High dv/dt Testing of Coil Winding Insulation Systems for Wide-Bandgap Applications

Vivien C. Grau,Laurids Schmitz,Rik W. De Doncker 전력전자학회 2023 ICPE(ISPE)논문집 Vol.2023 No.-

To increase efficiency and reduce material consumption, the increased use of wide-bandgap (WBG) power semiconductor devices becomes indispensable. However, challenges such as the accelerated aging of insulation materials have so far prevented exploiting the full potential of this technology. This paper provides an overview of experiments that can be performed to test insulation systems for their resilience with respect to fast switching transients. To this end, capacitive and inductive specimens are considered. Firstly, the test bench is briefly introduced. Secondly, measurements are performed with standardized twisted pair of enameled wire specimens. The lifetimes at two different voltage slopes are compared, the effect of a consistent discharge at steep voltage slopes is analyzed and the influence of a partial discharge (PD) resistant additive in the enamel is considered. Then, single-tooth coil windings with and without a PD-resistant additive in the enamel are investigated and the influence of an optimized winding configuration demonstrated.

차세대 고효율 전력반도체 연구: GaN HFET 전력스위칭 소자

장승엽,문성운,박진홍 한국물리학회 2015 새물리 Vol.65 No.1

Based on current research results, we introduce a GaN heterojunction field-effect transistor (HFET) for a next-generation power semiconductor device. The wide bandgap (E$_{G}$ = 3.4 eV) and the high-temperature stability of GaN make it attractive for high-power device applications. The low on-resistance and the fast switching speed of the GaN HFET will allow low-loss and high-power operation to be realized and consequently, allow the system size to be reduced. Here, first, we introduce the basics of the power semiconductor; then, we focus on the properties of the GaN HFET and the key technologies to make the GaN HFET a next-generation power switching device. 차세대 전력반도체 소자로 각광받고 있는 GaN 이종접합 전계효과 트랜지스터 (heterojunction field-effect transistor, HFET) 전력스위칭 소자에 대한 연구를 소개하고자 한다. GaN HFET는 와이드 밴드갭 (wide bandgap, E$_{G}$ = 3.4 eV) 특징과 고온 안정성 등의 재료적인 장점 및 이종접합 (heterojunction) 에 의한 2차원 전자가스 (2DEG) 를 활용하는 구조로 전력스위칭 소자로 큰 장점을 가진다. GaN HFET 전력스위칭 소자의 낮은 온저항, 높은 스위칭 속도는 고효율, 고주파 동작을 가능하게 하여, 전력 분배/변환 효율의 개선 및 전력 시스템 소형화를 가능하게 한다. 본 논문에서는 전력반도체에 대한 간단한 소개부터 시작하여, GaN 물질 특성 및 기본적인 HFET 소자 특성에 대해 기술하고, 현재 GaN HFET 전력스위칭 소자 구현의 핵심 기술에 대해 논의하고자 한다.

Highly transparent thin-film transistors using wide-bandgap organic semiconductors and multilayer transparent electrodes

문한얼,김민철,조현수,Kazuo Takimiya,유승협 한국정보디스플레이학회 2014 Journal of information display Vol.15 No.2

Highly transparent organic thin-film transistors operable at low voltages were demonstrated using a wide-bandgap organic semiconductor for channel layers, metal-based multilayers for transparent source/drain (S/D) electrodes, and an ultrathin fluoropolymer for gate dielectric layers. The devices optimized for high transparency based on characteristic-matrix formalism exhibited transmittances over 85% for the channel region and over 70% for the S/D region in almost the entire visible range. The validity of the multilayer S/Dcontact and the ultrathin fluoropolymer dielectrics on indium tin oxide (ITO) gate electrodes for favourable electrical characteristics were also verified. The resultant transparent thin-film transistors showed a typical p-channel operation switchable under 2V with ca. 0.72 cm2/Vs mobility.

Optimization of Field-plate AlGaN/GaN HFETs for High-voltage and High-frequency Operation

Hoonsang Yoon,김형탁 한국물리학회 2012 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.60 No.1

We performed physics-based 2-dimensional TCAD device simulations to optimize field-plated AlGaN/GaN heterostructure field effect transistors (HFETs) for high-power and high-frequency operation. The effects of the field plate dimensions and the passivation dielectric materials were investigated. The results showed that dimensional changes in the field plates significantly affected the breakdown and frequency performance. Silicon nitride, a widely-used passivation material for this technology, also turned out to have a benign effect on high-voltage operation whereas it had a detrimental effect on high-frequency operation. In this work, double-layered passivation with a source field plate was proposed and optimized to secure both high-voltage and high-frequency operation. The optimized devices maintained high breakdown voltage performance without compromising frequency response and without increasing fabrication complexity.

