Junction Capacitance Research Articles

Dark Current Transport and Junction Capacitance Mechanism in InP One-Side Junction Photodiodes

Dark Current Transport and Junction Capacitance Mechanism in InP One-Side Junction Photodiodes

Common Mode and Terminal Voltages With Effect of Device Junction Capacitance in Five-Level Transformerless PV Inverter

Common Mode and Terminal Voltages With Effect of Device Junction Capacitance in Five-Level Transformerless PV Inverter

Synthetic rotational Doppler shift on transmission lines and it’s microwave applications

Rotational Doppler shift of a circularly polarized wave impinging normally on a rotating anisotropic surface, causes scattered waves with frequency shift equals twice the surface rotation frequency. We show that virtual rotational Doppler shift can be realized in transmission line platforms through a time-varying junction. In a system consisting of a pair of decoupled but identical transmission lines, voltage waves with a 90-degree phase difference between the two lines mimic a circularly polarized wave. A junction, comprising three time-varying capacitors and a static two-port network, connects the two lines and acts as a synthetically rotating anisotropic surface. As a result, the reflected and transmitted voltage (or current) waves undergo a frequency shift equal to twice the synthetic rotation frequency. Utilizing this effect, a full frequency converter is then proposed by augmenting the synthetically rotating capacitive junction with a dispersive phase shifter, followed by a short circuit. The system efficiently converts the incident tone into a single down- or up-converted tone, with amplification observed in the case of up-conversion. The frequency converter is subsequently employed to design a magnetic-free isolator. Circuit simulations with both ideal and switch-based time-varying capacitors match theoretical predictions.

The effect of temperature variation on the transient response of RF PIN diode limiters for very high frequency applications

AbstractThis work presents the effect of temperature change on the capacitance of silicon PIN diodes and the resulting change in performance of RF limiters at very high frequency (VHF). Device temperatures were varied between −25 ºC and 100 ºC, with small‐signal parameters (including device capacitance) extracted at regular temperature increments and bias voltages from −20 Vdc to +3 Vdc using a multi‐bias parameter extraction method. It was found that the junction capacitance of the four PIN diodes under investigation increases with temperature, as expected from carrier lifetime behaviour, while results also confirmed prior observations of an inverse relationship between forward‐biased series resistance and temperature. Devices were subsequently tested in two different limiter topologies through high‐power transient measurements. It was found that the combination of increased capacitance and decreased resistance with increasing temperature increases the transient spike leakage and decreases the flat leakage of a limiter. It was also concluded that, for VHF, an anti‐parallel topology provides the best performance over a wide range of temperatures.

A Self-Biased Triggered Dual-Direction Silicon-Controlled Rectifier Device for Low Supply Voltage Application-Specific Integrated Circuit Electrostatic Discharge Protection

A direct bidirectional current discharge path between the input/output (I/O) and ground (GND) is essential for the robust protection of charging device models (CDM) in the tightly constrained design parameters of advanced low-voltage (LV) processes. Dual-direction silicon controlled rectifiers (DDSCRs) serve as ESD protection devices with high efficiency unit area discharge, enabling bidirectional electrostatic protection. However, the high trigger voltage of conventional DDSCR makes it unsuitable for ASICs used for the preamplification of biomedical signals, which only operate at low supply voltage. To address this issue, a self-biased triggered DDSCR (STDDSCR) structure is proposed to further reduce the trigger voltage. When the ESD pulse comes, the external RC trigger circuit controls the PMOS turn-on by self-bias, and the current release path is opened in advance to reduce the trigger voltage. As the ESD pulse voltage increases, the SCR loop opens to establish positive feedback and drain the amplified current. Additionally, the junction capacitance is decreased through high-resistance epitaxy and low-concentration P-well injection to further lower the trigger voltage. The simulation results of LTspice and TCAD respectively demonstrate that ESD devices can clamp transient high voltages earlier, with low parasitic capacitance and leakage current suitable for ESD protection of high-speed ports up to 1.5 V under normal operating conditions.

Versatile platform for electrically reconfigurable THz devices based on silicon Schottky-metasurfaces

