Showing papers on "Diffusion capacitance published in 2021"

Analysis of a Hybrid Variable-Frequency-Duty-Cycle-Modulated Low- $Q$ $LLC$ Resonant Converter for Improving the Light-Load Efficiency for a Wide Input Voltage Range

Abstract: Light load efficiency and output voltage regulation of a low- $Q$ LLC resonant converter is a critical problem for wide input voltage and load range applications. Parasitic capacitances such as rectifier diode junction capacitance ( $C_j$ ) degrade the soft switching performance. Compact size, high density, and high transformer turns-ratio requirements for microinverter applications add significant distributed capacitance ( $C_d$ ) of the low-profile transformer, worsening the output regulation and zero-voltage-switching (ZVS) capability at light loads. Wide switching frequency requirement for regulation at light loads, which increases core losses and turn- off switching losses in power MOSFETs, further degrades the power conversion efficiency. The conventional phase-shift modulation causes a high circulating current and loss of ZVS at light loads. Therefore, a hybrid adjustable switching-frequency-duty-cycle modulation technique for improving the light load efficiency is proposed and analyzed for a full-bridge $LLC$ resonant converter. Accurate loss analysis for the proposed modulation scheme, including the effect of parasitic capacitances, is performed using time-domain equations. The proposed methodology precalculates the optimal duty cycle at light load conditions for the required input voltage range such that minimum power losses are incurred. Variation in switching frequency at the preselected duty-cycle value regulates the output voltage. ZVS over a wide range of operating conditions is observed. An experimental prototype for a 20–40 V input, 380-V/300-W output $LLC$ converter is tested for the validation of theoretical analysis.

Response to Comment on “Resolving spatial and energetic distributions of trap states in metal halide perovskite solar cells”

Abstract: Ravishankar et al claimed that drive-level capacitance profiling (DLCP) cannot resolve trap density in perovskites of given thickness. We point out that the trap densities derived by DLCP are from the differential capacitance at different frequencies; thus, the background charges caused by diffusion and geometry capacitance have been subtracted. Even for the nondifferential doping analysis, the contribution from diffusion capacitance is negligible and that from geometry capacitance is excluded.

A New Approach to Designing High-Sensitivity Low-Dimensional Photodetectors.

Abstract: Photodetectors fabricated from low-dimensional materials such as quantum dots, nanowires, and two-dimensional materials show tremendous promise based on reports of very high responsivities. However, it is not generally appreciated that maximizing the internal gain may compromise the detector performance at low light levels, reducing its sensitivity. Here, we show that for most low-dimensional photodetectors with internal gain the sensitivity is determined by the junction capacitance. Thanks to their extremely small junction capacitances and reduced charge screening, low-dimensional materials and devices provide clear advantages over bulk semiconductors in the pursuit of high-sensitivity photodetectors. This mini-review describes and validates a method to estimate the capacitance from external photoresponse measurements, providing a straightforward approach to extract the device sensitivity and benchmark against physical limits. This improved physical understanding can guide the design of low-dimensional photodetectors to effectively leverage their unique advantage and achieve sensitivities that can exceed that of the best existing photodetectors.

An Efficient Three-Phase Resonant DC-Link Inverter With Low Energy Consumption

Abstract: A novel three-phase resonant dc-link inverter with low energy consumption is presented to achieve efficient operation of the inverter. When the auxiliary resonant circuit is used to make the input voltage across bridge-arms become zero during every switching period, the main switching devices could achieve zero-voltage switching turn- on and zero-current switching turn- off . When the metal oxide semiconductor field effect transistor (MOSFET) or the insulated gate bipolar transistor (IGBT) is used as the main switching device, the lossless switching could be completed, and the capacitive turn- on loss caused by the internal junction capacitance of MOSFET and the turn- off loss caused by the tail current of IGBT are eliminated. The working process of the circuit and the realization condition of the soft-switching are analyzed. The experimental results on the three-phase prototype of 2.5 kW show that the switching devices achieve the soft-switching and the performance of the inverter is improved. Therefore, the novel topology is of great significance for improving the efficiency of the inverter.

