• 전력전자학회논문지
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• 제24권3호
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• pp.201-206
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• 2019

This study presents the design and experimental result of a GaN-based DC-DC converter with an integrated gate driver. The GaN device is attractive to power electronic applications due to its superior device performance. However, the switching loss of a GaN-based power converter is susceptible to the common source inductance, and converter efficiency is severely degraded with a large loop inductance. The objective of this study is to achieve high-efficiency power conversion and the highest power density using a multiphase integrated half-bridge GaN solution with minimized loop inductance. Before designing the converter, several GaN and Si devices were compared and loss analysis was conducted. Moreover, the impact of common source inductance from layout parasitic inductance was carefully investigated. Experimental test was conducted in buck mode operation at 48 -12 V, and results showed a peak efficiency of 97.8%.

• 한국진공학회지
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• 제4권S1호
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• pp.168-173
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• 1995

$GaxIn{1_x}As$ epitaxial layers were grown by a simplified hydrode vapor phase epitaxy(VPE) method bsed on the utilization of Ga/In alloy as the source metal. The effects of a wide range of experimental variables(i.e.,inlet mole fraction of HCI, deposition temperature, Ga/In alloy composition) on the ternary composition and growth rate were investigated. Layers of $Ga_{0.47}In_{0.53}As$ lattice matched to InP were successfully grown from alloys containing 5 to 8 at.% Ga. These layers were used to produce state-of-the art p-i-n photodetectors having the following characteristics: dark current, $I_d$(-5V) = 10-20 nA: responsivity, R=0.84-0.86 A/W; dark current, Id(-5V)=10-20 nA; responsivity, R=0.84-0.86 A/W; capacitance, C=0.88-0.92 pF; breakdown voltage, $V_b$ >40V. This study demonstrated for the first time that a simplified hydride VPE process with a Ga/In alloy source is capable of producing device quality epitaxial layers.

• 대한전자공학회논문지
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• 제23권2호
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• pp.243-248
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• 1986

The impurities in As and Ga sources and the contamination of the GaAs substrate prior to growing of MBE GaAs epitaxial layer have been investigated using RHEED, AES and RGA methods. The as source was contaminated by H2O, CO, CO2 and AsO, and the Ga source was contaminated by H2, H2O, CO and CO2. These contaminants could easily be removed by prebaking the source. On the other hand, GaAs substrate was contaminated principally carbon and oxygen. The oxygen could easily be removed by heating the substrate above 480\ulcorner, and the carbon could also be reduced by sputtering the substrate with 1ke V Ar+. The chemically etched substrate surface prior to growing the layer was rough, but it was made to be smooth and clean by heating it above 530 \ulcorner.

• 한국결정성장학회지
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• 제16권4호
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• pp.162-165
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• 2006

혼합소스 HVPE(hydride vapor phase epitaxy) 방법으로 InGaN/AlGaN의 이종접합구조(heterostructure)의 LED (light emitting diode)를 선택성장(SAG : selective area growth)하였다. InGaN/AlGaN 이종접합구조를 혼합소스 HVPE로 연속 성장하기 위하여 새로운 디자인의 multi-sliding boat를 도입하였다. SAG-InGaN/AlGaN LED의 상온 EL(electroluminescence) 특성은 주입전류가 20mA일 때 중심파장은 425nm였다. Multi-sliding boat를 이용한 혼합소스 HVPE 방법이 질화물 반도체 LED를 성장하는 유용한 방법이 될 수 있음을 확인하였다.

• 한국결정성장학회지
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• 제22권1호
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• pp.11-14
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• 2012

AlGaN는 3.4~6.2 eV까지 넓은 밴드갭을 가지는 직접천이형 반도체이다. 최근에 자외영역의 광소자가 다양하게 응용되면서 자외선 발광이 가능한 AlGaN 역시 주목받고 있다. 이를 위해서는 고품질의 AlGaN 층이 필요하지만 GaN 층위에 AlGaN 층을 성장하는 것은 이들의 격자상수와 열팽창계수 차이로 인해 어렵다. 본 논문에서, multi-sliding boat법이 적용된 혼합소스 HVPE법을 이용하여 GaN template 위에 LED 구조를 성장하였다. 활성층의 Al 조성을 조절함으로써 AlGaN의 격자상수 변화와 광학적 변화를 관찰하고자 하였다. 에피 성장을 위해 HCl과 $NH_3$ 가스를 혼합소스 표면으로 흘려주었고, 수송가스로는 $N_2$를 사용하였다. 소스영역과 성장영역의 온도는 각각 900과 $1090^{\circ}C$로 안정화하였다. 성장 후 샘플은 x-ray diffraction(XRD)과 electro luminescence(EL) 측정을 하였다.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2003년도 하계학술대회 논문집 Vol.4 No.1
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• pp.263-266
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• 2003

The gate leakage current is first calculated using the experimental method between gate and drain by opening source electrode. Next, the gate to drain current has been obtained with a ground source. The difference of two current has been tested and provide that the existence of another source to Schotuy barrier height against the image force lowering effect.

