Junction Capacitance Research Articles

Switching Dynamics Analysis by Various Models of Hf0.5Zr0.5O2 Ferroelectric Thin Films

Recent discoveries of ferroelectric properties in ultrathin doped hafnium oxide (HfO2) have led to the expectation that HfO2 could overcome the shortcomings of perovskite materials and be applied to electron devices such as Fe-Random access memory (RAM), ferroelectric tunnel junction (FTJ) and negative capacitance field effect transistor (NC-FET) device. As research on hafnium oxide ferroelectrics accelerates, several models to analyze the polarization switching characteristics of hafnium oxide ferroelectrics have been proposed from the domain or energy point of view. However, there is still a lack of in-depth consideration of models that can fully express the polarization switching properties of ferroelectrics. In this paper, a Zr-doped HfO2 thin film based metal-ferroelectric-metal (MFM) capacitor was implemented and the polarization switching dynamics, along with the ferroelectric characteristics, of the device were analyzed. In addition, a study was conducted to propose an applicable model of HfO2-based MFM capacitors by applying various ferroelectric switching characteristics models.

High-Speed Light Signal Transmitters for Optical Communication Based on Ultraviolet Radiation

A light signal transmitter based on ultraviolet radiation is realized on GaN-on-silicon platform. The light signal transmitter with ultra-small active area is fabricated by a double-etching process. The absolute value of negative junction capacitance of transmitter is as low as the pF (picofarads) scale in positive bias voltage. Small capacitance is beneficial to improve the communication performance of a transmitter. The dominant EL (electroluminescence) peak of transmitter is located at about 380 nm in the ultraviolet range. With the increase of the current, the dominant peak of transmitter remains stable and the light output power is lineally modulated. A free-space data transmission test in the ultraviolet range with 250 Mbps was conducted to indicate a promising high-speed optical communication capability of a light signal transmitter in the ultraviolet range.

Electrodynamics of Highly Spin-Polarized Tunnel Josephson Junctions

The continuous development of superconducting electronics is encouraging several studies on hybrid Josephson junctions (JJs) based on superconductor/ferromagnet/superconductor (SFS) heterostructures, as either spintronic devices or switchable elements in quantum and classical circuits. Recent experimental evidence of macroscopic quantum tunneling and of an incomplete 0-pi transition in tunnel-ferromagnetic spin-filter JJs could enhance the capabilities of SFS JJs also as active elements. Here, we provide a self-consistent electrodynamic characterization of NbN/GdN/NbN spin-filter JJs as a function of the barrier thickness, disentangling the high-frequency dissipation effects due to the environment from the intrinsic low-frequency dissipation processes. The fitting of the IV characteristics at 4.2K and at 300mK by using the Tunnel Junction Microscopic model allows us to determine the subgap resistance Rsg, the quality factor Q and the junction capacitance C. These results provide the scaling behavior of the electrodynamic parameters as a function of the barrier thickness, which represents a fundamental step for the feasibility of tunnel ferromagnetic JJs as active elements in classical and quantum circuits, and are of general interest for tunnel junctions other than conventional SIS JJs.

Polycrystalline Silicon Solar Cell p-n Junction Capacitance Behavior Modelling under an Integrated External Electrical Field Source in Solar Cell System

The state of the p-n junction is very important to explain the performances of a solar cell. Some works give the influence of the electric field on the junction capacitance. However, these works do not relate the quality of the p-n junction under the electic field. The present manuscript is about a theoretical modelling of the p-n junction capacitance behavior of the polycrystalline silicon solar cell under an integration of the external electrical field source. An external electrical source is integrated in a solar cell system. The electronic carriers charge generated in the solar cell crossed mainly the junction with the great strength external electrical field. In open circuit, this crossing of the electronic charge carriers causes the thermal heating of the p-n junction by Joule effect. The p-n junction capacitance plotted versus the junction dynamic velocity and the photo-voltage for different external electrical fields. The electric field causes the decrease of the photo-voltage mainly the open-circuit photo-voltage. The decrease of the photo-voltage translates the narrowing of the Space Charge Region (SCR). The average value of the external electric field used in this study is not sufficient to cause the breakdown of the p-n junction of the solar cell system under integration of the external electrical field production source. The increase of the electrical field causes rather the narrowing of the SCR. That can provide an improvement of the solar cell’s electrical outputs.

