• Journal of Korea Society of Industrial Information Systems
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• v.19 no.2
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• pp.37-43
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• 2014

In this paper, we present the effect of forward current gain on emitter area in NPN transistors are used widely in the almost linear integrated circuits and integrated injection logic. Relations between forward current gain and emitter area were conformed with the simulation with examined calculation and experiments. At the same emitter length, as junction depth is increased, common emitter current gain is decreased. Ratio of Emitter bottom area comparing to side area increases, the emitter current gain is increased. The theory and simulation results were fitted in with the experimental data very well.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1996.11a
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• pp.10-12
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• 1996

AlGaAs/GaAs Heterojunotion Bipolar Transistors (HBTs) with various emitter areas were fabricated and the device size dependence on the current gain was examined. With the different emitter areas, the passivated devices having the same peripheral length were fabricated and measured. The measured base current density in the Gummel plots shows an ideality factor of nearly 2. It is found that as the emitter area becomes small, the base current density with the ideality factor of 2 increases linearly, and as the emitter perimeter/area ratio becomes large, the surface recombination current density component increases. The current gain performance in AlGaAs/GaAs HBTs is mainly determined by either the larger emitter area or the smaller ratio of the emitter perimeter to the emitter area. These results will be compared with experimental works for GaInP/GaAs HBTs

• 한국신재생에너지학회:학술대회논문집
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• 2010.11a
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• pp.50.2-50.2
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• 2010

Indium Tin Oxide (ITO)는 투과도가 높고, 전기 전도도가 뛰어나 TFT, 태양전지 등 여러 가지 산업에서 전극의 재료로 널리 사용되고 있다. 전극의 재료로써 가장 중요하게 고려되어야 할 사항 중의 하나는 전극과 접촉하는 물질과의 접촉 저항이다. 특히, 태양전지에서 높은 접촉 저항은 셀을 직렬저항 요소를 증가시켜 태양전지의 효율 저하를 가져 온다. 본 연구에서는 ITO를 실리콘 태양전지에 적용하기 위하여, ITO - n-type emitter간, ITO - Ag 간의 접촉 특성을 Transfer Length Method(TLM)을 통하여 분석하였다. p-type 실리콘의 전면을 도핑하여 pn접합을 형성한 후, 그 위에 ITO 패턴을 형성하여 ITO-emitter 간의 접촉 특성을 측정하였고, 두껍게 증착한 SiNx 박막 전면에 ITO를 증착한 후, Ag 패턴을 형성하여 ITO-Ag간의 접촉 특성을 측정 하였다. 측정 결과, ITO와 emitter 간의 접촉 비저항은 $0.9{\Omega}-cm^2 $을 나타내었고, ITO와 Ag와의 접촉 비저항은 $0.096{\Omega}-cm^2 $을 나타내었다.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.08a
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• pp.383-383
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• 2011

Generally, field emitters can be categorized into two types according to the emitter shape, one is a planar field emitter and the other is a point emitter. The planar field emitter is used for displays, flat lamps and signage boards. On the other hands, the point field emitter is expected to play a significant role in x-ray sources and electron beam sources. Such applications of the point field emitters, especially, need large emission current and high emission stability with a small electron beam size. A few reports announced point emitters made by carbon nanotubes (CNTs). However, they still have suffered from poor reproducibility and low emission current. Here, we demonstrated high performance CNT point emitters by attaching CNTs onto graphite rod. Graphite rod exhibited good electrical conductivity and chemical stability. In this method, the shape of the point emitter could be easily controlled by changing the length and diameter of the graphite rod. The CNT point emitter showed emission current over 1 mA at an applied electric field of 1.4 V/${\mu}m$. We consider that the stable emission performance is attributed to the stable contact between CNTs and graphite rod.

• Journal of IKEEE
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• v.25 no.2
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• pp.371-375
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• 2021

In this paper, a SiC-based LIGBT structure that can be used at high voltage and high temperature is presented. In order to improve the low current characteristic, a dual-emitter symmetrical around the gate is inserted. In order to verify the characteristics of the proposed device, simulation and design were conducted using Sentaurus TCAD simulation, and a comparative study was conducted with a general LIGBT. In addition, splitting was performed by designating a variable for the length of the N-drift region in order to verify the electrical characteristics of the minority carriers. As a result of the simulation it was confirmed that the proposed dual-emitter structure flows a higher current at the same voltage than the conventional LIGBT.

