Enhanced Breakdown Voltage Research Articles

Analysis and Manufacturing of GaN Trench‐Gate MOSFETs with Thick Bottom Dielectric

Herein, A high‐performance GaN vertical trench‐gate metal‐oxide‐semiconductor field‐effect transistor (MOSFET (UMOSFET)) with polyimide (PI) as the thick‐bottom dielectric (TBD) is numerically studied and experimentally demonstrated. It is demonstrated that the inclusion of TBD can effectively suppress the peak electric field at the bottom corner of the gate trench and prevent premature breakdown of the devices. According to the technology computer‐aided design simulation results, the UMOSFETs with larger TBD thickness (tTBD) exhibit enhanced breakdown voltage (VBR) with minor expense of specific on‐resistance (Ron,sp) and a significantly improved Baliga's figure of merit. Compared with the conventional GaN UMOSFETs without TBD, the fabricated GaN UMOSFETs with 500 nm‐thick PI as TBD feature a remarkable 1.5 times enhancement in breakdown voltage VBR to 407 V, highlighting the feasibility and potential of the PI‐TBD to propel the further development of GaN vertical devices toward the inherent material and device ultimate.

Normally-Off Trench-Gated AlGaN/GaN Current Aperture Vertical Electron Transistor with Double Superjunction

This study proposes an AlGaN/GaN current aperture vertical electron transistor (CAVET) featuring a double superjunction (SJ) to enhance breakdown voltage (BV) and investigates its electrical characteristics via technology computer-aided design (TCAD) Silvaco Atlas simulation. An additional p-pillar was formed beneath the gate current blocking layer to create a lateral depletion region that provided a high off-state breakdown voltage. To address the tradeoff between the drain current and off-state breakdown voltage, the key design parameters were carefully optimized. The proposed device exhibited a higher off-state breakdown voltage (2933 V) than the device with a single SJ (2786 V), although the specific on-resistance of the proposed method (1.29 mΩ·cm−2) was slightly higher than that of the single SJ device (1.17 mΩ·cm−2). In addition, the reverse transfer capacitance was improved by 15.6% in the proposed device.

Device structural engineering and modelling of emerging III-nitride/β-Ga2O3 nano-HEMT for high-power and THz electronics

Abstract III-nitrides, such as gallium nitride (GaN) and aluminium nitride (AlN), possess a wide bandgap, a high breakdown voltage, and a high thermal conductivity, making them an attractive choice for high frequency and high-power applications. A further benefit of III-nitride-based HEMTs is their high current density, low noise figure, and higher electron mobility, which enable efficient radio-frequency signal amplification. In this research work, the polarization induced graded buffer technique and improved lattice matched β-Ga2O3 substrate is employed to minimize the buffer-related issues in III-Nitride Nano-HEMTs (high electron mobility transistors), such as reduction in the buffer leakage current losses. The polarization-induced doping in buffer region can considerably reduce the buffer leakage current, enhance breakdown voltage and RF characteristics, and bend the conduction band upwardly convex, improving two-dimensional electron gas (2DEG) confinement. A detailed comparison between the graded buffer technique of the HEMT and the HEMT having normal buffer has been conducted. The results demonstrated that the suggested HEMT demonstrated better DC and RF characteristics up to the Tera (1012) hertz range of frequencies. The improved characteristics of the proposed HEMT allow it to be a feasible solution for emerging technologies and cutting-edge communication systems that require efficient signal processing at very high frequencies.

Enhanced breakdown voltage for p-GaN gate AlGaN/GaN HEMT on AlN/Si with triple trenches: A simulation study

This study presents an analysis of an AlGaN/GaN high-electron-mobility transistor (HEMT) with a triple-trench structure (TT-HEMT) for the enhancement of breakdown voltage, which is often limited by the high electric field near the gate edge. Using COMSOL Multiphysics, simulations were run, with trenches made of gallium nitride (GaN) constructed between the GaN and aluminum nitride (AlN) nucleation layers. Each trench was positioned directly beneath the source, gate, and drain contacts. Under the metal gate, a p-type doped GaN cap is added to produce an enhancement mode device, which is more desirable in high-power applications. The results indicate that the effective dispersion of the electric field distribution enhances the breakdown voltage of the device by 70 % in comparison to a conventional HEMT. Additionally, the impact of various design parameters, such as the p-GaN doping concentration and the metal gate work function on the electrical performance, was also investigated. Overall, the proposed device structure exhibits superior electrical properties for high-power applications.

