Breakdown Characteristics Research Articles

Mechanism of frequency-dependent gate breakdown in p-GaN/AlGaN/GaN HEMTs

In this Letter, time-dependent gate breakdown (TDB) characteristics under dynamic switching conditions were investigated in p-GaN/AlGaN/GaN high-electron-mobility transistors (HEMTs) with either Schottky-type or Ohmic-type gates. The dynamic TDB of the Schottky-type devices increased with frequencies ranging from 100 Hz to 100 kHz, while that of the Ohmic-type devices remained frequency-independent. This was analyzed by the frequency-dependent electroluminescence (EL) characteristics on both types of devices with semi-transparent gate electrodes. The electroluminescence (EL) emission intensity of Schottky-type devices increased with elevated frequencies, notably for blue and ultraviolet emissions, which exhibited a pronounced positive correlation with frequency. In contrast, the EL emissions of Ohmic-type devices were frequency-independent. Energy band diagrams were drawn to explain the different TDB and EL behaviors between two types of devices. The frequency-enhanced EL emissions of the Schottky-type devices indicated the frequency-enhanced hole injection and radiative recombination, which then suppressed the hot-electron effects on the metal/p-GaN junction and enhanced the dynamic TDB in p-GaN/AlGaN/GaN HEMTs.

Epilayer thickness effect on the electrical and breakdown characteristics of vertical β-Ga2O3 Schottky barrier diode

The current–voltage and breakdown characteristics of Au/Ni/β-Ga2O3 Schottky barrier diodes were investigated as a function of β-Ga2O3 epilayer thickness in the range of 6–19 μm. The X-ray rocking curves indicated that the full-width half-maximum is reduced with increasing epilayer thickness, implying an improvement in the crystallinity of β-Ga2O3 epilayer. The barrier heights of the field-plated β-Ga2O3 Schottky barrier diode with epitaxial layer thickness of 6, 12, and 19 μm were obtained as 1.01, 1.03, and 1.04 eV, with the ideality factor values being 1.21, 1.19, and 1.46, respectively. The higher ideality factors could be associated with the existence of inhomogeneity at the metal–semiconductor interface. The series resistance of the Schottky diode obtained increased with increasing epilayer thickness. The Schottky diode fabricated on 19 μm thick epitaxial layer exhibited a higher breakdown voltage of 490 V. The increase in epilayer thickness led to the widening of depletion region, resulting in lower electric field over a larger distance. This could be a main cause of the enhancement of the breakdown voltage characteristics of β-Ga2O3 Schottky barrier diode.

Effects of Temperature Gradients on Breakdown Characteristics of Tri-Post Insulator in HVAC GIL

Effects of Temperature Gradients on Breakdown Characteristics of Tri-Post Insulator in HVAC GIL

Improved DC and RF Characteristics of GaN-Based Double-Channel HEMTs by Ultra-Thin AlN Back Barrier Layer.

In order to improve the off-state and breakdown characteristics of double-channel GaN HEMTs, an ultra-thin barrier layer was chosen as the second barrier layer. The strongly polarized and ultra-thin AlN sub-barrier and the InAlN sub-barrier are great candidates. In this article, the two epitaxial structures, AlGaN/GaN/AlN/GaN (sub-AlN) HEMTs and AlGaN/GaN/InAlN/GaN (sub-InAlN) HEMTs, were compared to select a more suitable sub-barrier layer. Through TEM images of the InAlN barrier layer, the segregation of In components can be seen, which decreases the mobility of the second channel. Thus, the sub-AlN HEMTs have a higher output current density and transconductance than those of the sub-InAlN HEMTs. Because the high-quality AlN barrier layer shields the gate leakage current, a 294 V breakdown voltage was achieved by the sub-AlN HEMTs, which is higher than the 121 V of the sub-InAlN HEMTs. The current gain cut-off frequency (fT) and maximum oscillation frequency (fmax) of the sub-AlN HEMTs are higher than that of the sub-InAlN HEMTs from low to high bias voltage. The power-added efficiency (PAE) and output power density (Pout) of the sub-AlN HEMTs are 57% and 11.3 W/mm at 3.6 GHz and 50 V of drain voltage (Vd), respectively. For the sub-InAlN HEMTs, the PAE and Pout are 41.4% and 8.69 W/mm, because of the worse drain lag ratio. Thus, the Pout of the sub-AlN HEMTs is higher than that of the sub-InAlN HEMTs.

