High Breakdown Voltage Research Articles

NiO/Ga2O3 Vertical Rectifiers of 7 kV and 1 mm2 with 5.5 A Forward Conduction Current

In this study, we present the fabrication and characterization of vertically oriented NiO/β polymorph n-Ga2O3/n+ Ga2O3 heterojunction rectifiers featuring a substantial area of 1 mm2. A dual-layer SiNX/SiO2 dielectric field plate edge termination was employed to increase the breakdown voltage (VB). These heterojunction rectifiers exhibit remarkable simultaneous achievement of high breakdown voltage and substantial conducting currents. In particular, the devices manifest VB of 7 kV when employing a 15 µm thick drift layer doping concentration of 8.8 × 1015 cm−3, concurrently demonstrating a forward current of 5.5 A. The thick drift layer is crucial in obtaining high VB since similar devices fabricated on 10 µm thick epilayers had breakdown voltages in the range of 3.6–4.0 kV. Reference devices fabricated on the 15 µm drift layers had VB of 5 kV. The breakdown is still due to leakage current from tunneling and thermionic emission and not from avalanche breakdown. An evaluation of the power figure-of-merit, represented by VB2/RON, reveals a value of 9.2 GW·cm−2, where RON denotes the on-state resistance, measuring 5.4 mΩ·cm2. The Coff was 4 nF/cm2, leading to an RON × Coff of 34 ps and FCO of 29 GHz. The turn-on voltage for these rectifiers was ~2 V. This exceptional performance surpasses the theoretical unipolar one-dimensional (1D) limit of both SiC and GaN, underscoring the potential of β-Ga2O3 for forthcoming generations of high-power rectification devices.

4H-SiC layer with multiple trenches in lateral double-diffused metal-oxide-semiconductor transistors for high temperature and high voltage applications

In this paper, we present a novel lateral double-diffused metal-oxide-semiconductor (LDMOS) transistor for high-temperature and high breakdown voltage applications. The key idea in our study is replacing a 4H-SiC layer in a part of the buried oxide region (BOX) to reduce temperature effects. Moreover, the top of the 4H-SiC layer has multiple trenches to increase the breakdown voltage. These multiple trenches have been filled with an N-type silicon material. So, we call the proposed structures as multiple trenches 4H-SiC LDMOS (MTSiC-LDMOS). The proposed device is simulated by a two-dimensional ATLAS simulator, and we have shown that the maximum lattice temperature decreases and the breakdown voltage improves by optimization of multiple trenches in the 4H-SiC region. Also, the results show that the current flow and specific on-resistance have improved. Therefore, the MTSiC-LDMOS structure is more reliable than a conventional LDMOS (C-LDMOS) for high-temperature and high breakdown voltage applications.

Enhanced Energy Storage Properties of Polypropylene/Glycidyl Methacrylate Grafted Polypropylene/Nano-ZrO2 Ternary System

Extensive research has focused on enhancing the energy storage density of polypropylene (PP) to meet the demands of high-power and compact electronic devices and electrical systems. However, there is a lack of studies addressing the delicate balance between energy storage density and dielectric loss. Dielectric loss can lead to excessive heat generation, posing a threat to the operation of energy storage capacitors. In this study, PP grafted with glycidyl methacrylate (GMA) was used as a compatibilizer and incorporated into a PP/nano ZrO2 blend to form a ternary system of PP/nano ZrO2/PP grafted GMA. A comparative study was conducted to analyze the effects of GMA grafting and individual doping of nano ZrO2 on the dielectric performance of PP. The results demonstrate that the ternary system not only ensures a high breakdown voltage (382.29 MV/m) but also possesses a high dielectric constant (2.67), thereby achieving an energy storage density of 1.7275 J/cm3 while maintaining low dielectric loss. Furthermore, grafting GMA introduces a significant number of deep traps, a phenomenon substantiated by the results of thermal stimulated depolarization current tests and molecular simulation calculations. However, the ternary system partially avoids the introduction of excessive deep traps associated with GMA grafting. This ternary system exhibits excellent energy storage performance, ease of fabrication, and stability, thereby enriching the research on polymer-based high-energy density dielectric materials.

