature. This device exhibits threshold currents as low as 1.9 mA and operate up to 70°C. The development of bipolar cascaded VCSELs has also allowed increasing the optical power on large diameter multimode, with a maximum output power of 300 µW and 950 µW@20°C for the classic and the bipolar cascaded VCSEL respectively.

A forte polarisation (V >1V), une jonction tunnel planaire peut émettre de la lumière dans le domaine optique à des fréquences f<eV/h ~ 10¹⁴Hz. Cette émission résulte du rayonnement de plasmons-polariton de surface, générés par le bruit de grenaille dans la jonction. La densité spectrale de rayonnement dP/df est alors directement reliée à la densité spectrale des fluctuations du courant SII via une simple impédance de rayonnement: dP/df = R × SII. De la même manière, la densité spectrale de rayonnement du corps noir est reliée aux fluctuations thermiques du courant dans un conducteur ohmique via le théorème fluctuation-dissipation (TFD). Il semble alors naturel de décrire le rayonnement d'une jonction tunnel par la relation fluctuation-dissipation, dérivée par Scalapino et Rogovin [Annals of Physics 1974], généralisant le TFD aux conducteurs hors équilibre (V≠0). Nous avons étudié cette relation dans un régime où la jonction tunnel est fortement hors équilibre, lorsque eV ~1eV est de l'ordre de la hauteur de la barrière tunnel. La RFD est vérifiée à fréquence nulle (MHz), mais est violée de manière flagrante à fréquence finie (10¹⁴Hz). Nous attribuons cette violation à la non linéarité intrinsèque de la jonction. Nous dérivons une nouvelle expression pour la puissance émise, à partir de l'approche quantique de Landaueur-Büttiker du transport électronique. L'émission est alors interprétée en terme de recombinaison électron-trou dans les électrodes et rend compte d'une accumulation de charges dans la barrière. L'efficacité du couplage électron-photon est évaluée quantitativement via l'impédance de rayonnement de la jonction. Ce travail de thèse s'adresse à deux communautés, celle de la physique mésoscopique étudiant les mécanismes du transport électronique, et celle des opticiens voulant comprendre et optimiser l'émission de lumière dans ces systèmes. / In a strongly voltaged biased tunnel junction, optical photon emission occurs at frequencies below the threshold f<eV/h ~ 10¹⁴Hz, mediated by the shot-noise-generated surface plasmon-polaritons. The spectral power density dP/df depends only on the current fluctuation spectral density SII and a radiation impedance: dP/df = R × SII . This expression is analogous to the relation between the power spectral density of a black body and thermal current fluctuations in a ohmic conductor, via the fluctuation-dissipation theorem (FDT). Therefore, it seems natural that the optical power emitted by a tunnel junction be given by the fluctuation-dissipation relation (FDR) derived by Scalapino and Rogovin [Annals of Physics 1974], which extends the FDT to out-of-equilibrium conductors (V≠0). When the junction is far-from-equilibrium, i.e. when eV ~1eV is of the order of magnitude of the tunnel barrier height, our experiments show that the FDR holds at zero frequency (MHz), but breaks down at finite frequency (10¹⁴Hz). We attribute the discrepancy between the FDR and our measurements to the junction's intrinsic current-voltage non-linearity. We derive a new expression for emitted optical power, based on the Landauer-Büttiker formalism for quantum electronic transport. Light emission from the junction can then be interpreted as due to electron-hole recombination processes in the electrodes. This expression also account for charge accumulation in the tunnel barrier. The resulting estimate of the junction's radiation impedance is a measure of the electron-photon coupling e_ciency in our device. This work should be of interest to both mesoscopic physicists studying electronic transport mechanisms, and those of optics community studying light emission in microstructures.

