• Journal of the Korean Institute of Telematics and Electronics
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• v.25 no.12
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• pp.1656-1662
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• 1988

Auger depth profiles of various In Ga As P/In P heterojunctions grown by liquid phase epitaxial techniques under different growth conditions such as diffusion temperature, diffusion time and dopants, have been obtained. The surface contaminations of In Ga As have been investigated. We found that the samples with Zn diffusion exhibit significant interface grading phenomena including In depletion, Ga richness and P richness at the In Ga As P/In P interface, and In outdiffusion at the surface. The main surface contamination was found to be due to carbon and oxygen species. It can be suggested that Zn gettering takes a major role in such phenomena as interface grading, in depletion, and Ga and P richness at the interface.

• 한국신재생에너지학회:학술대회논문집
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• 2010.11a
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• pp.53.1-53.1
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• 2010

결정질 실리콘 태양전지의 효율을 향상시키기 위하여 수광면에 서로 다른 도핑농도를 가지는 고농도 도핑영역과 저농도 도핑영역으로 이루어진 emitter를 형성하는 것이 요구되며 이를 selective emitter라 칭한다. Selective emitter를 형성하면 고농도 도핑영역에서 금속전극과 저항 접촉이 잘 형성되기 때문에 직렬 저항이 최소화되고 저농도 도핑영역에서는 전하 재결합의 감소로 인하여 태양전지의 변환효율이 상승하는 이점이 있다. Selective emitter의 형성방법은 이미 다양한 방법이 제안되고 있으나, 본 연구에서는 기존에 제시된 방법과는 다르게 열산화 시 dopant redistribution에 의한 Boron depletion 현상을 이용하여 selective emitter를 형성하는 방법을 제안하였고, 이를 Simulation을 통하여 검증하였다. 초기 emitter 확산 후 junction depth는 0.478um, 면저항은 $104.2{\Omega}/sq.$ 이었으며, nitride masking layer 두께는 0.3um로 설정하였다. $1100^{\circ}C$에서 30분간 습식산화 공정을 거친 후 nitride mask가 있는 부분의 junction depth는 1.48um, 면저항은 $89.1{\Omega}/sq$의 값을 보였고, 산화막이 형성된 부분의 junction depth는 1.16um, 면저항은 $261.8{\Omega}/sq$의 값을 보였다. 위 조건의 구조를 가진 태양전지의 변환 효율은 19.28%의 값을 나타내었고 Voc, Jsc 및 fill factor는 각각 645.08mV, $36.26mA/cm^2$, 82.42%의 값을 보였다. 한편 일반적인 구조로 설정한 태양전지의 변환 효율, Voc, Isc 및 fill factor는 각각 18.73%, 644.86mV, $36.26mA/cm^2$, 80.09%의 값을 보였다.

• Journal of the Korean Society for Heat Treatment
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• v.26 no.3
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• pp.105-112
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• 2013

The microstructural changes of Fe-20Mn-12Cr-1Cu alloy have been studied during high temperature gas nitriding (HTGN) at the range of $1000^{\circ}C{\sim}1150^{\circ}C$ in an atmosphere of nitrogen gas. The mixed microstructure of austenite and ${\varepsilon}$-martensite of as-received alloy was changed to austenite single phase after HTGN treatment at the nitrogen-permeated surface layer, however the interior region that was not affected nitrogen permeation remained the structure of austenite and ${\varepsilon}$-martensite. With raising the HTGN treatment temperature, the concentration and permeation depth of nitrogen, which is known as the austenite stabilizing element, were increased. Accordingly, the depth of austenite single phase region was increased. The outmost surface of HTGN treated alloy at $1000^{\circ}C$ appeared Cr nitride. And this was in good agreement with the thermodynamically calculated phase diagram. The grain growth was delayed after HTGN treatment temperature ranges of $1000^{\circ}C{\sim}1100^{\circ}C$ due to the grain boundary precipitates. For the HTGN treatment temperature of $1150^{\circ}C$, the fine grain region was shown at the near surface due to the grain boundary precipitates, however, owing to the depletion of grain boundary precipitates, coarse grain was appeared at the depth far from the surface. This depletion may come from the strong affinity between nitrogen and substitutional element of Al and Ti leading the diffusion of these elements from interior to surface. Because of the nitrogen dissolution at the nitrogen-permeated surface layer by HTGN treatment, the surface hardness was increased above 150 Hv compared to the interior region that was consisted with the mixed microstructure of austenite and ${\varepsilon}$-martensite.