1540 V 21.8mΩ·cm2 4H-SiC lateral MOSFETs with DOUBLE RESURFs for power integration applications

This work demonstrates 4H-SiC lateral MOSFETs for power integrated circuits application designed with DOUBLE-RESURFs (reduced surface field) technology. Optimized by device simulation, the P-top RESURF dose was designed to be 10 × 1012cm−2. Various RESURF lengths (LRESURF) have been employed in the device manufacturing. As the result, the blocking capability of the fabricated device is significantly improved, and the highest breakdown voltage (BV) reaches 1540 V. Moreover, the best figure of merit (BFOM) achieved is 108 MW/cm2 with the specific ON-resistance (RON,sp) of 21.8mΩ·cm, which is competitive compared to these of reported SiC lateral MOSFETs’.

Novel technique of vibration minimization during hard machining

AbstractThis research paper explores the performance of electrorheological fluids, widely known as smart fluids, which are popular because they experience immediate changes in their characteristics when applied to exterior magnetic or electric field. On application of high voltage, the ER fluid alters its form to semisolid from viscous liquid within a few milliseconds, which is reversible. The reversible nature of ER fluid was employed to absorb vibrations during hard machining. In this research, the consequence of the application of electric field to the ER characteristics of numerous non‐Newtonian fluids with an accumulation of TiO2 and Al2O3 nano elements are investigated. The purpose of this research is to discover the ER sample, which has the highest viscosity, highest breakdown voltage, but less sedimentation. So the selected sample can be used in ER dampers for the purpose of shock absorption. The ER fluid behaves as a mainspring with nonlinear vibration features that are managed by an arrangement of ER fluid, the structure of plunger, and the constraints of applied electric field. In this research, we have employed steel metallic specimens made from EN24T of 302BHN and the machining experiments are conducted to attain the shape parameters that can reduce the tool vibration and help improve the process of cutting at the time of machining with minimum application of fluid utilizing hard metal inserts. In this work, cutting tool parameters were analyzed like cutting force, tool wear, tool vibration amplitude, and surface roughness. It was observed that ER damper has shown its better performance at 5KV. At 5KV, cutting force was the least, tool wear was the least, tool vibration amplitude was the least, and surface roughness was the least. The use of an ER fluid damper decreases tool vibrations and successfully enhances machining performance. The machining industry will be benefited with commercialization of this technique.

Advancements and trends in GaN HEMT

Gallium Nitride based High Electron Mobility Transistors (GaN HEMTs) technology has made significant advancements, revolutionizing the field of power electronics. With their unique properties such as high breakdown voltage, high frequency, and high electron mobility and high-power capabilities, GaN HEMTs offer significant advantages over traditional silicon-based devices, such as improved power density, higher operating temperature, and enhanced reliability. GaN HEMTs have shown great potential in sensing applications, such as gas and biosensors. This thesis explores the advancements and trends in GaN HEMT technology, including crystal growth technology, sensing applications, packaging technology, and performance optimization. Despite significant progress, challenges such as heat dissipation, production costs, and yield and reliability issues need to be addressed. Future research directions may focus on improving integration with other technologies, exploring potential applications in emerging fields such as 5G communication, and addressing these challenges. Overall, GaN HEMT technology has made significant advancements and is set to play a pivotal role in various industries.

Trap Characterization Techniques for GaN-Based HEMTs: A Critical Review.

Gallium nitride (GaN) high-electron-mobility transistors (HEMTs) have been considered promising candidates for power devices due to their superior advantages of high current density, high breakdown voltage, high power density, and high-frequency operations. However, the development of GaN HEMTs has been constrained by stability and reliability issues related to traps. In this article, the locations and energy levels of traps in GaN HEMTs are summarized. Moreover, the characterization techniques for bulk traps and interface traps, whose characteristics and scopes are included as well, are reviewed and highlighted. Finally, the challenges in trap characterization techniques for GaN-based HEMTs are discussed to provide insights into the reliability assessment of GaN-based HEMTs.

Low working loss Si/4H–SiC heterojunction MOSFET with analysis of the gate-controlled tunneling effect