Thickness-modulated lateral MoS2 diodes with sub-terahertz cutoff frequency

Abstract: Thickness-modulated lateral MoS2 diodes with an extracted benchmark cutoff frequency (fc) of up to 126 GHz are implemented and fully characterised. Fabricated diodes demonstrate an on–off current ratio of more than 600 and a short circuit current responsivity at zero-bias of 7 A/W. The excellent performance achieved in our device is attributed to reduced contact resistance from using In/Au contacts and low junction capacitance due to the lateral device structure. In addition, the use of multilayer MoS2 crystals enabled relatively high current flow. Small- and large-signal models are extracted from DC and RF characterisation of the fabricated diode prototype. Extracted compact models are compared to the measured DC and S-parameters of the diode, demonstrating excellent matching between models and measurements. The presented diode is suitable for switching circuits and high frequency applications.

A Family of Zero-Voltage-Switched Resonant Converters: Derivation, Operation, and Design

Abstract: Soft switching based on resonant operation, through mitigating switching loss and alleviating electromagnetic interference, is essential to high-frequency operation to achieve high power density. To overcome the obstacles of high switch voltage stress and ease the contradiction between voltage stress and conduction loss for traditional single-switch resonant converters, a family of zero-voltage-switched (ZVS) isolated resonant converters is proposed which utilizes a novel resonant switch. The converters enable parasitic components, including transformer leakage inductance, switch output capacitance, and diode junction capacitance to act as a part of resonant components, which facilitates ZVS and zero-current-switching operation and pushes up switching frequency. The specific derivation of the topologies is expounded, and one of the proposed converters is taken for example to perform in-depth analysis, whose mode analysis, operation principles, and parameter design method are minutely presented. Synchronous rectification is employed to further improve efficiency. A prototype was built in the laboratory and the experimental results validate the theoretical analysis well.

TSPEM Parameter Extraction Method and Its Applications in the Modeling of Planar Schottky Diode in THz Band

Abstract: In this paper, a new method for the parameter extraction of Schottky barrier diode (SBD) is presented to eliminate the influence of parasitic parameters on the intrinsic capacitance-voltage (C-V) characteristics of the Schottky diodes at high frequencies. The method is divided into the de-embedding and parameter extraction, including six auxiliary configurations and, is referred tos as Two-step Six-configuration Parameter Extraction Method (TSPEM). Compared to the traditional junction capacitance extraction method, this method can extract the value of junction capacitance at higher frequencies with higher accuracy. At the same time, compared to the other de-embedding methods, this method shows better performance in de-embedding the contributions of parasitic structures from the transmission line measurements. The intrinsic junction capacitances obtained by this method and the three-dimensional (3-D) electromagnetic model are combined to form a diode simulation model, which accurately characterizes the capacitance characteristics of the SBD. It was verified with a 200 GHz double frequency multiplier, and the simulation results and measurement results showed good consistency.

Design and fabrication of CuInS2/ZnS-based QLED for automotive lighting systems.

Abstract: This work reports the design, manufacturing and numerical simulation approach of a 6-pixel (4.5mm2/pixel) electroluminescent quantum dot light emitting device (QLED) based on CuInS2/ZnS quantum dots as an active layer. Following a conventional thin-film deposition multilayer approach, the QLED device was fabricated. In addition, the electrical I-V curve was measured for each pixel independently, observing how the fabrication process and layer thickness have an influence in the shape of the plot. This experimental device fabricated, enabled us to create a computational model for the QLED based on the Transfer Hamiltonian approach to calculate the current density J(mA/cm2), the band diagram of the system, and the accumulated charge distribution. Besides, it is worth highlighting that the simulator allows the possibility to study the influence of different parameters of the QLED structure like the junction capacitance between the distinct multilayer set. Specifically, we found that Anode-HIL interface capacitance has a greater influence in the I-V plot shape. That junction capacitance plays an important role in the current increase and the QLED turn-on value when a forward voltage is applied to the device. Thanks to the simulator, that influence could be put under control by the selection of the optimal thickness and transport layers during the experimental fabrication process. This work is remarkable since it achieves to fit simulation and experiment results in an accurate way for electroluminescent QLED devices; particularly the simulation of the device current, which is critical when designing the automotive electronics to control these new nanotechnology lighting devices in the future.