Enhanced interface electrical insulation of aramid‐reinforced resin composites via iron phthalocyanine self‐assembled structures on the surface of aramid

AbstractAramid fiber‐reinforced epoxy resin composites (AFRP) are the main components of electrical equipment such as GIS insulated tie rods, but the poor interfacial bonding between aramid fibers (AF) and epoxy resin (EP) results in a degradation of the material's insulating properties. In this paper, iron phthalocyanine (FePc) molecules are introduced on the AF surface, and the π‐π interaction effect between the metal phthalocyanine rings is used as a driving force to guide the spontaneous assembly of FePc into a three‐dimensional microstructure, and the effect of microstructures with different FePc contents on the insulating properties of AFRP interfaces is investigated. Combining a series of test simulation methods such as surface potential attenuation test, electric tree test, interlayer shear test, and molecular dynamics simulation, reveals the enhancement mechanism of the electrical insulation performance of the interface. The results show that FePc at four contents has an enhancement effect on the flashover voltage along the AF and the breakdown voltage at the AFRP interface, with a maximum enhancement of 25.63% for the flashover voltage and 232.23% for the breakdown voltage.Highlights Self‐assembled three‐dimensional structures on aramid surfaces were constructed via iron phthalocyanine molecules. The effects of self‐assembled structures on physicochemical properties are compared. Modifications substantially increase the breakdown voltage and flashover voltage. The mechanism of microstructure on interface breakdown voltage enhancement is revealed. The overall effect of multiple factors on insulation properties is analyzed.

Breakdown voltage enhancement and specific on-resistance reduction in depletion-mode GaN HEMTs by co-modulating electric field

In this letter, a depletion-mode GaN high electron mobility transistors (GaN HEMTs) with high breakdown voltage and low on-resistance are designed and experimentally demonstrated. It combines the gate field plate and partial unintentionally doped GaN (u-GaN) cap layer (gate field plate and partial u-GaN cap HEMTs: GPU-HEMTs) to co-modulate the surface electric field distribution, which results in the electric field peak being far away from the gate edge, thus improving the breakdown voltage and decreasing the on-resistance. The optimized GPU-HEMTs exhibit a larger output current (I DS) of 495 mA mm−1 and a correspondingly smaller specific on-resistance of 4.26 mΩ·cm2. Meanwhile, a high breakdown voltage of 1044 V at I DS = 1 mA mm−1 compared to the conventional GaN HEMTs of 633 V was obtained. This approach is highly effective in simultaneously optimizing the breakdown voltage and the specific on-resistance of GaN HEMTs, while maintaining a large output current.

Breakdown Voltage Enhancement of Nanosheet Transistors by Ultrathin Bodies

Breakdown Voltage Enhancement of Nanosheet Transistors by Ultrathin Bodies

Optimisation of Negative Fixed Charge Based Edge Termination for Vertical GaN Schottky Devices.

This study focuses on the impact of negative fixed charge, achieved through fluorine (F) implantation, on breakdown voltage (BV) enhancement in vertical GaN Schottky diodes. Several device and implant-related parameters are examined using Synopsys Sentaurus TCAD simulations in order to determine the optimum fixed negative charge concentration required to achieve the highest BV. The simulated structure consisted of a Schottky diode with a box consisting of negative fixed charges to achieve the edge termination of the Schottky device. An empirical equation is proposed to determine the optimum fixed charge concentration for the highest BV based on depth. The simulation also considered implantation profiles derived from SIMS data from an actual device implanted with multi-energy and multi-dose F. It is demonstrated that the BV has a similar dependence on the key parameters like in the box profile. In summary, this work provides valuable insights into optimizing edge termination techniques using negative fixed charge for improved BV in vertical GaN power devices.