<p>Probabilistic computing has been proposed as an attractive alternative for bridging the computational gap between the classical computers of today and the quantum computers of tomorrow. It offers to accelerate the solution to many combinatorial optimization and machine learning problems of interest today, motivating the development of dedicated hardware. Similar to the ‘bit’ of classical computing or ‘q-bit’ of quantum computing, probabilistic bit or ‘p-bit’ serve as a fundamental building-block for probabilistic hardware. p-bits are robust classical quantities, fluctuating rapidly between its two states, envisioned as three-terminal devices with a stochastic output controlled by its input. It is possible to implement fast and efficient hardware p-bits by modifying the present day magnetic random access memory (MRAM) technology. In this dissertation, we evaluate the design and performance of low-barrier magnet (LBM) based p-bit realizations.<br> </p> <p>LBMs can be realized from perpendicular magnets designed to be close to the in-plane transition or from circular in-plane magnets. Magnetic tunnel junctions (MTJs) built using these LBMs as free layers can be integrated with standard transistors to implement the three-terminal p-bit units. A crucial parameter that determines the response of these devices is the correlation-time of magnetization. We show that for magnets with low energy barriers (Δ ≤ k_BT) the circular disk magnets with in-plane magnetic anisotropy (IMA) can lead to correlation-times in <i>sub-ns</i> timescales; two orders of magnitude smaller compared to magnets having perpendicular magnetic anisotropy (PMA). We show that this striking difference is due to a novel precession-like fluctuation mechanism that is enabled by the large demagnetization field in mono-domain circular disk magnets. Our predictions on fast fluctuations in LBM magnets have recently received experimental confirmation as well.<br></p> <p>We provide a detailed energy-delay performance evaluation of the stochastic MTJ (s-MTJ) based p-bit hardware. We analyze the hardware using benchmarked SPICE multi-physics modules and classify the necessary and sufficient conditions for designing them. We connect our device performance analysis to systems-level metrics by emphasizing problem and substrate independent figures-of-merit such as flips per second and dissipated energy per flip that can be used to classify probabilistic hardware. </p>

<p>Vertically aligned nanocomposite (VAN) thin films are a promising thin-film platform that allows the combination of a highly desired material with another complementary oxide. Traditionally, VANs have been limited to combining an oxide with another oxide which has shown a wide range of functionality, and, by adjusting the different growth parameters, it has led to the tuning of their physical properties. While VANs have already shown to be an effective platform with immense potential, further enhancement of physical properties can be performed by replacing one of the oxides with a metal forming metal-oxide VANs. </p> <p>In this dissertation, by the inclusion of the 3d transition metals, e.g., Fe and Co, into various oxide matrices, such as La_0.5Sr_0.5FeO₃, BaZrO₃, and BaTiO₃, strong, highly anisotropic, ferromagnetic properties have been achieved. By varying the growth parameters, tunable physical properties, mainly coercivity and anisotropic ratio, have been demonstrated. Furthermore, in the case of Co-BaZrO₃, a multi-layer stack has been successfully grown and demonstrated a tailorable magnetoresistance. Additionally, a novel system by combining Fe pillars into a BaTiO₃ matrix has been demonstrated. This new system allows for the combination of the room temperature Fe ferromagnetic properties with the ferroelectric properties of BaTiO₃, allowing for coupling between the two with coercivity tuning and tailorable ferromagnetic properties. </p> <p>Lastly, it has been shown a possible framework by adding additional metals into the existing metal-oxide VAN platform. By adding the third phase, another metal, it opens up a new avenue to induce additional functionality while creating a method to introduce coupling between the different metals and physical properties. </p> <br>