Nonlinearity and parameterization of Schottky diodes-based battery-free harmonic transponder for millimeter-wave 5G applications

Abstract: Deployment of 5G network infrastructure is a timely opportunity for millimeter-sized battery-free sensors. However, millimeter-wave (mmW) devices often suffer from high conversion loss and path loss that are heavily limiting their communication/detection distance, especially for the case of harmonic transponders based on Schottky diodes. A deep and comprehensive parametric understanding of the second-harmonic generation mechanism of Schottky diodes in the mmW 5G bands can help us to identify suitable diodes or guide diode fabrication to reduce transponder conversion loss. This work reveals that both diode nonlinear junction resistance and capacitance contribute to the second-harmonic generation across the mid-band (sub-7 GHz) and high-band (mmW) 5G frequency bands. However, the nonlinear junction capacitance dominates the second-harmonic generation in the mmW bands. Without Joule heating during the conversion process, the capacitive nonlinearity is more efficient than the resistive nonlinearity, which means that a Schottky diode with a lower junction capacitance will efficiently reduce its associated conversion loss. The VDI GaAs zero bias diode with a low zero bias nonlinear junction capacitance (19.19 fF) shows superior conversion loss performance, which indicates that it can be employed to enhance the detection distance of battery-free harmonic transponders in the mmW 5G bands.

Terahertz Rectennas on Flexible Substrates Based on One-Dimensional Metal–Insulator–Graphene Diodes

Abstract: Flexible energy harvesting devices fabricated in scalable thin-film processes are crucial for wearable electronics and the Internet of Things. We present a flexible rectenna based on a one-dimensional junction metal–insulator–graphene diode, offering low-noise power detection at terahertz (THz) frequencies. The rectennas are fabricated on a flexible polyimide film in a scalable process by photolithography using graphene grown by chemical vapor deposition. A one-dimensional junction reduces the junction capacitance and enables operation up to 170 GHz. The rectenna shows a maximum responsivity of 80 V/W at 167 GHz in free space measurements and minimum noise equivalent power of 80 pW/√Hz.

Highly Efficient Near-Infrared Detector Based on Optically Resonant Dielectric Nanodisks.

Abstract: Fast detection of near-infrared (NIR) photons with high responsivity remains a challenge for photodetectors. Germanium (Ge) photodetectors are widely used for near-infrared wavelengths but suffer from a trade-off between the speed of photodetection and quantum efficiency (or responsivity). To realize a high-speed detector with high quantum efficiency, a small-sized photodetector efficiently absorbing light is required. In this paper, we suggest a realization of a dielectric metasurface made of an array of subwavelength germanium PIN photodetectors. Due to the subwavelength size of each pixel, a high-speed photodetector with a bandwidth of 65 GHz has been achieved. At the same time, high quantum efficiency for near-infrared illumination can be obtained by the engineering of optical resonant modes to localize optical energy inside the intrinsic Ge disks. Furthermore, small junction capacitance and the possibility of zero/low bias operation have been shown. Our results show that all-dielectric metasurfaces can improve the performance of photodetectors.

