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Nonvolatile memory using intersubband transitions and quantum-well electron accumulation in GaN/AlN resonant tunneling diodes (RTDs) is a promising candidate for high-speed nonvolatile memory operating on a picosecond timescale. This memory has been fabricated on sapphire(0001) substrates to date because of the high affinity between the nitride materials and the substrate. However, the fabrication of this memory on Si(111) substrates is attractive to realize hybrid integration with Si devices and nonvolatile memory and three-dimensional integration such as chip-on-wafer and wafer-on-wafer. In this study, GaN/AlN RTDs are fabricated on a Si(111) substrate using metal-organic vapor phase epitaxy. The large strain caused by the differences in the thermal expansion coefficients and lattice constants between the Si(111) substrate and nitride materials are suppressed by a growth technique based on the insertion of low-temperature-grown AlGaN and thin AlN layers. The GaN/AlN RTDs fabricated on Si(111) substrates show clear GaN/AlN heterointerfaces and a high ON/OFF ratio of >220, which are equivalent to those for devices fabricated on sapphire(0001) substrates. However, the nonvolatile memory characteristics fluctuate by repeated write/erase memory operations. Evaluation of the ON/OFF switching time and endurance characteristics indicates that the instability of the nonvolatile memory characteristics is caused by electron leakage through deep levels in the quantum-well structure. Possible methods for suppressing this are discussed with an aim of realizing high-speed and high-endurance nonvolatile memory. [ABSTRACT FROM AUTHOR]

This work examines a polytope-type approach for observer-based security control of a fractional-order system that is under multiple attacks via an event-triggered scheme. A novel multiple-attack model is first proposed for fractional-order systems such as denial-of-service attacks and reply attacks, which can destroy the system's security during the signal process. In contrast to previous studies, the design of the controller is developed using an observer-based event-triggered scheme in the presence of multiple attacks. An event-triggering strategy is proposed to reduce the communication burden of the output measurement signals. An observer-based control is designed to keep the fractional-order system stable in all scenarios where one or more simultaneous attacks may occur. These findings can ensure the absence of Zeno behaviour and considerably reduce data transmissions. By employing the suitable Lyapunov–Krasovskii functional, sufficient conditions are derived to ensure fractional-order system stability. Controller and observer-gain matrices are obtained by using the linear matrix inequality technique. Finally, two examples are provided to demonstrate the feasibility and usefulness of the suggested methodology. [ABSTRACT FROM AUTHOR]

ABSTRACT The lattice loop formed by adjacent coupling of tunnel diode LC oscillators has been shown to generate topological defects due to broken mirror symmetry, which rotate in the opposite direction to the rotating pulse. Leveraging the injection locking of the rotational dynamics of these topological defects can lead to a subharmonic injection locking scheme with a large division ratio. This paper aims to enhance the design by elucidating the relationship between loop size, the number of topological defects, and the division ratio. Furthermore, we perform bifurcation analysis of the injection locking system, demonstrating that when the external signal strength reaches a certain threshold, defect pinning by the external signal occurs, leading to an extension of the lock range. The dynamics of topological defects are well suited to the so‐called progressive multiphase injection locking. In this paper, we clarify the degree of lock range extension achieved by introducing this technique. [ABSTRACT FROM AUTHOR]

Aiming at the security consensus control problem of leader‐following multi‐agent systems (MASs) under hybrid random cyber attack, this article proposes a novel sampled information related adaptive event‐triggered control mechanism (SIRAETCM). While ensuring the safety performance of the MASs, the mechanism adaptively and dynamically adjusts the trigger threshold of every agent to achieve discontinuous communication by using only the current and latest sampled signals. According to the MASs communication mode and Bernoulli attack model, a security consensus control protocol is constructed, and a bilateral sampled‐interval Lyapunov functional (BSILF) method is introduced to obtain more sampling interval information and establish sufficient conditions for the leader‐following state error system to stabilize asymptotically under hybrid random cyber attacks. Meanwhile, under a large sampling interval, the controller gain and adaptive event‐triggered parameters are designed and obtained. The simulation of the tunnel diode circuit system shows that the SIRAETCM can reduce the number of communications between agents to improve bandwidth utilization, and the adopted safety cooperative control protocol can improve the safety and effectiveness of the MASs. [ABSTRACT FROM AUTHOR]

We investigate the high-pressure phase of the iron-based superconductor FeSe0.89S0.11 using transport and tunnel diode oscillator studies using diamond anvil cells. We construct detailed pressure-temperature phase diagrams that indicate that the superconducting critical temperature is strongly enhanced by more than a factor of four towards 40 K above 4 GPa. The resistivity data reveal signatures of a fan-like structure of non-Fermi liquid behaviour which could indicate the existence of a putative quantum critical point buried underneath the superconducting dome around 4.3 GPa. With further increasing the pressure, the zero-field electrical resistivity develops a non-metallic temperature dependence and the superconducting transition broadens significantly. Eventually, the system fails to reach a fully zero-resistance state, and the finite resistance at low temperatures becomes strongly current-dependent. Our results suggest that the high-pressure, high-Tc phase of iron chalcogenides is very fragile and sensitive to uniaxial effects of the pressure medium, cell design and sample thickness. This high-pressure region could be understood assuming a real-space phase separation caused by nearly concomitant electronic and structural instabilities. [ABSTRACT FROM AUTHOR]

We demonstrated GaN-based resonant tunneling diode (RTD) oscillators employing monolithic microwave integrated circuits. The GaN-based RTDs with a GaN quantum well and AlN double barriers were grown on freestanding c-plane semi-insulating GaN substrates using metal–organic chemical vapor deposition. The circuit components, including an RTD, a coplanar waveguide, a metal–insulator–metal capacitor, and shunt resistors, were monolithically fabricated on the GaN substrate. The circuits oscillated at a fundamental frequency of 17 GHz, which closely matched an estimated frequency using a three-dimensional electromagnetic simulator and a circuit simulator. This study contributes to the advancement of semiconductor high-frequency devices for millimeter wave and terahertz applications. [ABSTRACT FROM AUTHOR]