• Ocean Systems Engineering
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• v.2 no.1
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• pp.33-47
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• 2012

This study revealed the behavior of droplets formed through leak process in deep water. There was a threshold depth named the universal attraction depth (UAD). Droplets rose upward in the zone below the UAD called the rising zone, and settled down in the zone above the UAD called the settling zone. Three mass loss modes were identified and formulated: dissolution induced by mass transfer, condensation by heat transfer and phase separation by pressure decrease. The first two were active for the settling zone, and all the three were effective for the rising zone. In consequence, the life time of the droplets in the rising zone was far shorter than that of the droplets in the settling zone.

• Bulletin of the Korean Chemical Society
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• v.18 no.11
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• pp.1175-1179
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• 1997

The adsorption of oxygen on ZnO was monitored by measuring the capacitance of two contacting crystals which have depletion layers originated from the interaction between oxygen and ZnO at 298 K-473 K. An admission of oxygen to the sample induced an irreversible increase in the depth and the amount of adsorbed oxygen was less than 0.001 monolayer in the experimental condition. The relation between pressure of oxygen and variation of the depth was tested from the view point of Langmuir or Freundlich isotherm. Using Hall effect measurement and kinetic experiment, a model equation on the adsorption process was proposed. From the results, it was suggested that oxygen adsorption depended on the rate of electron transfer from ZnO to oxygen while the amount of adsorbed oxygen was kinetically restricted by the height of surface potential barrier.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.13 no.1
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• pp.13-20
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• 2000

In this paper, we demonstrated an analytical description method of forward votage drop and reverse leakage current of the junction barrier controlled schottky rectifier with linearly graded junction and abrupt junction models. In this case, the vertical depths of device are 1[${\mu}{\textrm}{m}$] and 2[${\mu}{\textrm}{m}$], respectively. Through ion implantation and annealing process, we obtain the data of lateral and depth from implanted 2-dimensional profiles. Also we applied these data to models that indicate the change of depletion each on linearly-graded and abrupt juction as the forward and revers bias. After applied depletion changes to electric characteristics of JBS rectifiers, we calculated the forward I-V, the reverse leakage current and temperatures vs. power dissipations according to each junction. When we compared the rectifier with calculated and measured data, from the calculated results, forward votage drop with linearly graded junction is lower than that of abrupt junction and reverse leakage current with linearly graded junction is lower(≒1$\times$10\ulcorner times) than that of abrupt junction. Also, the power dissipations according to different juction depth(1[${\mu}{\textrm}{m}$], 2[${\mu}{\textrm}{m}$]) of device are calculated. Seeing the calculated results, we confirmed it from analytic model that the rectifier with linearly graded junction retained a low power dissipation up to 600[$^{\circ}C$] in comparison with the rectifier with abrupt junction.

• Ocean and Polar Research
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• v.26 no.2
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• pp.377-384
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• 2004

Annual variations of inorganic nutrients such as nitrate(+nitrite), phosphate and silicate in association with thermocline were investigated in the upper 200 m of the water column at KODES Long-term Monitoring (KOMO) station in the northeast equatorial Pacific from 1995 to 2002. Global climatic disturbances such as El Nino and La Nina, should have affected KODES area during the study period. In 1995-97 and 2000-2002, a thermocline where temperatures rapidly decrease with depth, was formed at 50-70 m water depth. Nutrient depletion, specially for nitrate and phosphate, was extended down to approximately 50 m depth, which coincided with the surface mixed layer depth. In 1998 and 1999, however a very fluctuating thermocline was observed at 20-100 m water depth. In the photic zone (up to 100 m depth), depth integration of nitrate, phosphate and silicate ranged from 2.02 to $23.14\;gN/m^2$, from 0.87 to $4.05\;gP/m^2$ and from 35.67 to $176.21\;gSi/m^2$, respectively. As a result of changes in the water column structures, nutrient concentrations also showed fluctuation parallel to the changes of thermocline in the study area.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.40 no.4
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• pp.383-391
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• 2020

