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Jong-MinLee,Byoung-GueMin,Seong-IlKim,Kyung-HoLee,SungHoPark,In-HoonChoi 한국물리학회 2002 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.40 No.2
In this study, AlGaAs/GaAs heterojunction bipolar transistors (HBTs) with AlGaAs-ledge structures were fabricated, and their electrical performances at various substrate temperatures were comparatively characterized with respect to DC performances. To improve the surface properties of the HBTs, we employed an AlGaAs-ledge structure by using a simple ledge technique. Compared with the no-ledge HBT, the ledge HBT showed improvements in the current gain about 14\%, and exhibited comparable high-frequency performances. The extracted surface recombination current was $5.13 \times 10^{-7}$ A/$\mu$m, which confirmed that the AlGaAs-ledge structure effectively suppressed the surface recombination. We also present the temperature-dependent electrical performances of HBTs. The temperature coefficient of the base-emitter turn-on voltage was $-$2.29 mV/K, and the offset voltage was increased from 0.172 to 0.247 V as the temperature was increased in the temperature range of 240 - 420 K. The HBT showed a negative temperature coefficient at all collector currents, and the current gain at a collector current of $1 \times 10^{-3}$ A was reduced from 135.6 to 19.11 as the temperature was increased from 240 K to 420 K.
KwanLee,HoonSangChoi,Jong-HanLee,YuMinJang,In-HoonChoi 한국물리학회 2002 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.40 No.4
It has been found that the crystallinity of the ferroelectric phase for SrBi2Ta2O9 (SBT) thin lms prepared by metalorganic decomposition (MOD) depends on the partial oxygen pressure during rapid thermal annealing (RTA). Under a partial oxygen pressure as high as 130 Torr, the crystallization temperature inducing the ferroelectric SBT phase could be lowered to 650 C. Those lms processed at 650 C presented satisfactory ferroelectric properties; that is, the memory window was 1.22.2 V at an applied voltage of 37 V. This memory window is superior to that of SBT annealed using the conventional MOD method. In comparison with the SBT thin lms prepared at 800 C in an O2 ambient by using furnace annealing, the SBT thin lms prepared at 650 C in a partial oxygen pressure by using the RTA process showed good crystallization and electrical properties.
Two Cases of Aquagenic Wrinkling of the Palms in Korean Healthy Women: Easily Overlooked Disease
( Hoon Choi ),( In Ho Bae ),( Min Sung Kim ),( Chan Ho Na ),( Bong Seok Shin ) 대한피부과학회 2020 Annals of Dermatology Vol.32 No.2
Aquagenic wrinkling of the palms (AWP) is a rare condition, which is characterized by appearance of whitish papules and plaques and an excessive wrinkling and swelling of the palmar skin after exposure to water. Herein, we report two cases of AWP. A 17-year-old woman presented prickling focal various sized whitish papules, plaques with wrinkles on both palms after water contact for 6 months ago. Histologic findings were consistent with AWP. A 26-year-old woman presented asymptomatic multiple various sized whitish papules, plaques with wrinkles on both palms after water contact for 1 year ago. Both patients underwent a cystic fibrosis transmembrane conduct receptor test but were negative and improved without any treatment. (Ann Dermatol 32(2) 151∼154, 2020)
APPLICATION OF ALANINE/ESR SPECTRUM SHAPE CHANGE IN GAMMA DOSIMETRY
HOON CHOI,JEONG IN KIM,BYUNG ILL LEE,YOUNG KI LIM 한국원자력학회 2010 Nuclear Engineering and Technology Vol.42 No.3
Alnine pellets were installed in a nuclear power plant for one or two operation cycles and measured by electron spin resonance (ESR) spectrometers for dosimetry. Dose and “x/y ratio”, i.e., satellite peak over main center peak ratio, were measured for the returned alanine dosimeters from the nuclear power plant and compared to the values of reference alanine dosimeters exposed only to gamma rays. The variation of the x/y ratio change depended on the population of radicals from each radiation component with different LET. The gamma dose in a mixed radiation field was estimated by an additive gamma ray irradiation experiment and the measured dose rate at specified locations in the containment building.