• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.31 no.6
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• pp.367-371
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• 2018

1,200 V class junction barrier schottky (JBS) diodes and schottky barrier diodes (SBD) were simultaneously fabricated on the same 4H-SiC wafer. The resulting diodes were characterized at temperatures from room temperature to 473 K and subsequently compared in terms of their respective I-V characteristics. The parameters deduced from the observed I-V measurements, including ideality factor and series resistance, indicate that, as the temperature increases, the threshold voltage decreases whereas the ideality factor and barrier height increase. As JBS diodes have both Schottky and PN junction structures, the proper depletion layer thickness, $R_{on}$, and electron mobility values must be determined in order to produce diodes with an effective barrier height. The comparison results showed that the JBS diodes exhibit a larger effective barrier height compared to the SBDs.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.35 no.3
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• pp.241-245
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• 2022

In this study, we measured and comparatively analyzed the characteristics of MPS (Merged Pin Schottky) diodes in 4H-SiC by changing the areal ratio between the Schottky and PN junction region. Increasing the temperature from 298 K to 473 K resulted in the threshold voltage shifting from 0.8 V to 0.5 V. A wider Schottky region indicates a lower on-resistance and a faster turn-on. The effective barrier height was smaller for a wider Schottky region. Additionally, the depletion layer became smaller under the influence of the reduced effective barrier height. The wider Schottky region resulted in the ideality factor being reduced from 1.37 to 1.01, which is closer to an ideal device. The leakage saturation current increased with the widening Schottky region, resulting in a 1.38 times to 2.09 times larger leakage current.

• Journal of the Semiconductor & Display Technology
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• v.21 no.4
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• pp.138-143
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• 2022

We analyzed the influence of post-annealing on Ga₂O₃/n-type 4H-SiC heterojunction diode. Gallium oxide (Ga₂O₃) thin films were deposited by radio frequency (RF) sputtering. Post-deposition annealing at 950℃ in an Oxygen atmosphere was performed. The material properties of Ga₂O₃ and the electrical properties of the diodes were investigated. Atomic Force Microscopy (AFM), X-Ray Diffraction and Scanning Electron Microscope (SEM) images show a significant increase in the roughness and crystallinity of the O₂-annealed films. After Oxygen annealing X-ray Photoelectron Spectroscopy (XPS) shows that the atomic ratio of oxygen increases which is related to a decrease in oxygen vacancy within the Ga₂O₃ film. The O₂-annealed diodes exhibited higher on-current and lower leakage current. Moreover, the ideality factor, barrier height, and thermal activation energy were derived from the current-voltage curve by increasing the temperature from 298 - 434K.

• Electronics and Telecommunications Trends
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• v.29 no.6
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• pp.53-62
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• 2014

본고는 최근 화두가 되고 있는 에너지 절감을 위해 고효율, 친환경의 WBG(Wide Band-Gap) 화합물반도체인 SiC(Silicon Carbide), GaN(Gallium Nitride) 전력반도체 소자 및 전력변환 모듈의 기술동향과 ETRI에서 연구개발 진행 중인 GaN 전력반도체 관련 기술에 대해 기술한다. WBG 전력반도체는 기존의 실리콘 전력반도체와 비교하여 열 특성 향상, 고속 스위칭, 고전압/고전류 특성 및 스위칭 손실 최소화 등이 가능하고 이에 따른 시스템의 소형화 및 전력효율 향상 효과를 얻을 수 있다. 특히, GaN 전력반도체 소자는 시장이 가장 넓게 형성되어 있는 900V 이하에 적용이 가능하며, 앞으로 시장이 커질 것으로 예상되는 HEV(Hybrid Electric Vehicle)/EV(Electric Vehicle)의 친환경 자동차에도 활용될 것으로 기대되고 있다. 본고는 최근의 일본과 미국에서의 WBG 전력반도체에 대한 관심 및 투자 방향과 GaN 전력반도체 소자에 대한 해외 기업의 업계동향에 대해서도 함께 살펴본다. 이러한 WBG 전력반도체에 대한 해외 선진업체의 산업동향과 더불어 ETRI에서 연구개발 중인 GaN 전력반도체 기술현황에 대해 전력소자 설계 및 제조공정, 패키징, 전력모듈 설계 제작 기술을 포함하여 기술한다.