Effects of External Magnetic Field and Air Mass on Space Charge Region Width Extension of a Bifacial Solar Cell Front Side Illumination

The environmental and economical merits of converting solar energy into electricity via photovoltaic cells have caused an ever increasing interest among developed and developing countries to allocate more budget on photovoltaic systems in order to boost up their efficiency in recent years. Besides the material and design parameters, there are several external factors such as magnetic field, air mass, intense light, external electric field, solar spectrum…. that can influence the PV cell’s performance. There have been a handful of studies conducted on the effect of various influential parameters on the efficiency and performance of photovoltaic cells; however none has taken these two parameters (magnetic field and air mass) into account simultaneously. In this 3D study the effects of magnetic field and the air mass illumination on space charge region width extension of a bifacial polycristalline solar cell front side illumination will be elaborated. Based on the columnar model of the grain and the quasi-neutral base, the continuity equation is established and the boundaries conditions are defined in order to use Green’s functions to solve this equation. New analytical expression of charge carriers’ density is found and the diffusion capacitance to the junction is calculated. The normalized carriers’ density plot versus base depth and magnetic field with various air mass illumination are presented and analyzed. The effects of magnetic field and air mass illumination on space charge region width extension are then deducted. The influences of magnetic field and air mass illumination on the junction capacitance and on the reverse of junction capacitance are also shown and analyzed.

Comparative Validation of SRAM Cells Designed using 18nm FinFET for Memory Storing Applications

The limitation of CMOS to operate under 25nm is a major concern, which is viewed in this paper. Also, scaling issues like leakage current, lower carrier mobility, higher junction capacitance limits the transistor operation is discussed. At lower voltage values, CMOS productive decreases drastically, which reflects on the performance of the circuit to achieve its criteria’s. In the present-day scenario of electronic industry, the speed of the processor is increasing, the urge for speed cache memory is also increasing. In cache memory design, SRAM cell is mainly used, CMOS SRAM Cells are producing more delay and also limitations like mentioned above. Therefore, an alternative preferred choice for SRAM Cells is FinFET, which increases the speed of the Cell by avoiding limitations caused by the bulk CMOS. By considering the advantages of the FinFET, SRAM Cells are implemented in Cadence virtuoso using FinFET 18nm Spectre. In this paper, standard SRAM Cells like 7T, 8T, 9T, and 1oT are simulated and parameters like power, delay, power delay product (PDP), energy-delay product (EDP) are calculated and respective values are presented by varying the voltage (V). SRAM Cells behavior under different voltages is graphically represented. CMOS SRAM Cell values have been taken from previous works of SRAM. By comparing the parameters, a drastic increase in the speed of the FinFET SRAM Cells can be observed over CMOS SRAM Cells.

Quad-Band Rectenna for RF Energy Harvesting System

The design of multiband microstrip rectenna for radio frequency energy harvesting applications is presented in this paper. The designed antenna has good performance in the GSM-900/1800, WiFi and WLAN bands. In addition, the rectifier circuit is designed at multi resonant frequencies to collect the largest amount of RF ambient power from different RF sources. The developed antenna is matched with the rectifier at four desired frequencies using several rectifier branches to collect the largest of RF power. The proposed rectenna is printed on FR4 substrate with modified ground plane to achieve suitable impedance bandwidth. The proposed antenna consists of elliptical radiating plane with stubs and stepped modified ground plane. The rectenna resonates at quad frequency bands at (GSM 900/1800, WiFi band and WLAN bands) with rectifier power conversion efficiency up to 56.4% at 0 dBm input power using the HSMS-2850 Schottky diode. The efficiency is more enhanced by using SMS-7630-061 Schottky diode which is characterized by a low junction capacitance and a low threshold voltage to achieve higher conversion efficiency up to 71.1% at the same 0 dBm input power for the same resonating frequency band.

Development of Low-Noise Charge-Sensitive Preamplifier Based on PIPS Detector

In this paper, a low-noise charge-sensitive preamplifier (CSA) is designed based on passivation ion implanted planar silicon (PIPS: The Passivated Implanted Planar Silicon) detectors. This charge-sensitive preamplifier uses Junction Field-Effect Transistor (JFET) as the first stage of the amplifier. In order to maximize the signal-to-noise ratio and consider the resistance-capacitance matching problem, according to different PIPS detector junction capacitances, different numbers of junction field effect transistors are matched in parallel in the first stage. Slotting technology is used at the feedback end to reduce the influence of the parasitic capacitance of the PCB board on the feedback, and the feedback capacitor resistance is adjusted to achieve the best signal-to-noise ratio. Experimental test results show that the charge-sensitive preamplifier can achieve a signal-to-noise ratio greater than 100 at room temperature, the output signal rise time is less than 60 ns, and the electronic equivalent capacitance noise is 19 eV/pF. The charge-sensitive preamplifier is connected to the Canberra PD450-17-100AM PIPS detector, and the standard α source 238Pu is measured in a vacuum environment. The energy resolution can reach 17keV@5499keV.