We propose a versatile platform to design tunable metasurface devices based on Au/n-Si Schottky diodes embedded in a split-ring resonator (SRR) devised on a Si-on-insulator (SOI) wafer. The horizontally formed diodes are connected in the SRR radial direction, reducing the overall junction capacitance of the metasurface array compared to its counterparts with vertically formed Schottky junctions. This reduction in the junction capacitance has an essential role in the switching speed of the metasurface between the On and Off states. By carefully varying the externally applied bias voltage to the Schottky diodes, one can manipulate the incident THz signal at the metasurface resonance frequencies by converting its resonance mode by switching states. We use the forenamed platform to design three fundamental THz devices: a modulator, a polarization switch, and a polarizing beam splitter. A reverse bias of V R =5V excites two LC resonances at 0.3 THz and 0.89 THz in the modulator, which fade away by switching the gate voltage to V F =0.49V, exciting a dipole resonance in the metasurface at 0.75 THz. The numerical results show that this THz modulator enjoys modulation depths of ≥92% at the LC resonances and a phase modulation of ∼1.16rad at 0.86 THz. An identical electric bias change of the Schottky diodes in the polarization switch alters the resonators from anisotropic to isotropic, changing the output wave polarization from circular with nearly 99% of the circular polarization percentage to linear or quasi-linear at four frequencies simultaneously. Additionally, the proposed THz polarization splitter can deflect the cross-polarized transmitted component from the normally outgoing co-polarized one with an angle of 70° at 0.56 THz. The splitting ratio is switched from 1:1 in reverse bias to 14:1 in forward bias by changing the bias to forward bias. We expect that the proposed designs in the THz frequency domain, benefiting from the several hundred GHz switching speed of the Schottky diodes array, will be beneficial in applications such as analysis of the complex organic structures or polarization modulation and polarization-dependent multiplexing/demultiplexing in wireless communication systems.

RLC resonator with diode nonlinearity: Bifurcation comparison of numerical predictions and circuit measurements

A nonlinear RLC resonator is investigated experimentally and numerically using bifurcation analysis. The nonlinearity is due to the parallel combination of a semiconductor rectifier diode and a fixed capacitor. The diode’s junction capacitance, diffusion capacitance, and DC current–voltage relation each contribute to the nonlinearity. The closely related RL-diode resonator has been of interest for many years since its demonstration of period-doubling cascades to chaos. In this study, a direct comparison is made of dynamical regime maps produced from simulations and circuit measurements. The maps show the variety of limit cycles, their bifurcations, and regions of chaos over the 2D parameter space of the source voltage’s frequency and amplitude. The similar structures of the simulated and experimental maps suggest that the diode models commonly used in circuit simulators (e.g., SPICE) work well in bifurcation analyses, successfully predicting complex and chaotic dynamics detected in the circuit. These results may be useful for applications of varactor-loaded split ring resonators.

Cell-Electrode Models for Impedance Analysis of Epithelial and Endothelial Monolayers Cultured on Microelectrodes.

Electric cell-substrate impedance sensing has been used to measure transepithelial and transendothelial impedances of cultured cell layers and extract cell parameters such as junctional resistance, cell-substrate separation, and membrane capacitance. Previously, a three-path cell-electrode model comprising two transcellular pathways and one paracellular pathway was developed for the impedance analysis of MDCK cells. By ignoring the resistances of the lateral intercellular spaces, we develop a simplified three-path model for the impedance analysis of epithelial cells and solve the model equations in a closed form. The calculated impedance values obtained from this simplified cell-electrode model at frequencies ranging from 31.25 Hz to 100 kHz agree well with the experimental data obtained from MDCK and OVCA429 cells. We also describe how the change in each model-fitting parameter influences the electrical impedance spectra of MDCK cell layers. By assuming that the junctional resistance is much smaller than the specific impedance through the lateral cell membrane, the simplified three-path model reduces to a two-path model, which can be used for the impedance analysis of endothelial cells and other disk-shaped cells with low junctional resistances. The measured impedance spectra of HUVEC and HaCaT cell monolayers nearly coincide with the impedance data calculated from the two-path model.

Harnessing Quantum Capacitance in 2D Material/Molecular Layer Junctions for Novel Electronic Device Functionality.

Two-dimensional (2D) materials promise advances in electronic devices beyond Moore's scaling law through extended functionality, such as non-monotonic dependence of device parameters on input parameters. However, the robustness and performance of effects like negative differential resistance (NDR) and anti-ambipolar behavior have been limited in scale and robustness by relying on atomic defects and complex heterojunctions. In this paper, we introduce a novel device concept that utilizes the quantum capacitance of junctions between 2D materials and molecular layers. We realized a variable capacitance 2D molecular junction (vc2Dmj) diode through the scalable integration of graphene and single layers of stearic acid. The vc2Dmj exhibits NDR with a substantial peak-to-valley ratio even at room temperature and an active negative resistance region. The origin of this unique behavior was identified through thermoelectric measurements and ab initio calculations to be a hybridization effect between graphene and the molecular layer. The enhancement of device parameters through morphology optimization highlights the potential of our approach toward new functionalities that advance the landscape of future electronics.

