Reduction Of Breakdown Voltage Research Articles

Operational Characteristics of AlGaN/GaN High-Electron-Mobility Transistors with Various Dielectric Passivation Structures for High-Power and High-Frequency Operations: A Simulation Study

This study investigates the operational characteristics of AlGaN/GaN high-electron-mobility transistors (HEMTs) by employing various passivation materials with different dielectric constants and passivation structures. To ensure the simulation reliability, the parameters were calibrated based on the measured data from the fabricated basic Si3N4 passivation structure of the HEMT. The Si3N4 passivation material was replaced with high-k materials, such as Al2O3 and HfO2, to improve the breakdown voltage. The Al2O3 and HfO2 passivation structures achieved breakdown voltage improvements of 6.62% and 17.45%, respectively, compared to the basic Si3N4 passivation structure. However, the increased parasitic capacitances reduced the cut-off frequency. To mitigate this reduction, the operational characteristics of hybrid and partial passivation structures were analyzed. Compared with the HfO2 passivation structure, the HfO2 partial passivation structure exhibited a 7.6% reduction in breakdown voltage but a substantial 82.76% increase in cut-off frequency. In addition, the HfO2 partial passivation structure exhibited the highest Johnson’s figure of merit. Consequently, considering the trade-off relationship between breakdown voltage and frequency characteristics, the HfO2 partial passivation structure emerged as a promising candidate for high-power and high-frequency AlGaN/GaN HEMT applications.

Picosecond laser filament-guided electrical discharges in air at 1 kHz repetition rate

Laser-induced filaments have been shown to reduce the voltage necessary to initiate electrical discharges in atmospheric air and guide their propagation over long distances. Here we demonstrate the stable generation of laser filament-guided electrical discharge columns in air initiated by high energy (up to 250 mJ) 1030 nm wavelength laser pulses of 7 ps duration at repetition rates up to 1 kHz and we discuss the processes leading to breakdown. A current proportional to the laser pulse energy is observed to arise as soon as the laser pulse arrives, initiating a high impedance phase of the discharge. Full breakdown, characterized by impedance collapse, occurs 100 ns to several µs later. A record 4.7-fold reduction in breakdown voltage for dc-biased discharges, which remains practically independent of the repetition rate up to 1 kHz, is observed to be primarily caused by a single laser pulse that produces a large (∼80%) density depression. The radial gaps between the filamentary plasma channel and the hollowed electrodes employed are shown to play a significant role in the breakdown dynamics. A rapid increase of 3-4 orders of magnitude in current is observed to follow the formation of localized radial current channels linking the filament to the electrodes. The increased understanding and control of kHz repetition rate filament-guided discharges can aid their use in applications.

Effect of Field Plate on Device Performance of Wide Bandgap HEMT

Background: Devices with field plates have gained much popularity in high power and high voltage applications. The work done in this paper is related to designing and studying the different DC and RF characteristics of a field plated GaN HEMT. The results obtained were compared with that of non-field plated GaN HEMT. This comparison and study reported the effect of field plate on device performance. Methods: A GaN HEMT device with and without a field plate was designed and simulated in the SILVACO ATLAS TCAD tool. The performance of both the devices was compared in terms of the exhibited DC and RF characteristics in order to study the effect of the field plate on the device. We have also studied the variation in the cut-off frequency and maximum frequency of both the field plate and without field plate GaN HEMT with respect to gate-source voltage. We have further investigated the device performance by varying the length of the field plate from 0 to 2.5 μm. Results: The study reflects the advantageous feature of GaN HEMT with field plate by exhibiting high breakdown voltage of 292 V in comparison to GaN HEMT without field plate which exhibits a breakdown voltage of 98 V. As a result of using field plate in the GaN HEMT structure, a rise in the Cgs and Cgd capacitances are witnessed. This in turn affects the other RF characteristics of the GaN HEMT with field plate even though the GaN HEMT with and without field plate exhibits nearly same DC characteristics. The field plated GaN HEMT exhibits a reduced cut-off frequency and maximum frequency of 7 GHz and 20 GHz, respectively, in comparison to the GaN HEMT without field plate’s cut-off frequency and maximum frequency of 10 GHz and 25 GHz, respectively. Conclusion: The study reports that using a field plate helps in enhancing the breakdown voltage but at the cost of reduced frequency performance. We have compared our proposed field plated device with different non-field plated devices and concluded that our device exhibits much higher breakdown voltage in spite of reduced device dimension. With the attainment of higher breakdown voltage our proposed GaN HEMT device can be used for high power applications. From the study, it is reported that while increasing the length of the field plate the breakdown voltage also increases. For a particular set of device dimensions, an optimum field plate length provides the highest breakdown voltage but increasing the length of the field plate beyond the optimum value results in reduction in breakdown voltage.

