• Title/Summary/Keyword: wide bandgap

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Design of Half-Wavelength Low-PASS Filter using EBG Structure (EBG 구조를 이용한 반파장 저역통과 여파기 설계)

  • Kang, Myung-Soo;Kim, Young-Tae;Park, Jun-Seok
    • Proceedings of the Korea Electromagnetic Engineering Society Conference
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    • 2003.11a
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    • pp.376-379
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    • 2003
  • In this raper, proposed easy half-wavelength LPF and acceptor structure in actuality manufacture using EBG (Electromagnatic Bandgap) structure for application of micro-strip circuit. Because conventional half-wavelength LPF and acceptor is narrow line-width of High impedance, actuality manufacture is difficult. Width that in proposed structure narrow microstrip line of High impedance EBG structure use and has equal impedance embodied to wide microstrip line. Also, it is seen that actuality manufacture is available applying to half-wavelength LPF that have cut-off Frequency of 3GHz.

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UV Emission Characterization of ZnO Thin Films Depending on the Variation of Oxygen Pressure (분위기 산소압변화에 따른 ZnO박막의 UV발광 특성분석)

  • Baek, Sang-Hyeok;Lee, Sang-Yeol;Jin, Beom-Jun;Im, Seong-Il
    • The Transactions of the Korean Institute of Electrical Engineers C
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    • v.49 no.2
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    • pp.103-106
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    • 2000
  • ZnO is a wide-bandgap II-IV semiconductor and has a variety of potnetial applications. ZnO exhibits good piezoelectric, photoelectric and optical properties, and is a good candidate for an electroluminescence device. ZnO films have been deposited on (001) sapphire by PLD technique. Nd:YAG pulsed laser was operated at a wavelength of $\lambda=355nm$. The ZnO films were deposited at oxygen pressures from base to 500 mTorr. The substrate temperatures was increased from $200^{\circ}C\; to\;700^{\circ}C$ films showed strong UV emission by increasing the partial oxygen pressure. We have investigated the relationship between partial oxygen pressure and the intensity of UV emission.

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Differences in Design Considerations between InGaN and Conventional High-Brightness Light-Emitting Diodes

  • Lee, Song-Jae
    • Journal of the Optical Society of Korea
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    • v.2 no.1
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    • pp.13-21
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    • 1998
  • Based on the escape cone concepts, high-brightness light-emitting diodes (LEDs) have been analyzed. In AlGaAs or InGaAlP LEDs, photon absorption in the ohmic region under the electrode is known to be significant. Thus, ins general, a thick window layer (WL) and a transparent substrate (TS) would minimize photon shielding by the electrodes and considerably improve photon output coupling efficiency. However, the schemes do not seem to be necessary in InGaN system. Photon absorption in ohmic contact to a wide bandgap semiconductor such as GaN may be negligible and, as a result, the significant photon shielding by the electrodes will not degrade the photon output coupling efficiency so much. The photon output coupling efficiency estimated in InGaN LEDs is about 2.5 - 2.8 times that of the conventional high-brightness LED structures based on both WL and TS schemes. As a result, the extenal quantum efficiency in InGaN LEDs is as high as 9% despite the presumably very low internal quantum efficiency.

Enhanced Properties of IZO Thin Film Prepared by Nano-Powder Target

  • Ji, Seung-Hun;Youn, Hyun-Oh;Seo, Sung-Bo;Kim, Mi-Sun;Sohn, Sun-Young;Kim, Jong-Jae;Kim, Hwa-Min
    • 한국정보디스플레이학회:학술대회논문집
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    • 2009.10a
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    • pp.1428-1429
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    • 2009
  • Compared to the indium zinc oxide (IZO) film fabricated by micro-powder target, the IZO film with nano-powder target exhibited improved optoelectronic properties of wide bandgap, high transmittance, surface uniformity, and low sheet resistance due to the high film density.

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Current Variation in ZnO Thin-Film Transistor under Different Annealing Conditions (ZnO 박막트랜지스터의 어닐링 조건에 따른 전류 변화)

  • Yoo, Dukyean;Kim, Hyoungju;Kim, Junyeong;Jo, Jungyol
    • Journal of the Semiconductor & Display Technology
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    • v.13 no.1
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    • pp.63-66
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    • 2014
  • ZnO is a wide bandgap (3.3 eV) semiconductor with high mobility and good optical transparency. However, off-current characteristics of ZnO thin-film transistor (TFT) need improvements. In this work we studied the variation in ZnO TFT current under different annealing conditions. Annealing usually modifies gas adsorption at grain boundaries of ZnO. When oxygen is adsorbed, electron density decreases due to strong electronegativity of the oxygen, and TFT current decreases as a result. Our experiments showed that current increased after vacuum annealing and decreased after air annealing. We explain that the change of off-current is caused by the desorption and adsorption of oxygen at the grain boundaries.