We studied the transport properties of graphene–insulator–metal tunneling diodes. Two sets of tunneling diodes with Ti–Cu and Cr–Au top contacts are fabricated. Transport measurements showed state-of-the-art non-linearity and a critical influence of the top metals on the dielectric strength of the tunneling barrier. X-ray photoelectron spectroscopy indicated two methods for enhancing the dielectric strength of the tunneling barrier. These are the optimized seed layers for the growth of high-quality conformal insulators and the selection of appropriate top metal layers with a small diffusion coefficient and electromigration into the Al2O3 barrier. The Cr–Au top contact provides superior characteristics to the Ti–Cu metallization. X-ray photoelectron spectroscopy showed significant diffusion of titanium during the Al2O3 growth and the formation of titanium inclusions after annealing. Chromium diffusion is slower than that of titanium, making chromium contact more suitable for the reliable operation of tunneling diodes. As a result, we demonstrate a 40% improvement in the dielectric strength of the tunneling barrier compared to state-of-the-art metal–insulator–metal diodes. [ABSTRACT FROM AUTHOR]

This work presents an analysis and design of the two barrier-quantum well asymmetric spacer tunnel layer (QW-ASPAT) diodes for implantable rectenna circuits application. The RF and DC characteristic of a 10×10 μm² QW-ASPAT devices based on GaAs and In0.53Ga0.47As platform was simulated and extracted by using SILVACO atlas software. The highest extracted curvature coefficient, kv value of the both QW-ASPAT devices at zero bias was about 33V-1 compared with the standard structure GaAs/InGaAs was about 13V-1. The effects of changing in the thickness of the thin AlAs-barrier, the well width, and the spacer layer are fully investigated on the non-linear relationship between current and voltage of these diodes. A CV simulation was carried out, and it was found that the addition of the quantum-well layer between spacers and barrier reduced the junction capacitance of the QW-ASPAT device when compared with standard devices. The cut-off frequency of the proposed QW-GaAs and QW-InGaAs devices are 26GHz and 46GHz respectively. Finally, we conclude that the QW-ASPAT device is the best structure and can be used for microwave rectifiers in the miniaturized integrated rectenna systems. [ABSTRACT FROM AUTHOR]

This study explores the dynamics of sequentially arranged coupled oscillator loops, focusing on inducing steadily rotating phase waves. Notably, when interconnected loops of differing sizes are analyzed, the resulting phase waves exhibit a synchronization pattern, either in-phase or out-of-phase, with pulse counts proportional to their size ratios. This synchronization is further investigated through the introduction of subharmonic injection locking, achieved by applying an external frequency signal matching one of the pulses within the rotating phase waves. Our research delineates the core characteristics of phase waves across oscillator loops of varying sizes, offering a novel approach to generate multiple rotary pulses and amplify the subharmonic response by fine-tuning the oscillators' bias voltage. This paper sheds light on the underlying mechanisms of phase wave synchronization and subharmonic injection locking, with potential applications in enhancing the functionality of coupled oscillator systems. [ABSTRACT FROM AUTHOR]

Oscillators based on resonant tunneling diodes (RTDs) are able to reach the highest oscillation frequency among all electronic THz emitters. However, the emitted power from RTDs remains limited. Here, we propose linear RTD oscillator arrays capable of supporting coherent emission from both in-phase and anti-phase coupled modes. The oscillation modes can be selected by adjusting the mesa areas of the RTDs. Both the modes exhibit constructive interference at different angles in the far field, enabling high-power emission. Experimental demonstrations of coherent emission from linear arrays containing 11 RTDs are presented. The anti-phase mode oscillates at ∼450 GHz, emitting about 0.7 mW, while the in-phase mode oscillates at around 750 GHz, emitting about 1 mW. Moreover, certain RTD oscillator arrays exhibit dual-band operation: changing the bias voltage allows for controllable switching between the anti-phase and in-phase modes. Upon bias sweeping in both directions, a notable hysteresis feature is observed. Our linear RTD oscillator array represents a significant step forward in the realization of large arrays for applications requiring continuous-wave THz radiation with substantial power. [ABSTRACT FROM AUTHOR]

We present here the fabrication at the wafer level and the electrical performance of two types of graphene diodes: ballistic trapezoidal-shaped graphene diodes and lateral tunneling graphene diodes. In the case of the ballistic trapezoidal-shaped graphene diode, we observe a large DC current of 200 µA at a DC bias voltage of ±2 V and a large voltage responsivity of 2000 v/w, while in the case of the lateral tunneling graphene diodes, we obtain a DC current of 1.5 mA at a DC bias voltage of ±2 V, with a voltage responsivity of 3000 v/w. An extended analysis of the defects produced during the fabrication process and their influences on the graphene diode performance is also presented. [ABSTRACT FROM AUTHOR]

Summary: This study provides design criteria of multiphase injection locking for an oscillator loop with multiple rotary pulses that can be utilized for an effective frequency multiplier. Coupled oscillator lattice loops can support phase waves. In the case where N pulses rotate in the loop, the oscillatory signal exhibits N times higher frequency than the rotation frequency of a single rotary pulse. Once an external signal succeeds in injection locking the single‐pulse rotation, the loop operates as an efficient N times frequency multiplier. As in a ring oscillator, the progressive multiphase injection locking is best employed, when the loop supports only a single rotary pulse. Because the phase of the external signal becomes different for each pulse, progressive phase assignment does not work well for multiple rotary pulses; therefore, a more efficient scheme of phase assignment is investigated and validated by bifurcation analyses and measurements. The most effective multiphase injection locking is expected for the phase difference between two neighboring oscillators to be set to −4π/N (4π/N), when N pulses rotate to the cell address increases (decreases) in an oscillator loop. [ABSTRACT FROM AUTHOR]