Water Content in Transformer Insulation System: A Review on the Detection and Quantification Methods

Water can be an irritant to a power transformer, as it is recognized as a major hazard to the operation of transformers. The water content of a transformer insulation system comprises the water in the transformer insulation oil and in the cellulose paper. The increase in the water content in the insulation system leads to reduced breakdown voltage, accelerated aging of the oil–paper insulation system, and the possibility of producing bubbles at high temperatures. Therefore, various techniques have been applied to measure the water content in both oil and paper insulation. This article comprehensively reviews and analyzes the methods (technically or nontechnically) that have been used to monitor the water content in transformer insulation systems. Apart from discussing the advantages and major drawbacks of these methods, the accuracy, measurement time, and cost of each technique are also elucidated in this review. This review can be extremely useful to the utility in monitoring and maintaining the good condition of transformers. Based on the reviewed methods and their challenges, a few future research directions and prospects for determining the water content in transformer insulation systems are outlined, such as utilizing artificial intelligence and enhancing current techniques.

Modeling study on temporal nonlinear behaviors in CO2 dielectric barrier discharges under Martian pressure

In recent years, dielectric barrier discharges (DBDs) have become one of the most potential candidates for in situ resource utilization of CO 2 ${\text{CO}}_{2}$ in the Martian atmosphere. The nonlinear behaviors in DBDs are directly associated with the stability of discharges, and understanding the formation mechanism of the nonlinear behaviors can effectively enhance the ability to control the plasmas. In this paper, to further explore the underpinning physics of temporal nonlinear behaviors in CO 2 ${\text{CO}}_{2}$ discharges, the tailored sinusoidal voltages with power-on and power-off phases are applied to ignite the plasmas under Martian pressure. The simulation results from a fluid model with hundreds of reactions show that the discharge can evolve from period-one state into period-four state via period-two state by reducing the power-off duration; the electron density drops rapidly and the heavy ions of CO 2 + ${\text{CO}}_{2}^{+}$ and CO 3 − ${\text{CO}}_{3}^{-}$ become the dominant charged particles after the discharge is extinguished. With the power-off duration further reduced, the heavy ions produced by the previous discharge cannot be completely dissipated and remain in the sheath region to enhance the electric field before the next discharge event; thus, the next ignition takes place more easily with a reduced breakdown voltage and a lower discharge current, indicating the discharge transits from a period-one state to a period-two state. In the transition from period-two discharge to period-four discharge, the heavy ions produced by the second discharge event cannot be completely transported to the surface of barriers, affecting the ignition in the third voltage period. When the power-off duration is less than 10 μs $\mathrm{\mu s}$ in the simulation, electrons become the dominant residual negative charges in the discharge region, and the rapid increase in memory voltage results in a smaller positive discharge current and a stronger negative discharge current. As the power-off duration continues to decrease, the discharge undergoes an inverse period-doubling bifurcation from reverse period-four discharge to reverse period-two discharge. This study provides a deeper insight into the underlying physics of nonlinear behaviors in CO 2 ${\text{CO}}_{2}$ DBDs under Martian pressure.

