Tunneling Diodes Research Articles

Investigation of heat-dissipation structures in resonant tunneling diodes and their characteristics on terahertz oscillators

This study investigates the heat dissipation structures for resonant tunneling diodes (RTDs). The n+-InGaAs conductive layer beneath the RTD double-barrier layer, which possesses low thermal conductivity and disrupting heat dissipation, has been replaced with n+-InP, which has high thermal conductivity. We manufactured simple RTD mesa structures with varying areas to analyze the impact of heat dissipation. Additionally, we conducted a study to explore the relationship between mesa area and power consumption at the RTD mesa under current–voltage measurements. The results clearly indicate that the proposed structure, incorporating an n+-InP layer, can function over an area twice as large without experiencing heat-induced destruction. By integrating this proposed structure, we successfully fabricated terahertz oscillators equipped with rectangular-cavity resonators. These oscillators achieved relatively high output power, approximately 0.2 mW was achieved at a frequency of 0.53 THz, all without any heat-induced damage, even within a large-area RTD device.

Strong nonlinear effects of a transmission line stub on resonant tunneling diode oscillators

Strong nonlinear effects of a transmission line stub on resonant tunneling diode oscillators

Enhanced coupling current in center MIS tunnel diode by effective control of the edge trapping in ring with Al2O3/SiO2 gate stack

Enhanced coupling current in center MIS tunnel diode by effective control of the edge trapping in ring with Al2O3/SiO2 gate stack

Effect of Structural Parameters on Current-Voltage Properties of GaAs-based Resonant Tunneling Diodes Using Device Simulator

The resonant tunneling diode (RTD) was first introduced by Tsu and Esaki back in 1973. The RTD has a nano-meter scale dimension and is capable to operate in the terahertz range of frequency, thanks to its unique negative differential resistive (NDR) property. There are tons of potential of RTD capable to implement in many applications if the optimum scales and parameters of the RTD’s structure can be determined. Hence, this is the reason and purpose of this work being conducted. The effects of structural parameters of RTD are studied and analyzed. From the simulation results generated by the WinGreen simulator, the barrier layer thickness has exhibited to be the most performance-affective structural parameter for RTD, when compared to other parameters such as thicknesses of spacer and quantum-well layers, and doping concentration of emitter and collector layers. The highest peak-to-valley current ratio (PVCR) of InGaAs/AlAs RTD achieved is approximately 78.36 with its barrier layer thickness of 1.6 nm. For GaAs/AlAs RTD, the highest PVCR obtained is approximately 59.29 at 1.6 nm thick of its barrier layer.

(Invited) Simulations of Ultra-Scaled Electronic Devices with a Novel Flexible Nano-TCAD Nano-Electronic Simulation Software (NESS) Environment

Simulation of conventional and emerging electronic devices using Technology Computer Aided Design (TCAD) tools has been an essential part of the semiconductor industry as well as academic research. Computational efficiency and accuracy of the numerical modeling are the key criteria on which quality and utility of a TCAD tool is ascertained. Further, the ability of the tool to incorporate different modeling paradigms and to be applicable to a wide range of device architectures and operating conditions is essential.In this talk, I will provide an overview of the new device simulator NESS (Nano-Electronic Software Simulator) developed at Device Modelling Group at University of Glasgow. NESS is a fast, modular software with its own structure and mesh generators, and contains different modules for classical, semi-classical, and quantum transport solvers, mobility calculation, kinetic Monte-Carlo etc. NESS can simulate numerous device architectures such as nanowire and bulk transistors, tunnelling field effect transistors (TFET) and resonant tunnelling diodes. Moreover, NESS accounts for various sources of statistical variability in nano-size electronic devices and it can perform statistical simulations for thousands microscopically different devices.

Metasurfaces for Resonant Tunneling Diodes with Double Metal Waveguides

The paper proposes designs of distributed resonant tunneling diodes (RTDs) with a double metal waveguide (DMW), in the top electrode of which a periodic pattern (metasurface) is formed based on holes in a hexagonal array and a chain of slotted (split-ring) resonators. This solution will make it possible to control the phase velocity of the propagating wave and increase the wave impedance in order to reduce ohmic losses in the waveguide, as well as to create a generation mode in it. For the proposed designs of metasurfaces, electromagnetic modeling was carried out and the input impedances of the resonators were calculated.

Nanoarray of Vivaldi Rectenna for Infrared-energy Harvesting

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.