In this study, Hunt's analytical solution and Ward & Lough's analytical solution for two-layered leaky aquifer system were used to estimate stream depletions due to shallow and deep groundwater pumping, and their differences were compared. Depending on the combination of the separation distance between the stream and the well, the transmissivity and the storage coefficient of the aquifer, and the leakage coefficient between the upper and lower layers, the stream depletion, which is the amount of stream water reduction compared to the amount of groundwater pumping, for each of 45,000 cases was calculated for both shallow and deep groundwater pumping, and the differences were analyzed quantitatively. When the leakage coefficient was very small, with a value of 10^-61/d, the difference in the average five-year stream depletion due to the pumping of shallow and deep groundwater showed a large deviation of up to 0.9 depending on the given hydraulic characteristics; this value exponentially decreased as the stream depletion factor (SDF) increased. This exponential relationship gradually weakened as the leakage coefficient increased due to interaction effects between layers, resulting in a small difference of up to 0.2 when the leakage coefficient reached 10^-31/d. Under the condition of greater interlayer hydraulic connectivity, there was little influence of the depth of groundwater pumping on the stream water reduction.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.49 no.1
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• pp.24-29
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• 2000

We propose a simple method to control the crystallization depth of amorphous silicon (a-Si) deposited by PECVD or LPCVD during the excimer laser annealing (ELA). Employing the new method, we have formed poly-Si/a-Si double film and fabricated a new poly-Si TFT with vertical a-Si offsets between the poly-Si channel and the source/drain of TFT without any additional photo-lithography process. The maximum leakage current of the new poly-Si TFT decreased about 80% due to the highly resistive vertical a-Si offsets which reduce the peak electric field in drain depletion region and suppress electron-hole pair generation. In ON state, current flows spreading down through broad a-Si cross-section in the vertical a-Si offsets and the current density in the drain depletion region where large electric field is applied is reduced. The stability of poly-Si TFT has been improved noticeably by suppressing trap state generation in drain region which is caused by high current density and large electric field. For example, ON current of the new TFT decreased only 7% at a stress condition where ON current of conventional TFT decreased 89%.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.08a
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• pp.229-229
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• 2011

부유 게이트 Floating gate (FG) 플래시 메모리 소자의 단점을 개선하기 위해 전하 포획 층에 전하를 저장하는 전하 포획 플래시 메모리 Charge trap flash (CTF)소자에 대한 연구가 활발히 진행되고 있다. CTF소자는 FG플래시 메모리 소자에 비해 비례축소가 용이하고 긴 retention time을 가지며, 낮은 구동 전압을 사용하는 장점을 가지고 있다. CTF 소자에서 비례축소에 따라 단채널 효과와 펀치-쓰루 현상이 증가하는 문제점이 있다.본 연구에서는 CTF 단채널 효과와 펀치-쓰루 현상을 감소시키기 위한 방법으로 silicon-on-insulator (SOI) 기판을 사용하였으며 SOI기판에서 절연층의 깊이에 따른 전기적 특성을 고찰하였다. silicon-oxide-nitride-oxide-silicon(SONOS) 구조를 가진 CTF 메모리 소자를 사용하여 절연층의 깊이 변화에 따른 subthreshold swing특성, 쓰기-지우기 동작 특성을 TCAD 시뮬레이션 툴인 Sentaurus를 사용하여 조사하였다. 소스와 드레인의 junction depth는 20 nm 사용하였고, 절연층의 깊이는 5 nm~25 nm까지 변화하면서 절연층의 깊이가 20 nm이하인 fully depletion 소자에 비해, 절연층의 깊이가 25 nm인 소자는 partially depletion으로 인해서 드레인 전류 레벨이 낮아지고 subthreshold swing값이 증가하는 현상이 나타났다. 절연층의 깊이가 너무 얕을 경우, 채널 형성의 어려움으로 인해 subthreshold swing과 드레인 전류 레벨의 전기적성질이 SOI기판을 사용하지 않았을 경우보다 떨어지는 경향을 보였다. 절연층의 깊이가 17.5 nm인 경우, CTF소자의 subthreshold swing과 드레인 전류 레벨이 가장 좋은 특성을 보였다.