• Journal of Information Display
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• v.7 no.4
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• pp.13-16
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• 2006

II-$III_{2}-(S,Se)_{4}$ structured of phosphor have been used at various fields because they have high luminescent efficiency and broad emission band. Among these phosphors, europium doped $BaGa_{2}S_{4}$ was prepared by solid-state method. We investigated the possibility of applying [ ] due to emissive property of UV region. Also, general sulfide phosphors were synthesized by using injurious $H_{2}S$ $CS_{2}$ gas. However, this study prepared $BaGa_{2}S_{4}:Eu^{2+}$ phosphor is addition to excess sulfur under 5% $H_{2}$/95% $N_{2}$ reduction atmosphere. So, this process could involved large scale synthesis because of non-harmfulness and simple process. The photo-luminescence efficiency of the prepared $BaGa_{2}S_{4}:Eu^{2+}$ phosphor increased by 20% compared with commercial $BaGa_{2}S_{4}:Eu^{2+}$ phosphor. From this, we could conclude that the prepared $BaGa_{2}S_{4}:Eu^{2+}$ could be applied to green phosphor for white LED of three wavelengths.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.11 no.3
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• pp.153-163
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• 1986

GaAs, one of the III-V compounding semicondnctors, has been widely employed as base materials for the fabrication of the ultra-high-speed devices in the filelds of DBS, optical communications, MMIC'S and digital IC'S. There have been some reports on 4Kx4bit SRAM by D/E MESFET'S, 4K bit SRAM by HEMT'S, and receiver front ends for X-band by MMIC technologies, respectively. This paper reviews GaAs materials, wafer fabrication processes, device applications, and design aspects, and, finally, descusses the future of the ultra-high-spped-devices.

• Korean Journal of Materials Research
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• v.16 no.12
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• pp.761-765
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• 2006

[ $II-III_2-(S,Se)_4$ ] structured of phosphor has been used at various field because those have high luminescent efficiency and broad emission band. Among these phosphors, the europium doped $BaGa_2S_4$ was prepared by solid-state method and had high potential application due to an emissive property of UV region. Also, the common sulfide phosphors were synthesized by using injurious $H_2S\;or\;CS_2$ gas. However, in this study $BaGa_2S_4:Eu^{2+}$ phosphor in addition to excess sulfur was prepared under at 5% $H_2/95%\;N_2$ reduction atmosphere. Thus, this process could be considered as large scale synthesis because of non-harmfulness and simplification. The photoluminescence efficiency of the prepared $BaGa_2S_4:Eu^{2+}$ phosphor increased 20% than that of commercial $SrGa_2S_4:Eu^{2+}$ phosphor. The prepared $BaGa_2S_4:Eu^{2+}$ could be applied to green phosphor for white LED of three wavelengths.

• 한국신재생에너지학회:학술대회논문집
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• 2009.06a
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• pp.156-158
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• 2009

우리 연구팀은 $SiO_2$ nanospheres를 이용한 natural lithography를 통해 2가지 방법으로 GaAs 기판의 반사율을 감소시켰다. 먼저 GaAs 기판 위에 benzocyclobutene(BCB) 고분자를 코팅한 후, 그 위에 $SiO_2$ nanospheres를 코팅한다. 그리고 고분자의 유리전이 온도이상으로 가열하면 $SiO_2$ nanospheres가 고분자 속으로 가라앉게 되어 렌즈 형태의 표면이 형성된다. 또한, 이 상태에서 BOE 용액을 통해 $SiO_2$ nanospheres를 제거하여 오목한 형태의 표면을 형성할 수 있다. 이러한 2가지 방법의 surface texturing을 통해 우리는 GaAs 표면의 반사도를 각각 400~800nm의 파장에서 평균 13.6%~16.52%의 반사율을 얻을 수 있었다.

• 전기의세계
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• v.25 no.6
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• pp.45-48
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• 1976

과거 수십년간 전력계통의 절연에 쓰여 온 공기에 대치하여 근년 고기압 SF$_{6}$gas에 의한 gas절연 방식이 급속도로 진전되고 있으며 거기에 수반하여 SF$_{6}$gas의 방전특성 해명이 초고압 장 gap영역에서 급선무로 되어 있다. 또한 초고압송전에 대응하는 각종 전력기기 cable등의 고기압 절연이 실용화 하게 되었으며 신뢰도가 높고 합리적인 gas 절연기기의 설계를 목표로 부성기체 특히 고기압 SF$_{6}$gas의 절연파괴 특성의 연구가 진행되고 있다. 고기압 SF$_{6}$gas는 높은 파괴 전체를 가지므로 극히 적은 원인으로도 절연 특성에 영향을 미치며 공기, 질소등 기체와는 매우 다른 방전 특성을 나타낸다. 여기서는 SF$_{6}$gas의 특이한 방전 특성과 고기압 SF$_{6}$gas 중에서의 impulse corona의 특성을 고찰하려고 한다.