Initial transient stage of pin-to-pin nanosecond repetitively pulsed discharges in air

In this work, evolution of parameters of nanosecond repetitively pulsed (NRP) discharges in pin-to-pin configuration in air was studied during the transient stage of initial 20 discharge pulses. Gas and plasma parameters in the discharge gap were measured using coherent microwave scattering, optical emission spectroscopy, and laser Rayleigh scattering for NRP discharges at repetition frequencies of 1, 10, and 100 kHz. Memory effects (when perturbations induced by the previous discharge pulse would not decay fully until the subsequent pulse) were detected for the repetition frequencies of 10 and 100 kHz. For 10 kHz NRP discharge, the discharge parameters experienced significant change after the first pulse and continued to substantially fluctuate between subsequent pulses due to rapid evolution of gas density and temperature during the 100 μs inter-pulse time caused by intense redistribution of the flow field in the gap on that time scale. For 100 kHz NRP discharge, the discharge pulse parameters reached a new steady-state at about five pulses after initiation. This new steady-state was associated with well-reproducible parameters between the discharge pulses and substantial reduction in breakdown voltage, discharge pulse energy, and electron number density in comparison to the first discharge pulse. For repetition frequencies 1–100 kHz considered in this work, the memory effects can be likely attributed to the reduction in gas number density and increase in the gas temperature that cannot fully recover to ambient conditions before subsequent discharge pulses.

Application of SiGe layer for reinforcing conductivity modulation in trench insulated gate bipolar transistor

In this work, an investigation for inserting a SiGe layer in an insulated-gate bipolar transistor (IGBT) has been performed to analyze the relation between on-state property and breakdown voltage (BV) with the help of technology computer-aided design simulation. For a carrier storage (CS) IGBT, which is widely studied for enhancing conductivity modulation by increasing hole density, the BV decreases by increased conductivity in the CS layer. However, by using the SiGe layer instead of the CS layer, the on-state property is improved with lower BV reduction than a CS IGBT due to the absence of impurity doping. Finally, an optimization for a Ge mole fraction is performed. Based on the results, it is found that the SiGe with 0.3 mole fraction shows the best performance because over 0.3 Ge mole fraction, the excessive energy band bending induced by over-accumulated holes makes low carrier velocity in the n-drift layer.

Passivation Schemes for ScAlN-Barrier mm-Wave High Electron Mobility Transistors

This article presents improvements of large-signal RF power performance at <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Ka</i> -band of gallium nitride high electron mobility transistors (HEMTs) utilizing a scandium aluminum nitride barrier. Three samples were fabricated and measured having different passivation schemes, including gallium nitride, silicon nitride, and aluminum gallium nitride. The pinning of the Fermi level against the valence band reduced the gain and output power density of the gallium nitride passivated device, resulting in 4.5 W/mm at a drain bias of 32 V. With silicon nitride alone as the passivation, dc/RF dispersion was reduced, and gain increased significantly, boosting the output power for this device to 8.0 W/mm at 28 V, though at the cost of a reduced breakdown voltage. Adding an epitaxial aluminum gallium nitride passivating layer increased the maximum bias voltage that the devices can operate at compared to devices with the silicon nitride passivation. When biased at 40 V, the output power of the devices reached 10.8 W/mm at 30 GHz. These devices show the importance of the passivation design to large-signal RF performance in scandium aluminum nitride-based HEMTs and will help guide further improvements.

Understanding the Impact of Lime Stabilization on Expansive Soil for Grounding and Analysis Adopting LIBS

Stabilization of soil for grounding purposes has been performed by adding different wt% of lime. Electrical breakdown measurements under lightning impulse voltage showed a reduction in breakdown voltage and the time to breakdown with increment in the lime content in the soil. These parameters also increased with curing period for all concentrations of lime of stabilized soil samples. The results show that pH and electrical conductivity of the expansive soil increase as the lime content increases, but decrease with increasing the curing period. Mineralogical and micro-structural analysis has been made by means of X-ray diffraction (XRD) studies and by scanning electron microscope (SEM) analysis. The axial strength obtained from unconfined compressive strength (UCS) analysis, the plasma temperature and the electron number density calculated from Laser Induced Breakdown Spectroscopy (LIBS) data tend to increase with increment in lime content as well as the curing period of the lime stabilized soil. Using univariate analysis, the normalized intensity ratio of Ca II peaks from LIBS spectral data are correlated with lime content in the soil samples at various curing periods. The partial least squares regression (PLSR) technique is successful in determining the soil parameters with the help of LIBS spectral data, at different curing periods with an R <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> value greater than 0.95 and the percentage RMSE value smaller than 4%.