Upcoming THz applications require compact, robust, and efficient sources with high output‐power. Among electronic devices, resonant tunneling diodes are a promising candidate for THz operation. Triple‐barrier resonant tunneling diodes provide a high degree of design and operation freedom. Zero‐bias detection and THz emission are possible with the same device due to the asymmetric structure and IV curve. However, more investigations in the layer stack design are required. An investigation is presented into the effect of collector spacer thickness and doping profile in the subcollector contact region. The aim is to simultaneously optimize the RF output‐power and cut‐off frequency in triple‐barrier structures. A series of devices with different collector spacers and two distinct doping profiles are fabricated. A trade‐off between collector spacer thickness and doping profile for either higher output power or cut‐off frequency is observed. In addition, the simulation results are presented from a nonequilibrium Green's function solver implemented in Python. Herein, a need for accurate determination of the extent of the nonequilibrium region to achieve simulation results matching the IV measurements is observed. [ABSTRACT FROM AUTHOR]

As a key component for next-generation wireless communications (6 G and beyond), terahertz (THz) electronic oscillators are being actively developed. Precise and dynamic phase control of ultrafast THz waveforms is essential for high-speed beam steering and high-capacity data transmission. However, measurement and control of such ultrafast dynamic process is beyond the scope of electronics due to the limited bandwidth of the electronic equipment. Here we surpass this limit by applying photonic technology. Using a femtosecond laser, we generate offset-free THz pulses to phase-lock the electronic oscillators based on resonant tunneling diode. This enables us to perform phase-resolved measurement of the emitted THz electric field waveform in time-domain with sub-cycle time resolution. Ultrafast dynamic response such as anti-phase locking behaviour is observed, which is distinct from in-phase stimulated emission observed in laser oscillators. We also show that the dynamics follows the universal synchronization theory for limit cycle oscillators. This provides a basic guideline for dynamic phase control of THz electronic oscillators, enabling many key performance indicators to be achieved in the new era of 6 G and beyond. Researchers using femtosecond lasers generate offset-free THz pulses to phase-lock the electronic oscillators. This enables the phase-resolved measurement of the emitted THz pulses with sub-cycle time resolution. Ultrafast dynamic response, such as anti-phase locking behavior, is also observed. [ABSTRACT FROM AUTHOR]

This work studies the behavior of electrical signals in resonant tunneling diodes through the application of the Lonngren wave equation. Utilizing the method of Lie symmetries, we have identified optimal systems and found symmetry reductions; we have also found soliton wave solutions by applying the tanh technique. The bifurcation and Galilean transformation are found to determine the model implications and convert the system into a planar dynamical system. In this experiment, the equilibrium state, sensitivity, and chaos are investigated and numerical simulations are conducted to show how the frequency and amplitude of alterations affect the system. Furthermore, local conservation rules are demonstrated in more detail to unveil the whole system of movements. [ABSTRACT FROM AUTHOR]

This study deals with the Lonngren wave equation, which is used to model the transmission of electrical signals in a type of semiconductor material called a tunnel diode. The aim of this study is to produce dark soliton, singular soliton, trigonometric, complex rational solutions to the Lonngren wave equation by using the sub-equation method. Graphs representing the Lonngren wave are drawn by giving different values to the variables in the solutions obtained. Graphs are presented using a special package program. In the light of the data obtained as a result of the study, it is thought that this new method used in the research of the solution of the Lonngren wave equation will contribute to the literature. [ABSTRACT FROM AUTHOR]

We experimentally demonstrate the creation of defects in monolayer WSe2 via nanopillar imprinting and helium ion irradiation. Based on the first method, we realize atomically thin vertical tunneling light-emitting diodes based on WSe2 monolayers hosting quantum emitters at deterministically specified locations. We characterize these emitters by investigating the evolution of their emission spectra in external electric and magnetic fields, as well as by inducing electroluminescence at low temperatures. We identify qualitatively different types of quantum emitters and classify them according to the dominant electron-hole recombination paths, determined by the mechanisms of intervalley mixing occurring in fundamental conduction and/or valence subbands. [ABSTRACT FROM AUTHOR]

This study undertakes a comprehensive examination of the classical Lonngren wave equation, a fundamental computational model used for simulating electrical signals in semiconductor materials, with specific emphasis on the tunnel diode. The primary objective of this study is to attain novel and more comprehensive solutions beyond those documented in existing literature. To achieve this goal, we have employed well-established mathematical methods, specifically analysis via Lie symmetry, coupled with other specialized techniques such as the power series method and Jacobi elliptic expansion technique. Notably, this marks the inaugural application of these methodologies to the classical Lonngren wave equation, signifying a pioneering endeavor in the exploration of this equation using these analytical tools. These methodologies yield solutions characterized by elliptic functions. The results are visually presented through 3D, 2D, and density plots, effectively illustrating the characteristics of these solutions. The visual representations reveal a range of patterns, including periodic and singular periodic solutions. Furthermore, the paper applies the multiplier method and leverages the conservation theorem introduced by Ibragimov to derive conserved vectors. These conserved vectors play a pivotal role in the examination of physical quantities, such as energy and momentum conservation, thereby enhancing our understanding of the underlying physics within the system. [ABSTRACT FROM AUTHOR]

This article investigates the problem of secure memory adaptive event‐triggered filter design for nonlinear network systems under hybrid network attacks. First, the introduction of memory adaptive event‐triggered mechanism and numerical quantization is employed to enhance system performance, optimize network channel utilization, and prevent network congestion. Second, we consider the impact of deceptive attacks and DoS attacks occurring in the network channel on data transmission, which form the hybrid network attacks studied in this article. Subsequently, based on the established error model, we derive sufficient conditions for the mean‐square exponential stability of the system under a given H∞$$ H\infty $$ performance index using Lyapunov–Krasovskii function and linear matrix inequality (LMI) techniques. Furthermore, the filter parameters are determined using the LMI method. Finally, we illustrate the feasibility and generality of the conclusions through numerical simulation examples and a tunnel diode circuit system. [ABSTRACT FROM AUTHOR]