1D modeling of plasma streamers at ammonia-air flame conditions

Abstract This work is a self-consistent 1D modeling of streamers in ammonia-oxygen-nitrogen-water mixtures. A fluid model that includes species transport, electrostatic potential, and detailed chemistry was developed and verified. This model is then used to simulate the avalanche, streamer formation and propagation phases, driven by a nanosecond voltage pulse, at different thermochemical conditions derived from a 1D laminar premixed ammonia-air flame. The applicability of the Meek’s criterion in predicting the streamer inception location was successfully confirmed. Streamer formation and propagation duration were found to vary significantly with different thermochemical conditions, due to the difference in ionization rates. The thermochemical state also affected the breakdown characteristics which was tested by maintaining the background reduced electric field constant. Detailed kinetic analyses revealed the importance of O(1D) in the production of key radicals, such as O, OH, and NH2. Furthermore, the contributions of the dissociative electronic excitation of NH3 towards the production of H and NH2 radicals have also been reported. Spatial and temporal evolution of the electron energy loss fractions for various inelastic collision processes at different thermochemical states uncovered the input plasma energy spent of fuel dissociation and the large variability in the dominant processes during the avalanche and streamer propagation phases. The methodology and analyses reported in this work are key towards developing effective strategies for controlled nanosecond-pulsed non-equilibrium plasma sources used for ammonia ignition and flame stabilization.

Electrical surface breakdown characteristics of micro- and nano-Al2O3 particle co-doped epoxy composites

Abstract Epoxy microcomposites are basic materials for gas-insulated switchgear (GIS) spacers that are subjected to huge electrical stress. Previous works have indicated that nanoparticles are beneficial to dielectric performance. However, surface electrical breakdown, a typical fault in GIS of co-doped micro- and nanoparticles in epoxy composites, is seldom studied. In this work, numerous concentrations of micro- and nano-Al2O3 are co-doped into an epoxy matrix; the surface traps, surface charging, and surface breakdown voltages (V sb) of the co-doped composites are studied, and the influence of micro- and nano-Al2O3 on the electrical surface breakdown is clarified. The results show that V sb first decreases and then increases with the microparticles, and V sb decreases from 25.34 kV to 19.52 kV. As the number of nanoparticles increases, V sb increases and then decreases when the microparticle loading is low, but decreases and then increases when the microparticle loading exceeds 40 wt%. Micro-Al2O3 particles introduce surface shallow traps into epoxy composites, while small amounts of nano-Al2O3 introduce deep traps. Two different mechanisms dominate the surface charging and V sb of epoxy micro-nanocomposites. When the surface conductivity is lower than 7 × 10−14 S, the surface charges are reduced by the suppression of electrode injection as the trap depth increases, and V sb increases. When the surface conductivity exceeds 7 × 10−14 S, the surface charge dissipation rate increases with the surface conductivity and V sb increases as the surface conductivity increases. Our work indicates that co-doped micro- and nano-particles should keep the surface conductivity away from the specic value (7 × 10−14 S) to safeguard insulation properties for GIS spacers.

Enhanced device performance of GaN high electron mobility transistors with in situ crystalline SiN cap layer

In this paper, a ∼2 nm in situ SiN cap layer on AlGaN barrier layer is grown, which is revealed to be crystalline using high-resolution cross-sectional transmission electron microscopy. Benefitting from superior interface quality of epitaxial crystalline SiN/AlGaN interface, the gate diodes with in situ SiN cap layer feature lower interface trap state density than that with GaN cap layer. By comparing the GaN high electron mobility transistors (HEMTs) with the conventional GaN cap layer, the GaN HEMTs with in situ SiN cap layer exhibit improved device performance, showing higher electron mobility, higher drain current, larger on/off current ratio, and higher transconductance. For breakdown characteristics, the devices with in situ crystalline SiN cap layer show prominent advantages over the GaN cap layer with a 30% breakdown voltage increase to 810 V.