On the validity of the Fourier law in a Resonant Tunneling Diode

On the validity of the Fourier law in a Resonant Tunneling Diode

Numerical Simulation and Design of All-Thin-Film Homojunction Perovskite/c-Si Tandem Solar Cells

Double-junction solar devices featuring wide-bandgap and narrow-bandgap sub-cells are capable of boosting performance and efficiency compared to single-junction photovoltaic (PV) technologies. To achieve the best performance of a double-junction device, careful selection and optimization of each sub-cell is crucial. This work presents the investigation of an all-thin-film two-terminal (2T) monolithic homojunction perovskite (PVK)/c-Si tandem cell using Silvaco TCAD simulation. The front sub-cell utilizes homojunction PVK that has a bandgap of 1.72 eV, whereas the rear sub-cell uses thin c-Si with a bandgap of 1.12 eV. Both cells are connected via a p++/n++ silicon tunnel diode. Experimental calibration of the heterojunction PVK and c-Si cells yields power conversion efficiencies (PCE) of 18.106% and 17.416%, respectively. When integrated into an initial PVK/c-Si tandem, the resulting cell achieves a PCE of 29.38%. To compare the performance, the heterojunction PVK layer is replaced with an n-p homojunction PVK layer, revealing the impact of the absence of a surplus built-in electric field in the perovskite film as a strong limiting factor. Further, a thorough investigation of four distinct structures for the n-p homojunction PVK cell is conducted. The four structures include a complete cell, electron transport layer (ETL)-free, hole transport layer (HTL)-free, and carrier transport layer (CTL)-free structures. The results show that the CTL-free structure has significant potential after applying certain optimization techniques that result in reducing surface recombination, enhancing the built-in electric field, and improving light absorption. With the current-matching condition achieved, the tandem efficiency reaches 36.37%.

Investigation of junction capacitance in Zener tunnelling tunnel diode partially depleted silicon on insulator

Junction capacitance variation in Zener Tunnelling Tunnel Diode Partially Depleted Silicon On Insulator (ZT-TDPDSOI), due to the geometry effects of source and drain are discussed in this paper. Electric field profile and a capacitance equivalent circuit are used to reveal the gate-source capacitance dependence on the P+ region in ZT-TDPDSOI. It is demonstrated how the inclusion of a P+ region below the source/drain region impacts the gate substrate capacitance using the hole concentration and valence band energy at the source channel junction. A decrease of 42 % was noted in gate-substrate capacitance for a P+ doping of 2*1020/cm3 and thickness of 0.05 μm under fixed biased condition. The use of the trapezoidal approximation is also suggested as an extraction technique for the depletion width.

Membership-function-dependent [formula omitted] bumpless transfer control for switched interval type-2 fuzzy systems with time-delay

This paper addresses the H∞ bumpless transfer control for switched nonlinear delayed systems with exogenous perturbations via the interval type-2 fuzzy model. We firstly establish a novel characterization of bumpless transfer performance, which provides a framework to the bumpless transfer control of switched nonlinear systems. By using the multiple Lyapunov-Krasovskii functionals and the state-dependent switching strategy, sufficient conditions for asymptotically stability with H∞ bumpless transfer performance are obtained. More incisively, different from the existing results where the H∞ bumpless transfer control design conditions do not involve the information of membership functions, we adopt the piecewise-linear-membership-function technique to remove this limitation. Correspondingly, novel membership-function-dependent H∞ bumpless transfer criteria are derived, under which the state-dependent switching law and H∞ bumpless transfer controllers are jointly designed. Finally, a tunnel diode circuit model is exploited to verify the applicability and validity of the developed method.

Fuzzy $\mathcal {H}_{\infty }$ Control of Semi-Markov Jump Singularly Perturbed Nonlinear Systems With Partial Information and Actuator Saturation

This paper focuses on the fuzzy control problem for a class of semi-Markov jump singularly perturbed nonlinear systems with actuator saturation. Nonlinearities in the underlying systems are tackled with the Takagi-Sugeno fuzzy model. As distinct from the previous achievements, the case that the semi- Markov kernel with partially known information is taken into account such that the underlying systems can be extended to a wider scope. Given that actuator saturation is ubiquitous in engineering systems, the convex hull method is embraced to address this circumstance. To reduce the conservativeness of the obtained results, on the basis of Lyapunov stability theory and LaSalle's invariance principle, some criteria related to the sojourn time are presented. Next, the mean-square exponential stability of the underlying system is obtained based on the derived results. Finally, further experiment to verify the feasibility of the proposed methodology is given by a tunnel diode circuit model.

Mathematical analysis of electric signal transmission in semi-conductor materials

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.

Improved dynamic event-triggered [formula omitted] control for networked fuzzy singularly perturbed systems with hidden Markov fading channels

In this paper, the dynamic event-triggered H∞ control problem is explored for networked fuzzy slow sampling singularly perturbed systems (S3PSs) subject to hidden Markov fading channels. To alleviate the communication burden more effectively, an improved dynamic event-triggered scheme (DETS) is constructed for networked fuzzy S3PSs, under which two auxiliary internal dynamic variables are considered into event-triggered condition. The fading channel phenomena with randomly time-varying amplitudes are characterized by the finite state Markov process. Meanwhile, considering the actual network mode may be unmeasurable, a hidden Markov mode detector is exploited to estimate the actual network mode, by which the control signal can be adjusted appropriately. By constructing the singular perturbation parameter (SPP)-dependent Lyapunov functional, sufficient conditions are obtained to guarantee the mean square stability of networked fuzzy S3PSs. Besides, the numerical ill-conditioned problem of networked fuzzy S3PSs can be avoided. Finally, a tunnel diode circuit example is proposed to illustrate the effectiveness of the main results.

