• Journal of Magnetics
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• v.10 no.3
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• pp.108-112
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• 2005

GaAs nanowires were grown on GaAs (111)B substrates in a gas source molecular beam epitaxy system, using self-assembled Au particles with diameters between 25 and 200 nm as the catalytic agents. The growth rate and structure of the nanowires were investigated for substrate temperatures between 500 and $600^{\circ}C$ to study the mass transport mechanisms that drive the growth of these crystals. The possibilities for fabrication of novel magnetic nanostructures by suitable choice of growth conditions are discussed.

• Electronics and Telecommunications Trends
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• v.33 no.6
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• pp.12-23
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• 2018

In this paper, we review the technical trends of diamond and gallium oxide ($Ga_2O_3$) semiconductor technologies among ultra-wide bandgap semiconductor technologies for harsh environments. Diamond exhibits some of the most extreme physical properties such as a wide bandgap, high breakdown field, high electron mobility, and high thermal conductivity, yet its practical use in harsh environments has been limited owing to its scarcity, expense, and small-sized substrate. In addition, the difficulty of n-type doping through ion implantation into diamond is an obstacle to the normally-off operation of transistors. $Ga_2O_3$ also has material properties such as a wide bandgap, high breakdown field, and high working temperature superior to that of silicon, gallium arsenide, gallium nitride, silicon carbide, and so on. In addition, $Ga_2O_3$ bulk crystal growth has developed dramatically. Although the bulk growth is still relatively immature, a 2-inch substrate can already be purchased, whereas 4- and 6-inch substrates are currently under development. Owing to the rapid development of $Ga_2O_3$ bulk and epitaxy growth, device results have quickly followed. We look briefly into diamond and $Ga_2O_3$ semiconductor devices and epitaxy results that can be applied to harsh environments.

• Journal of Preventive Medicine and Public Health
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• v.32 no.4
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• pp.467-472
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• 1999

Objectives: This study was conducted to evaluate the cytotoxicity of gallium arsenide(GaAs), indium phosphide(InP) and indium arsenide(InAs) all of which are used a$ the semiconductor eletments in semiconductor industry. Methods: Cytotoxicity id the alveolar macrophage was evaluated by the measurement of in vitro magnetometry, LDH release assay and histological examination. Results: The relaxation curves by the in vitro magnetometry showed that GaAs has the cytotoxicity for the alveolar macrophage which is more significant in the higher dosages, while this cytotoxicity is not appeared in the groups added with InP or InAs or PBS. In the decay constant for two minutes after magnetization, GaAs-added groups showed a significant decrease with increasing doses, but both InP- and InAs-added groups did not show any significance. The LDH release assay showed a dose-dependent increasing tendency in the GaAs-, InP- and InAs-added groups. In terms of cellular morphological changes, GaAs-added groups revealed such severe cellular damages as prominent destructions in cell membranes and their morphological changes of nucleus, while InP- and InAs-added groups remained intact in intracellular structures, except for cytoplasmic degenerations. Conclusions: It is suggested that GaAs is more influential to cytotoxicity of alveolar macrophages than InP and InAs.

• Electronics and Telecommunications Trends
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• v.34 no.5
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• pp.71-80
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• 2019

Gallium nitride (GaN) can be used in high-voltage, high-power-density/-power, and high-speed devices owing to its characteristics of wide bandgap, high carrier concentration, and high electron mobility/saturation velocity. In this study, we investigate the technology trends for X-/Ku-band GaN RF power devices and MMIC power amplifiers, focusing on gate-length scaling, channel structure, and power density for GaN RF power devices and output power level and output power density for GaN MMIC power amplifiers. Additionally, we review the technology trends in gallium arsenide (GaAs) RF power devices and MMIC power amplifiers and analyze the technology trends in RF power devices and MMIC power amplifiers based on both GaAs and GaN. Furthermore, we discuss the current direction of national research by examining the national and international technology trends with respect to X-/Ku-band power devices and MMIC power amplifiers.