Numerical characteristics of DC breakdown and paschen curve of CF3I-N2 mixtures at low pressure

Numerical characteristics of DC breakdown and paschen curve of CF3I-N2 mixtures at low pressure

Analytical Modelling of the Quasi-Static Operation of a Monolithically Integrated 4H-SiC Circuit Breaker Device

In this work, an analytical model describing the quasi-static operation of a monolithically integrated SiC solid-state circuit breaker (SSCB) device is rederived and refined. This SSCB is based on a 4H-SiC JFET technology offering a self-sensed blocking mechanism. The proposed model is solely based on physical parameters including the SSCB design parameters. With respect to the refinement, the proposed model is not limited to one-sided pn-junctions, considers incomplete ionization of dopants, and is able to represent breakdown characteristics. In this regard, the JFET gate breakdown characteristics are derived taking thermionic emission, space-charge-limited current and impact ionization into account. To calculate the SSCB output characteristics, a bisection-based optimization algorithm is applied carefully considering individual JFET operating states.

AC breakdown and decomposition products detection characteristics of eco-friendly insulating medium in gas insulated switchgear

Gas Insulated Switchgear (GIS) was a crucial electrical equipment that provides the safety and security of power systems, and finding the eco-friendly alternatives of sulphur hexafluoride (SF6) as insulating medium in GIS has been an urgent demand in past decades. However, few studies reported the specific dielectric strength under various electrodes and partial discharge (PD) decomposition products detection of applying the eco-friendly gas in GIS. In this paper, the insulation properties among C4F7N/CO2 mixtures, dry air and CO2 were explored under the reduced-scale gas-insulated experimental device. The relationship between AC breakdown voltage and gas pressure was gained under the different electrodes and gap distances, and 0.6 MPa 7% C4F7N/93% CO2, 0.9 MPa dry air, 0.9 MPa CO2 all possess the capacity to be the insulating medium in eco-friendly gas insulated switchgear. Furthermore, the partial discharge experimental was also carried out to realize the decomposition products detection of dry air, which designs three common defect types including metal protrusion defects, air gap defects, and metal contamination defects. The decomposition products detection result shows that the contains of CO2, CO, and NO2 linearly increase with the increasing applied voltages and times, and the partial discharge defects are distinguished according to the ratios of c(CO2 + CO)/c(NO2) and c(CO2)/c(CO). The results can provide the basis for the further development of eco-friendly gas insulated switchgear.

Improved high temperature energy storage density and efficiency of polyimide nanocomposites via hindering charge and molecular motions

Electric vehicles and renewable energy consumption have huge demands for high-performance polymer dielectric capacitors. However, the resistivity and breakdown strength of existing polymer dielectrics deteriorate significantly at high temperatures, reducing the energy storage density and charge-discharge efficiency of capacitors below service requirements. The charge transport and molecular chain motion characteristics in linear polymers determine their conductivity, breakdown, and energy storage properties, but the quantitative relationship between them is not clear. An in-situ polymerization method was used to prepare polyimide/Al2O3 nanocomposites (PI/Al2O3 PNCs). Experimental results show that the resistivity, breakdown strength, energy storage density, and charge-discharge efficiency of PNCs increase initially and then decrease with increasing doping content, peaking at 3 wt%. The discharged energy density of PI/Al2O3-3 wt% PNCs at 180°C is 207.52 % higher than pure PI. A conductance-breakdown-energy storage co-simulation model based on charge transport and molecular chain displacement was used to simulate the voltage-current, breakdown, and energy storage characteristics of PNCs. The simulation results are consistent with the experiments. Comparative studies between simulation and experiments show that the independent interface zone between nanofillers and PI hinders charge transport and molecular chain movement, reducing electric field distortion and molecular chain spacing, thereby improving high-temperature breakdown and energy storage performance of PNCs.