Superior peak-to-valley current ratio in Esaki diode by utilizing a quantum well

Superior peak-to-valley current ratio in Esaki diode by utilizing a quantum well

A deep dive into structural, electronic, optical, and mechanical properties of ATiO3 (A = Ba, Th): DFT insights

Different physical characteristics (structural, optical, electronic, and mechanical) of ThTiO3 were explored using DFT and compared to BaTiO3. ThTiO3 has been determined to be mechanically and thermodynamically stable based on the simulation results, which were validated using the Born stability criteria and formation energy. Furthermore, a significant modification in the traits of ThTiO3 has been revealed compared to BaTiO3. For example, after the complete substitution of Ba by Th, in the case of GGA-PBE, the band gap increases from 1.82 eV to 3.37 eV, while in the case of HSE-06, it increases from 3.254 eV to 4.21 eV, also converting from indirect to direct bandgap. Not only that, but ThTiO3 has become an n-type degenerate semiconductor from a conventional semiconductor, which assures potential applications in tunnel diodes, high-frequency transistors, photocatalysts, etc. ThTiO3 is an appropriate material for capacitors, optoelectronic, and high k nanoelectronics devices based on the high dielectric constant value, which is higher than BaTiO3. Moreover, with Th substitution, BaTiO3 transitioned from brittle to ductile, which ensures its suitability for industrial machining processes. Furthermore, this substitution also improved the material’s anisotropic behavior, as the Zener Anisotropy value for ThTiO3 is also higher than BaTiO3. We believe this investigation will open another door in the field of materials for microelectronics and optoelectronics enthusiasts.

Experimental and Theoretical Investigation of Collector Spacer and Doping Profile on Triple‐Barrier Resonant Tunneling Diodes

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.

Resonant tunneling injection of electrons through double stacked GaAs/InAs quantum dots with nanohole electrode

Resonant tunneling diodes containing closely double-stacked InAs quantum dots (QDs) were grown on GaAs substrates by MBE. After growing a thin GaAs capping layer on the double-stacked InAs QDs, nanoholes were selectively formed just above the larger second QDs by thermal annealing. The Au thin film was deposited directly on top surface of the larger second QDs through the nanoholes. The second QDs contacted with Au film served as conducting dots, which can locally inject electrons into the underlying first QDs. In current versus voltage (I–V) measurements, (dI/dV) peaks were clearly observed in the forward bias voltage region. It was due to the tunneling current through a non-doped GaAs thin layer between double-stacked QDs and n-GaAs conduction band. The (dI/dV) peaks shifted toward the lower forward voltage region with increasing temperature. It was explained by the temperature dependence of the electron energy distribution in the GaAs conduction band.

Fuzzy H∞ Control of Discrete-Time Nonlinear Markov Jump Systems via a Novel Hybrid Reinforcement Q -Learning Method.

In this article, a novel hybrid reinforcement Q -learning control method is proposed to solve the adaptive fuzzy H∞ control problem of discrete-time nonlinear Markov jump systems based on the Takagi-Sugeno fuzzy model. First, the core problem of adaptive fuzzy H∞ control is converted to solving fuzzy game coupled algebraic Riccati equation, which can hardly be solved by mathematical methods directly. To solve this problem, an offline parallel hybrid learning algorithm is first designed, where system dynamics should be known as a prior. Furthermore, an online parallel Q -learning hybrid learning algorithm is developed. The main characteristics of the proposed online hybrid learning algorithms are threefold: 1) system dynamics are avoided during the learning process; 2) compared with the policy iteration method, the restriction of the initial stable control policy is removed; and 3) compared with the value iteration method, a faster convergence rate can be obtained. Finally, we provide a tunnel diode circuit system model to validate the effectiveness of the present learning algorithm.

Development of a simple two-step lithography fabrication process for resonant tunneling diode using air-bridge technology

This article reports on the development of a simple two-step lithography process for double barrier quantum well (DBQW) InGaAs/AlAs resonant tunneling diode (RTD) on a semi-insulating indium phosphide (InP) substrate using an air-bridge technology. This approach minimizes processing steps, and therefore the processing time as well as the required resources. It is particularly suited for material qualification of new epitaxial layer designs. A DC performance comparison between the proposed process and the conventional process shows approximately the same results. We expect that this novel technique will aid in the recent and continuing rapid advances in RTD technology.