• JSTS:Journal of Semiconductor Technology and Science
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• 제4권2호
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• pp.117-123
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• 2004

A 30 nm $In_{0.7}GaAs$ High Electron Mobility Transistor (HEMT) with triple-gate has been successfully fabricated using the $SiO_2/SiN_x$ sidewall process and BCB planarization. The sidewall gate process was used to obtain finer lines, and the width of the initial line could be lessened to half by this process. To fill the Schottky metal effectively to a narrow gate line after applying the developed sidewall process, the sputtered tungsten (W) metal was utilized instead of conventional e-beam evaporated metal. To reduce the parasitic capacitance through dielectric layers and the gate metal resistance ($R_g$), the etchedback BCB with a low dielectric constant was used as the supporting layer of a wide gate head, which also offered extremely low Rg of 1.7 Ohm for a total gate width ($W_g$) of 2x100m. The fabricated 30nm $In_{0.7}GaAs$ HEMTs showed $V_{th}$of -0.4V, $G_{m,max}$ of 1.7S/mm, and $f_T$ of 421GHz. These results indicate that InGaAs nano-HEMT with excellent device performance could be successfully fabricated through a reproducible and damage-free sidewall process without the aid of state-of-the-art lithography equipment. We also believe that the developed process will be directly applicable to the fabrication of deep sub-50nm InGaAs HEMTs if the initial line length can be reduced to below 50nm order.

• 센서학회지
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• 제10권6호
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• pp.328-337
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• 2001

수평 전기로에서 $CdGa_2Se_4$ 다결정을 합성하여 HWE 방법으로 $CdGa_2Se_4$ 단결정 박막을 반절연성 GaAs(100) 위에 성장하였다. $CdGa_2Se_4$ 단결정 박막은 증발원과 기판의 온도를 각각 $630^{\circ}C$, $420^{\circ}C$로 성장하였다. 10K에서 측정한 광발광 exciton 스펙트럼과 이중결정 X-선 요동곡선(DCRC)의 반치폭(FWHM)을 분석하여 단결정 박막의 최적 성장 조건을 얻었다. Hall 효과는 van der Pauw 방법에 의해 측정되었으며, 온도에 의존하는 운반자 농도와 이동도는 293K에서 각각 $8.27{\times}10^{17}/cm^3$, $345\;cm^2/V{\cdot}s$였다. 광전류 봉우리의 10K에서 단파장대의 가전자대 갈라짐(splitting)에 의해서 측정된 ${\Delta}Cr$ (crystal field splitting)은 106.5 meV, ${\Delta}So$ (spin orbit splitting)는 418.9 meV였다. 10K의 광발광 측정으로부터 고품질의 결정에서 볼 수 있는 free exciton 과 매우 강한 세기의 중성 주개 bound exciton등의 피크가 관찰되었다. 이때 중성 주개 bound exciton의 반치폭과 결합 에너지는 각각 8 meV와 13.7 meV였다. 또한 Haynes rule에 의해 구한 불순물의 활성화 에너지는 137 meV 였다.

• 한국재료학회지
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• 제22권4호
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• pp.185-189
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• 2012

We report plasma-assisted molecular beam epitaxy of $In_XGa_{1-X}N$ films on c-plane sapphire substrates. Prior to the growth of $In_XGa_{1-X}N$ films, GaN film was grown on the nitride c-plane sapphire substrate by two-dimensional (2D) growth mode. For the growth of GaN, Ga flux of $3.7{\times}10^{-8}$ torr as a beam equivalent pressure (BEP) and a plasma power of 150 W with a nitrogen flow rate of 0.76 sccm were fixed. The growth of 2D GaN growth was confirmed by $in-situ$ reflection high-energy electron diffraction (RHEED) by observing a streaky RHEED pattern with a strong specular spot. InN films showed lower growth rates even with the same growth conditions (same growth temperature, same plasma condition, and same BEP value of III element) than those of GaN films. It was observed that the growth rate of GaN is 1.7 times higher than that of InN, which is probably caused by the higher vapor pressure of In. For the growth of $In_xGa_{1-x}N$ films with different In compositions, total III-element flux (Ga plus In BEPs) was set to $3.7{\times}10^{-8}$ torr, which was the BEP value for the 2D growth of GaN. The In compositions of the $In_xGa_{1-x}N$ films were determined to be 28, 41, 45, and 53% based on the peak position of (0002) reflection in x-ray ${\theta}-2{\theta}$ measurements. The growth of $In_xGa_{1-x}N$ films did not show a streaky RHEED pattern but showed spotty patterns with weak streaky lines. This means that the net sticking coefficients of In and Ga, considered based on the growth rates of GaN and InN, are not the only factor governing the growth mode; another factor such as migration velocity should be considered. The sample with an In composition of 41% showed the lowest full width at half maximum value of 0.20 degree from the x-ray (0002) omega rocking curve measurements and the lowest root mean square roughness value of 0.71 nm.