Spin-torque nano-oscillators (STNOs) are prospective successors of transistor-based emitters and receivers of radio-frequency signals in commonly used remote communication systems. In comparison to the conventional electronic oscillators, STNOs offer the advantage of being tunable over a wide range of frequencies simply by adjusting the applied current, the smaller lateral size (up to 50 times) and the lower power consumption as the lateral size of the device is reduced. It has already been demonstrated that the output signal characteristics of STNOs are compatible with the requirements for applications: they can provide output powers in the µW range, frequencies of the order of GHz, quality factors Q (equal to df/f, where f is the frequency, and df is the linewidth) up to several thousands (e.g., 3 200), and can be integrated into Phase-Locked Loop (PLL) circuits. The most promising type of spin-torque oscillators is the hybrid geometry STNOs utilizing an in-plane magnetized fixed layer, an out-of-plane magnetized free layer and the MgO tunnel barrier as a spacer. This geometry maximizes the output power, since the full parallel-to-antiparallel resistance variation can be exploited in the limit of large magnetization precession angle (i.e., when the magnetization oscillates fully within the plane of the STNO stack). Moreover, the considered hybrid geometry allows for the reduction of the critical currents, enables functionality regardless of the applied magnetic or current history and requires a simplified fabrication process in comparison to the opposite hybrid geometry, consisting of an in-plane magnetized free layer and an out-of-plane reference layer, which requires an additional read-out layer. Simultaneously, the choice of the spacer material in considered STNOs is motivated by the increase of both the output power (via large magnetoresistance ratios) and the power conversion rate ('output power to input power' ratio), compared to their fully metallic counterparts. Despite the many advantages of MgO-based hybrid geometry STNOs, unexplained issues related to the physics behind their principle of operation remained. In this thesis, the main focus is put on the two key aspects related to the out-of-plane steady-state precession in hybrid STNOs: the precession mechanism (combined with the analysis of the influence of the bias dependence of the tunnel magnetoresistance) and the zero-field oscillations stabilized by an in-plane shape anisotropy. State-of-the-art theoretical studies demonstrated that stable precession in hybrid geometry STNOs can only be sustained if the in-plane component of the spin-transfer torque (STT) exhibits an asymmetric dependence on the angle between the free and the polarizing layer (which is true for fully metallic devices, but not for the MgO-based magnetic tunnel junctions (MTJs)). Nevertheless, recent experimental reports showed that spin-transfer driven dynamics can also be sustained in MgO-based STNOs with this particular configuration. In this thesis, a phenomenological and straightforward mechanism responsible for sustaining the dynamics in considered system is suggested. The mechanism is based on the fact that, in MgO-based MTJs, the strong cosine-type angular dependence of the tunnel magnetoresistance, at constant applied current, translates into an angle-dependent voltage component, which results in an angle-dependent spin-transfer torque giving a rise to the angular asymmetry of the in-plane STT and, thus, enabling steady-state precession to be sustained. Subsequently, the bias dependence of the tunnel magnetoresistance (TMR), which has been so far neglected in similar calculations, is taken into account. According to the results of analytical and numerical studies, the TMR bias dependence brings about a gradual quenching of the dynamics at large applied currents. The theoretical model yields trends confirming our experimental results. The most important conclusion regarding to this part of the thesis is that, while the angular dependence of the tunnel magnetoresistance introduces an angular asymmetry for the in-plane spin transfer torque parameter (which helps maintain steady-state precession), the bias dependence of the resistance works to reduce this asymmetry. Thus, these two mechanisms allow us to tune the asymmetry of the in-plane STT as function of current and to control the dynamical response of the actual device. Except for the precession mechanism, the thesis is also focused on the issue of zero-field oscillations, which would be especially desirable from the point of view of potential applications. According to the state-of-the-art theoretical studies, for hybrid geometry devices with circular cross-section (i.e., exhibiting no other anisotropy terms), current-driven dynamics cannot be excited at zero applied field. Indeed, zero-field oscillations have only been experimentally observed for systems having the free layer magnetization slightly tilted from the normal to the plane, which has usually been achieved by introducing an in-plane shape anisotropy. In the thesis, the influence of the in-plane shape anisotropy of the MTJ on zero-field dynamics in the hybrid geometry MgO-based STNOs is analytically and numerically investigated. In agreement with the previous reports, no zero-field dynamics for circular nano-pillars is observed; however, according to