Resistive random-access memory (RRAM) is a crucial element for next-generation large-scale memory arrays, analogue neuromorphic computing and energy-efficient System-on-Chip applications. For these applications, RRAM elements are arranged into Crossbar arrays, where rectifying selector devices are required for correct read operation of the memory cells. One of the key advantages of RRAM is its high scalability due to the filamentary mechanism of resistive switching, as the cell conductivity is not dependent on the cell area. Thus, a selector device becomes a limiting factor in Crossbar arrays in terms of scalability, as its area exceeds the minimal possible area of an RRAM cell. We propose a tunnel diode selector, which is self-aligned with an RRAM cell and, thus, occupies the same area. In this study, we address the theoretical and modeling aspects of creating a self-aligned selector with optimal parameters to avoid any deterioration of RRAM cell performance. We investigate the possibilities of using a tunnel diode based on single- and double-layer dielectrics and determine their optimal physical properties to be used in an HfOx-based RRAM Crossbar array. [ABSTRACT FROM AUTHOR]

This work investigates the ℋ∞$$ {\mathscr{H}}_{\infty } $$ control problem of discrete‐time singular Markov jump systems against denial of service attacks, in which the Markov state information is seen as restricted access. To solve this situation, a hidden Markov model is introduced. The main objective is to construct a controller with the help of hidden Markov model such that the stochastically admissible of the closed‐loop singular Markov jump systems with limited access mode information can be guaranteed under denial of service attacks. To produce the needed hidden Markov model‐based controller, a matrix contract transformation approach is developed. At the end, a numerical example and a tunnel diode circuit are presented to demonstrate the effectiveness and benefit of the design technique described in this research. [ABSTRACT FROM AUTHOR]

The main aim of this work is to optimize a Quantum Drift Diffusion model (QDD) (V. Romano, M. Torrisi, and R. Tracinà, "Approximate solutions to the quantum drift-diffusion model of semiconductors," J. Math. Phys., vol. 48, p. 023501, 2007; A. El Ayyadi and A. Jüngel, "Semiconductor simulations using a coupled quantum drift-diffusion schrödinger-Poisson model," SIAM J. Appl. Math., vol. 66, no. 2, pp. 554–572, 2005; L. Barletti and C. Cintolesi, "Derivation of isothermal quantum fluid equations with Fermi-Dirac and bose-einstein statistics," J. Stat. Phys., vol. 148, pp. 353–386, 2012) by comparing it with the Boltzmann-Wigner Transport Equation (BWTE) (O. Muscato, "Wigner ensemble Monte Carlo simulation without splitting error of a GaAs resonant tunneling diode," J. Comput. Electron., vol. 20, pp. 2062–2069, 2021) solved using a signed Monte Carlo method (M. Nedjalkov, H. Kosina, S. Selberherr, C. Ringhofer, and D. K. Ferry, "Unified particle approach to Wigner-Boltzmann transport in small semiconductor devices," Phys. Rev. B, vol. 70, pp. 115–319, 2004). A situation of high non equilibrium regime is investigated: electron transport in a Resonant Tunneling Diode (RTD) made of GaAs with two potential barriers in GaAlAs. The range of the suitable voltage bias applied to the RTD is analyzed. We find an acceptable agreement between QDD model and BWTE when the applied bias is low or moderate with a threshold of about 0.225 V over a length of 150 nm; it is found out that the use of a field dependent mobility is crucial for getting a good description of the negative differential conductivity in such a range. At higher bias voltages, we expect that QDD model loses accuracy. [ABSTRACT FROM AUTHOR]

Multi-junction photovoltaics approaches are being explored to mitigate thermalization losses that occur in the absorption of high-energy photons. However, the design of tandem cells faces challenges such as light reflection and parasitic absorption. Nanostructures have emerged as promising solutions due to their anti-reflection properties, which enhances light absorption. III-V nanowires (NWs) solar cells can achieve strong power conversion efficiencies, offering the advantage of potentially integrating tunnel diodes within the same fabrication process. Metal halide perovskites (MHPs) have gained attention for their optoelectronic attributes and cost-effectiveness. Notably, both material classes allow for tunable bandgaps. This study explores the integration of MHPs with III-V NWs solar cells in both two-terminal and three-terminal configurations. Our primary focus lies in the optical analysis of a tandem design using III-V semiconductor nanowire arrays in combination with perovskites, highlighting their potential for tandem applications. The space offered by the compact footprint of NW arrays is used in an interpenetrated tandem structure. We systematically optimize the bottom cell, addressing reflectivity and parasitic absorption, and extend to a full tandem structure, considering experimentally feasible thicknesses. Simulation of a three-terminal structure highlights a potential increase in efficiency, decoupling the operating points of the subcells. The two-terminal analysis underscores the benefits of nanowires in reducing reflection and achieving a higher matched current between the top and the bottom cells. This research provides significant insights into NW tandem solar cell optics, enhancing our understanding of their potential to improve photovoltaic performance. [ABSTRACT FROM AUTHOR]

Vertical stacking of different two-dimensional (2D) materials into van der Waals heterostructures exploits the properties of individual materials as well as their interlayer coupling, thereby exhibiting unique electrical and optical properties. Here, we study and investigate a system consisting entirely of different 2D materials for the implementation of electronic devices that are based on quantum mechanical band-to-band tunneling transport such as tunnel diodes and tunnel field-effect transistors. We fabricated and characterized van der Waals heterojunctions based on semiconducting layers of WSe2 and MoS2 by employing different gate configurations to analyze the transport properties of the junction. We found that the device dielectric environment is crucial for achieving tunneling transport across the heterojunction by replacing thick oxide dielectrics with thin layers of hexagonal-boronnitride. With the help of additional top gates implemented in different regions of our heterojunction device, it was seen that the tunneling properties as well as the Schottky barriers at the contact interfaces could be tuned efficiently by using layers of graphene as an intermediate contact material. [ABSTRACT FROM AUTHOR]