• 원예과학기술지
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• 제18권3호
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• pp.383-386
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• 2000

$GA_{4+7}$ 도포제의 처리시기가 '감천배'와 '황금배'의 생육과 과실의 품질 및 성숙에 미치는 영향을 구명하기 위하여 만개 후 25일, 35일 및 45일에 과경에 25 mg을 도포하였다. '감천배'의 과중은 처리시기가 늦어질수록 무거워지는 경향을 보였다. 두 품종 모두 산도는 만개 후 45일 처리구에서 가장 높았으며, 경도는 '감천배'는 유의성이 없었으나 '황금배'는 처리로 증가하였다. 숙기는 두 품종 모두 4일 촉진되었다. '감천배'는 7월 상순경부터 모든 처리구에서 과중이 급격히 증가한 것에 비해, 대조구에서는 9월 상순 이후 완만한 증가를 보였다. '황금배'에서도 같은 경향이었으나, 9월 상순 이후부터 처리에 관계없이 모든 처리구에서 과중의 증가가 둔화되었다.

• 한국통신학회논문지
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• 제27권3C호
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• pp.234-240
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• 2002

AlGaAs/InGaAs/GaAs HBT를 이용하여 준밀리미터파 광대역 무선망(BWLL) 시스템의 가입자용 장치에 사용 가능한 전력증폭기를 개발하였다. 베이스 접지 HBT 소자의 비선형 등가 회로를 추출하여 선형 및 비선형 회로 시뮬레이션을 통하여 출력 전력 정합 회로를 갖는 증폭기를 설계하였으며, 이를 기초로 하여 세라믹 기판 위의 스텁을 이용하여 하이브리드 형태로 증폭기를 구현하였다. 제작된 전력증폭기는 24.4 GHz에서 최대 포화 출력 25.5 dBm, 35%의 전력 부가 효율을 얻었으며, 24.8 GHz에서는 7.5 dB의 최대 선형 이득을 얻었다. 또한, 24.25 GHz∼24.75 GHz의 주파수 대역에서 22 dBm 이상의 포화 출력 전력과 25% 이상의 전력 부가 효율을 얻었다.

• 대한의용생체공학회:의공학회지
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• 제20권4호
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• pp.443-449
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• 1999

현재 시판되고 있는 치과용 76.5%Pd-11.6%Cu-7.2^%GarP 합금의 주조상태 및 임상열처리에 따른 미세조직의 변화를 X-선 회절기, 광학현미경, 시차열분석기를 이용하여 관찰하였다. 주조상태, 탈개스 및 세리믹소성처리 후 미세조직은 Pd고용체와 금속간화합물 Pd2Ga으로 구성되어 나타났고, 이들 상들은 열처리에 따라 상당한 변화를 보였다. 또한 Pd은 아르곤 분위기 내의 산소와 반응하여 산화물 형성 및 분해로 인해 질량변화곡선(TG)이 변하였고, 시차열분석(DTA)에서는 약 815$^{\circ}C$ 정도에서 Pd2Ga에 기인하는 흡열피크를 확인하였다. 이러한 실험의 결과들은 Cu가 이원계 Pd-Ga 합금의 Ga의 고용량을 낮추어 공정반응이 저 Ga 쪽으로 이동하기 때문인 것으로 설명하였다. 그러나 앞으로 보다 명확한 상변태 규명을 위해서 TEM등의 분석장비를 사용하여 체계적인 연구가 요구된다.

• 전자공학회논문지A
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• 제31A권10호
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• pp.71-78
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• 1994

We have developed GaAs power metal semiconductor field effect transistors (MESFETs) for 4.7V operation under 900 MHz using a low-high deped structures grown by molecular beam epitaxy (MBE). The fabricted MESFETs with a gate widty of 7.5 mm and a gate length of 1.0.mu.m show a saturated drain current (Idss) of 1.7A and an uniform transconductance (Gm) of around 600mS, for gate bias ranged from -2.4 V to 0.5 V. The gate-drain breakdown voltage is measured to be higher than 25 V. The measured rf characteristics of the MESFETs at a frequency of 900 MHz are the output power of 31.4 dBm and the power added efficiency of 63% at a drain bias of 4.7 V.

