• Journal of Sensor Science and Technology
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• v.8 no.2
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• pp.108-114
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• 1999

Surface acoustic wave (SAW) device is very attractive for gas sensor applications because of their small size, low cost, high sensitivity, and good reliability. A dual delay line surface acoustic wave $NO_2$ gas sensors have been designed and fabricated on the $LiTaO_3$ piezoelectric single crystal substrate. The capacitance of the fabricated IDTs was 326.34pF at the frequency of 79.3MHz. The maximum reflection loss of the impedence-matched IDTs was -16.74dB at the frequency of 79.3MHz. The SAW oscillator was constructed and the stable oscillation was obtained by controlling the gain of rf amplifier properly. The oscillation frequency shift of the SAW oscillator to the $NO_2$ gas was 28Hz/ppm.

• Journal of the Microelectronics and Packaging Society
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• v.14 no.3
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• pp.15-20
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• 2007

Low temperature processed ZnO-TFTs on glass below $270^{\circ}C$ for plastic substrate applications were fabricated and their electrical properties were investigated. Films in ZnO-TFTs with bottom gate configuration were made by RF magnetron sputtering system except for $SiO_2$ gate oxide deposited by ICP-CVD. ZnO channel films were grown on glass with various Ar and $O_2$ flow ratios. All of the fabricated ZnO-TFTs showed perfectly the enhancement mode operation, a high optical transmittance of above 80% in visible ranges of the spectrum. In the ZnO-TFTs with pure Ar process, the field effect mobility, threshold voltage, and on/off ratio were measured to be $1.2\;cm^2/Vs$, 8.5 V, and $5{\times}10^5$, respectively. These characteristic values are much higher than those of the ZnO-TFTs of which ZnO channel layers were processed with additional $O_2$ gas. In addition, ZnO-TFT with pure Af process showed smaller swing voltage of 1.86v/decade compared to those with $Ar+O_2$ process.

• The Journal of the Korea institute of electronic communication sciences
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• v.9 no.11
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• pp.1311-1316
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• 2014

To be used in a transmitter of a satellite transponder of this paper, X band 25W power amplifier module, a part constituting of high-power amplifier is transmitted to the equipment for transmitting to geostationary communications satellites(36,000Km distance). PAM consisted a total of four power amplifier module has a high output characteristic of the high-output amplifier is used in the ground station. Used in conjunction with the structured type power amplifier module is composed of Serial Combining Structure. This PAM(Power Amplifier Module) configured by combining the circuit with the power amplifier, 10 MMIC chips and the Al2O3 thin film substrate using a Hybrid Technique of power amplifier module, was implemented at X band PAM(Power Amplifier Module) of 25W grade.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.06a
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• pp.162-163
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• 2008

이 논문에서는 Polyimide 기판의 $O_2$ 플라즈마 처리효과에 따른 GZO 박막의 구조적, 전기적, 광학적인 특성을 고찰하였다. ICP-RIE 방법을 이용하여 Polyimide 기판의 $O_2$ 플라즈마 처리의 변수로 RF power와 처리시간을 각 100 ~ 400 W, 120 ~ 600 초까지 조절하였다. RF 스퍼터링 방법으로 $O_2$ 플라즈마 처리효과에 따른 Polyimide 기판을 4인치의 GZO(ZnO : 95 wt%, $Ga_2O_3$ 5 wt%) 타겟을 사용하여 RF power 90 W, 공정압력 5 mTorr, Ar gas 20 sccm, 기판거리 5 cm, 박막두께 500nm, 상온의 조건으로 GZO 박막을 증착 하였다. Polyimide 기판에 $O_2$ 플라즈마 처리를 하지 않고 증착한 GZO 박막의 비저황은 $1.02\times10^{-2}\Omega$-cm 이었고 RF power 100W, 처리시간 120 초로 $O_2$ 플라즈마 처리 후에 증착한 GZO 박막의 비저항이 $1.89\times10^{-3}\Omega$-cm인 최적의 값이 측정되었으며 RF power가 증가할수록 투과도는 감소하였지만 처리시간의 변화에 따라서는 투과도 변화가 거의 없었다.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.06a
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• pp.138-139
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• 2009