Investigation of De-embedding Techniques Applied on Uni-Traveling Carrier Photodiodes

Abstract: This work reviews and investigates two de-embedding methods contributing to the characterization of the active region within uni-traveling carrier photodiodes De-embedding techniques remove the parasitic effects of the waveguides connected to the active area of these devices allowing the calculation of their series resistance and junction capacitance The Open-Short method is examined where a systematic error introduced by the technique is identified This error is analytically extracted and a correction is implemented The properties of an S-Parameter based de-embedding are also analyzed through simulation approaches The lumped components calculated and verified by these processes are compared for diodes with different sizes

High-speed and large-responsivity synchronous-traveling carrier photodetector.

Abstract: A synchronous-traveling carrier photodetector (STC-PD) with a thick absorption region and large diameter is presented and investigated for 100 Gbps PAM4 applications. In the STC structure, a suitable electric field is introduced to synchronize the traveling of electrons and holes, which achieves high bandwidth while maintaining large responsivity. The characteristics of STC-PD, including electric field distribution, energy band diagram, responsivity, junction capacitance, and frequency response, have been studied carefully.

A complete small-signal HBT model including AC current crowding effect

Abstract: An improved small-signal equivalent circuit of HBT concerning the AC current crowding effect is proposed in this paper. AC current crowding effect is modeled as a parallel RC circuit composed of Cbi and Rbi, with distributed base-collector junction capacitance also taken into account. The intrinsic portion is taken as a whole and extracted directly from the measured S-parameters in the whole frequency range of operation without any special test structures. An HBT device with a 2 × 20 μm2 emitter-area under three different biases were used to demonstrate the extraction and verify the accuracy of the equivalent circuit.

The analysis of the capacitance of p-InAlAs/i-InGaAs/n-InAlAs infrared photodetector

Abstract: The capacitance of the photodiode still remains some ignored issues. It will facilitate the further analysis and simulation of the capacitance of photodiodes to analyze on the capacitance of the p–i–n InAlAs/InGaAs/InAlAs infrared photodiode. In this paper, the capacitance is divided into two parts, diffusion capacitance and depletion capacitance, to discuss with models in which we solve the divergence of depletion capacitance(CT) at forward bias and take the deep level traps into consideration. Furthermore, we explore the dependence with the delay factor by the calculation of capacitance–voltage (C–V) characteristics. It shows that the delay factor is related to the applied voltage and the frequency.

Transistor Subthreshold Swing Lowered by 2-D Heterostructures

Abstract: Steep-slope transistors are required for low-power electronic applications. However, the strategy to lower the subthreshold swing (SS) remains elusive. Here, we present a method based on altering capacitance constitution to lower the SS of 2-D transistors close to thermionic limit (60 mV/dec). By inducing other 2-D materials with opposite carrier type into the channel, the extra junction capacitance is in series with the channel capacitance, leading to lower semiconductor capacitance and lower SS. The electrical performance of conventional 2-D transistor with pure WSe2 channel and WSe2-BP-MoS2 heterojunction channel is studied and compared. The 2-D transistor with pure WSe2 channel shows SS ~ 110 mV/dec. After forming WSe2-BP-MoS2 heterojunction channel, the SS reduces to ~62 mV/dec and maintains over three orders of magnitude. To reveal the mechanism, a compact model based on Landauer formula has been established. The simulation results indicate that lower SS has strong relation with the reduction of semiconductor capacitance. The proposed structure provides a new way to develop steep-slope transistors.

Investigation of de-embedding techniques applied on uni-traveling carrier photodiodes

Abstract: The generation and transmission of millimeter-wave signals for 5G applications require the use of broadband and high output power photodetectors to bridge from the optical and electronic domains. Therefore, the deep knowledge on the equivalent circuit characteristics of these devices is vital. This study reviews and analyzes de-embedding techniques contributing to the characterization of the physical aspects within the active region of uni-traveling carrier photodiodes. De-embedding methods analytically remove the parasitic effects of the electrical transmission lines connected to their active area allowing the extraction of their series resistance and junction capacitance toward the synthesis of an equivalent circuit with lumped elements. The open-short technique is examined and a systematic error introduced by this process underlines the vulnerability of the method on removing parasitics with higher complexity. This error is quantified leading to the implementation of a corrected equation converging with the characteristic features of an -parameter-based de-embedding. These characteristics are also analyzed through simulation approaches showing minimal equivalent inaccuracies on eliminating more complex symmetrical parasitics. A thorough comparison between these three methods is conducted through the calculation of lumped components corresponding to the active region of diodes with different sizes.