Characteristics study of heterojunction III-nitride/β-Ga2O3 nano-HEMT for THz applications

In this research study, a recessed gate III-Nitride high electron mobility transistor (HEMT) grown on a lattice matched β-Ga2O3 substrate is designed. This research investigation aims to enhance DC and RF performance of AlGaN/GaN HEMT, and minimize the short-channel effects by incorporating an AlGaN back layer and field plate technique, which can enhances electron confinement in two-dimensional electron gas (2DEG). A precise comparison analysis is done on the proposed HEMT’s input characteristics, output characteristics, leakage current characteristics, breakdown voltage properties, and RF behaviour in presence and absence of AlGaN back layer in regards to field plate configuration. The inclusion of back barrier aids in raising the level of conduction band, which reduces leakage loss beneath the buffer, and aids in keeping the 2DEG to be confined to narrow channel. Furthermore, the field plate design offers an essential electric field drift between gate and drain, resulting to enhanced breakdown voltage characteristics.

Enhanced Breakdown Voltage of AlGaN/GaN MISHEMT using GaN Buffer with Carbon-Doping on Silicon for Power Device

In recent years, Gallium Nitride (GaN)-based metal-insulator-semiconductor high-electron-mobility transistors (MISHEMTs) have attracted interest in high-power and high-frequency applications. The breakdown mechanism in E-mode GaN MISHEMTs with carbon doping in the GaN buffer grown on a Silicon (Si) substrate (Sub) was investigated using technology computer-aided design simulations. Results showed that GaN MISHEMTs without Si Sub had a breakdown voltage (BV) of 600 V. However, after adding Si Sub to the GaN buffer layer, the electric field (EF) increased, creating a vertical breakdown through the total buffer thickness, therefore, BV was reduced to around 240 V. On the other hand, BV is increased to approximately >1100 V, and the Electric field is reduced after employing a carbon deep acceptor with the proper doping concentration in this device. The GaN MISHEMTs with Si Sub is presented as threshold voltage +1.5 V with transconductance of 700 mS/mm, which is an excellent result compared to GaN MISHEMTs without Si Sub. Eventually, the study device depicted higher BV performance compared to other C-doped GaN HEMT devices. This suggests that the designed GaN MISHEMTs device could effectively be used in power semiconductor devices with optimum performance.

Performance limiting inhomogeneities of defect states in ampere-class Ga2O3 power diodes

Impacts of spatial charge inhomogeneities on carrier transport fluctuations and premature breakdown were investigated in Schottky ampere-class Ga2O3 power diodes. Three prominent electron traps were detected in Ga2O3 epilayers by a combination of the depth-resolved capacitance spectroscopy profiling and gradual dry etching. The near-surface trap occurring at 1.06 eV below the conduction band minimum (EC), named E3, was found to be confined within a 180 nm surface region of the Ga2O3 epilayers. Two bulk traps at EC − 0.75 eV (E2*) and at EC − 0.82 eV (E2) were identified and interconnected with the VGa- and FeGa-type defects, respectively. In the framework of the impact ionization model, employing the experimental trap parameters, the TCAD simulated breakdown characteristics matched the experimental breakdown properties well, consistently with inverse proportionality to the total trap densities. In particular, the shallowest distributed E3 trap with the deepest level is responsible for higher leakage and premature breakdown. In contrast, Ga2O3 Schottky diodes without E3 trap exhibit enhanced breakdown voltages, and the leakage mechanism evolves from variable range hopping at medium reverse voltages, to the space-charge-limited conduction at high reverse biases. This work bridges the fundamental gap between spatial charge inhomogeneities and diode breakdown features, paving the way for more reliable defect engineering in high-performance Ga2O3 power devices.