폴리머 기판위에서 ICP-RIE 방법을 이용하여 $O_2$ 플라즈마 전처리효과에 따른 GZO박막의 전기적, 광학적인 특성을 고찰 하였다. ICP-RIE 방법을 이용하여 폴리머 기판 위에 $O_2$ 플라즈마 전처리의 공정 값은 공정압력은 20 mTorr, 파워는 100 W로 하고 변수로는 시간을 60초 ~ 600초로 하였다. $O_2$ 플라즈마 전처리한 기판위에 RF Sputtering 방법을 이용하여 4인치의 GZO(ZnO: 95 wt%, $Ga_2O_3$: 5 wt%) 타겟을 사용하여 공정압력은 5 mTorr, 파워는 150 W, 박막의 두께는 500 nm의 조건으로 박막을 증착하였다. PET 기판의 600초의 $O_2$ 플라즈마 처리 후 증착한 GZO 박막의 비저항이 $6.2\times10^{-3}\;{\Omega}$-cm이었고, PEN 기판의 120초의 $O_2$ 플라즈마 처리 후 증착한 GZO 박막의 비저항이 $1.1\;{\times}\;10^{-3}\;{\Omega}$-cm이었다. 또한 300 nm 이하의 자외선 영역에서는 뛰어난 광 차단 효과를 가지고 있었으며, 가시광선 영역 (400 nm ~ 700 nm)에서 증착 된 시편들이 80 % 광 투과율을 나타내었다.

• Proceedings of the KIEE Conference
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• 2006.10a
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• pp.53-54
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• 2006

Arsenic doped p-type ZnO thin films have been realized on intrinsic (100) GaAs substrate by RF magnetron sputtering and thermal annealing treatment. p-Type ZnO exhibits the hole concentration of $9.684{\times}10^{19}cm^3$, resistivity of $2.54{\times}10^{-3}{\Omega}cm$, and mobility of $25.37\;cm^2/Vs$. Photoluminescence (PL) spectra of As doped p-type ZnO thin films reveal neutral acceptor bound exciton ($A^{0}X$) of 3.3437 eV and a transition between free electrons and acceptor levels (FA) of 3.2924 eV. Calculated acceptor binding energy ($E_A$) is about 0.1455 eV. Thermal activation and doping mechanism of this film have been suggested by using X-ray photoelectron spectroscopy (XPS). p-Type formation mechanism of As doped ZnO thin film is more related to the complex model, namely, $As_{Zn}-2V_{Zn}$, in which the As substitutes on the Zn site, rather than simple model, Aso, in which the As substitutes on the O site. ZnO-based p-n junction was fabricated by the deposition of an undoped n-type ZnO layer on an As doped p-type ZnO layer.

• Proceedings of the Korean Vacuum Society Conference
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• 2001.07a
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• pp.67-67
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• 2001

• 한국신재생에너지학회:학술대회논문집
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• 2006.06a
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• pp.222-224
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• 2006

A non-vacuum process for $Cu(In,Ga)Se_2$ (CIGS) thin film solar cells from nanoparticle precursors was described in this work CIGS nanoparticle precursors was prepared by a low temperature colloidal route by reacting the starting materials $(CuI,\;InI_3,\;GaI_3\;and\;Na_2Se)$ in organic solvents, by which fine CIGS nanoparticles of about 20nm in diameter were obtained. The nanoparticle precursors were mixed with organic binder material for the rheology of the mixture to be adjusted for the doctor blade method. After depositing the mixture of CIGS with binder on Mo/glass substrate, the samples were preheated on the hot plate in air to evaporate remaining solvents ud to burn the organic binder material. Subsequently, the resultant (porous) CIGS/Mo/glass simple was selenized in a two-zone Rapid Thermal Process (RTP) furnace in order to get a solar ceil applicable dense CIGS absorber layer. Complete solar cell structure was obtained by depositing. The other layers including CdS buffer layer, ZnO window layer and Al electrodes by conventional methods. The resultant solar cell showed a conversion efficiency of 0.5%.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.4 no.3
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• pp.238-244
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• 1994

We investigated solution growth of silicon on borosilicate and quartz glass substrates in the temperature range of $800^{\circ}C~520^{\circ}C$. A thin Al-Si layer evaporated onto the substrate serves to improve the wetting between the substrate and the Al/Ga solvent. Nucleation takes place by a reaction of Al with $SiO_2$ from the substrate. We obtained silicon deposits with a grain size up to a few 100 $\mu\textrm{m}$. There was a perferential (111) orientation for the case of quartz glass substrates while there is a strong contribution of other orientations for the deposition of Si on borosilicate glass substrates.

• Journal of the Microelectronics and Packaging Society
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• v.26 no.3
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• pp.15-22
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• 2019

In these days, importance of the power electronic devices and modules keeps increasing due to electric vehicles and energy saving requirements. However, current silicon-based power devices showed several limitations. Therefore, wide band gap (WBG) semiconductors such as SiC, GaN, and $Ga_2O_3$ have been developed to replace the silicon power devices. WBG devices show superior performances in terms of device operation in harsh environments such as higher temperatures, voltages and switching speed than silicon-based technology. In power devices, the reliability of the devices and module package is the critically important to guarantee the normal operation and lifetime of the devices. In this paper, we reviewed the recent trends of the power devices based on WBG semiconductors as well as expected future technology. We also presented an overview of the recent package module and fabrication technologies such as direct bonded copper and active metal brazing technology. In addition, the recent heat management technologies of the power modules, which should be improved due to the increased power density in high temperature environments, are described.