Reduced breakdown voltage for in-liquid plasma discharges using moveable electrodes

Minimizing the breakdown voltage and discharge current required to initiate direct in-liquid discharges, thus lowering power-source requirements and avoiding electrode ablation, is crucial for industrial applications of in-liquid plasmas. Here we demonstrate such considerable reductions by employing movable electrodes, without changing the electrode configuration or increasing the system complexity. The new mechanism is based on electrostatic electrode attraction resulting in a reduction in the discharge spacing by up to 6 times and facilitating a plasma initiation at lower breakdown voltages. The accumulated charges consumed by the discharge revert the electrodes to the initial positions, forming a gliding arc between the enlarged gaps and thus inhibiting current increases and electrode ablation.

Impact of Moisture on AC Breakdown Voltage of Crude, Refined and Transesterified Groundnut Oil-based Liquid Insulations

With the aim of analyzing the ability of vegetable oil-based liquid insulation as alternate medium under moisture-rich environment, this study presents an experimental analysis of impact on breakdown voltage characteristics vegetable oil-based insulating liquids for the moisture inclusion with oil sample. The study has been proposed to carry out with different categories of groundnut oil in crude form, refined form and transesterified form. The moisture inclusion range of 5 ppm to 25 ppm is considered based on the literature with the scope of having lower solubility level and less than 50% of water saturation level for avoiding wet transformer conditions. Experimental investigations have been done on AC breakdown voltage of three categories of groundnut oil for inclusion of proposed range of moisture. With an increased moisture level from 5 to 25 ppm, significant reduction in breakdown voltage of oil samples has been obtained with the average percentage of 53 to 67% which may be due to possible modification in the molecular component of oil with the influence of moisture's polarization characteristics. Based on the experimental observations, the empirical power equations developed based on the regression method to predict the approximate breakdown voltage at different moisture levels.

Influence of temperature and dimension in a 4H-SiC vertical power MOSFET

A study of the impact of dimension and temperature on a state of the art 4H-SiC power vertical DMOSFET has been carried out using drift-diffusion calculations in conjunction with electrical characterizations to extract physical parameters and doping profiles in a 6 μm channel length device. The model presented in this paper includes the effect of trapping in the channel/oxide interface. Using these parameters, the performance of corresponding lateral and vertical scaled devices are studied. Electrothermal simulations showing self-heating effects are also carried out. The results are qualitatively discussed with the help of an analytical physical model, which considers the interplay between the different device resistances. At low drain bias, the drain current is increased by 42.86% (I D = 5 A at V G = 20 V) when reducing the dimension vertically, whereas it is decreased by 28.57% (I D = 2.5 A at V G = 20 V) when reducing the dimension laterally. These effects are enhanced at high drain bias. In addition, the effect of dimension reduction for breakdown voltage, electric field and impact ionization is investigated. A substantial reduction in breakdown voltage was found when the vertical dimensions were decreased as compared to the lateral dimensions.

Simulation-Based Ultralow Energy and High-Speed LIF Neuron Using Silicon Bipolar Impact Ionization MOSFET for Spiking Neural Networks

The silicon bipolar impact ionization MOSFET offers potential for the realization of leaky integrated fire (LIF) silicon neuron due to the presence of parasitic bipolar junction transistor (BJT) in the floating body. In this article, we have proposed an L-shaped gate bipolar impact ionization MOS (L-BIMOS) with reduced breakdown voltage ( ${V}_{B} = {1.68}$ V) and demonstrated the functioning of LIF neuron based on the positive feedback mechanism of parasitic BJT. Using the 2-D TCAD simulations, we manifest that the proposed L-BIMOS exhibits a low threshold voltage (0.2 V) for firing a spike, and the minimum energy required to fire a single spike for L-BIMOS is calculated to be 0.18 pJ, which makes the proposed device 194 times more energy efficient than the PD-SOI MOSFET silicon neuron and ${5}\times {10}^{{3}}$ times more energy efficient than the analog/digital circuit-based conventional neurons. Furthermore, the proposed L-BIMOS silicon neuron exhibits spiking frequency in the gigahertz range when the drain is biased at ${V}_{\text {DG}} = {2.0}$ V.