Advancing MRI capacitors: Design, fabrication, and characterization

AbstractIn today's healthcare landscape, MRI (magnetic resonance imaging) plays a pivotal role in early diagnosis and treatment decisions. However, the quest for higher frequencies to achieve micron‐level resolutions poses technological challenges. This paper focuses on coils and capacitors, with special attention to air gap considerations for movable electrodes. The paper delves into the development of adjustable capacitors using high‐fired NP0 ceramic, tailored for 128‐MHz MRI systems. These capacitors boast impressive specs: a 3‐kV breakdown voltage (VBreakdown), a 3‐pF minimum capacitance (Cmin), a 30‐pF maximum capacitance (CMax), and a 1.5‐pF stepwise capacitance variation (Cvariation step). Notably, they enhance breakdown voltage while preserving frequency stability with MgTiCa ceramic between the fixed and mobile electrode, critical for adaptive blocks. Leveraging geometrical parameters analyzed through the ANSYS simulator, the authors meticulously designed an optimized 25–40 pF capacitor with a 15‐mm height and 1600 mm2 surface area. Post‐fabrication and sintering, extensive testing using a vector network analyzer across 10 MHz to 100 MHz validated performance against simulated expectations.

Boron-Implanted Termination Structures for Vertical GaN Power Devices with Highly Enhanced Breakdown Voltage

Boron-Implanted Termination Structures for Vertical GaN Power Devices with Highly Enhanced Breakdown Voltage

Improvement of single event transients effect for a novel AlGaN/GaN HEMT with enhanced breakdown voltage

A novel AlGaN/GaN HEMT is proposed to improve its single event transient (SET) effect and breakdown characteristics. The device features an AlGaN back barrier layer and a buried P-GaN island in the back barrier layer (BP-HEMT). First, the P-GaN island not only modulates the electric field distribution and reduces impact ionization at both the blocking state and after ion strike but also increases the hole-electron recombination rate. Therefore, it not only effectively increases the breakdown voltage (BV), but also improves the anti-SET performance owing to decreasing the current peak after ion strike. Second, the AlGaN back barrier confines electrons in the channel, and thus, on one hand, it is beneficial to the high saturation drain current (Id,sat) and low on-state resistance (Ron); on the other hand, it effectively prevents the electrons in the buffer layer introduced by ion strike from reaching the drain electrode both at the blocking state and after ion strike. The TCAD simulation results show that the SET peak drain current of the BP-HEMT is significantly dropped to 0.49 A/mm from 4.17 A/mm of the conventional HEMT with a linear energy transfer (LET) of 0.6 pC/μm, and the BV is significantly increased to 1318.3 V from 175.2 V, as well as the Ron decreases by 11.1%.

Asymmetric GaN High Electron Mobility Transistors Design with InAlN Barrier at Source Side and AlGaN Barrier at Drain Side

The InAlN/GaN HEMT has been identified as a promising alternative to conventional AlGaN/GaN HEMT due to its enhanced polarization effect contributing to higher 2DEG in the GaN channel. However, the InAlN barrier usually suffers from high leakage and therefore low breakdown voltage. In this paper, we propose an asymmetrical GaN HEMT structure which is composed of an InAlN barrier at the source side and an AlGaN barrier at the drain side. This novel device combines the advantages of high 2DEG density at the source side and low electrical-field crowding at the drain side. According to the TCAD simulation, the proposed asymmetric device exhibits better drain current and transconductance compared to AlGaN/GaN HEMT, and enhanced breakdown voltage compared to InAlN/GaN HEMT. The current collapse effects have also been evaluated from the process-related point of view. Possible higher interface traps related to the two-step epitaxial growth for the asymmetric structure fabrication will not exacerbate the current collapse and reliability.