• JSTS:Journal of Semiconductor Technology and Science
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• v.6 no.3
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• pp.210-224
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• 2006

A new analytical model for the static I-V characteristics of GaAs MESFET’s under optically controlled conditions in both linear and saturation region is presented in this paper. The novelty of the model lies in characterizing both photovoltaic (external, internal) and photoconductive effects. Deep level traps in the semi insulating GaAs substrate are also included in this model. Finally, effect of backgate voltage on I-V characteristics is explained analytically for the first time in literature. Small signal parameters of GaAs MESFET are derived under both dark and illuminated conditions. Some of the results are compared with reported experimental results to show the validity of the proposed model. Since accurate dc modeling is the key to accurate ac modeling, this model is very useful in the designing of photonic MMIC’s and OEIC’s using GaAs MESFET.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.8 no.2
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• pp.211-220
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• 1998

The stochiometric composition of $AgGaS_2$polycrystal source materials for the single crystal thin films were prepared from horizontal furnace. From the extrapolation method of X-ray diffraction patterns, it was found that the polycrystal $AgGaS_2$has tetragonal structure of which lattice constant $a_0\;and \;c_0$ were 5.756 $\AA$ and 10.305 $\AA$, respectively. $AgGaS_2$single crystal thin film was deposited on throughly etched GaAs(100) substrate from mixed crystal $AgGaS_2$by the Hot Wall Epitaxy (HWE) system. The source and substrate temperature were $590^{\circ}C$ and $440^{\circ}C$ respectively, and the growth rate of the single crystal thin films was about 0.5 $mu \textrm{m}$/h. The crystallinity of the grown single crystal thin films was investigated by the DCRC (double crystal X-ray diffraction rocking curve). The optical energy gaps were found to be 2.61 eV for $AgGaS_2$single crystal thin films at room temperature. The temperature dependence of the photocurrent peak energy is well explained by the Varshni equation, then the constants in the Varshni equation are given by${\Alpha};=;8.695{\times}10^{-4};eV/K,and;{\beta};=;332;K$. from the photocurrent spectra by illumination of polarized light of the $AgGaS_2$single crystal thin film, we have found that crystal field splitting $\Delta$Cr was 0.28 eV at 20 K. From the PL spectra at 20 K, the peaks corresponding to free and bound excitons and a broad emission band due to D-A pairs are identified. The binding energy of the free excitons are determined to be 0.2676 eV and 0.2430 eV and the dissociation energy of the bound excitons to be 0.4695 eV.

• Journal of the Korean Institute of Telematics and Electronics D
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• v.34D no.3
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• pp.52-59
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• 1997

Design and performance of principal four ICs for the 10-Gb/s optical communication system are presented. AlGaAs/GaAs HBTs are basic devices to implement a laser diode driver, apre-amplifier, and a limiting amplifier, and GaInP/GaAs HBTs are used for an AGC amplifier. We fbricated 11.5-GHz LD driver, a pre-amplifier, and a limiting amplifier, an dGaInP/GaAs HBTs are used for an AGC amplifier. We fabricated LD deriver, 10.5 GHz pre amplifier, 7.2 GHz AGC amplifier, and 10.3 GHz limiting amplifier, optimized circuit design and the stabilized MMIC fabrication process.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.21 no.3
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• pp.110-113
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• 2011

In this paper, we propose a new method for the fabrication of GaN microstructures formed only on the vertex of GaN pyramid by using of metal catalysts. GaN pyramidal structures were selectively grown on 3 ${\mu}m$ $SiO_2$ dot patterns followed by thin film deposition of Au and Cr only on the vertex area of the GaN pyramids with precisely controlled photolithography. After the metal deposition, the samples were loaded in the MOVPE reactor for the growth of GaN microstructures for 10 minutes. Temperature for the growth of the GaN microstructures was changed from $650^{\circ}C$ to $750^{\circ}C$. Rod type GaN microstructures were grown in the direction of vertical to the six {1-101} facets and the shape of the GaN microstructures was changed depend on the type of metal.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.11 no.5
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• pp.365-370
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• 1998

We studied a electrical properties in GaAs/AlGaAs/InGaAs pseudomorphic high electron mobility transistors(PHEMT s) recessed by electron cyclotron resonance(ECR) plasma and wet etching. Using the $NH_4OH$ solution, a nonvolatile AlF$_3$layer formed on AlGaAs surface after selective gate recess is effectively eliminated. Also, we controlled threshold voltage($V_th$) using $H_3PO_4$ etchant. We have fabricated a device with 540 mS/mm maximum transconductance and -0.2 V threshold voltage by using $NH_4OH$ and $H_3PO_4$dip after ECR gate recessing. In a 2-finger GaAs PHEMT with a gate length of 0.2$\mu m$ and width of 100 $\mu m$, a current gain of 15 dB at 10 GHz and a maximum cutoff frequency of 58.9 GHz have been obtained from the measurement of current gain as a function of frequency at 12mA $I_{dss}$ and 2 V souce-drain voltage.