Investigation on thermally aged natural ester oil for real‐time monitoring and analysis of transformer insulation

Thermal aging of natural ester oil shows drastic reduction in partial discharge inception voltage (PDIV) and a significant variation is observed only above a certain aging time, under AC, DC, high frequency AC voltages and with harmonic voltages with different total harmonic distortion. Weibull distribution studies on PDIV measurements indicate a reduction in scale parameter (α) with increase in thermal aging temperature. A characteristic reduction in breakdown voltage was observed with the thermally aged ester oil, under AC, DC and standard lightning impulse voltage. The breakdown voltage variation with aged ester oil follows normal distribution. Ultraviolet (UV) analysis of ester oil thermally aged at 160°C has revealed a regular shift of the derived absorbance parameter to longer wavelengths. The interfacial tension and turbidity exhibits an inverse relationship with the thermally aged ester oil. Gas chromatography/mass spectrometric analysis of the thermally aged ester oil predicted the formation of more carboxylic acids and ketones with aging duration. The steady-state fluorescence on thermally aged ester oil exhibits a shift in its emission profile, which is in tandem with the UV absorption spectroscopic analysis. Fluorescence analysis can be adopted as a real-time monitoring tool in transformers, to understand the condition of liquid insulation. The viscosity dependence on the wavelength of derivative absorption maxima follows a direct relationship with the thermally aged natural ester oil.

On the Nitrogen Doping in Erbium and Nitrogen Codoped Magnesium Zinc Oxide Diode by Spray Pyrolysis

Diodes with an erbium and nitrogen codoped magnesium zinc oxide (MgZnO:Er,N) active layer were fabricated by spray pyrolysis on Si substrate with aqueous solutions including magnesium nitrate, zinc acetate, erbium acetate, ammonium acetate, and indium nitrate precursors. Diodes with different nitrogen content in their precursor were prepared and their properties were investigated. With scanning electron microscopy, film surface with mixed hexagonal flakes and tiny blocks was characterized for all samples. Certain morphologies varied for samples with different N contents. In the photoluminescence analyses, the intensity of the oxygen-related defects peak increased with the increasing of nitrogen content. The diodes were fabricated with an Au and In deposition on the top and backside. The diode current–voltage as well as capacitance–voltage characteristics were examined. An ununiformed n-type concentration distribution with high concentration near the interface in the MgZnO:Er,N layer was characterized for all samples. Diodes with high nitrogen content exhibit reduced breakdown voltage and higher interface concentration characteristics. Under reversed bias conditions with an injection current of 50 mA, a light spectrum with two distinct green emissions around wavelengths 532 and 553 nm was observed. A small spectrum variation was characterized for diodes prepared from different nitrogen content. The diode luminescence characteristics were examined and the diode prepared from N/Zn=1 in the precursor showed an optimal injection current-to-luminescence property. The current and luminescence properties of the diode were characterized and discussed.

Device Design Assessment of GaN Merged P-i-N Schottky Diodes

Device characteristics of GaN merged P-i-N Schottky (MPS) diodes were evaluated and studied via two-dimensional technology computer-aided design (TCAD) after calibrating model parameters and critical electrical fields with experimental proven results. The device’s physical dimensions and drift layer concentration were varied to study their influence on the device’s performance. Extending the inter-p-GaN region distance or the Schottky contact portion could enhance the forward conduction capability; however, this leads to compromised electrical field screening effects from neighboring PN junctions, as well as reduced breakdown voltage. By reducing the drift layer background concentration, a higher breakdown voltage was expected for MPSs, as a larger portion of the drift layer itself could be depleted for sustaining vertical reverse voltage. However, lowering the drift layer concentration would also result in a reduction in forward conduction capability. The method and results of this study provide a guideline for designing MPS diodes with target blocking voltage and forward conduction at a low bias.