Physical insights into the reliability of sunken source connected field plate GaN HEMTs for mm-wave applications

This article investigates the incorporation of field plates in AlGaN/GaN High Electron Mobility Transistors (HEMTs) which leading to enhancement in the device breakdown voltage and a reduction in the reverse leakage current. Using Atlas TCAD software breakdown behavior of gate-connected field plate (GFP), gate-source (dual) field plate, and discrete source-connected field plate (Sunken SC-FP) designs with field plate length variation is probed and physical insight is developed through electric field profile, and impact ionization contour plots. By employing a Sunken SC-FP with gate length of 0.4 μm in the gate-drain access region the device breakdown voltage is improved and has high JFOM (4.8 THz·V). Also, on-resistance (RON) degradation is minimum in the Sunken SCFP (20.12 %), compared with GFP (31.20 %) and dual FP (24.96 %) architectures, when the device is stressed in the off-state (VGS = −40 V) for 1 min. The RF performance of the Sunken SC-FP HEMT is studied using small signal parameters and the load pull measurements as a function of drain bias.

A self-aligned Ga2O3 heterojunction barrier Schottky power diode

We report an alignment-free gallium oxide (Ga2O3) heterojunction barrier Schottky (HJBS) power diode, which utilizes the self-assembled Ni nanostructures as in situ masks for the trench etching of Ga2O3 and the subsequent selective-area filling of p-type NiO. By increasing the trench depth to 200 nm, the relevant HJBS diode exhibits improved reverse blocking capabilities including the reduced leakage current density of 10−8 A/cm2 (at a reverse bias of 100 V) and the enhanced breakdown voltage of 748 V, while maintaining the forward biasing characteristics similar to the Schottky barrier diode (SBD). The variation of turn-on voltage and the reverse breakdown features indicate the conversion of the HJBS diodes characteristics from Ni/Ga2O3 SBD to the NiO/Ga2O3 p-n heterojunction diode. The electrical field simulations and experimental facts imply that the remarkable lateral pinch-off effect in the 200-nm trenched diodes shields the electric field in the depletion region underneath the Ni/Ga2O3 Schottky contact. This work provides a straightforward strategy to simplify the fabrication process of Ga2O3-based HJBS diodes with both promising forward and reverse performances.

Enhanced breakdown voltage and dynamic performance of GaN HEMTs with AlN/GaN superlattice buffer

The characteristics of an AlGaN/GaN high-electron-mobility transistor buffer structure are studied and optimized by employing an AlN/GaN superlattice (SL) structure. Through vertical leakage analysis and back-gate measurement, combined with Silvaco-TCAD simulation, the influence of buffer trapson the carrier transport behaviors and electrical performance for SL buffer structures under a high electric field is analyzed. The AlN/GaN SL buffer structures are further optimized with various AlN/GaN thickness ratios and their total thickness through both simulation and experimental studies. As a result, a high breakdown voltage of up to 1.3 kV with a maximum breakdown electric field of 2.8 MV cm−1 has been achieved. Moreover, the buffer trapping effect is dramatically suppressed, leading to a minimum drop of channel current for the optimized sample, in which donor traps are found to play a positive role in the device dynamic characteristics.

Breakdown voltage enhancement of vertical diamond Schottky barrier diodes by selective growth nitrogen-doped diamond field plate

Breakdown voltage enhancement of vertical diamond Schottky barrier diodes by selective growth nitrogen-doped diamond field plate

Breakdown voltage enhancement in Ga2O3 based Schottky diode

The easiness of today’s era cannot be visualized with generation and distribution of power. The loss of power during its distribution and management is the prime focus of power device community. For this, wide bandgap semiconductors are choice compared to its conventional counterparts. However the power devices developed on wide bandgap semiconductor have reliability issues like long term operation and limited performance in reverse bias. The aim of the present study is to introduce a technique to improve the early breakdown of the device, which is area efficient as well. Efforts have been made to enhance the blocking voltage of the device via terminating its edges. In this work, device is designed with atlas module of the Silvaco TCAD software. Relevant models like Schokely-Read-Hall recombination, conductivity dependent mobility, impact ionization, etc., have been. The electric field and potential profiles in the unterminated and terminated devices have been compared. Moreover, breakdown voltage in the same structures have been estimated and compared.