Hole-tunneling Si0.82Ge0.18/Si asymmetric triple-barrier (TB) resonant tunneling diodes (p-RTDs) were created by sputter epitaxy instead of conventional chemical vapor phase epitaxy. As a result, a peak current density (PCD) of 297 kA/cm2 with a peak-to-valley current ratio of 7.3 was recorded at room temperature. The observed high planarity of the films grown by sputter epitaxy is also considered one of the factors behind the high PCD. From the results of self-consistent theoretical calculations of current–voltage characteristics using box-shaped potentials as a first approximation and considering space charge effects of quantum wells, heavy-hole-to-heavy-hole and light-hole-to-light-hole state transitions under the tunneling conditions of the TB potential structure applied in this study were found to be inherent current paths. Moreover, the light and heavy hole currents contribute almost equally to the overall device current, resulting in a theoretical PCD of 637 kA/cm2, which is close to the experimental result. Further analytical simulations with adjusted series resistance and thickness of the nondoped layer allowed the alignment of the theoretically obtained PCD voltage position with the experimentally obtained one. Thus, the theoretical and analytical calculations explain the operation mechanisms of SiGe/Si p-RTDs, and the proposed fabrication method using our sputter epitaxy method is very useful for the actual production of high-PCD SiGe/Si p-RTDs operating at room temperature. [ABSTRACT FROM AUTHOR]

Rectenna is the key component in radio-frequency circuits for receiving and converting electromagnetic waves into direct current. However, it is very challenging for the conventional semiconductor diode switches to rectify high-frequency signals for 6G telecommunication (>100 GHz), medical detection (>THz), and rectenna solar cells (optical frequencies). Such a major challenge can be resolved by replacing the conventional semiconductor diodes with tunneling diodes as the rectenna switches. In this work, metal–insulator–metal (MIM) tunneling diodes based on 2D insulating materials were designed, and their performance was evaluated using a comprehensive simulation approach which includes a density-function theory simulation of 2D insulator materials, the modeling of the electrical characteristics of tunneling diodes, and circuit simulation for rectifiers. It is found that novel 2D insulators such as monolayer TiO2 can be obtained by oxidizing sulfur-metal layered materials. The MIM diodes based on such insulators exhibit fast tunneling and excellent current rectifying properties. Such tunneling diodes effectively convert the received high-frequency electromagnetic waves into direct current. [ABSTRACT FROM AUTHOR]

This work demonstrates high-performance AlN/GaN double-barrier resonant tunneling diodes (RTDs) with high peak current density grown by plasma-assisted molecular beam epitaxy on c-plane free-standing GaN substrates, featuring stable and repeatable negative differential resistance (NDR) characteristics at room temperature. By scaling down the barrier thickness of AlN barrier and the lateral mesa size of collector, the record peak current density of 1551 kA/cm2 is achieved along with a peak-to-valley current ratio (PVCR) of 1.24, which is attributed to the reduced resonant tunneling time under thinner AlN barrier and the suppressed external incoherent valley current by reducing the dislocation number contained in the RTD device with the smaller size of collector. By statistically analyzing the NDR performance of RTD devices with different thicknesses of AlN barrier, the average peak current density increases from 145.7 to 1215.1 kA/cm2, while the average PVCR decreases from 1.45 to 1.1, correspondingly, accompanying with a decreased peak voltage from 6.89 to 5.49 V, with downscaling the AlN barrier thickness from 1.5 to 1.25 nm. The peak current density obtained in this work is the highest value among all the reported nitride-based RTDs up until now while maintaining high PVCR value simultaneously, which illustrates that ultra-scaled RTD based on vertical quantum-well structure and lateral collector size is a valuable approach for the development of nitride-based RTDs with excellent NDR characteristics and reveals their great potential applications in high-frequency oscillation sources and high-speed switch circuits. [ABSTRACT FROM AUTHOR]

This research addresses the problems of finite-time boundedness and disturbance rejection for T-S fuzzy networked systems that are vulnerable to actuator faults, linear fractional uncertainties and multiple disturbances through a reliable anti-disturbance control design. In particular, multiple disturbances encompasses two kinds, where the first kind of disturbance is matched, which is produced by fuzzy exogenous systems and the second kind is mismatched disturbance, which is norm-bounded. Moreover, in order to depict the reality more precisely, the actuator faults are taken into account in the system under consideration. In particular, the fuzzy disturbance observer is constructed for closely estimating the matched disturbances. After that, a reliable anti-disturbance controller is designed in accordance with the output of the conceived disturbance observer. Furthermore, the (ξ 1 , ξ 2 , ξ 3) - η dissipative performance is deployed in order to reduce the imprints of mismatched disturbances to the greatest extent feasible. Moreover, by constructing a Lyapunov-Krasovskii functional, a set of adequate criteria in the form of linear matrix inequalities is established, which guarantees that the undertaken system achieves finite-time boundedness. In conclusion, two numerical examples are shown, one of which is a model of a tunnel diode circuit, which reveals the competence and applicability of the suggested control mechanism. [ABSTRACT FROM AUTHOR]

Miniaturized spectrometers are of immense interest for various on-chip and implantable photonic and optoelectronic applications. State-of-the-art conventional spectrometer designs rely heavily on bulky dispersive components (such as gratings, photodetector arrays, and interferometric optics) to capture different input spectral components that increase their integration complexity. Here, we report a high-performance broadband spectrometer based on a simple and compact van der Waals heterostructure diode, leveraging a careful selection of active van der Waals materials- molybdenum disulfide and black phosphorus, their electrically tunable photoresponse, and advanced computational algorithms for spectral reconstruction. We achieve remarkably high peak wavelength accuracy of ~2 nanometers, and broad operation bandwidth spanning from ~500 to 1600 nanometers in a device with a ~ 30×20 μm2 footprint. This diode-based spectrometer scheme with broadband operation offers an attractive pathway for various applications, such as sensing, surveillance and spectral imaging. Here, the authors report a high-performance broadband spectrometer based on a van der Waals heterostructure tunnel diode containing MoS2 and and black phosphorus, leveraging their electrically tunable photoresponse and advanced computational algorithms for spectral reconstruction. [ABSTRACT FROM AUTHOR]