• Asian Pacific Journal of Cancer Prevention
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• 제14권4호
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• pp.2269-2272
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• 2013

Matrix metalloproteinases (MMPs) degrade various components of the extracellular matrix and functional polymorphisms in encoding genes may contribute to genetic susceptibility to many cancers. Up to now, associations between MMP-7 (-181A>G) and digestive system cancer risk have remained inconclusive. To better understand the role of the MMP-7 (-181A>G) genotype in digestive cancer development, we conducted this comprehensive meta-analysis encompassing 3,518 cases and 4,596 controls. Overall, the MMP-7 (-181A>G) polymorphism was associated with higher digestive system cancer risk on homozygote comparison (GG vs. AA, OR=1.21, 95% CI = 1.12-1.60) and in a dominant model (GG/GA vs. AA, OR=1.16, 95% CI =1.03-1.46). On subgroup analysis, this polymorphism was significantly linked to higher risks for gastric cancer (GG vs. AA, OR=1.22, 95% CI = 1.02-1.46; GA vs. AA, OR=1.82, 95% CI =1.16-2.87; GG/GA vs. AA, OR=1.13, 95% CI =1.01-1.27; GG vs. GA/AA, OR= 1.25, 95% CI = 1.06-2.39. We also observed increased susceptibility to colorectal cancer and esophageal SCC in both homozygote (OR = 1.13, 95% CI = 1.06-1.26) and heterozygote comparisons (OR = 1.45, 95% CI = 1.11-1.91). In the stratified analysis by controls, significant effects were only observed in population-based studies (GA vs. AA, OR=1.16, 95% CI=1.08-1.50; GA/AA vs. GG, OR=1.10, 95% CI=1.01-1.72). According to the source of ethnicity, a significantly increased risk was found among Asian populations in the homozygote model (GG vs. AA, OR=1.40, 95% CI=1.12-1.69), heterozygote model (GA vs. AA, OR=1.26, 95% CI=1.02-1.51), and dominant model (GG/GA vs. AA, OR=1.18, 95% CI=1.08-1.55). Our findings suggest that the MMP-7 (-181A>G) polymorphism may be a risk factor for digestive system cancer, especially among Asian populations.

• 한국전기전자재료학회논문지
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• 제20권10호
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• pp.829-838
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• 2007

The stochiometric mix of evaporating materials for the $CdGa_2Se_4$ single crystal thin films was prepared from horizontal furnace. To obtain the single crystal thin films, $CdGa_2Se_4$ mixed crystal was deposited on thoroughly etched semi-insulating GaAs(100) substrate by the Hot Wall Epitaxy (HWE) system. The source and substrate temperature were $630^{\circ}C$ and $420^{\circ}C$, respectively. The crystalline structure of single crystal thin films was investigated by the photoluminescence and double crystal X-ray diffraction (DCXD).The carrier density and mobility of $CdGa_2Se_4$ single crystal thin films measured from Hall effect by van der Pauw method are $8.27{\times}10^{17}\;cm^{-3},\;345\;cm^2/V{\cdot}s$ at 293 K. respectively. The temperature dependence of the energy band gap of the $CdGa_2Se_4$ obtained from the absorption spectra was well described by the Varshni's relation, $Eg(T)\;=\;2.6400\;eV\;-\;(7.721{\times}10^{-4}\;eV/K)T^2/(T+399\;K)$. After the as-grown single crystal $CdGa_2Se_4$ thin films were annealed in Cd-, Se-, and Ga -atmospheres, the origin of point defects of single crystal $CdGa_2Se_4$ thin films has been investigated by PL at 10 K. The native defects of $V_{Cd}$, $V_{Se}$, $Cd_{int}$, and $Se_{int}$ obtained by PL measurements were classified as donors or accepters. We concluded that the heat-treatment in the Cd-atmosphere converted single crystal $CdGa_2Se_4$ thin films to an optical p-type. Also, we confirmed that Ga in $CdGa_2Se_4/GaAs$ did not form the native defects because Ga in single crystal $CdGa_2Se_4$ thin films existed in the form of stable bonds.

• 한국광학회지
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• 제9권6호
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• pp.428-432
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• 1998

장파장영역의 적외선 검출을 위해 구속­비구속 상태간 전이를 이용한 GaAs/AlGaAs 이종접합 다중양자우물구조형태 검출기를 제작하여 전기적, 광학적 특성을 살펴보았다. 시료는 MBE를 이용하여 SI-GaAs(100)기판 위에 장벽 500${\AA} $, 폭 40${\AA} $의 양자우물구조를 25층 성장시켰으며, Al의 몰분율은 0.28로 하였고 우물의 중심부 20${\AA} $은 $2{\times}10^{18}cm^{-3}$의 농도로 Si n-도핑을 하였다. 200$\times$200$\mu\textrm{m}^2$ 면적의 사각형 화소가 되도록 시료를 식각한 후 Au/Ge로 전극을 붙여 1$\times$8 검출기 배열을 제작하였다. 10K의 온도에서 적외선 광원에 대한 광특성을 조사한 결과 1차원으로 배열한 8개의 단일소자 모두 7.8$\mu\textrm{m}$파장에서 최대반응을 보였으며 검출률($D^＊$)은 최대 $4.9{\times}10^9cm\sqrt{Hz}/W$이었다.