DC Characteristics of Wide-bandgap Semiconductor Field-effect Transistors at Cryogenic Temperatures

김형탁,임종태,차호영 한국물리학회 2010 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.56 No.5

We investigated the characteristics of AlGaN/GaN heterostructure field-effect transistors (HFETs) and 4H-SiC metal semiconductor field-effect transistors (MESFETs) at cryogenic temperatures to evaluate potential for extreme environmental applications. AlGaN/GaN HFETs demonstrated increased output currents and a negative shift of channel pinch-off voltage as the temperature decreased from 300 K to 50 K. 4H-SiC MESFETs demonstrated dependence on temperature opposite to that of the AlGaN/GaN HFETs. The negative temperature coefficient of the output current in AlGaN/GaN HFETs is attributed to a mobility enhancement accompanying a channel resistance reduction at cryogenic temperatures. AlGaN/GaN HFETs benefit from a heterostructure without intentional doping, showing no degradation in the channel carrier density. In 4H-SiC MESFETs,the reduction in the channel carrier density due to the deactivation of channel dopants results in a positive shift of the threshold voltage, and thereby a significant degradation of the output current. Our results confirm AlGaN/GaN HFETs to be strong candidates for cryogenic applications compared to 4H-SiC MESFETs.

Fast Wide-bandgap Device Overcurrent Protection with Direct Current Measurement

Wen Zhang,Fred Wang,Zheyu Zhang,Bernhard Holzinger 전력전자학회 2019 ICPE(ISPE)논문집 Vol.2019 No.5

A fast and reliable overcurrent protection scheme is crucial for the converter reliability. It is also critical for double pulse test stations where newer devices or even engineering samples are tested, and device failures can be costly. A fast overcurrent protection scheme using the direct current measurement in the double pulse test is demonstrated and 7.55 ns fault response delay time is achieved. The total fault clearing time is determined by the fault signal propagation and device switching speed. Around 100 ns and 60 ns fault clearing time is achieved for SiC and GaN devices, respectively. The much faster protection can potentially simplify the gate driver design and reduce the energy rating of the coaxial shunt resistor. Since the overcurrent detection is directly attached to the current measurement, its impact on the measurement bandwidth is also discussed.

4H to 3C Polytypic Transformation in Al+ Implanted SiC during High Temperature Annealing

L. Kuebler,E. Hershkovitz,D. Kouzminov,H.‑J. Gossmann,S. Charnvanichborikarn,C. Hatem,H. Kim,K. S. Jones 대한금속·재료학회 2024 ELECTRONIC MATERIALS LETTERS Vol.20 No.3

Polytypism in SiC has created interest and opportunity for device heterostructures and bandgap engineering in power electronicapplications. As each SiC polytype possesses a diff erent bandgap, electron mobility, and degree of anisotropy, unique interfacescan be created without changing its chemical composition. The 4H polytype is commonly used, but the 3C polytype off ers highsurface electron mobility with isotropic properties as the only cubic polytype. This has driven research on heteroepitaxy with limitedsuccess in traditional chemical vapor deposition chambers. Discussion on polytype control and stability has been restrictedto bulk and epitaxial crystal growth, despite numerous reports of polytypic transformations occurring during other processingsteps. This study revealed the polytypic transformation of 4H-SiC to 3C-SiC after high temperature annealing using high resolutioncross-sectional transmission electron microscopy (TEM) and scanning transmission electron microscopy (STEM). Above1750 °C, the surface signifi cantly roughened under a reduced pressure of Ar, whereas surface planarity was maintained underAr atmospheric pressure. The formation of 3C-SiC islands occurred adjacent to large surface pits through an epitaxial growthprocess for the reduced pressure condition only. Loss of SiC stoichiometry at the surface with Si enrichment and availability ofon-axis terraces enabled 3C nucleation. 3C-SiC growth was retarded using a protective carbon cap (C-cap) where defect-freesingle crystal 3C-SiC has a coherent interface with the 4H-SiC substrate underneath. These fi ndings demonstrate that the 3Cpolytype can be stable at high temperatures, encouraging the need for a better understanding of polytype stability and control.