In this work, the concentric structure of MIS tunnel diodes with coupling effect was explored for memory application. The thickness of the charge storage layer (Al2O3/SiO2) and annealing temperature were controlled to result in an efficient charge trapping with electrons from the substrate. This led to a significant reduction in operation time. In addition, it was found that the signal of non-uniform charge trapping at the device edge could be amplified (about three times) in the tunneling current of nearby MIS TD through the coupling effect. This phenomenon was initially observed and subsequently validated through TCAD simulation. Utilizing the coupling effect and the non-uniform charge storage, the proposed device's operating window is 1 V, with an on/off ratio of approximately 100. Furthermore, it exhibits small cycle-to-cycle variation (3%) and low power consumption. [ABSTRACT FROM AUTHOR]

Herein thin films of CrSe deposited by the thermal evaporation technique onto Pt substrates are designed as Schottky diodes. It is observed that the Pt/CrSe/C (PCC) Schottky diodes are of tunneling type showing barrier height and widths of 0.56 eV and 18 nm, respectively. These diodes displayed biasing dependent nonlinearity and negative slope of differential resistance. The analyses of the cutoff frequency spectra indicated that PCC devices can exhibit high cutoff frequency up to 17 GHz based on the driving signal frequency. The features of the PCC devices make it promising as electronic component suitable for 5G/6G technology applications. [ABSTRACT FROM AUTHOR]

We propose a novel structure for the Esaki tunnel diode that utilizes a quantum well in order to increase the peak-to-valley current ratio. The quantum well is formed by sandwiching a thin layer of GaP between the Si and Ge layers, which creates a potential barrier for carriers. The quantum well enhances the tunneling probability of carriers, resulting in a higher peak current while the valley current remains low; which in total results in a superior peak-to-valley current ratio. We achieve a peak-to-valley current ratio significantly higher than those of conventional heterojunction structures, almost 3.8 fold of them. We use ATLAS TCAD for simulations, which can accurately calculate band-to-band tunneling current. [ABSTRACT FROM AUTHOR]

The technology for production one and two-cascade power laser converters was presented in this paper. According to the measurement results of the grown samples, an efficiency of 34.5% was achieved. A promising design of a cascade photoelectric converter is proposed, in which the cascades are connected with using conduction channels based on GaP microcrystallites. [ABSTRACT FROM AUTHOR]

C2N-ring-based molecular chains were designed at the molecular level and theoretically demonstrated to show distinctive and valuable electron transport properties that were superior to the parent carbonaceous system and other similar nanoribbon-based molecular chains. This new -type molecular chain presented an exponential attenuation of the conductance and electron transmission with the length. Essentially, the molecular chain retained the electron-resonant tunneling within 7 nm and the dominant transport orbital was the LUMO. Shorter molecular chains with stronger conductance anomalously possessed a larger tunnel barrier energy, attributing to the compensation of a much smaller HOMO–LUMO gap, and these two internal factors codetermined the transport capacity. Some influencing factors were also studied. In contrast to the common O impurity with a tiny effect on electron transmission of the C2N rings chain, the common H impurity clearly improved it. When the temperature was less than 400 K, the electron transmission varied with temperature within a narrow range, and the structural disorder deriving from proper heating did not greatly modify the transmission possibility and the exponentially decreasing tendency with the length. In a non-equilibrium condition, the current increased overall with the bias but the growth rate varied with size. A valuable negative differential resistance (NDR) effect appeared in longer molecular chains with an even number of big carbon–nitrogen rings and strengthened with size. The emergence of such an effect originated from the reduction in transmission peaks. The conductance of longer molecular chains was enhanced with the voltage but the two shortest ones presented completely different trends. Applying the bias was demonstrated to be an effective way for C2N-ring-based molecular chains to slow down the conductance decay constant and affect the transport regime. C2N-ring-based molecular chains show a perfect application in tunneling diodes and controllable molecular devices. [ABSTRACT FROM AUTHOR]

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This study integrates the (1 + 1)-dimensional time M-fractional Lonngren-wave (tM-fLW) equation. This equation is useful to describe the phenomenon of the electric signals in telegraph lines at the source of the tunnel diode. To extract some soliton solutions, two reliable analytical techniques, the new form of modified Kudryashov's and the simplest equation, are used to accomplish this job. By implementing these techniques, the obtained solutions are expressed as rational, exponential, trigonometric, and hyperbolic functions with some free constraints. For the special values of the constraints, we obtained w-shape wave, bell-shaped wave, linked rogue wave, and multi-bell wave solutions by the NMK method, and dark bell and bright bell-shaped wave, linked rogue wave, periodic rogue wave, and w-shape wave by the SE method. The graphical depiction analyzes these traits, demonstrating the validity and efficacy of the suggested techniques. The obtained solutions, which have never been done before and show a good balance between the nonlinear physical components, are what make this research novel. It is remarkable to perceive that the simplest equation technique and the new form of modified Kudryashov's technique are relaxed, companionable, and authoritative mathematical tools to elucidate a non-linear model. The movement role of the waves is explored and the modulation instability analysis is used to discuss the stability analysis of the obtained solutions, confirming that all created solutions are accurate and stable. [ABSTRACT FROM AUTHOR]

This paper deals with the issue of adaptive event-driven (AED) fault detection (FD) filter design for discrete-time networked control systems which is modeled by the Takagi–Sugeno (T–S) fuzzy model. First, a new AED scheme is designed to reduce the utilization of limited network resources. Compared with the existing works, the threshold of the AED scheme can be dynamically adjusted in real time by an adaptive law which utilizes the latest released data and the historical released data information. Then, an FD fuzzy filter with mismatched membership functions and AED mechanism is designed, which is used to generate a residual signal and detect system faults. A membership functions iteration strategy is utilized to optimize the membership functions of the FD fuzzy filter in real time, which can achieve better system performance. Furthermore, the sufficient conditions for designing the FD fuzzy filter are obtained in terms of the Lyapunov stability theory. Finally, a simulation example of the tunnel diode circuit system is utilized for proving the effectiveness and showing the advantages of the proposed AED FD strategy. By giving the initial values of relevant parameters, the MATLAB LMI toolbox is used to solve the result experiment. [ABSTRACT FROM AUTHOR]