A silicon (Si)/silicon carbide (4H–SiC) heterojunction double-trench metal-oxide-semiconductor field effect transistor (MOSFET) (HDT-MOS) with the gate-controlled tunneling effect is proposed for the first time based on simulations. In this structure, the channel regions are made of Si to take advantage of its high channel mobility and carrier density. The voltage-withstanding region is made of 4H–SiC so that HDT-MOS has a high breakdown voltage (BV) similar to pure 4H–SiC double-trench MOSFETs (DT-MOSs). The gate-controlled tunneling effect indicates that the gate voltage (VG) has a remarkable influence on the tunneling current of the heterojunction. The accumulation layer formed with positive VG can reduce the width of the Si/SiC heterointerface barrier, similar to the heavily doped region in an Ohmic contact. This narrower barrier is easier for electrons to tunnel through, resulting in a lower heterointerface resistance. Thus, with similar BV (approximately 1770 ​V), the specific on-state resistance (RON-SP) of HDT-MOS is reduced by 0.77 ​mΩ‧cm2 compared with that of DT-MOS. The gate-to-drain charge (QGD) and switching loss of HDT-MOS are 52.14 ​% and 22.59 ​% lower than those of DT-MOS, respectively, due to the lower gate platform voltage (VGP) and the corresponding smaller variation (ΔVGP). The figure of merit (QGD ​× ​RON-SP) of HDT-MOS decreases by 61.25 ​%. Moreover, the heterointerface charges can reduce RON-SP of HDT-MOS due to trap-assisted tunneling while the heterointerface traps show the opposite effect. Therefore, the HDT-MOS structure can significantly reduce the working loss of SiC MOSFET, leading to a lower temperature rise when the devices are applied in the system.

1.7-kV vertical GaN p-n diode with triple-zone graded junction termination extension formed by ion-implantation

Edge termination has emerged as an important area in the design and realization of vertical GaN power electronic devices. While the material properties of GaN are promising for high-performance devices, in practice the breakdown voltage can be compromised by inadequate edge termination (ET). While solutions in other materials (e.g. Si, SiC) are well-known, these are challenging to implement in GaN due to inherent difficulties in p-type doping GaN. In this work, we report a etch-free triple-zone graded junction termination extension (JTE) for vertical GaN diodes formed by Nitrogen ion implantation. The triple-zone design offers lower peak fields for effective field control. In addition, the proposed triple-zone JTE is beneficial for increasing the fabrication process window and allowing for more variability in epitaxial wafer growth in terms of p-GaN doping and thickness while maintaining high breakdown voltage. The fabricated GaN p-n diodes with triple-zone JTE obtain a maximum breakdown voltage of 1.73 kV with specific on-resistance Ron of 0.4 mΩcm2. Temperature-dependent reverse characteristics show that the devices have a positive temperature coefficient of the breakdown voltage indicating an avalanche breakdown mechanism. These results suggest that vertical GaN p–n diodes with N-implanted triple-zone JTE are promising for power applications.

Normally-off n-ZnO/p-diamond heterojunction field effect transistor with recessed gate and current distribution layer

In this paper, an n-ZnO/p-diamond heterojunction field effect transistor (HJ-FET) with recessed gate and current distribution layer is designed and optimized by using TCAD software. It demonstrates that the threshold voltage and breakdown voltage can be remarkably affected by the doping concentration and thickness of both n-ZnO and p-diamond. Additionally, the threshold voltage can be further enhanced by introducing a recessed gate due to the enhanced depletion capacity on the channel layer. Although the conduction modulation by the enhanced electric field decreases the on-resistance, the obviously decreased breakdown voltage by the recessed gate degrades the electrical performances. Finally, a current distribution layer between source and drain electrodes is added to decrease the on-resistance of diamond HJ-FET. After optimizing the parameters, the diamond HJ-FET exhibits a larger threshold voltage, a smaller on-resistance and a higher breakdown voltage.

Deposition of oxidation-resistant coatings by vacuum-pulse-arc melting of NiAl-based granules to protect Ni superalloys

Here we report an innovative contactless method for vacuum-pulse-arc melting of single Ni41Al41Cr12Co6Hf0.25 (at.%) granules with a size of 160 ± 20 μm using a non-consumable electrode. A dense, uniform, and oxidation-resistant coating 100 μm thick, formed by a monolayer of molten granules, was obtained on the surface of a Ni-based superalloy fabricated by laser powder bed fusion. A distinctive feature of the proposed technology is the use of high-voltage breakdown to initiate a subsequent relatively low-voltage arc discharge with adjustable duration and energy. The utilization of granules of a certain size and precise control of the discharge energy makes it possible to control the monolayer thickness and the degree of substrate melting. A mechanism is proposed for melting a single granule located on the substrate surface. The resulting coating has a submicron structure consisting of NiAl and Ni3Al intermetallic compounds. The high resistance of the coating to oxidation at 1000 °C is evidenced by the formation of an oxide scale 500 nm thick, consisting of two sublayers: an upper layer about 200 nm thick with relatively large α-Al2O3 grains up to 150 nm in size and a lower layer consisting of a mixture of α-Al2O3 and θ-Al2O3 grains smaller than 40 nm.

