• 한국섬유공학회:학술대회논문집
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• 한국섬유공학회 2003년도 봄 학술발표회 논문집
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• pp.356-357
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• 2003

Organic materials are suitable for use in photoelectric conversion devices. Thus, Organic semiconductors are promising materials for photovoltaic devices and other optoelectronic applications such as light emitting diodes(LED). The organic solar cell seems to be the usefulness in comparison with the inorganic solar cell in terms of workability, ease of processing, low cost, flexibility and area expansion. (omitted)

• Journal of Information Display
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• 제13권1호
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• pp.1-6
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• 2012

Decreasing the thermal resistance is the critical issue for high-brightness light-emitting diodes. In this paper, the effects of some design factors, such as chip size (24 and 35 mil), substrate material (AlN and high-temperature co-fired ceramic), and die-attach material (Ag epoxy and PbSn solder), on the thermal-dissipation characteristics were investigated. Using the thermal transient method, the temperature sensitivity parameter, $R_{th}$ (thermal resistance), and junction temperature were estimated. The 35-mil chip showed better thermal dissipation, leading to lower thermal resistance and lower junction temperature, owing to its smaller heat source density compared with that of the 24-mil chip. By adopting an AlN substrate and a PbSn solder, which have higher thermal conductivity, the thermal resistance of the 24-mil chip can be decreased and can be made the same as that of the 35-mil chip.

• 한국재료학회지
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• 제19권8호
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• pp.443-446
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• 2009

This study develops a highly transparent ohmic contact scheme using indium oxide doped ZnO (IZO) as a current spreading layer for p-GaN in order to increase the optical output power of nitride-based lightemitting diodes (LEDs). IZO based contact layers of IZO, Ni/IZO, and NiO/IZO were prepared by e-beam evaporation, followed by a post-deposition annealing. The transmittances of the IZO based contact layers were in excess of 80% throughout the visible region of the spectrum. Specific contact resistances of $3.4\times10^{-4}$, $1.2\times10^{-4}$, $9.2\times0^{-5}$, and $3.6\times10^{-5}{\Omega}{\cdot}cm^2$ for IZO, Ni/Au, Ni/IZO, and NiO/IZO, respectively were obtained. The forward voltage and the optical output power of GaN LED with a NiO/IZO ohmic contact was 0.15 V lower and was increased by 38.9%, respectively, at a forward current of 20 mA compared to that of a standard GaN LED with an Ni/Au ohmic contact due to its high transparency, low contact resistance, and uniform current spreading.

• 한국재료학회:학술대회논문집
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• 한국재료학회 2011년도 춘계학술발표대회
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• pp.20.2-20.2
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• 2011

III-nitrides have attracted much attention for optoelectronic device applications whose emission wavelengths ranging from green to ultraviolet due to their wide band gap. However, due to the strong polarization properties of conventional c-plane III-nitrides, the built-in polarization-induced electric field limits the performance of optical devices. Therefore, there has been a renewed interest in the growth of nonpolar III-nitride semiconductors for polarization free heterostructure optoelectronic and electronic devices. However, the crystal and the optical quality of nonpolar/semipolar GaN have been poorer than those of conventional c-plane GaN, resulting in the relative poor optical and electrical properties of light emitting diodes (LEDs). In this presentation, I will discuss the growth and characterization of high quality nonpolar a-plane and semipolar (11-22) GaN and InGaN multiple quantum wells (MQWs) grown on r- and m-plane sapphire substrates, respectively, by using metalorganic chemical vapor deposition (MOCVD) without a low temperature GaN buffer layer. Especially, the epitaxial lateral overgrowth (ELO) technique will be also discussed to reduce the dislocation density and enhance the performance of nonpolar and semipolar GaN-based LEDs.

• 한국전기전자재료학회논문지
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• 제22권7호
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• pp.559-562
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• 2009

Due to the enormous progress achieved in light emitting diodes (LEDs) LEDs have been become a good solution for lightings. In LED driver for lighting applications, it is required high input voltage to drive more LEDs. Therefore, high-voltage should be changed to low-voltage to supply power for drive IC. In this paper, LED drive IC using voltage clamp bias circuit, it use a hysteretic-buck converter topology was proposed and verified through experiments.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2009년도 춘계학술대회 논문집
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• pp.85-87
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• 2009

Due to the enormous progress in light emitting diodes (LEDs), LEDs have been become a good solution for lightings. In LED driver for lighting applications, it is required a high input voltage to drive more LEDs. Therefore, a high-voltage should be changed to low-voltage to supply power for drive IC. In this paper, a LED drive IC with hysteretic-buck converter topology using a voltage clamp bias circuit was proposed and verified through simulations.