The integration of communication channels with the feedback loop in a networked control system (NCS) is attractive for many applications. A major challenge in the NCS is to reduce transmissions over the network between the sensors, the controller, and the actuators to avoid network congestion. An efficient approach to achieving this goal is the event-triggered implementation where the control actions are only updated when necessary from stability/performance perspectives. In particular, periodic event-triggered control (PETC) has garnered recent attention because of its practical implementation advantages. This paper focuses on the design of stabilizing PETC for linear time-invariant systems. It is assumed that the plant state is partially known; the feedback signal is sent to the controller at discrete-time instants via a digital channel; and an event-triggered controller is synthesized, solely based on the available plant measurement. The constructed event-triggering law is novel and only verified at periodic time instants; it is more adapted to practical implementations. The proposed approach ensures a global asymptotic stability property for the closed-loop system under mild conditions. The overall model is developed as a hybrid dynamical system to truly describe the mixed continuous-time and discrete-time dynamics. The stability is studied using appropriate Lyapunov functions. The efficiency of the technique is illustrated in the dynamic model of the tunnel diode system. [ABSTRACT FROM AUTHOR]

We investigate the opto-electronic transport properties of AlGaAs/GaAs double-barrier resonant tunneling diodes (RTDs) with GaAs1−xSbx type-II postwells and compare these to RTDs with InxGa1−xAs type-I postwells. Samples grown with Sb containing type-II postwells show a significant photocurrent enhancement for x = 24% compared to 5.5% and 34%, respectively, which is attributed to an efficient hole trapping based on the large hole trapping barrier of 396 meV. By contrasting the RTDs with type-I InGaAs quantum well RTDs, we observe an increased photoresponsivity by one order of magnitude. Our finding allows realizing RTD with efficient hole trapping in the vicinity of the active region of the double barrier structure with confinement energies well above the thermal energy at room temperature, which may allow the observation of single charge configurations even at elevated temperatures. [ABSTRACT FROM AUTHOR]

The optical properties of GaAsN system alloys have not been clarified, particularly for the localized level around the bottom of the conduction band induced by nitrogen atoms. Herein, the recombination mechanism is systematically investigated for heavily Be-doped p-type GaAsN using both continuous-wave (CW) and time-resolved (TR) photoluminescence (PL) characteristics, which is expected to be applied to devices such as a p+-n+ tunnel diode inserted into a multijunction solar cell composed of GaAs system alloys and as the base layer of a heterojunction bipolar transistor. The S-shape characteristic weakened with increasing hole concentration (p) in the CW-PL spectra of Be-doped GaAsN. Both short and long lifetimes were evaluated using TR-PL decay curves. Specifically, the long lifetime was distributed between 0.7 and 1 ns independent of temperature and p. This long lifetime corresponds to radiative recombination lifetime from a localized level, supporting that a localized level is formed in Be-doped GaAsN despite high p on the order of 1019 cm−3. Electrons are tightly bound at a localized level, equivalent to this long lifetime, whereas the electron lifetime decreases with increasing p, resulting in the S-shape characteristic vanishing in the temperature dependence of the CW-PL spectra for ultraheavily Be-doped GaAsN with p of 5 × 1019 cm−3. Moreover, this S-shape characteristic vanished in the temperature dependence of TR-PL spectra for moderately Be-doped GaAsN with p of 8 × 1018 cm−3, indicating that the density of states is limited for a localized level. [ABSTRACT FROM AUTHOR]

Extrinsic impurity defect engineering is demonstrated to increase the maximum asymmetry of metal/insulator/metal (MIM) tunnel diodes. Using atomic layer deposition, transition metal Ni impurities are inserted at precise physical locations within the thickness of the insulating tunnel barrier in asymmetric electrode TiN/Al2O3/Al MIM diodes. The presence of Ni in Al2O3 is found to suppress the onset of Fowler–Nordheim tunneling from the Al electrode without changing the relative dielectric constant or refractive index of the insulator. Current–voltage asymmetry, a performance metric for MIM diodes, is reversed in Al2O3(Ni) devices and is increased over the control Al2O3 device (without Ni impurities) when the Ni impurities are placed close to the Al electrode. Capacitance–voltage measurements on MIM and metal/oxide/semiconductor devices along with Fowler–Nordheim derivative analysis all indicate the introduction of negative charge highly correlated with the position of the Ni defect layer within the Al2O3. Internal photoemission measurements show little change in zero-field energy barrier heights at the electrode interfaces, but varying field dependencies with respect to the position of the Ni defect layer. Combined results suggest that the level of the deep states introduced by the Ni atoms in Al2O3 is consistent with DFT predictions for the corundum Al2O3 system. Overall, this work demonstrates the possibility of improving MIM diode performance using precisely placed extrinsic defects. [ABSTRACT FROM AUTHOR]

Here, we present a systematical investigation of AlN/GaN double-barrier resonant tunneling diodes (RTDs) grown by plasma-assisted molecular beam epitaxy on metal-organic chemical vapor deposition GaN-on-sapphire templates. The processed devices featured an active region composed of 2.5 nm GaN quantum well sandwiched by two 1.5 nm AlN barriers and RTD mesa diameter ranging from 1 to 20 μm. Room temperature current–voltage characteristics exhibited a repeatable negative differential resistance (NDR) free of degradation and hysteresis after 1000 times subsequently up-to-down voltage sweeps across different sizes. High peak-to-valley current ratios of 1.93 and 1.58 were obtained at room temperature for 1 and 12 μm diameter devices, respectively, along with peak current densities of 48 and 36 kA/cm2 corresponding to peak voltages of 4.65 and 5.9 V. The peak current density decreased quickly initially and then was less susceptible to this averaging effect with increasing the device diameter. Temperature-dependent measurements revealed that the valley current density displayed a positive relationship to the temperature, and an abruptly increasement was observed for the devices with a diameter of 20 μm when the temperature rose over 230 K. We attributed this abnormal phenomenon to the increased contribution from acoustic and longitudinal optical (LO) phonon scattering, especially for the LO phonon scattering. The area dependence of electrical performance suggested that the leakage pathway through dislocations played a vital role for charge transport and there existed a threshold of dislocation density for NDR characteristics. These results promote further study for future implementation of III-nitride-based RTD oscillators into high-frequency and high-power terahertz radiation. [ABSTRACT FROM AUTHOR]