• Transactions on Electrical and Electronic Materials
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• v.12 no.5
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• pp.204-208
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• 2011

In this paper, the design area of a fabricated solar cell has been analyzed with respect to its charge density. The mathematical calculation used for charge-density derivation was obtained from the 2001 version of a MATHCAD program. The parameter range for the calculations was ${\pm}1{\times}10^{17}cm^{-3}$, which is in the normal parameter range for n-type doping impurities ($7.0{\times}10^{17}cm^{-3}$) and also for p-type impurities ($4.0{\times}10^{17}cm^{-3}$). Therefore, it can be said that the fabricated solar-cell design area has a direct effect on charge-density changes.

• Proceedings of the KIEE Conference
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• 1992.07b
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• pp.839-842
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• 1992

This paper describes an improved analytic model for a gallium-arsenide MESFET computer simmulation and deals with application to microwave performance. The current-voltage characteristics, the dependence of the capacitances, transconductances and drainconductances on bias conditions and the dependences of s-parameters on various frequencies are calculated. The model is base on a physical picture revealed through two-dimensional numerical analysis, and takes into account transition region and diffusion process under gate but it require a very small computer time. Simulation results agree well with the experimental data found earlier by other author The proposed model can be used for a computer-aided design of GaAs MESFET devices and for a study of application to microwave performance.

• Journal of the Korean Society of Combustion
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• v.10 no.3
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• pp.17-24
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• 2005

A sub-millimeter scale catalytic combustor with a simple plate-shaped combustion chamber was fabricated. A porous ceramics support coated with platinum catalyst was placed in the chamber. The combustor has a gallium arsenide window on the top that is transparent to infrared ray. The temperature distribution in the combustion chamber was measured using infrared thermal imager while hydrogen-air premixture is steadily supplied to the combustor. The area where the catalytic reaction took place broaden for higher flow rate and lower equivalence ratio made activated area in the combustion chamber broaden. The amount of coated platinum catalyst did not affect the reaction. Stop of reaction, which is similar to flame quenching of conventional combustion, was investigated. Large content of heat generation and broad activated area are essential criteria to prevent stop of reaction that has a bad effect on the combustor performance.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.11a
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• pp.33-36
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• 2004

탄소 도핑$(5{\times}10^{19}\;cm^{-3})$된 p-type GaAsSb 에피층 위에, Ti/Pt/Au, Pd/Au, Pd/Ir/Au를 이용한 다층 오믹 접촉을 제작하였다. MOCVD(metal-organic chemical vapor deposition)를 이용하여 성장시킨 이 p-GaAsSb의 정공 이동도는 탄소의 도핑 농도가 매우 높음에도 불구하고, $50\;cm^2/Vs$로 측정되었다. 오믹 접촉의 전기적 특성을 측정하기 위하여 TLM(Transfer length method)를 이용하였다. Pd/Ir/Au을 이용한 오믹접촉의 specific contact resistivity는 $10^{-8}\;ohm-cm^2$ 보다 작은 수치를, transfer length는 100 nm보다 작은 수치를 보였으며, Ti/Pt/Au을 이용한 ohmic contact의 specific contact resistivity는 $10^{-7|\;ohm-cm^2$ 보다 작은 수치를, transfer length는 400 nm보다 작은 수치를 나타내었다.

• Proceedings of the KIEE Conference
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• 1996.07c
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• pp.1431-1433
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• 1996

Effective ionization coefficients for (100), (110) and (111) oriented gallium arsenide are extracted from the ionization coefficients far electrons and holes. Analytical formulas for the breakdown voltage of the GaAs Schottky rectifiers are derived by employing the ionization coefficients. The breakdown voltages obtained from our analytical model agree fairly well with the numerical results as well as the experimental ones reported in the range of $10^{14}\;cm^{-3}$ - $5{\times}10^{17}\;cm^{-3}$ doping concentrations.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.48 no.4
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• pp.226-231
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• 1999

Temperature dependence of effective ionization coefficients in GaAs is formulated as a single polynomial function of temperature, which allows analytical expressions for breakdown voltage of GaAs $p^+n$ junctions as a function of temperature. At 300 K, extracted effective ionization coefficient of GaAs $p^+n$ junction especially agrees well with the published result of <111> oriented GaAs. The analytic results agree with the simulation as well as the experimental ones reported within 10% in error for the doping concentrations in the range of $10_{14}cm_{-3}~10_{17}cm_{-3}$ at 100 K, 300 K and 500 K.