• ETRI Journal
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• 제39권1호
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• pp.62-68
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• 2017

In this paper, we present the design and characterization analysis of a cascode GaN field-effect transistor (FET) for switching power conversion systems. To enable normally-off operation, a cascode GaN FET employs a low breakdown voltage (BV) enhancement-mode Si metal-oxide-semiconductor FET and a high-BV depletion-mode (D-mode) GaN FET. This paper demonstrates a normally-on D-mode GaN FET with high power density and high switching frequency, and presents a theoretical analysis of a hybrid cascode GaN FET design. A TO-254 packaged FET provides a drain current of 6.04 A at a drain voltage of 2 V, a BV of 520 V at a drain leakage current of $250{\mu}A$, and an on-resistance of $331m{\Omega}$. Finally, a boost converter is used to evaluate the performance of the cascode GaN FET in power conversion applications.

• 대한전자공학회논문지
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• 제21권2호
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• pp.36-46
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• 1984

Ga1-xlnxSe 단결정을 X=0.0∼0.1영역과 X=0.8-1.0영역에서 Bridgman방법으로 성장시켰다. 성장된 Ga1-xlnxSe 단결정은 X=0.0∼0.1영역에서는 hexagonal구조, X=0.8∼1.0영역에서는 rhombohedral 구조를 가지고 있었다. CaInSe 단결정은 간접천이형 energy gap을 가지고 있었으며, 15°K에서 250°K로 시편의 온도가 상승할 때 energy gap 은 감소되었고, 온도계수는 (-2.4∼-4.3)×10-4eV/K으로 주어졌다. Ga1-xlnxSe 단결정의, energy gap에 온도 의존성은 Schmid의 electron-phonon 상호작용의 이론으로 설명할 수 있었다.

• Journal of Ceramic Processing Research
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• 제13권spc1호
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• pp.93-95
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• 2012

We report on the growth and characterization of the nano- and micro scale GaN structures selectively grown on the vertex of GaN stripes using the metal organic vapor phase epitaxy method and conventional photolithography technique. The triangular shaped nano- and micro GaN structures which have semi-polar {11-22} facets were formed only on the vertex of the lower GaN stripes. Crystalline defects reduction was observed by transmission electron microscopy for upper GaN stripes. We also have grown the InGaN/GaN multi-quantum well structures on the semi-polar facets of the upper GaN stripes. Cathodoluminescence images were taken at 366, 412 and 555 nm related to GaN band edge, InGaN/GaN layer and defects, respectively.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2011년도 추계학술대회 초록집
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• pp.47.1-47.1
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• 2011

We report on a direct measurement of two-dimensional chemical and electrical distribution on the surface of photovoltaic Cu(In,Ga)$Se_2$ thin-films using a nano-scale spectroscopic and electrical characterization, respectively. The Raman measurement reveals non-uniformed surface phonon vibration which comes from different compositional distribution and defects in the nature of polycrystalline thin-films. On the other hand, potential analysis by scanning Kelvin probe force microscopy shows a higher surface potential or a small work function on grain boundaries of the thin-films than on the grain surfaces. This demonstrates the grain boundary is positively charged and local built-in potential exist on grain boundary, which improve electron-hole separation on grain boundary. Local electrical transport measurements with scanning probe microscopy on the thin-films indicates that as external bias is increases, local current is started to flow from grain boundary and saturated over 0.3 V external bias. This accounts for carrier behavior in the vicinity of grain boundary with regard to defect states. We suggest that electron-hole separation at the grain boundary as well as chemical and electrical distribution of polycrystalline Cu(In,Ga)$Se_2$ thin-films.

• ETRI Journal
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• 제31권5호
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• pp.601-603
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• 2009

This letter presents a high performance 2.4 GHz two-stage power amplifier (PA) operating in the temperature range from $-30^{\circ}C$ to $+85^{\circ}C$ for IEEE 802.11g, wireless local area network application. It is implemented in InGaP/GaAs hetero-junction bipolar transistor technology and has a bias circuit employing a temperature compensation technique for error vector magnitude (EVM) performance. The technique uses a resistor made with a base layer of HBT. The design improves EVM performance in cold temperatures by increasing current. The implemented PA has a dynamic EVM of less than 4%, a gain of over 26 dB, and a current less than 130 mA below the output power of 19 dBm across the temperature range from $-30^{\circ}C$ to $+85^{\circ}C$.