An Assessment of Step Patterned Gate Oxide Superjunction Trench MOSFET for Potential Benefits

A 600 V-class step patterned gate oxide trench (SPGOT) superjunction vertical device incorporating gate engineering is proposed in this paper. An $$n^{+}$$ polysilicon gate is segregated into three steps of varied length and oxide thickness. To improve the device performance, the gate oxide in the SPGOT structure is narrow towards the source and wide towards the drain. This modification increases the gate–source capacitance, indicating higher transconductance, and reduces gate–drain capacitance, suggesting lower switching delay. The gate length is optimized to achieve enhanced performance indicators. Electrical performance is investigated and analyzed using 2-D numerical simulations. The optimized results reveal 9.7% and 26.14% reduction in specific resistance ( $$R_{\rm on} {\cdot} A$$ ) and gate–drain charge ( $$Q_{\rm GD}\cdot A$$ ), respectively, without any reduction in breakdown voltage. The engineered gate structure further exhibits a 43% and a 33.2% improvement in switching delay and figure of merit ( $$R_{\rm on}\cdot A$$ × $$Q_{\rm GD}\cdot A$$ ), respectively, over a conventional device.

An Impact Ionization MOSFET With Reduced Breakdown Voltage Based on Back-Gate Misalignment

In this paper, we propose a misaligned double-gate p-i-n impact ionization MOS (MIMOS) with a deliberate misalignment between the top and bottom gates. The presence of a misaligned bottom gate leads to band-to-band-tunneling of electrons at the source-intrinsic region interface and increases the number of carriers for impact ionization. The electric field redistribution provides a longer transport path for the carriers. Therefore, carriers gain higher kinetic energy, and the impact ionization rate is enhanced in the MIMOS. This results in a significantly lower avalanche breakdown voltage compared to conventional single-gate IMOS structure. Using calibrated 2-D simulations, we demonstrate that MIMOS exhibits a steep subthreshold slope (~6 mV/dec) at a significantly low-supply voltage of ( ${V}_{\text {DS}}= {0.59}$ V), which is ~48% lower than that of the corresponding single-gate IMOS ( ${V}_{\text {DS}}= {1.15}$ V).

Effect of Annealing Time on the Dielectric Properties of BaMn&amp;lt;sub&amp;gt;3&amp;lt;/sub&amp;gt;Ti&amp;lt;sub&amp;gt;4&amp;lt;/sub&amp;gt;O&amp;lt;sub&amp;gt;14.25&amp;lt;/sub&amp;gt; Pellets by Spark Plasma Sintering

In this paper, the effects of annealing time on the dielectric properties of the Spark Plasma Sintered (SPS) BaMn3Ti4O14.25 pellets were detail studied by the crystal structure analysis, micro structural observation and electrical properties research. The results showed that long annealing time was beneficial to the recovery of crystal structure damage caused by SPS, the formation of a reoxidation layer at the surface of grains and decreasing of the electrically insulating phase. All of these resulted in an increase in dielectric constant and loss, and a reduction in breakdown voltage.

Ps four-wave mixing measurements of electric field in a ns pulse discharge in a hydrogen diffusion flame

Time-resolved electric field in ns pulse discharge plasmas generated in room air and in an atmospheric pressure hydrogen diffusion flame has been measured by ps four-wave mixing, for plane-to-plane electrode geometry. Electric field is put on the absolute scale using the Laplacian field measured before breakdown. The results show that peak electric field during breakdown in the flame, approximately 40 kV/cm, is significantly lower compared to that in room air, 75 kV/cm, due to higher temperature of combustion products. In both cases, peak electric field is higher compared to DC breakdown field. Both in air and in the flame, the electric field follows the applied voltage before breakdown and decreases rapidly after breakdown, due to charge separation and plasma self-shielding. The electric field in air is compared with the predictions of an analytic model of ns pulse breakdown, showing good agreement between the predicted and the measured breakdown field. The model also predicts earlier breakdown as well as breakdown voltage reduction as the temperature is increased, in qualitative agreement with the experimental data. The use of the present ps four-wave mixing diagnostics for measurements of electric fields below ∼20 kV/cm in atmospheric pressure flames is challenging, due to low signal-to-noise. The sensitivity of the present diagnostics is controlled by the high temperature and low N2 fraction in the combustion product mixture, as well as by the limited bandwidth of the Stokes beam generated by the stimulated Raman cell, which provides access only to several rotational levels of nitrogen molecules. The present diagnostics will have much better sensitivity in high-pressure flames, since the four-wave mixing signal scales as the squared number density of nitrogen.