Analyzing the Effect of Parasitic Capacitance in a Full-Bridge Class-D Current Source Rectifier on a High Step-Up Push–Pull Multiresonant Converter

Abstract: This paper presents an analysis on the effect of a parasitic capacitance full-bridge class-D current source rectifier (FB-CDCSR) on a high step-up push–pull multiresonant converter (HSPPMRC). The proposed converter can provide high voltage for a 12 VDC battery using an isolated transformer and an FB-CDCSR. The main switches of the push–pull and diode full-bridge rectifier can be operated under a zero-current switching condition (ZCS). The advantages of this technique are that it uses a leakage inductance to achieve the ZCS for the power switch, and the leakage inductance and parasitic junction capacitance are used to design the secondary side of the resonant circuit. A prototype HSPPMRC was built and operated at 200 kHz fixed switching frequency, 340 VDC output voltage, and 250 W output power. In addition, the efficiency is equal to 96% at maximum load. Analysis of the effect of the parasitic junction capacitance on the full-bridge rectifier indicates that it has a significant impact on the operating point of the resonant tank and voltage. The proposed circuit design was verified via experimental results, which were found to be in agreement with the theoretical analysis.

Design of High-Efficiency Voltage Doubler for Energy Harvesting Application

Abstract: This paper focuses on a single-stage voltage doubler topology using two Schottky diodes, namely HSMS 280C. A single-stage voltage doubler is selected because the topology provides a sufficient DC voltage for powering a power management chip such as BQ25570 with input power starting with -5 dBm onwards. The Schottky diode is used due to its high junction capacitance, Cj of 1.6 pF. The rectifier is designed to operate in the industrial, scientific, and medical 868-MHz/915-MHz band. The maximum efficiency of 90.9 % and 78.11 % was obtained at 868 MHz and 915 MHz, respectively, using a load value of 200 Ω with a low input power of -5 dBm. The designed rectifier can be used as part of the receiver antenna's end side to form a rectenna. The rectifier has been studied and simulated using Advanced Design System and verified by using analytical equations. The same L-type impedance matching has been used throughout the study for consistency.

Analysis and Mechanism of Turn-on Current Spike of SiC MOSFETs

Abstract: Silicon Carbide MOSFET(SiC MOSFET) has the ability of bi-directional conduction and intrinsic body diode. In a voltage-source converter which has bridge legs, an external anti-parallel diode can be omitted compared with Insulated Gate Bipolar Transistor(IGBT) devices. However, the converter efficiency will be reduced when taken into account body diode reverse recovery and excessive conduction voltage drop. At present, SiC MOSFETs is still paralleled by SiC Schottky Barrier Diode(SBD) for freewheeling in many applications. Although the SiC SBD has no reverse recovery current, its junction capacitance will aggravate turn-on current spike. Three methods including SiC SBD, body diode and their paralleling connection are analyzed in the paper. Modeling, analysis and experimental validation are performed to research components of the turn-on current spike and the causes of each component when changing DC link voltages and switching speeds. The results show that the switching speed has the strongest effect on the current spike. The body diode in parallel with SBD deteriorate the turn-on current spike.