Modified EPS Control and Topology Modification for Two-Stage Bidirectional AC-DC Converter for V2G Applications

Abstract For the two-stage bidirectional AC-DC converter applied to vehicle-to-grid (V2G), this paper studies the modulation strategy and the topology of the dual active bridge (DAB) converter in the DC-DC stage. Aiming at the problem of large circulating current due to the fixed internal phase shift under the traditional extended phase shift (EPS) control, this paper modified the EPS modulation strategy by deciding whether the internal phase shift is generated by the primary or secondary side based on the voltage gain, which realizes the high-efficiency power transfer under wide voltage gain. To realize the full load range zero voltage switching (ZVS) with junction capacitors taken into account, it is proposed to parallel an additional auxiliary inductor between the bridge arms of the DAB converter, and the operating mechanism and the improved effect are analyzed in detail. Finally, a simulation circuit was built using PSIM software to verify the correctness.

Model Parameters and Degradation Mechanism Analysis of Indium Phosphide Hetero-Junction Bipolar Transistors Exposed to Proton Irradiation

The degradation properties of Indium phosphide hetero-junction bipolar transistors (InP HBTs) under proton irradiation are studied and modelled using a compact model for pre-irradiation, post-irradiation, and post-annealing. The variation rates of the model parameters, such as the base–emitter saturation current (ISE) and ideality factor in the ideal region (NE) in the forward Gummel characteristics, the zero-biased capacitance (Cje) and the grading factor (Mjer) in the BE junction capacitance, and the transit time parameter in the base region (Tfb), are analysed to delve into the degradation mechanism induced by proton irradiation. The displacement damage, induced by proton irradiation in the space charge region of the base–emitter junction and in the quasi-neutral bulk base region, is found to be responsible for the decrease in current gain and cut-off frequency. After annealing, the variation rates of the parameters decrease significantly compared to post-irradiation. This suggests that the recombination of unstable defects leads to a slight recovery in the degradation characteristics of InP HBTs after a period of annealing.

SiC MOSFET Active Gate Drive Circuit Based on Switching Transient Feedback

Due to the influence of parasitic internal parameters and junction capacitance, the silicon carbide (SiC) power devices are frequently marred by significant overshoots in current and voltage, as well as high-frequency oscillations during the switching process. These phenomena can severely compromise the reliability of SiC-based power electronic converters during operation. This study delves into the switching transient of the SiC MOSFET with the goal of establishing a quantitative correlation between the gate driving current and the overshoot in both the drain-source voltage and the drain current. In light of these findings, the innovative active gate drive (AGD) circuit, which features an adjustable gate current, is introduced. Throughout the switching process, the AGD circuit employs a dynamic monitoring and feedback mechanism that is responsive to the gate voltage and rate of change in the drain-source voltage and drain current of the SiC MOSFET. This adjustment enables gate driving current to be actively modified, thereby effectively mitigating the occurrence of overshoots and oscillations. To empirically validate the efficacy of the proposed AGD circuit in curbing voltage and current overshoots and oscillations, a double-pulse experimental setup was meticulously constructed and tested.

Evolutionary algorithm for minimizing the temperature influence of low power RF Energy Harvesting circuits

The aim of this work is to analyze and optimize the design of low-power Radio Frequency (RF) Energy Harvesting rectifiers by using an Evolutionary Algorithm. Although, generally neglected in the literature, the RF rectifier operation strongly depends on the operation temperature. When it varies, the input impedance can change significantly, affecting the circuit matching and its power conversion efficiency. In this work, an evolutionary algorithm is used to identify which parameters of an RF diode are responsible for the performance degradation as a function of temperature and to optimize the rectifier circuit in order to reduce the temperature influence. This work demonstrates that the saturation current, the zero-bias junction capacitance, the load and the series resistance have an important impact in designing an optimized circuit. Results indicate that the applied algorithm can be used aiming the project of a circuit more robust to temperature variations. The obtained results have also been compared to experimental ones, corroborating the analysis.

Discrete ZnO p-n homojunction piezoelectric arrays for self-powered human motion monitoring

Zinc oxide (ZnO), as a typical piezoelectric semiconductor, has gained significant attention in the field of wearable electromechanical coupling. However, the presence of an intrinsic screening effect becomes a bottleneck in developing high-performance ZnO-based piezoelectric devices. To address this limitation, we propose the formation of p-n homojunction by La doping in ZnO nanorods (NRs) as well as discrete structural design to improve their electrical output and flexibility. The enhanced performance and the mechanism behind it are explored and revealed in terms of morphology, structure, built-in electric field, depletion layer width, and junction capacitance, respectively. Benefitting from the excellent electromechanical coupling performance of the developed devices, different human motions can be recognized and classified with the aid of machine learning. These findings provide a new insight into the impact of doping on the output performance of piezoelectric semiconductor devices, thus facilitating advancements in piezoelectric device design and application exploration.