the numerical data, an additional in-plane anisotropy smaller than the effective out-of-plane anisotropy of the free layer enables zero-field steady-state precession. Accordingly, the lack of an in-plane anisotropy component (e.g., for circular cross-section nano-pillars), or the presence of an in-plane shape anisotropy equal or greater than the out-of-plane effective anisotropy, inhibits the stabilization of dynamics in the free layer at zero field. The results of analytical and numerical studies and the general trends identified in the corresponding experimental data are found to be in excellent qualitative agreement.:1. Introduction 1.1. Short history of magnetotransport applications 1.2. Spin-transfer torque induced effects and devices 1.3. Goals of the thesis 2. Fundamentals 2.1. Electronic transport in single transition metal layers 2.2. Tunnel magnetoresistance (TMR) 2.2.1. Electronic transport in magnetic tunnel junctions 2.2.2. Tunnel magnetoresistance versus structural properties of the multilayer 2.2.3. Bias voltage and temperature dependence of tunnel magnetoresistance 2.2.4. Angular dependence of tunnel magnetoresistance 2.3. Spin-transfer torque in GMR/TMR structures 2.3.1. Spin-transfer torque 2.3.2. Landau-Lifshitz-Gilbert (LLG) equation 2.3.3. LLG equation and spin-transfer torques 2.3.4. Bias voltage dependence of spin-transfer torques in MTJs 2.3.5. Angular dependence of spin-transfer torque 2.4. Spin-torque-based phenomena 2.4.1. Current-induced switching 2.4.2. Current-induced dynamics 3. Experimental 3.1. General characteristics of MgO-based magnetic tunnel junctions 3.2. STNO samples 3.2.1. Samples by AIST (Tsukuba, Japan) 3.2.2. Samples by HZDR / SINGULUS (Dresden / Kahl am Main, Germany) 3.3. Magnetotransport measurements 3.3.1. Experimental setup and data analysis 3.3.2. Experimental results 3.4. Aspects to be explained 4 Numerical and analytical calculations 4.1 Out-of-plane steady-state precession in hybrid geometry STNO 4.1.1 Angular dependence of tunnel magnetoresistance as a mechanism of stable precession 4.1.2. Influence of the bias dependence of tunnel magnetoresistance 4.1.3. Comparison with the experimental data 4.1.4. Comparison with the GMR-type counterpart 4.1.5. Summary 4.2. Zero-field dynamics in hybrid geometry STNO stabilized by in-plane shape anisotropy 4.2.1. Effect of the in-plane shape anisotropy 4.2.2. Zero-field dynamics 4.2.3. Summary 5. Conclusions 6. Outlook Appendix Bibliography

The research of III-nitride wide-bandgap semiconductor devices, such as laser diodes (LDs), ultra-violet (UV) light-emitting diodes (LEDs), and high electron mobility transistors (HEMTs), has recently increased. Numerous opportunities exist for performance improvement in the wide bandgap semiconductor device structure, including material selection, compound compositions, polarization effects, and layer thicknesses. On the other hand, they can make optimization more challenging. It still takes a lot of resources to analyze and test complicated structures in a systematic manner. This dissertation creates a new path for device design by using TCAD and machine learning to deliver quick forecasts of III-nitride semiconductor device performance. The dissertation includes three major components. In Chapter 2, the TCAD-assisted HEMT device design is discussed. We demonstrate the performance improvement of using the new material BAlN as an interlayer in GaN/AlGaN HEMT devices and compare the various interlayer design alternatives for HEMTs. In chapter 3, we propose asymmetrical p-AlGaN/i-InGaN/n-AlGaN tunnel junctions (TJs) by combining machine learning (ML) with TCAD calculations. The resistances for 22254 various TJ structures were predicted by the model, which creates a tool for real-time TJ resistance prediction. Based on our TJ predictions, we proposed asymmetric TJ with higher Al content in the p-layer and lower TJ resistance. In Chapter 4, using the stacked XGBoost/LightGBM algorithm, we thoroughly examined the superlattice (SL) electron blocking layer (EBL) for AlGaN deep ultra-violet (DUV) LEDs. Based on the ML model, we suggest a low Al-content SL-EBL (1 nm/5 nm Al0.7Ga0.3N/Al0.58Ga0.42N) that is simpler, experimentally realizable and can greatly improve carrier transport. Additionally, we examine the prediction data and show how the composition and thickness affect the improvement of the IQE. The work contributes to the advancement of using SL-EBLs for high-efficiency DUV LEDs by providing methodical research on SL-EBLs. This dissertation presents novel approaches to the design of electrical and optical wide bandgap semiconductor devices, which opens up a new avenue for future research. It is possible that it might be used in a broad variety of fields, including illumination, sensing, disinfection, and power devices.