• Journal of Radiation Protection and Research
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• 제42권4호
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• pp.212-221
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• 2017

Background: This study aims to calculate detector positions as a design of a radioactive source localizing radiation portal monitor (RPM) system using an improved genetic algorithm. Materials and Methods: To calculate of detector positions for a source localizing RPM system optimization problem is defined. To solve the problem, a modified iterative genetic algorithm (MIGA) is developed. In general, a genetic algorithm (GA) finds a globally optimal solution with a high probability, but it is not perfect at all times. To increase the probability to find globally optimal solution rather, a MIGA is designed by supplementing the iteration, competition, and verification with GA. For an optimization problem that is defined to find detector positions that maximizes differences of detector signals, a localization method is derived by modifying the inverse radiation transport model, and realistic parameter information is suggested. Results and Discussion: To compare the MIGA and GA, both algorithms are implemented in a MATLAB environment. The performance of the GA and MIGA and that of the procedures supplemented in the MIGA are analyzed by computer simulations. The results show that the iteration, competition, and verification procedures help to search for globally optimal solutions. Further, the MIGA is more robust against falling into local minima and finds a more reliably optimal result than the GA. Conclusion: The positions of the detectors on an RPM for radioactive source localization are optimized using the MIGA. To increase the contrast of the measurements from each detector, a relationship between the source and the detectors is derived by modifying the inverse transport model. Realistic parameters are utilized for accurate simulations. Furthermore, the MIGA is developed to achieve a reliable solution. By utilizing results of this study, an RPM for radioactive source localization has been designed and will be fabricated soon.

• 대한전자공학회논문지SD
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• 제41권4호
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• pp.49-55
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• 2004

본 논문은 고밀도 파장분할다중 (DWDM) 시스템의 응용을 위하여 quaternary/quaternary 다중양자우물 InGaAsP/InGaAsP QCSE 튜닝을 이용한 1550 ㎚ 다중 채널원에 관한 것이다. 본 채널 소스는 140 ㎓ 채널 간격을 갖으며 32 ㎚ 채널 선택 대역을 갖는다.

• 한국재료학회지
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• 제13권4호
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• pp.266-270
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• 2003

We studied BCl$_3$ dry etching of GaAs in a planar inductively coupled plasma system. The investigated process parameters were planar ICP source power, chamber pressure, RIE chuck power and gas flow rate. The ICP source power was varied from 0 to 500 W. Chamber pressure, RIE chuck power and gas flow rate were controlled from 5 to 15 mTorr, 0 to 150 W and 10 to 40 sccm, respectively. We found that a process condition at 20 sccm $BCl_3$ 300 W ICP, 100 W RIE and 7.5 mTorr chamber pressure gave an excellent etch result. The etched GaAs feature depicted extremely smooth surface (RMS roughness < 1 nm), vertical sidewall, relatively fast etch rate (> $3000\AA$/min) and good selectivity to a photoresist (> 3 : 1). XPS study indicated a very clean surface of the material after dry etching of GaAs. We also noticed that our planar ICP source was successfully ignited both with and without RIE chuck power, which was generally not the case with a typical cylindrical ICP source, where assistance of RIE chuck power was required for turning on a plasma and maintaining it. It demonstrated that the planar ICP source could be a very versatile tool for advanced dry etching of damage-sensitive compound semiconductors.

• 한국재료학회지
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• 제21권5호
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• pp.268-272
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• 2011

Due to their novel properties, GaN based semiconductors and their nanostructures are promising components in a wide range of nanoscale device applications. In this work, the gallium nitride is deposited on c-axis oriented sapphire and porous SWCNT substrates by molecular beam epitaxy using a novel single source precursor of $Me_2Ga(N_3)NH_2C(CH_3)_3$ with ammonia as an additional source of nitrogen. The advantage of using a single molecular precursor is possible deposition at low substrate temperature with good crystal quality. The deposition is carried out in a substrate temperature range of 600-750$^{\circ}C$. The microstructural, structural, and optical properties of the samples were analyzed by scanning electron microscopy, X-ray diffraction, Raman spectroscopy, and photoluminescence. The results show that substrate oriented columnar-like morphology is obtained on the sapphire substrate while sword-like GaN nanorods are obtained on porous SWCNT substrates with rough facets. The crystallinity and surface morphology of the deposited GaN were influenced significantly by deposition temperature and the nature of the substrate used. The growth mechanism of GaN on sapphire as well as porous SWCNT substrates is discussed briefly.