• 전자공학회논문지D
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• 제35D권8호
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• pp.24-30
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• 1998

A blue LED of $In_{x}Ga_{1-x}N$ multiple quantum well structure which had the blue emission spectrum of donor-acceptor pair transition generated form Si-Zn co-doped $In_{x}Ga_{1-x}N$ active layer, was fabricated. The $In_{x}Ga_{1-x}N$ MQW heterojunction LED structure was grown by MOCVD on the sapphire substrate with (0001) surface orientation at 800.deg. C. The fabricated LED exhibited forward cut-in voltage of 4~4.5V and reverse breakdown voltage of -13V. Its optical chracteristics showed that the center wavelength of peak emission occurred at 460nm and the optical intensity was increased linearly with respect to the injected electrical current above 5mA.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2006년도 추계학술대회 논문집 Vol.19
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• pp.127-128
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• 2006

The proposed differential LC cross-coupled VCO is implemented in InGap/GaAs HBT process for an adaptive Global Positioning system(GPS) application. Two filtering capacitors are used at the base of output buffer amplifiers at the both sides of the core m order to improve phase noise characteristics. The VCO produced a phase noise of -133 dBc/Hz at 3MHz offset frequency from the carrier frequency of 1.489GHz and the second harmonic suppression is significantly suppresed up to -49dBc/Hz in simulation result. The three pairs of BC diodes are integrated m the tank circuit to increase the VCO Tunning range.

• ETRI Journal
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• 제38권5호
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• pp.972-980
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• 2016

An ultra-wideband microwave monolithic integrated circuit high-power amplifier with excellent input and output return losses for phased array jammer applications was designed and fabricated using commercial $0.25-{\mu}m$ AlGaN/GaN technology. To improve the wideband performance, resistive matching and a shunt feedback circuit are employed. The input and output return losses were improved through a balanced design using Lange-couplers. This three-stage amplifier can achieve an average saturated output power of 15 W, and power added efficiency of 10% to 28%, in a continuous wave operation over a frequency range of 6 GHz to 18 GHz. The input and output return losses were demonstrated to be lower than -15 dB over a wide frequency range.

• 한국전자파학회논문지
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• 제28권9호
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• pp.685-697
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• 2017

본 논문에서는 탐색 레이다에서 사용되는 C-대역의 고출력전력증폭장치 및 구성품의 설계, 제작과 측정에 대하여 기술하였다. 반도체 소자인 GaN(질화갈륨)을 적용하여 반도체전력증폭조립체를 설계 및 제작하였고, 설계 제작된 도파관 형태의 송신신호결합조립체를 통해 병렬로 구성된 반도체전력증폭조립체의 송신신호 출력을 결합하여 고출력 송신신호 출력을 발생한다. 제작된 고출력전력증폭장치는 C-대역 500 MHz 대역폭, 최대 10.5 % 듀티, 송신펄스폭 $0.0{\sim}000{\mu}s$에서 송신출력 44.98 kW(76.53 dBm) 이상이다.

• 한국전자파학회논문지
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• 제24권11호
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• pp.1081-1090
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• 2013

본 논문에서는 C-대역에서 입출력 정합 회로가 패키지에 내장된 10 W급 내부 정합 증폭기 설계 및 제작을 하였다. 전력증폭기 설계에 사용한 트랜지스터로 GaAs pHEMT bare-chip을 사용하였다. 트랜지스터 패드 위치와 커패시터 크기를 고려한 와이어 본딩 해석으로 정확도 높은 설계를 하였다. 패키지와 정합 회로를 함께 EM simulation하여 패키지가 정합 회로에 미치는 영향을 해석하였다. 2-tone 측정 시 memory effect로 인해 발생되는 IMD3의 비대칭성을 줄이기 위한 memory effect 감쇄 바이어스 회로를 제안 및 설계하였다. 측정 결과, 7.1~7.8 GHz 대역에서 $P_{1dB}$는 39.8~40.4 dBm, 전력 이득은 9.7~10.4 dB, 효율은 33.4~38.0 %을 얻었고, 제안된 memory effect 감쇄 바이어스 회로로 IMD3(Upper)와 IMD3(Lower)차는 0.76 dB 이하를 얻었다.