• 대한치과보존학회:학술대회논문집
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• 대한치과보존학회 2003년도 제120회 추계학술대회 제 5차 한ㆍ일 치과보존학회 공동학술대회
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• pp.582-582
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• 2003

The purpose of this study was to apply the photoplethsmography(PPG) as a non-invasive tool to evaluate the blood flow of the anterior tooth in clinic. The system consist of two light-emitting diodes(LED) powered by 5V as the light source. The LED was designed to two weve lengths, 940(infrared) and 660(red)nm simultaneously with a 36nm bandwidth at half the peak intensity. The 54 anterior vital tooth were examined and the measured was analysed in frequency domian (power spectrum).(omitted)

• 전기학회논문지
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• 제62권8호
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• pp.1101-1107
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• 2013

A light emitting diodes(LED) lighting has been increasingly used due to its low power consumption, long life time, high efficiency, and environment friendly characteristics. Also various power converters has been applied to drive these LED lighting. Among many power converters, a LLC resonant converter could be applied for LED lighting because of its high efficiency and high power density. Furthermore, the function of power factor correction(PFC) might be added. In this paper, 1-stage asymmetrical LLC resonant converter is proposed. The proposed converter performs both input-current harmonics reduction and PFC using the discontinuous conduction mode(DCM). The proposed 1-stage LLC resonant converter approach has the lower voltage stress across switching devices and achieve the zero voltage switching(ZVS) in switching devices. To verify the performance of the proposed converter, simulation and experimental results from a 300[W] prototype are provided.

• 한국전기전자재료학회논문지
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• 제28권5호
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• pp.344-349
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• 2015

A new information society of late has arrived by the rapid development of various information & communications technologies. Accordingly, mobile devices which are light and thin, easy and convenient to carry on the market. Also, the requirements for the larger television sets such as fast response speed, low-cost electric power, wider visual angle display are sufficiently satisfied. The currently most widely studied display material, the Organic Light-emitting Diodes(OLEDs) overwhelms the Liquid Crystal Display(LCD), the main occupier of the market. This new material features a response speed of more than a thousand times faster, no need of backlight, a low driving voltage, and no limit of view angle. And the OLEDs has high luminance efficiency and excellent durability and environment resistance, quite different from the inorganic LED light source. The OLEDs with simple device structure and easy produce can be manufactured in various shapes such as a point light source, a linear light source, a surface light source. This will surely dominate the market for the next generation lighting and display device. The new display utilizes not the glass substrate but the plastic one, resulting in the thin and flexible substrate that can be curved and flattened out as needed. In this paper, OLEDs device was produced by changing thickness of Teflon-AF of hole injection material layer. And as for the electrical properties, the four layer device of ITO/TPD/$Alq_3$/BCP/LiF/Al and the five layer device of ITO/Teflon AF/TPD/$Alq_3$/BCP/Lif/Al were studied experimentally.

• 마이크로전자및패키징학회지
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• 제19권4호
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• pp.19-23
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• 2012

최근 발광다이오드(LED)의 출력 성능을 높이고, 전력 소비를 줄이기 위해 LED 패키지 분야에서 실리콘 기판 연구가 집중되고 있다. 본 연구에서는 공정 비용이 낮고 생산성이 높은 습식 식각을 이용하여 실리콘 기판의 실리콘 관통 비아 식각 공정을 살펴보았다. KOH를 이용한 양면 습식 식각 공정과 습식 식각과 건식 식각을 병행한 두 가지 공정 방법으로 실리콘 관통 비아를 제작하였고, 식각된 실리콘 관통 비아에 Cu 전극과 배선은 전기도금으로 증착하였다. Cu 전극을 연결하는 배선의 전기저항은 약 $5.5{\Omega}$ 정도로 낮게 나타났고, 실리콘 기판의 열 저항은 4 K/W으로 AlN 세라믹 기판과 비슷한 결과를 보였다.