Wide Tuning Range Varactor Diodeless LC-tank VCO (Miller 커패시터를 이용한 넓은 가변 범위의 LC-tank 전압 제어 발진기)

  • Ryu, J.Y.;Ryu, S.T.;Jung, S.H.;Cho, G.H.
    • Proceedings of the KIEE Conference
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    • 2001.07d
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    • pp.2579-2581
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    • 2001
  • 넓은 가변 범위를 가지는 LC 탱크 전압 제어 발진기에 관해 본 논문에서 소개하고자 한다. LC 탱크 전압 제어 발진기의 발진을 소멸시키는 밀러 증폭기의 ESR을 제거함으로써 넓은 가변 범위를 얻을 수 있다. LC 탱크 전압 제어 발진기는 발진기 코어와 버퍼, 밴드갭(bandgap) 기준 전압 발생기 그리고 드라이브 증폭기로 구성되어 있다. 발진기 코어는 1.3mA의 전류를 소모하고 약 1GHz의 가변 범위를 가진다. 출력주파수의 가변 범위내에 발진기의 출력 전력은 3dBm 이내로 변한다. 이러한 LC 탱크 전압 제어 발진기는 BiCMOS 공정을 이용하여 제작되었고 2.7V 단일 전원에서 31.5mW의 전력을 소모한다.

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Review on Gallium Nitride HEMT Device Technology for High Frequency Converter Applications

  • Yahaya, Nor Zaihar;Raethar, Mumtaj Begam Kassim;Awan, Mohammad
    • Journal of Power Electronics
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    • v.9 no.1
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    • pp.36-42
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    • 2009
  • This paper presents a review of an improved high power-high frequency III-V wide bandgap (WBG) semiconductor device, Gallium Nitride (GaN). The device offers better efficiency and thermal management with higher switching frequency. By having higher blocking voltage, GaN can be used for high voltage applications. In addition, the weight and size of passive components on the printed circuit board can be reduced substantially when operating at high frequency. With proper management of thermal and gate drive design, the GaN power converter is expected to generate higher power density with lower stress compared to its counterparts, Silicon (Si) devices. The main contribution of this work is to provide additional information to young researchers in exploring new approaches based on the device's capability and characteristics in applications using the GaN power converter design.

Interfaces of Stacking $TiO_2$ Thin Layers Affected on Photocatalytic Activities

  • Ju, Dong-U;Bu, Jin-Hyo
    • Proceedings of the Korean Vacuum Society Conference
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    • 2013.08a
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    • pp.189.1-189.1
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    • 2013
  • Titanium dioxide (TiO2) is a wide bandgap semiconductor possessing photochemical stability and thus widely used for photocatalysis. However, enhancing photocatalytic efficiency is still a challenging issue. In general, the efficiency is affected by physio-chemical properties such as crystalline phase, crystallinity, exposed crystal facets, crystallite size, porosity, and surface/bulk defects. Here we propose an alternative approach to enhance the efficiency by studying interfaces between thin TiO2 layers to be stacked; that is, the interfacial phenomena influencing on the formation of porous structures, controlling crystallite sizes and crystallinity. To do so, multi-layered TiO2 thin films were fabricated by using a sol-gel method. Specifically, a single TiO2 thin layer with a thickness range of 20~40 nm was deposited on a silicon wafer and annealed at $600^{\circ}C$. The processing step was repeated up to 6 times. The resulting structures were characterized by conventional electron microscopes, and followed by carrying out photocatalytic performances. The multi-layered TiO2 thin films with enhancing photocatalytic efficiency can be readily applied for bio- and gas sensing devices.

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Fabrication and Characterization of Hexagonal Tungsten Oxide Nanopowders for High Performance Gas Sensing Application (육방정계 텅스텐옥사이드 나노분말의 합성과 고성능 가스센서응용을 위한 성능 평가)

  • Park, Jinsoo
    • Journal of Powder Materials
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    • v.26 no.1
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    • pp.28-33
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    • 2019
  • The gas sensor is essential to monitoring dangerous gases in our environment. Metal oxide (MO) gas sensors are primarily utilized for flammable, toxic and organic gases and $O_3$ because of their high sensitivity, high response and high stability. Tungsten oxides ($WO_3$) have versatile applications, particularly for gas sensor applications because of the wide bandgap and stability of $WO_3$. Nanosize $WO_3$ are synthesized using the hydrothermal method. As-prepared $WO_3$ nanopowders are in the form of nanorods and nanorulers. The crystal structure is hexagonal tungsten bronze ($MxWO_3$, x =< 0.33), characterized as a tunnel structure that accommodates alkali ions and the phase stabilizer. A gas detection test reveals that $WO_3$ can detect acetone, butanol, ethanol, and gasoline. This is the first study to report this capability of $WO_3$.

SiC Motor Drive for Elevator System (엘리베이터 시스템을 위한 SiC 권상기 드라이브)

  • Gwon, Jin-Su;Moon, Seok-Hwan;Kim, Ju-Chan;Lee, Joon-Min
    • The Transactions of the Korean Institute of Power Electronics
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    • v.24 no.3
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    • pp.147-152
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    • 2019
  • With the recent emphasis on the importance of energy conservation, studies on high-efficiency elevator systems are being continuously conducted. Therefore, pulse width modulation converters are commonly used in traction drives on elevator systems. Wide bandgap devices have been increasingly commercialized, and their application to power conversion systems, such as renewable and energy storage system, has been gradually increasing. In this study, a SiC inverter for an elevator traction drive is investigated. In particular, an inverter is designed to minimize stray and parasitic inductance. Input and output filters are designed by considering switching frequency. The designed SiC inverter reduces volume by approximately 32% compared with that of a Si inverter, and power converter efficiency is over 98.8%.