Reliable Method for the Measurement of Diffusion Capacitance in Solar Photovoltaic Cells

Abstract: The dynamic parameters of solar photovoltaic (PV) cells, especially the intrinsic diffusion capacitance, are important when they are connected to switched-mode converters or are used in switched-capacitor structures. Furthermore, the dynamic parameters can be used for the minority carrier lifetime measurement of solar PV cells. Among the different small-signal measurement methods suggested in the literature, voltage-biased methods are common. However, diffusion capacitance is an exponential function of the cell voltage over the temperature. Thus, for a given voltage, the diffusion capacitance varies greatly by temperature. In this paper, a current-biased small-signal measurement method is investigated which can not only measure the diffusion capacitance of solar PV cells, but also the parasitic inductance, and the quality factor of the cells. Additionally, different external inductors are used to resonate the solar PV cell at different test frequencies. As a result, the diffusion capacitance, the parasitic inductance, and the quality factor are measured at different frequencies. The method is demonstrated through a hardware prototype.

Analysis of junction capacitance characteristics of trench gate IGBT

Abstract: Trench gate field termination IGBT represents the latest structure of insulated gate bipolar transistor (IGBT) Because the internal current of IGBT includes the charging and discharging current of gate capacitance and internal junction capacitance during switching transient, the influence of junction capacitance should be considered The conductive channel of trench gate structure is different from that of planar gate structure, and the analysis method of junction capacitance using planar gate structure will inevitably bring some deviation Based on the characteristics of trench gate structure, this paper analyzes the different expressions of internal gate-drain junction capacitance in two cases according to whether the base depletion layer can be widened to cover the trench gate, and finally carries out simulation and experimental verification

Semiconductor oscillation suppression circuit

Abstract: The purpose of the present invention is to provide a semiconductor oscillation suppression circuit capable of suppressing the voltage oscillation of a switching element with low loss. The semiconductor oscillation suppression circuit (1) is provided with a wide-bandgap semiconductor element (111a) and a capacitor(13) having a larger capacitance than the junction capacitance of the wide-bandgap semiconductor element (111a) and connected in parallel with the wide-bandgap semiconductor element (111a).

Bidirectional ESD protection device and circuit

Abstract: The invention provides a bidirectional ESD protection device and circuit. The bidirectional ESD protection device comprises a buried oxide layer located on a substrate, three N wells located on the buried oxide layer, a first PMOS transistor arranged in the first N well, a second PMOS transistor arranged in the second N well and a PNP triode arranged in the third N well. Each N well is isolated through a shallow trench isolation structure, and a P+ injection region and an N+ injection region in each N well are isolated through a silicon oxide buried groove; the source electrode of the first PMOS transistor is connected with an input/output port, the grid electrode is connected with the reference ground, and the drain electrode is connected with the base electrode of the PNP triode; the drain electrode of the second PMOS transistor is connected with the base electrode of the PNP triode, the grid electrode is connected with the input/output port, and the source electrode is connected with the reference ground; the emitter of the PNP triode is connected with the input/output port, and the collector is connected with the reference ground. The silicon-on-insulator process is adopted, junction capacitance is small, device frequency is high, power consumption is low, noise is low, and wide application prospects are achieved; and the potential of the base region is controlled through the grid electrode and the substrate of the PNP triode so as to realize the adjustability of the trigger voltage.

Terahertz rectennas on flexible substrates based on one-dimensional metal-insulator-graphene diodes

Abstract: Flexible energy harvesting devices fabricated in scalable thin-film processes are important components in the field of wearable electronics and the Internet of Things. We present a flexible rectenna based on a one-dimensional junction metal-insulator-graphene diode, which offers low-noise power detection at terahertz (THz) frequencies. The rectennas are fabricated on a flexible polyimide film in a scalable process by photolithography using graphene grown by chemical vapor deposition. A one-dimensional junction area reduces the junction capacitance and enables operation in the D-band (110 - 170 GHz). The rectenna on polyimide shows a maximum voltage responsivity of 80 V/W at 167 GHz in free space measurements and minimum noise equivalent power of 80 pW/$\sqrt{\text{Hz}}$.