Field management in NiO x /β-Ga2O3 merged-PIN Schottky diodes: simulation studies and experimental validation

In recent years, p-type NiO x has emerged as a promising alternative to realize kilovolt-class β-Ga2O3-based PN junction diodes. However, only a handful of studies could realize β–Ga2O3-based unipolar diodes using NiO x as a guard ring or floating rings. In this work, we investigate the device design of NiO x /β-Ga2O3 unipolar diodes using the technology computer aided design simulations and experimental validations. We show that a systematic electric field management approach can potentially lead to NiO x /β-Ga2O3 heterojunction unipolar diode and offer enhanced breakdown characteristics without a severe compromise in the ON-state resistance. Accordingly, the NiO x /β-Ga2O3 heterojunction diode in the merged-PIN Schottky configuration is shown to outperform the regular Schottky diode or junction barrier Schottky diode counterpart. The analysis performed in this work is believed to be valuable in the device design of β-Ga2O3-based unipolar diodes that use a different p-type semiconductor candidate as guard rings and floating rings.

Design and characteristics of a fiber laser powered repetitive micro-plasma jet triggered gas switch.

To satisfy the need for low jitter in gas switches at repetition rate and enhance insulation reliability during high voltage operation of the trigger, we propose a micro-jet triggering system. This system requires less energy and can use a laser power supply as an energy source. It effectively improves the insulation stability of the trigger when working at high potentials and achieves a good triggering effect with low jitter at low working coefficients. The breakdown characteristics were tested by double-pulse experiments. Ensuring the same operating conditions for both pulses, the pulse interval was varied to obtain the breakdown voltage dispersion at different repetition rates. The results indicate that the dispersion of the breakdown voltages can reach 0.16% at a frequency of 50Hz with a pulse front of 30 μs, representing an order of magnitude reduction compared to the 1.45% at switching self-breakdown, and decreases further as the air pressure rises. In addition, the size of the microcapillary has an impact on the dispersion of breakdown voltage. It was found that for a range of lengths from 2 to 6mm and aperture sizes from 80 to 400μm, the trigger jitter was lower when the length was larger and the aperture was smaller. Furthermore, a trigger life test was performed on the ceramic capillary, and after one million triggers, the system remained stable with no degradation in trigger performance.

Effect of aluminum particles on the insulating properties of C4F7N/CO2 mixed gas

The C4F7N/CO2 mixed gas is most expected to replace SF6 in high-voltage power equipment, and the generation of free metal particles in gas-insulated equipment is unavoidable and highly susceptible to inducing insulation failures. In this paper, the effects of flaky, spherical, and mixed shape aluminum particle defects on the breakdown characteristics of C4F7N/CO2 mixed gas are investigated and compared to those of SF6 under the same conditions. The experimental results show that the effect of particle defects on the insulating properties of C4F7N/CO2 gas mixtures is visualized by the fact that particle defects reduce the breakdown voltage of C4F7N/CO2 gas mixtures, increase their stochasticity, and reduce the enhancement of the insulating properties of C4F7N/CO2 gas mixtures by increasing the air pressure. The greater the number of particles, the greater is the degree of influence. Comparison of the SF6 and C4F7N/CO2 gas mixtures reveals that, in the case of flake defects, increasing the air pressure improves the insulation performance of the SF6 gas better than that of the C4F7N/CO2 gas mixture. Under the condition of the same number of particles, the larger the proportion of spherical particles in the hybrid particles, the smaller is the influence of metal particles on the C4F7N/CO2 mixed gas and on SF6 gas.

Electrical Breakdown Characteristics in High-Vacuum Conditions for the Design of Superconducting Coils

Electrical Breakdown Characteristics in High-Vacuum Conditions for the Design of Superconducting Coils

Thermal breakdown characteristics and damage mechanisms of novel GaN HEMT aviation nanodevices in high-intensity radiation fields

Thermal breakdown characteristics and damage mechanisms of novel GaN HEMT aviation nanodevices in high-intensity radiation fields

Diffusosphere engineering in BNT-based multilayer heterogeneous film capacitors for high performance

Combining layers with high breakdown resistance and high polarization is a promising approach for designing dielectric capacitors with high energy density and efficiency. However, such combinations often accompany strong interfacial polarization, magnification of local electric fields, leading to premature breakdown. This work addresses this issue via controlled formation of diffusospheres. We constructed multilayer heterogeneous films using two Bi0.5Na0.5TiO3 (BNT)-based substances with high breakdown resistance and high polarization properties. Experimental results and finite element simulations demonstrate that the energy storage capacity of these films effectively harnesses the advantages of both phases. Notably, the interface polarization is minimal. Instead, a solid solution-like diffusosphere, formed by the mutual diffusion of ions between the two phases, plays a crucial role. The diffusosphere acts as a transition zone, mitigating charge aggregation at the interfaces and optimizing the relaxor and breakdown characteristics of the capacitor. With six diffusospheres, the multilayer heterogeneous capacitor achieves a recoverable energy storage density of 94 J/cm3, a significant advancement in BNT-based energy storage films. This work proposes and validates the concept of diffusospheres and their role in reducing interfacial polarization in multilayer heterogeneous films, enhancing the understanding of heterogeneous composite structures and advancing the field of dielectric energy storage.

