• Proceedings of the Korean Vacuum Society Conference
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• 2009.02a
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• pp.157-157
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• 2009

• Proceedings of the Materials Research Society of Korea Conference
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• 2007.11a
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• pp.47.2-47.2
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• 2007

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2007.11a
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• pp.25-25
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• 2007

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.14 no.2
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• pp.123-129
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• 2001

The optimal high temperature processing conditions for the formation of Ohmic contact of Ti/Al/Pt/Au multiple layers were established for the fabrication of n$^{+}$-GaN/AlGaN/GaN HFET device. Contact resistivity as low as 3.4x10$^{-6}$ ohm-$\textrm{cm}^2$ was achieved by the annealing of the sample at 100$0^{\circ}C$ for 10 sec. using the RTA (Rapid Thermal Annealing) system. The fabricated HFET (Heterostructure Field Effect Transistor) with a structure of n'-GaN/undoped AlGaN/undoped GaN exhibited a low knee voltage of 3.5 V and a maximum source-drain current density of 180 mA/mm at Vg=0V.V.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.31A no.9
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• pp.114-120
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• 1994

We have been successfully fabricated the low nois HEMT device with AlGaAs and GaAs structure. The epitazial layer with n-type AlgaAs and undoped GaAs was grown by molecular beam epitaxy(MBE) system. Ohmic resistivity of the ource and drain contact is below 5${\times}10^{6}{\Omega}{\cdot}cm^{2}$ by the rapid thermal annealing (RTA) process. The ideality factor of the Schottky gate is below 1.6 and the gate material was Ti/Pt/Au. The HEMTs with 0.25$\mu$m-long and 200$\mu$m-wide gates have exhibited a noise figure of 0.65dB with associated gain of 9dB at 12GHz, and a transconductance of 208mS/mm.

• Applied Science and Convergence Technology
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• v.24 no.1
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• pp.22-26
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• 2015

The optical properties of InP/GaP short-period superlattice (SPS) structures grown at various temperatures from $400^{\circ}C$ to $490^{\circ}C$ have been investigated by using temperature-dependent photoluminescence (PL) and emission wavelength-dependent time-resolved PL measurements. The PL peak energy for SPS samples decreases as the growth temperature increases. The decreased PL energy of ~10 meV for the sample grown at $425^{\circ}C$ compared to that for $400^{\circ}C$-grown sample is due to the CuPt-B type ordering, while the SPS samples grown at $460^{\circ}C$ and $490^{\circ}C$ exhibit the significant reduction of the PL peak energies due to the combined effects of the formation of lateral composition modulation (LCM) and CuPt-B type ordering. The SPS samples with LCM structure show the enhanced carrier lifetime due to the spatial separation of carriers. This study represents that the bandgap energy of InP/GaP SPS structures can be controlled by varying growth temperature, leading to LCM formation and CuPt-B type ordering.

• Proceedings of the Korea Association of Crystal Growth Conference
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• 1996.06a
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• pp.351-374
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• 1996

Various types of garnet compounds were synthsized by iso-and aliovalent substitutions and sintering method. Among them, fiber shapes of garnet crystals were grown from the $Ca_3Li_xNb_{(1.5+x)}Ga_{(3.5-2x)}O_{12}$ melt where x = 0 ~ 0.5 by modified micro-pulling down method in air using Pt crucibles. The measured lattice constants as a function of solidification fraction of grown fiber crystals are about $12.54\;{\AA}$ irrespective of x. It was found that the $Ca_3Li_{0.275}Nb_{1.775}Ga_{2.95}O_{12}$ garnet melts congruently at about $1450\;^{\circ}C$ based on the purities of garnet phase and variations of lattice parameter. Transparent and bubble-free crystals of x = 0.25 and 0.275 were grown by Czochralski techniques in air using Pt crucibles. An absorption spectrum is also reported.

• New & Renewable Energy
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• v.5 no.3
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• pp.26-31
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• 2009

Using MBE growth method, GaAs/AlGaAs solar cell structure was grown. Deposited electrodes are Au/Ni/Ge for n-type and Au/Pt/Ti for p-type electrodes were deposited by E-beam evaporator. Indoor light concentrators were devised and fabricated in order to concentrate artificial solar rays. Also mirror and prism and Fresnel lens concentration system with solar simulator were devised and fabricated. Results of solar cell characteristics were measured with shutting system which can control the amount of light. Maximum power density was 2.13 W/$cm^2$ and maximum concentration was 124 sun, when mirror with Fresnel lens was used at $7854\;mm^2$ of shutter hole.

• Journal of Pharmaceutical Investigation
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• v.23 no.2
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• pp.61-69
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• 1993

Prodrug of cefazolin (CFZ) was prepared with the objective of improving its oral bioavailability. Cefazolin phthalidyl ester (CFZ-PT) was synthesized and evaluated as potential prodrug form. The successful synthesis of CFZ-PT was identified by spectroscopic analysis. Partition coefficient studies showed that CFZ-PT is more lipophilic than CFZ and the ester was hydrolyzed enzymatically into the parent drug in blood, liver and intestinal homogenates. The pharmacokinetic characteristics of CFZ-PT and CFZ were compared following oral administrations to rabbits. Serum CFZ concentration was determined by HPLC method and the ester compound (prodrug) was not detected in serum following oral administration of CFZ-PT. CFZ-PT did not have antimicrobial activity in vitro against Bacillus subtilis ATCC 6633, whereas CFZ-PT in serum after oral administration to rabbits had antimicrobial activity. From above observations, it was noted that CFZ-PT is rapidly hydrolyzed to CFZ in the body and the bioavailability of CFZ-PT was increased by 3.5-fold than that of CFZ. From these results of this study, it was concluded that CFZ-PT may be a novel prodrug of CFZ which can improve the oral absorption of CFZ.

• ETRI Journal
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• v.13 no.4
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• pp.35-41
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• 1991

저전력 고집적 GaAs 디지틀 IC에 적합한 기본 논리회로인 DCFL (Direct Coupled FET Logic) 을 구현하기 위한 소자로 WSi게이트 MESFET 공정을 연구하였으며, 이와 함께 TiPtAu 게이트 소자를 제작하였다. MESFET 의 제작은 내열성게이트를 이용한 자기정렬 이온주입 공정을 사용하였으며 주입된 Si 이온은 급속열처리 방법으로 활성화하였다. 또한 제작공정중 저항성 접촉의 형성은 절연막을 이용한 리프트 - 오프 공정을 이용하였다. 제작된 WSi게이트 MESFET은 $1\mum$ 게이트인 경우 222mS/mm의 트랜스컨덕턴스를 나타내어 우수한 동작특성과 집적회로 공정의 적합성을 보였으며 이와 동등한 공정조건으로 제작된 TiPtAu 게이트 MESFET 은 2" 기판 내에서 84mV의 임계전압 변화를 나타내었다.