Research on the electro-magnetic protection technique of SCB bridge based on vertical punch through PN junction

Pyrotechnic device is the key initiating component of weapon system, and its function reliability will directly affect the triggering of detonation and actuation mechanism. In order to enhance the survival ability of pyrotechnic device in intricate electromagnetic interference environment, it is necessary to carry out in-depth research on the electromagnetic protection technique of pyrotechnic device. In this paper, a new electromagnetic protection circuit based on vertical punch through PN junction device is proposed, which monolithically integrates the circuit with polysilicon semiconductor bridge on a single chip. The Electro-static Discharge (ESD) test was carried out according to the method specified by standard electrostatic standard 500 pF/500 Ω/25 kV, and the ESD capability of the proposed new chip was not less than 25 kV. Compared with the electromagnetic protection circuit by transient voltage suppressor diode based on lateral punch through junction device structure, the new chip increases the effective junction area of PN junction, reduces the current density, and increases the current conduction ability and electrostatic roughness of the diode. The new chip has a larger diode effective junction capacitance, which not only improves the ESD capability but also improves the RF protection capability at the same time.

A partial soft-switching SiC-based ANPC single-phase inverter with loss model-based dead time optimization for grid-tied PV systems

Single-phase string inverter has been widely applied to grid-tied photovoltaic (PV) rooftop applications for its renewable energy. However, the inherent attribute of intermittency in solar energy may induce instability and unqualified power. To meet the grid-interconnection standards, high demands of efficiency and harmonic distortion need to be imposed on DC/AC inverters. Conventional soft-switching inverters used to sacrificing auxiliary resonant circuits to exchange for soft switching. This requires additional costs as well as sufficient dead time to discharge junction capacitances of all switches, which exacerbates total harmonics distortion (THD) induced by dead-time effect. To improve, this paper proposes a partial soft-switching silicon carbide (SiC) -based active neutral-point-clamped (ANPC) inverter, which possesses high efficiency, eligible dead time, and no auxiliaries. 650-V SiC MOSFET is adopted for its smaller output capacitance compared with Si device. Hybrid PWM modulation is utilized to achieve partial soft switching. Whereas, the soft switching realization range and power losses highly depend on the dead time. To achieve less power loss and improved dead time effect, this paper proposes a loss model-based dead time algorithm through a Power Loss VS. Dead Time mathematical loss model. Moreover, the mechanism of the dead time affected by soft switching is explored. The transition modes, dead time configurable boundaries, and design procedure are also analyzed in detail. A 1-kW prototype is demonstrated with the input of 800 V and the rated output of 220 V/ 4.5 A. Its efficiency could reach 99.6% with THD=0.95% at full power level.

Impact of Current on the Parallel Resistance and Junction Capacitance of Light-Emitting Diodes

Impact of Current on the Parallel Resistance and Junction Capacitance of Light-Emitting Diodes

The enhancing energy efficiency in hyperthermia treatment: a frequency-reconfigurable L-Shape antenna design and analysis

The object of research is a frequency-reconfigurable L-Shape antenna. This paper presents an innovative study focusing on the design and analysis of a frequency-reconfigurable L-Shape antenna with a specific application in Hyperthermia Treatment. The antenna, operating in the frequency range of 2.5 to 8 GHz, utilizes a varactor to achieve agility and simplify design, thereby reducing component count. Constructed with a Roggers RT5880 (lossy) substrate, the L-Shape configuration ensures optimal performance. The incorporation of a single varactor, acting as a junction capacitance, not only enables straightforward tuning but also contributes to enhanced energy efficiency by reducing overall power consumption in the reconfigurable antenna system. The study employed CST Microwave Studio's 3D Electromagnetic field simulation software for time domain solver-based simulations, with validation conducted using the frequency domain solver. Results from the simulations showcase the antenna's performance at different frequency states. At the tuning state frequency of 2.7 GHz, the antenna exhibits an impressive gain of 1.905 dB and a directivity of 7.530 dB. Similarly, at the tuning state frequency of 6.89 GHz, the gain is measured at 6.806 dB with a directivity of 7.490 dB. The proposed L-Shape antenna design not only demonstrates significant potential for Hyperthermia Treatment, allowing targeted heating within the 2.5 to 8 GHz frequency range but also aligns with the multidisciplinary focus of medical science. This contribution reflects the commitment to advancing medical science through original research, fostering innovation, and promoting energy-efficient solutions with practical applications in clinical settings.

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.

Effects of Nonlinear Junction Capacitance of Rectifiers on Performance of High Voltage Power Supplies

Effects of Nonlinear Junction Capacitance of Rectifiers on Performance of High Voltage Power Supplies