Stability Prediction of Soft Switched Isolated DC-DC Converter

Mathematical analysis and stability prediction of soft switched isolated dc-dc converter is presented in this paper. Half bridge dc-dc converter is an attractive topology for low voltage applications due to its simplicity, lower cost, improved reliability and enhanced dynamic performance. Both power semiconductor switches of the proposed isolated converter operate asymmetrically under Zero Voltage Switching (ZVS) to achieve high efficiency and low voltage stress. Furthermore, the ringing resulted from the oscillation between the transformer leakage inductance and the junction capacitance of two switches is eliminated. Conversion efficiency is also improved by providing synchronous rectifier with very small output filter. The operating principle, state space analysis and control strategy of proposed converter is explained with small signal model. Experimental results are presented to explain the zero voltage switching capability and stability features of proposed converter.

Air Stable Indium-Gallium-Zinc-Oxide Diodes With a 6.4 GHz Extrinsic Cutoff Frequency Fabricated Using Adhesion Lithography

High speed rectifiers that can be fabricated at low cost whilst still maintaining a high performance are of interest for wireless communication applications. In this letter amorphous indium gallium zinc oxide (a-IGZO) has been used with adhesion lithography (a technique to create asymmetric planar electrodes separated by a nanogap) to fabricate high performance Schottky diode rectifiers. The diode area and junction capacitance can be significantly reduced using this technique, improving device cut-off frequencies. Devices of different widths have been fabricated showing rectification ratios between 103-104. Capacitances measured for devices of various sizes were all on the order of 0.1 pF. By applying ac signals to the diode and measuring the output voltage across a load resistor a cut-off frequency was found. a-IGZO diodes with an extrinsic cut-off frequency of 6.4 GHz at a 15 dBM input power have been realized. The devices also show good air stability with little change in current-voltage characteristics after 12 months.

Analysis of Diode Reverse Recovery Effect on ZVS Condition for GaN-Based LLC Resonant Converter

LLC resonant converter can achieve zero voltage switching (ZVS) for primary-side devices and zero current switching (ZCS) for secondary-side rectifiers. However, the reverse recovery and junction capacitance ( Cj ) of secondary-side diode critically affect the ZVS condition of primary-side switches. The effect of Cj has been discussed in literature, but not the reverse recovery. In this paper, the reverse recovery charge ( Q rr) is converted to an equivalent capacitance $(C_{{\rm rr}\_{\rm eq}})$ for the study of primary-side ZVS performance. An accurate model during deadtime is derived and further applied to characterize ZVS performance with different reverse recovery charges in different regions. The concept of establishing parameter C total to consider both Cj and $C_{{\rm rr}\_{\rm eq}}$ is proposed to evaluate the effect of the secondary-side rectifiers. This concept provides the guideline for diode and synchronous rectification mosfet selection to ensure ZVS condition for LLC converters. To verify the concept and the derived model, a 200/400 V 400 W LLC resonant converter prototype operating from 200 to 700 kHz is built and its ZVS performances with different diodes are compared. Two issues caused by Q rr effect, including $V_{\rm ds}$ reverse charging and asymmetrical waveform during deadtime, are explained thoroughly as well.

High Performance Van der Waals Graphene–WS2–Si Heterostructure Photodetector

Abstract2D materials have become a major focus in material science due to their exotic properties originated from quantum confinement effects. Van der Waals heterostructures composed of 2D materials and conventional semiconductors always show enhanced optoelectronic performance and have attracted much attention in recent years. Here, high performance photodetectors based on graphene–WS2–Si van der Waals heterostructure is reported. The photodetector shows wide spectrum response from visible to near infrared with a maximum photoresponsivity of 54.5 A W−1 at 800 nm. Furthermore, the photodetector has a fast response speed with rise time of 45 µs and decay time of 210 µs. Photocurrent mapping shows that not only the graphene–WS2–Si area, but also the graphene–WS2–SiO2–Si area contributes to the photocurrent. With the increase of lateral size of the junction area, the photoresponsivity is reduced due to increased recombination. The response speed decreases with the increase of lateral size of the junction area, which is due to increased junction capacitance. The results indicate that this kind of van der Waals heterostructure has excellent photodetection performance and is suitable for application in high performance broadband photodetectors. Also, the simple fabrication method has a great potential for large scale device integration.