Influence of annealing treatment on performance of 4H–SiC SBD irradiated by heavy ions under room temperature and low temperature

The influence of the annealing treatment on the performance of commercial 4H–SiC Schottky barrier diodes (SBDs) subjected to heavy ion irradiation under room temperature (RT) and low temperature (LT) are presented. Experimental results confirm that annealing treatment effectively eliminates defects and interface states caused by heavy ion irradiation, particularly for 4H–SiC SBD under LT irradiation. Increasing the annealing temperature leads to the slight improvement in forward current, leakage current and breakdown voltage. However, the annealing process may result in the formation of Ti and Si compounds at the interface between the Schottky metal and SiC, as well as a significant number of vacancies. Combined with Technology Computer Aided Design (TCAD) simulations, it is concluded that the interface trap charge concentrations exceeding 1 × 1012 cm−2 significantly impact the breakdown characteristics of 4H–SiC SBDs.

Analysis of Breakdown Characteristics in Nanofluid Insulation Materials with Metal Particle Contamination

Optimal insulation in transformers is essential to maintain their performance and reliability. However, insulation-related problems, particularly transformer oil contamination, often result in premature transformer failure. To address this issue, a solution has been proposed in the form of a nanofluid, a mixture of transformer oil, and nanoparticles. This study aims to investigate the impact of metal particle contamination on the breakdown and levitation voltage characteristics of nanofluids as liquid insulating materials. The nanofluids were prepared by mixing mineral oil with Fe3O4 nanoparticles at three different concentrations. Tests were conducted to evaluate the AC breakdown and levitation voltages for various contaminant metal particle sizes. The experimental results demonstrate that contaminant particle size has a significant impact on the breakdown voltage. The nanofluid with a concentration of 0.008% Fe3O4 exhibited superior breakdown voltage performance compared to mineral oil and 0.016% Fe3O4 nanofluid. Furthermore, an increase in the levitation stress was observed as the contaminant particle size increased. The findings of this study emphasize the importance of controlling contamination and selecting the appropriate concentration of nanoparticles to enhance transformer insulation performance. This study also highlights the necessity of monitoring the size of contaminant particles to prevent potential damage. Consequently, this study makes a significant contribution to the advancement of more reliable and efficient transformer insulation technology.

Designation and characterization of cold-set whey protein isolate-low acyl gellan gum emulsion-filled gel for enhancing limonene flavor perception: A study on structure, breakdown characteristics, and sensory perception in the human mouth

Flavor perception depends on food structure and oral processing behavior. Emulsion-filled gel (EFG) is a category of soft to solid food products that utilizes the advantages of emulsions to deliver lipid-soluble ingredients, such as the limonene flavor. This paper aimed to design a cold-set EFG system as a carrier to improve limonene flavor perception using whey protein isolate and low-acyl gellan gum (LAGG) (0–0.7% w/w). With increasing LAGG levels, the EFGs shifted towards forming a true gel structure with a brittle and hard 3D network based on the steady shear, amplitude (increasing GLVE′ and decreasing tanδLVE), frequency sweep (increasing K′ and decreasing n′), and uniaxial compassion (increasing Young's modulus and decreasing fracture strain) tests. EFG with 0.7% LAGG needed a higher chewing process, and the fragmentation increased as EFG hardness increased. According to the time-intensity test, the highest and lowest limonene perception were found in the EFG-contained 0.3% (Imax: 5.14, area: 79.20) and 0.7% (Imax: 4.35, area: 57.40) LAGG. In conclusion, by manipulating the structure, custom architectures can be created in the oral cavity, resulting in specific performance and controlled release of their components.