Novel Polyetherimide Dielectrics: Molecular Design, Energy Storage Property, and Self-Healing Performance.

The development of high-temperature resistant dielectrics with excellent dielectric properties and self-healing behavior is crucial for the application of metallized film capacitors. In this work, a series of polyetherimide (PEI) dielectric films are designed and fabricated. The introduction of polar groups is in favor to the increase of permittivity, and the flexible connection such as the ether group will facilitate the reduction of dielectric loss. Moreover, the oxygen elements are beneficial to the "self-healing" of metallized film capacitors. Consequently, the permittivity of 3.53-4.00, dissipation factor of 0.281-0.517%, and Weibull breakdown strength of 347-674MVm-1 are obtained for the PEI dielectrics. In addition, PEI-4 (BPADA-BAPP) and PEI-8 (BPADA-MDA) are selected to further investigate dielectric breakdown (150°C), electrical displacement-electric filed (D-E) loop (at room temperature and 150°C) as well as self-healing performance, which will evaluate their potential in practical applications. The results show that PEI-8 has stable breakdown field strength and high charge-discharge efficiency at elevated temperatures. Metallized film capacitor based on PEI-8 exhibits excellent self-healing performance, with pleasing self-clear morphology, high breakdown voltage, and reduced self-healing energy. Therefore, PEI-8 is considered as a potential candidate for metallized film capacitors applied under harsh conditions.

7.86 kV GaN-on-GaN PN power diode with BaTiO3 for electrical field management

Devices based on gallium nitride (GaN) have great potential for high power switching applications due to the high breakdown field and high electron mobility. In this work, we present a vertical GaN-on-GaN PN power diode using high dielectric constant material, BaTiO3, for electrical field management and high breakdown voltages, in together with an optimized guard-ring and field plate design. Numerical simulation shows that with high-k dielectrics implemented, the peak electrical field at the PN interface is mitigated from 3.5 to 3.1 MV/cm under a reverse bias of −9.05 kV. The device design with BaTiO3 shows a breakdown voltage of 9.65 kV or about 600 V improvement. The fabricated diodes with a 57 μm thick drift layer demonstrate a breakdown voltage of 7.86 kV on a bulk GaN substrate. The device has an on-resistance of 2.8 mΩ cm2 and a Baliga figure of merit of 22 GW/cm2.

Design Optimization of High Breakdown Voltage AlGaN/GaN High Electron Mobility Transistor with Insulator Dielectric Passivation Layer

Design Optimization of High Breakdown Voltage AlGaN/GaN High Electron Mobility Transistor with Insulator Dielectric Passivation Layer

A novel stepped AlGaN hybrid buffer GaN HEMT for power electronics applications

In this paper, a novel p-type gallium nitride (p-GaN) high electron mobility transistor (HEMT) is proposed and investigated for high power electronic applications. In the proposed device, a stepped hybrid Aluminium GaN (AlGaN) buffer layer with low Al content has been introduced to improve the performance of the device. The low aluminium mole concentration decreases the surface defects which reduces the leakage current, thereby increasing the breakdown voltage of the device. To validate the simulation results, calibration of the device models has been performed with experimental results. Results present that the proposed device exhibits high breakdown voltage, high transconductance and low small signal capacitances. The proposed device achieves improvement in breakdown voltage, transconductance and small signal capacitances as compared to the conventional hybrid buffer high electron mobility transistor (HB-HEMT). Furthermore, the processing steps have been proposed for the possible fabrication of the proposed device. Also, the optimization is performed to achieve the optimal device performance with respect to breakdown voltage. Finally, the performance of the proposed device has been compared with the state-of-the-art devices.

Experimental Investigation on Thermal Conductivity of Palm Oil and Zinc Oxide PFAE-based Nanofluids

Vegetable oil (VO) have been constantly researched as an alternative to the conventional mineral oil (MO) in the application of transformer insulation liquid. VO is deemed as a suitable replacement for MO as they are a renewable source, cheaper in price, and have a high thermal conductivity, high flashpoint, and high breakdown voltage value. In addition, the trending interest in nanofluids has made it possible to further improved the insulating properties of VOs. This paper reports the experimental results of thermal conductivity test of Palm oil-based nanofluids and Palm fatty acid ester (PFAE)-based nanofluids. The nanoparticles used in this work is Zinc Oxide (ZnO) <50nm nano powder and the nanofluid (NF) samples are varied by low, medium and high concentrations. The test was conducted at 9 different temperatures from 25°C to 65°C with 5°C gap. The result shows that a low and medium concentration nanofluid has an improvement in thermal conductivity value, up to 42.6% and 59.5% respectively for palm oil-based nanofluid. Meanwhile, the high concentration palm oil-based nanofluid has lower enhancement in thermal conductivity value at certain temperatures. As for PFAE-based nanofluids, the thermal conductivity value has improved by up to 27% and 14.4% for medium and high concentration respectively. Nanofluids with medium concentration of ZnO, has the highest enhancement in insulating and cooling properties for both palm oil and PFAE-based nanofluids. This observation is supported by the kinematic viscosity value of the mentioned nanofluid.