A Fast and Precise Method for Modeling EMI Source in Two-Level Three-Phase Converter

Currently, frequency-domain electromagnetic interference (EMI) modeling has become the most commonly used method for EMI prediction and filter design. However, because of the unpredictability of the ringing effect in the present frequency-domain EMI modeling methods, the precision of the predicted EMI interference source is notably limited, which results in the inaccuracy of the system level EMI prediction. In order to achieve an accurate EMI prediction, this study presents a systematical study on the interference source of a 10 kVA three-phase bridge converter. The precise mathematical models of the common-mode and differential-mode interference source are constructed. Then, the characteristics of the multiple ringing effect, which is an important part of the interference source, are intensively analyzed. Based on the investigation of interference source, an improved interference source synthesis method is proposed. It can quickly and precisely predict the CM and DM interference source with multiple ringing effect, which can be used to achieve accurate frequency domain EMI prediction. Moreover, the multiple ringing effect is extended for IGBT parasitic parameter measuring. Instead of complicated device-level measurement, the grounding capacitance and junction capacitance can be effectively extracted through the ringing frequency measurement.

An Improved Hybrid-Bridge Transformerless Inverter Topology With Bidirectional Clamping and Reactive Power Capability

Transformerless inverters are getting popular in distributed photovoltaic power generation (PVPG) system due to its light weight, low cost, and higher efficiency in power conversion. However, the production of leakage current leads to severe electromagnetic interference and operational insecurity, which declines the reliability and efficiency of the overall system. Besides that many of the topologies have been addressed with real power injection capabilities in the literature. Therefore, in this paper, an improved hybrid-bridge (IH-B) inverter for transformerless PVPG system is proposed with 1) reduced leakage current by abolishing the fluctuations in common-mode voltage (CMV) due to switch junction capacitances and 2) reactive power capability with a modified sinusoidal pulsewidth modulation technique. This topology is constructed with the combination of bidirectional clamping branch and hybrid-bridge (H-B) inverter topology to maintain CMV at half of the dc-link voltage and ensure better quality of output waveforms at different power factors of the grid. Further, MATLAB simulation results of the IH-B and H-B topologies are presented and compared to prove the potential benefits of the proposed topology. Finally, a 500W prototype model is built and tested to validate the effectiveness of the IH-B topology in reduction of leakage current and reactive power capability.

Response of Waveguide-Integrated Germanium-on-Silicon p-i-n Photodiodes to Neutron Displacement Damage

The effects of 14-MeV neutron displacement damage (DD) on waveguide (WG)-integrated germanium-on-silicon p-i-n photodiodes (PDs) for silicon photonics have been investigated up to the fluences of $7.5\times 10^{12}$ n/cm2 (14 MeV) or $1.4\times 10^{13}\,\,\text{n}_{1\text {-MeV}_{\mathrm{ eq}}}$ /cm2(Si). This article includes the measurements of dark current–voltage characteristics across temperature from 150 to 375 K, measurements of PD junction capacitance, spectral response measurements from 1260 to 1360 nm, and frequency-response measurements. The devices are found to be susceptible to DD-induced carrier removal effects; however, they also continue to operate without meaningful impact to performance for the DD dose levels examined. Since the PD test chips include silicon photonic integrated grating couplers and WGs, which carry the optical signal to the PD, some assessment of the impact of DD on these passive devices can also be inferred. This article does not examine the short-term annealing or transient behavior of the DD, and instead, it has only considered the lasting damage that remains after any initial period of room-temperature annealing.

A High Efficiency Model-Based Adaptive Dead-Time Control Method for GaN HEMTs Considering Nonlinear Junction Capacitors in Triangular Current Mode Operation

Gallium nitride (GaN) high-electron-mobility transistor (HEMT) has the advantages of high switching speed and low ON-resistance, which make it widely used in high-frequency applications to realize high power density. Triangular current mode (TCM) modulation has been used in GaN-based converters to simultaneously achieve high power density and high efficiency through full-range zero voltage switching (ZVS). However, as switching frequency increases, the effect of dead time becomes more significant. Meanwhile, because of the junction capacitors of GaN HEMTs, the optimum dead time changes greatly with the turn-off current. Inappropriate dead time will induce extra loss that goes against the further improvement of power density. In order to minimize the dead-time loss in GaN HEMT-based TCM converter, this article proposes a strategy of adaptive dead-time control. An accurate turn-off transient model is proposed to calculate optimal dead time with consideration of the nonlinear capacitors. Based on this model, a loss model is established to evaluate the effect of dead time involving the short circuit in dead time. A new method of drive signal generation in TCM is proposed to increase the accuracy of dead-time control and reduce the current ripple. By reusing the detection signal in TCM, the adaptive dead-time control is realized without extra sensors. The proposed model is verified by a dual-pulse test, which shows the maximum error between the calculated and the experimental turn-off time is below 3 ns. The proposed adaptive dead-time control is implemented in a GaN HEMT-based boost converter. The experimental results show that the adaptive dead-time control can improve the efficiency over all operation conditions compared with using the fixed dead time, and the total loss is reduced by 26.7% at 800-W load and 70.8% at 50-W load.