Heterostructure WSe₂−Ga₂O₃ Junction Field-Effect Transistor for Low-Dimensional High-Power Electronics

Kim, Janghyuk,Mastro, Michael A.,Tadjer, Marko J.,Kim, Jihyun American Chemical Society 2018 ACS APPLIED MATERIALS & INTERFACES Vol.10 No.35

<P>Layered materials separated from each bulk crystal can be assembled to form a strain-free heterostructure by using the van der Waals interaction. We demonstrated a heterostructure n-channel depletion-mode β-Ga<SUB>2</SUB>O<SUB>3</SUB> junction field-effect transistor (JFET) through van der Waals bonding with an exfoliated p-WSe<SUB>2</SUB> flake. Typical diode characteristics with a high rectifying ratio of ∼10<SUP>5</SUP> were observed in a p-WSe<SUB>2</SUB>/n-Ga<SUB>2</SUB>O<SUB>3</SUB> heterostructure diode, where WSe<SUB>2</SUB> and β-Ga<SUB>2</SUB>O<SUB>3</SUB> were obtained by mechanically exfoliating each crystal. Layered JFETs exhibited an excellent <I>I</I><SUB>DS</SUB>-<I>V</I><SUB>DS</SUB> output as well as <I>I</I><SUB>DS</SUB>-<I>V</I><SUB>GS</SUB> transfer characteristics with a high on/off ratio (∼10<SUP>8</SUP>) and low subthreshold swing (133 mV/dec). Saturated output currents were observed with a threshold voltage of −5.1 V and a three-terminal breakdown voltage of +144 V. Electrical performances of the fabricated heterostructure JFET were maintained at elevated temperatures with outstanding air stability. Our WSe<SUB>2</SUB>-Ga<SUB>2</SUB>O<SUB>3</SUB> heterostructure JFET paves the way to the low-dimensional high-power devices, enabling miniaturization of the integrated power electronic systems.</P> [FIG OMISSION]</BR>

은 기반 페이스트를 이용한 전력 반도체 소자의 칩 소결접합

이나연(Na Yeon Lee),이종현(Jong-Hyun Lee),현창용(Chang-Yong Hyun) 대한용접·접합학회 2019 대한용접·접합학회지 Vol.37 No.5

Existing Si-based semiconductors are being replaced with wide bandgap materials such as SiC and GaN for more efficient operation in power devices, and this has stimulated extensive research on technologies to form a heat-tolerant joint. Sinter-bonding technologies using silver (Ag) with excellent thermal conductivity have been in the spotlight, and pastes containing Ag particles have been the developed and applied. In this paper, recent studies on sinter-bonding technologies using Ag-particle-based paste, which can be classified into pressure-assisted and pressureless processes, were analyzed. The size and shape of the Ag particles, type of solvent or formulation, type of metal finish, atmosphere, and bonding temperature/time were considered, as typical process parameters. The effects of changes in the parameters on bonding results were compared and analyzed, with a focus on shear strength value and microstructure. Contrary to expectations, recently reported pressureless sinter-bonding results were found to exhibit excellent bonding properties. For example, a bonding strength approaching 35 MPa was reported for pressureless sinter-bonding at 250 ℃ for 10 min in air. The excellent bonding result can be attributed to the use of an optimal solvent during the preparation of the paste.

Temperature dependence of the lifetime of nonequilibrium charge carriers in GaP diodes under condition of recombination current domination

Vasily A. Krasnov,Stanislav V. Shutov,Sergey Yu Yerochin 한국물리학회 2015 Current Applied Physics Vol.15 No.4

Temperature dependence of the lifetime of nonequilibrium charge carriers limited by recombination process in a p-n junction space-charge region has been obtained from currentevoltage, capacitance evoltage and thermometric characteristics of GaP p+-n junctions in the temperature range 150-500 K. The results have been refined using the data of the junction relaxation characteristics. Parameters of the carriers' lifetime sensitivity to the temperature and current have been determined. It has been established that the charge carriers recombine predominantly through deep single-level amphoteric-type centres. The depth of the centres makes approx. (EC-1.25 eV). We suppose that the nature of the centres formation is not connected with the junction fabrication technology. It has rather fundamental origin. The results of the present investigation could be used in the development of devices based on wide bandgap semiconductors and particularly high temperature diode sensors.