• Clean Technology
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• v.23 no.3
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• pp.314-324
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• 2017

To verify the viability of Co, Ru and Zr-based catalyst for $CO_2$ (dry) reforming reaction, catalysts were fabricated using cordierite, silicon carbide and rota monolithic substrates, and they were compared with the conventional $Co-Ru-Zr/SiO_2$ catalyst in terms of performance and durability. Cordierite monolith was showed high activity with the least amount of active component. In addition, when Cordierite monolith was coated with Co-Ru-Zr in various ways, most excellent performance was showed at a precursor solution coating method. In particular, when 0.9 wt% Co-Ru-Zr/Cordierite was used for reaction, it was observed that 95% $CO_2$ conversion was maintained for 300 h at $900^{\circ}C$.

• Smart Structures and Systems
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• v.13 no.4
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• pp.501-515
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• 2014

This paper presents a linear computational homogenization framework to evaluate the effective (or generalized) electromechanical coupling coefficient (EMCC) of adaptive structures with piezoelectric structural fiber (PSF) composite elements. The PSF consists of a silicon carbide (SiC) or carbon core fiber as reinforcement to a fragile piezo-ceramic shell. For the micro-scale analysis, a micromechanics model based on the variational asymptotic method for unit cell homogenization (VAMUCH) is used to evaluate the overall electromechanical properties of the PSF composites. At the macro-scale, a finite element (FE) analysis with the commercial FE code ABAQUS is performed to evaluate the effective EMCC for structures with the PSF composite patches. The EMCC is postprocessed from free-vibrations analysis under short-circuit (SC) and open-circuit (OC) electrodes of the patches. This linear two-scale computational framework may be useful for the optimal design of active structure multi-functional composites which can be used for multi-functional applications such as structural health monitoring, power harvest, vibration sensing and control, damping, and shape control through anisotropic actuation.

• Journal of Korea Foundry Society
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• v.17 no.1
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• pp.93-99
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• 1997

A possibility of production of aluminium matrix composites by using the lost foam process was investigated. Silicon carbide particles, graphite particles, and stainless steel wires were used as reinforcement materials. The reinforcement materials were introduced to the polystyrene to form patterns via injection molding process. The results obtained from this experiment can be summarized as follows. In Al/SiCp system, the particles with the radius of $100{\mu}m$ and over were entrapped in the matrix in the case of upward freezing of which solidification direction was opposite to floating direction of the particles. And few particles were entrapped in the matrix in downward freezing. In Al/graphite system, almost no particles were entrapped in the matrix except the area chill attatched. When the thickness of polystyrene slice was 4mm in Al/stainless steel wire system, the floating tendency of fibers was observed to increase as the distance from the ingate was increased.

• Proceedings of the KIPE Conference
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• 2017.07a
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• pp.18-19
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• 2017

This paper shows the design of the high voltage capacitor charger which using a modified series parallel resonant converter. The used silicon carbide Metal-Oxide Semiconductor Field Effect Transistor (SiC MOSFET) is proper for the few hundred kHz of high switching frequency to overcome the bulk resonant inductor and snubber capacitors. Furthermore, to increase the amount of the charging current, three phase delta transformer is used as well as the secondary sides are connected in parallel. In this paper, the design procedure of the high voltage capacitor charger is suggested and the output power is verified by the experimental results with the rated resistor load.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.05a
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• pp.62-65
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• 2005

We studied the nematic liquid crystal (NLC) alignment capability by the Ultraviolet (UV) alignment method on a-C:H thin-films, and investigated electro-optical performances of the UV aligned twisted nematic (TN)-liquid crystal display (LCD) with the UV exposure on a-C:H thin film surface. A good LC alignment by UV irradiation on a-C:H thin-film surfaces was achieved. Monodomain alignment of the UV aligned TN-LCD can be observed. The good electro-optical (EO) characteristics of the UV aligned TN-LCD was observed with oblique UV exposure on the a-C:H thin film surface for 1min.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.26 no.5
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• pp.188-192
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• 2016

In this work, the SiC powders were synthesized through the carbonized matter from the mixture of silica powder and rice husks. The SiC powders, obtained from the carbothermal reduction reaction of silica and carbonized rice husks, were investigated by XRD patterns, XPS, FE-SEM and FE-TEM. In the XRD patterns, the specimens showed clearly very high strong peak of (111) plane near $35^{\circ}$ as well as weak (220) and (311) peak respectively at approximately $60^{\circ}$ and $72^{\circ}$. Under Ar atmosphere, the power synthesized from the mixture (in case of mixing ratio, 6 : 4) of carbonized rice husks and silica showed mainly cubic SiC crystalline phase showing relatively lower ratio of hexagonal phase without residual carbon in XRD pattern. In the TEM analysis, the specimen, synthesized from carbonized rice husks and silica with mixing ratio of 6 : 4 under Ar atmosphere, showed relatively fine particles under $5{\mu}m$ and a crystalline SiC phase of (100) diffraction pattern.