Band structure and diode characteristics of transparent pn-homojunction using delafossite CuInO2

Technologically relevant highly rectifying all transparent delafossite pn homojunctions with CuInO2 as n-type layer and Ca doped CuInO2 as p-type layer are fabricated by oxygen plasma assisted thermal evaporation method. The best diode gives a forward to reverse current ratio ~619, which is about 62 times than that reported to date in a delafossite pn homojunction, with an ideality factor of 2.42 and a cut-in voltage of 0.87 V. Optical transmittance is 50%–70% in the visible region. Junction capacitance is in picoFarads and it is independent of frequency in the range 2 kHz to 2 MHz at a reverse voltage of 5 V. The band structure of the transparent delafossite diode is deduced for the first time by a combined analysis of the valence band spectra from x-ray photoelectron spectroscopy and the optical data.

Determination of the Parameters of Tunneling Barriers of Superconducting Tunnel Structures for Submillimeter Receivers

Abstract—The parameters of the tunneling barrier of Nb/Al–AlOx/Nb Josephson junctions were estimated in a wide range of current densities using the Simmons method. It is shown that with an increase in resistivity RnS from 60 to 2100 Ω μm2 (a reduction in the density of the tunneling current of junction J from 3.5 to 0.1 kA/cm2), the height of the tunneling barrier increases from 0.85 to 1.18 eV and its width increases from 10.7 to 13.3 A. The experimentally observed linear dependence of the tunneling barrier parameters on RnS made it possible to estimate the capacitance of junctions in the range of RnS 10–30 Ω μm2 required to create low-noise submillimeter-range receivers.

Lateral GaN Schottky Barrier Diode for Wireless High-Power Transfer Application With High RF/DC Conversion Efficiency: From Circuit Construction and Device Technologies to System Demonstration

In this article, we have carried out a comprehensive study on the wireless power transfer (WPT) concept from the rectifier circuit construction and state-of-art GaN Schottky barrier diode (SBD) device technology to the WPT system demonstration. Benefited from the wide bandgap, high mobility, and saturation velocity of the gallium nitride (GaN) two-dimensional electron gas, engineered lateral GaN SBD with low turn-ON voltage (V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">on</sub> ) of 0.47 V, ON-resistance (R <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">on</sub> ) of 4 Ω, breakdown voltage of 170 V, and junction capacitance (C <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">j</sub> ) of 0.32 pF at 0 V bias are achieved, which satisfy the fundamental requirements for microwave power rectification. After incorporating the high-performance GaN SBD into the optimized rectifier circuit, high radio frequency (RF)/dc conversion efficiency of 79% is achieved, and the input power of per single GaN SBD is increased by 10X when compared with that of a commercially available silicon (Si) SBD at the same efficiency of 50% and frequency of 2.45 GHz. Based on the rectifier circuit, a microwave power transfer system is constructed with 400 light emitting diodes lighted up, verifying the great promise of adopting high-power GaN SBD for the wireless high-power transfer as an alternative energy-harvesting technique for future WPT application.

A 5.8-GHz High-Power and High-Efficiency Rectifier Circuit With Lateral GaN Schottky Diode for Wireless Power Transfer

In this letter, we propose to implement a microwave lateral GaN Schottky barrier diode (SBD) in a designed 5.8-GHz rectifier circuit for future high-power and high-efficiency wireless power transfer. The low-pressure chemical vapor deposition SiN-passivated lateral GaN SBD demonstrates a low turn- on voltage of 0.38 V, a low on -resistance of 4.5 Ω, a low junction capacitance of 0.32 pF at 0-V bias, and a high breakdown voltage of 164 V, which are essentials for a high-efficiency and high-power rectifying application. By incorporating this lateral GaN SBD in a well-designed 5.8-GHz rectifier circuit, an unprecedented combination of high efficiency and high power is achieved simultaneously. The rectifier circuit demonstrates a high RF/dc conversion efficiency ( η RF/DC) of 71 ± 4.5% with an input power ( P in) of 2.5 W and η RF/DC = 50 ± 4.5% with P in = 6.4 W per single diode, showing the great promise of embracing lateral GaN SBD for future wireless high-power transfer application.