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Les mémoires non-volatiles (MNV) sont l'objet d'un effort de recherche croissant du fait de leur capacité à limiter la consommation statique, qui obère habituellement la réduction des dimensions dans la technologie CMOS. Dans ce contexte, cette thèse aborde plus spécifiquement deux technologies de mémoires non volatiles : d'une part les jonctions tunnel ferroélectriques (JTF), dispositif non volatil émergent, et d'autre part les dispositifs à transfert de spin (TS) assisté par effet Hall de spin (EHS), approche alternative proposée récemment pour écrire les jonctions tunnel magnétiques (JTM). Mon objectif est de développer des modèles compacts pour ces deux technologies et d'explorer, par simulation, leur intégration dans les circuits non-volatiles.J'ai d'abord étudié les modèles physiques qui décrivent les comportements électriques des JTF : la résistance tunnel, la dynamique de la commutation ferroélectrique et leur comportement memristif. La précision de ces modèles physiques est validée par leur bonne adéquation avec les résultats expérimentaux. Afin de proposer un modèle compatible avec les simulateurs électriques standards, nous j'ai développé les modèles physiques mentionnés ci-dessus en langue Verilog-A, puis je les ai intégrés ensemble. Le modèle électrique que j'ai conçu peut être exploité sur la plate-forme Cadence (un outil standard pour la simulation de circuit). Il reproduit fidèlement les comportements de JTF. Ensuite, en utilisant ce modèle de JTF et le design-kit CMOS de STMicroelectronics, j'ai conçu et simulé trois types de circuits: i) une mémoire vive (RAM) basée sur les JTF, ii) deux systèmes neuromorphiques basés sur les JTF, l'un qui émule la règle d'apprentissage de la plasticité synaptique basée sur le décalage temporel des impulsions neuronale (STDP), l'autre mettant en œuvre l'apprentissage supervisé de fonctions logiques, iii) un bloc logique booléen basé sur les JTF, y compris la démonstration des fonctions logiques NAND et NOR. L'influence des paramètres de la JTF sur les performances de ces circuits a été analysée par simulation. Finalement, nous avons modélisé la dynamique de renversement de l'aimantation dans les dispositifs à anisotropie perpendiculaire à transfert de spin assisté par effet Hall de spin dans un JTM à trois terminaux. Dans ce schéma, deux courants d'écriture sont appliqués pour générer l'EHS et le TS. La simulation numérique basée sur l'équation de Landau-Lifshitz-Gilbert (LLG) démontre que le délai d'incubation de TS peut être éliminé par un fort EHS, conduisant à la commutation ultra-rapide de l'aimantation, sans pour autant requérir une augmentation excessive du TS. Nous avons appliqué cette nouvelle méthode d'écriture à la conception d'une bascule magnétique et d'un additionneur 1 bit magnétique. Les performances des circuits magnétiques assistés par l'EHS ont été comparés à ceux écrits par transfert de spin, par simulation et par une analyse fondée sur le modèle théorique. / Non-volatile memory (NVM) devices have been attracting intensive research interest since they promise to solve the increasing static power issue caused by CMOS technology scaling. This thesis focuses on two fields related to NVM: the one is the ferroelectric tunnel junction (FTJ), which is a recent emerging NVM device. The other is the spin-Hall-assisted spin-transfer torque (STT), which is a recent proposed write approach for the magnetic tunnel junction (MTJ). Our objective is to develop the compact models for these two technologies and to explore their application in the non-volatile circuits through simulation.First, we investigated physical models describing the electrical behaviors of the FTJ such as tunneling resistance, dynamic ferroelectric switching and memristive response. The accuracy of these physical models is validated by a good agreement with experimental results. In order to develop an electrical model available for the circuit simulation, we programmed the aforementioned physical models with Verilog-A language and integrated them together. The developed electrical model can run on Cadence platform (a standard circuit simulation tool) and faithfully reproduce the behaviors of the FTJ.Then, using the developed FTJ model and STMicroelectronics CMOS design kit, we designed and simulated three types of circuits: i) FTJ-based random access memory (FTRAM), ii) two FTJ-based neuromorphic systems, one of which emulates spike-timing dependent plasticity (STDP) learning rule, the other implements supervised learning of logic functions, iii) FTJ-based Boolean logic block, by which NAND and NOR logic are demonstrated. The influences of the FTJ parameters on the performance of these circuits were analyzed based on simulation results.Finally, we focused on the reversal of the perpendicular magnetization driven by spin-Hall-assisted STT in a three-terminal MTJ. In this scheme, two write currents are applied to generate spin-Hall effect (SHE) and STT. Numerical simulation based on Landau-Lifshitz-Gilbert (LLG) equation demonstrates that the incubation delay of the STT can be eliminated by the strong SHE, resulting in ultrafast magnetization switching without the need to strengthen the STT. We applied this novel write approach to the design of the magnetic flip-flop and full-adder. Performance comparison between the spin-Hall-assisted and the conventional STT magnetic circuits were discussed based on simulation results and theoretical models.