Comparative performance investigation and sustainability assessment in electrical discharge machining of SS316 using different dielectrics

In electrical discharge machining, the material removal phenomenon is heavily influenced by the breakdown strength of the dielectric fluid and the inter-electrode gap monitoring. This innovative research addresses a comparative performance evaluation and sustainability assessment between biodegradable palm oil and conventional EDM oil during machining of stainless steel (SS-316) using copper electrode. The cutting performance is investigated by comprehensive result analysis of various machinability aspects including material removal rate, surface integrity, tool wear rate, radial overcut of machined components. According to the findings, machining with palm oil dielectric outperformed the usual EDM oil with regards to improved material removal, surface morphology and finish, increased machined surface hardness with minimum surface crack density and hole overcut. Pyrolysis of conventional EDM dielectric oil leads to deposition of thin film carbon on bottom surface of the copper electrode which prevents the quick tool wear due to its higher breakdown voltage. The total machining cost expenditure per component under palm oil (INR383) is reduced by 11% than expenditure in traditional EDM oil (INR426). Compared to EDM oil, machining under biodegradable palm oil as dielectric fluid is better socio-economical viable and environmental conscious to enhance sustainability.

Design of High I on/I off Fin-Statistic Induction Transistor Based on Gallium Nitride

Aiming at the problems of poor current control and high gate leakage current of traditional static induction transistors, we designed a new structure of GaN-based static induction transistor (SIT) using TCAD software. The SIT uses a new type of fin channel and a high-work function gate metal. In addition, this work simulates the electrical properties of different structure SIT and explores the influence of the channel shape on the channel barrier voltage. According to the simulation results, the GaN SIT has the following properties: high breakdown voltage (BV=830V), strong current control capability (switch current ratio I on/I off=1×1014), high turn-on current density, and low device conduction loss.

Study of ultra-low specific on-resistance and high breakdown voltage SOI LDMOS based on electron accumulation effect

A novel stepped L-shaped trench gate silicon-on-insulator (SOI) lateral double-diffused metal oxide semiconductor field-effect transistor (LDMOS) with N-pillar (SLTGN-LDMOS) is proposed. SLTGN-LDMOS contains a highly doped N-pillar, assisting in reducing the specific on-resistance (R on,sp). The stepped L-shaped trench gate (SLTG) attracts electrons to attach to the edge of the trench, thus directing more current to flow along the edge, which decreases R on,sp effectively. Furthermore, new electric field peaks are generated on the surface of the drift region, thus increasing the breakdown voltage (BV). As a result, compared with the conventional structure (C-LDMOS), the BV of SLTGN-LDMOS increases from 63 V to 162.7 V, and the R on,sp decreases from 1.85 mΩ·cm2 to 1.46 mΩ·cm2. Then, the figure of merit (FOM1, BV2 /R on.sp) increases remarkably from 2.15 MW·cm−2 to 18.13 MW·cm−2. In addition, the maximum surface temperature of SLTGN-LDMOS is 395.3 K, slightly lower than the 398.7 K of C-LDMOS.

(Invited) Fabrication and Device Performance of 2.7 Kv/2.5A NiO/Ga2O3 Heterojunction Power Rectifiers

In this study, The fabrication of a p-n junction NiO/Ga2O3 rectifier in which we employ a bilayer NiO structure with two different doping levels to achieve both high breakdown voltage and low on-state resistance was described. The band alignment of the NiO to the Ga2O3 was measured. Selective wet and dry etch processes for removing NiO from the underlying Ga2O3 was developed. Finally, the dc and switching performance of the rectifiers was characterized. The maximum breakdown voltage was 2.7 kV for a 1 mm diameter rectifier, with 2.5 A forward current and on/off ratio > 108 over a broad range of switching voltages. The reverse recovery time was limited by the measurement circuit but was < 100 µs. These results show the promise of heterojunction rectifiers based on Ga2O3 for future generations of power switching applications. Figure 1