The study of the bolometer response to terahertz (THz) radiation from a double-barrier resonant tunneling diode (RTD) biased into the negative differential conductivity region of the I–V characteristic revealed that the RTD emits two pulses in a period of intrinsic self-oscillations of current. The bolometer pulse repetition rate is a multiple of the fundamental frequency of the intrinsic self-oscillations of current. The bolometer pulses are detected at two critical points with a distance between them being half or one-third of a period of the current self-oscillations. An analysis of the current self-oscillations and the bolometer response has shown that the THz photon emission is excited when the tunneling electrons are trapped in (the first pulse) and then released from (the second pulse) miniband states. [ABSTRACT FROM AUTHOR]

A model for tunneling between conduction and valence band tail states in semiconductors is developed. Localized, lifetime-broadened wave functions originally proposed by Vinogradov [Fiz. Tverd. Tela 13, 3266 (1971)] facilitate the derivation of the microscopic transition rate in a homogeneous electric field of arbitrary orientation. A compact analytical form of the average macroscopic tunnel generation rate is approximately calculated assuming that the Gaussian or exponential band tail represents a ladder of closely spaced single-level densities of states. A fully analytical form yields insight into key quantities like the effective tunnel barrier, the tunneling mass, and the pre-exponential factor in comparison to band-to-band tunneling. Tail-to-tail, tail-to-band, and band-to-band tunneling rates are compared against each other over a broad range of field strengths and characteristic tail energies. The numerical implementation of the model into a commercial device simulator accounts for the inhomogeneous field in pn-junctions and excludes invalid tunnel paths. In the application to a fully characterized InGaAs p i n -Esaki diode, all physical processes and parameters that might affect the I V -characteristics are carefully investigated. The value of the bandgap of In 0.53 Ga 0.47 As as a function of density, doping, and temperature is revised. It is shown that tail-induced tunneling cannot explain the strong measured valley current of the diode. Besides band-to-band tunneling, zero- and multi-phonon defect-assisted tunneling are the physical mechanisms that allow to reproduce the entire forward characteristics. Whereas tail-to-band tunneling becomes only visible for very large values of the characteristic tail energy in the heavily doped regions, tail-to-tail tunneling remains a completely negligible process. [ABSTRACT FROM AUTHOR]

A model involving the classical theory of the tunnel diode has been built to describe the Negative Transconductance effect on T6/PDI-8CN 2 gated heterojunction. Fits of the transfer curves presented in the original paper have been performed, and the dependence of the fitting parameters on heterojunction underlying thickness has been analyzed. The good agreement suggests that a more precise explanation of the charge transport in the devices relies on the formation of an accumulation P–N diode-like structure at the interface and on the emergence of the tunneling current for an interval of gate voltages dictated by the specific properties of the two semiconductors. [ABSTRACT FROM AUTHOR]

This work presents the design, fabrication, and measured results of a fully integrated miniature rectenna using a novel tunnel diode known as the Asymmetrical Spacer Layer Tunnel (ASPAT). The term rectenna is an abbreviation for a rectifying antenna, a device with a rectifier and antenna coexisting as a single design. The ASPAT is the centrepiece of the rectifier used for its strong temperature independence, zero bias, and high dynamic range. The antenna is designed to be impedance matched with the rectifier, eliminating the need for a matching network and saving valuable real estate on the gallium arsenide (GaAs) substrate. The antenna is fully integrated with the rectifier on a single chip, thus enabling antenna miniaturisation due to the high dielectric constant of GaAs and spiral design. This miniaturisation enables the design to be fabricated economically on a GaAs substrate whilst being comparable in size to a 15-gauge needle, thus unlocking applications in medical implants. The design presented here has a total die size of 4 × 1.2 mm2, with a maximum measured output voltage of 0.97 V and a 20 dBm single-tone 2.35 GHz signal transmitted 5 cm away from the rectenna. [ABSTRACT FROM AUTHOR]

The system of transient Wigner-Poisson equations (TWPEs) is a common model to describe carrier transport in quantum devices. In this paper, we design a second-order semiimplicit time integration scheme for TWPEs with the inflow boundary conditions, and a hybrid sinc-Galerkin/finite-difference method [H. Jiang, T. Lu, and W. Zhang, J. Comput. Appl. Math., 409 (2022), 114152] is applied for the spatial discretization. The fully-discretized system is rigorously proved to be unconditionally L²-stable, and the computational cost is comparable with that of the second-order explicit Runge-Kutta scheme (ERK2). The numerical method is applied to study a double-barrier resonant tunneling diode (RTD), where representative characteristics of RTDs, including the resonant tunneling effect, bistability and the intrinsic high-frequency current oscillation, are simulated successfully. [ABSTRACT FROM AUTHOR]

This article presents the design of an array of rectennas operating at 28.3 THz for infrared (IR) energy harvesting applications. The basic element of the array consists of a Vivaldi-dipole rectenna composed of two arms made with different conductors (gold and titanium). A metal-insulator-metal (MIM) tunnel diode is used to rectify the THz ac current. The proposed MIM diode consists of a very thin layer of Al2O3 sandwiched between the two metal electrodes. Arrays of two, three, and four rectennas are investigated. The improvement of the energy captured by coupling several elements in the same structure with a common gap is also investigated. This array architecture, without feeding network, may reduce the number of rectifying diodes and, therefore, decrease losses and increase the overall efficiency. Finally, it has been found that the four-elements rectenna array has a maximum electric field intensity of 62.4 × 104 V/m at 28.3 THz. [ABSTRACT FROM AUTHOR]