• Proceedings of the KSME Conference
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• 2007.05a
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• pp.1277-1281
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• 2007

A Nano-tip as a cold field emitter for inducing a field emission current has manufactured in many ways. In the paper, the electrochemical etching method is used. Thus, in order to optimize the final shape as the field emitter, the reliable fabrication system for electrochemical etching was constructed. In addition, the effective parameters such as applied voltage, submerged length, meniscus height, electrolyte concentration and environmental condition(vibration, humidity, cut-off time) have investigated in detail. By controlling the parameters, reliable tungsten tip for field emitter was fabricated. And the fabricated tungsten tip was evaluated optically. Finally, the very sharp apex of the tungsten tip was observed with scanning electron microscope.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.33 no.2
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• pp.83-87
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• 2020

In this letter, we propose and analyze a new asymmetric structure that can be used for next-generation power semiconductor devices. We compare and analyze the electrical characteristics of the proposed device with respect to those of symmetric devices. The proposed device has a p-emitter on the right side of the cell. The peak electric field is reduced by the shielding effect caused by the p-emitter structure. Consequently, the breakdown voltage is increased. The proposed asymmetric structure has an approximately 100% higher Baliga's figure of merit (~94.22 MW/㎠) than the symmetric structure (~46.93 MW/㎠), and the breakdown voltage of the device increases by approximately 70%.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.07a
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• pp.318-321
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• 2002

This paper presents a proper condition to achieve high conversion efficiency using PC1D simulator on sri-crystalline Si solar cells. Various efficiency influencing parameters such as rear surface recombination velocity and minority carrier diffusion length in the base region, front surface recombination velocity, junction depth and doping concentration in the Emitter layer, BSF thickness and doping concentration were investigated. Optimized cell parameters were given as rear surface recombination of 1000 cm/s, minority carrier diffusion length in the base region 200 $\mu\textrm{m}$, front surface recombination velocity 100 cm/s, sheet resistivity of emitter layer 100 Ω/$\square$, BSF thickness 5 $\mu\textrm{m}$, doping concentration 5${\times}$10$\^$19/ cm$\^$-3/. Among the investigated variables, we learn that a diffusion length of base layer acts as a key factor to achieve conversion efficiency higher than 19 %.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.08a
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• pp.236-236
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• 2010

단일접합 $n^+-p/p^+$ (p-emitter) 및 $p^+-n/n^+$ (n-emitter) GaAs 태양전지 (Solar Cell)를 각각 제작하여, 그 소자특성을 비교 분석하였다. AM 1.5 (1 sun, $100\;mW/cm^2$) 표준광을 조사할 경우, p-emitter/n-emitter 소자의 개방회로전압 (Voc), 단락회로전류 (Jsc), 충전율 (FF), 효율 (Eff)은 각각 0.910/0.917 V, $15.9/16.1\;mA/cm^2$, 78.7/78.9, 11.4/12.1%로서, n-emitter 소자가 다소 크지만 거의 비슷한 값을 가지고 있었다. 태양전지의 집광 특성을 분석하기 위하여 조사광의 출력에 따른 태양전지의 소자 특성을 측정하였다. 조사광 강도가 높아짐에 따라 p-emitter 소자의 특성은 점진적으로 증가하는 반면, n-emitter는 1.3 sun에서 약 1.4 배의 최대 효율 (17%)을 나타내고 조사광이 더 증가함에 따라 급격히 감소하는 특성을 보여 주었다. (그림 참고) 본 연구에서 사용한 2종류 소자의 층구조는 서로 반대되는 대칭구조로서, 모두 가까이에 위치하고 있는 표면전극 (surface finger) 방향으로 소수전하 (minority carrier)가 이동하고 다수전하 (majority carrier)는 기판 (두께 $350\;{\mu}m$)을 통한 먼 거리의 후면전극 (back electrode)으로 표류 (drift)되도록 설계되어 있다. 이때, n-emitter에서는 이동도 (mobility)와 확산길이 (diffusion length)가 높은 전자가 후면전극으로 이동하기 때문에 적정밀도의 전자-정공 쌍 (EHP)이 여기될 경우에는 Jsc와 Eff가 극대화되지만, 조사광 강도 또는 EHP가 더 높아질 경우에는 직렬저항의 증가와 함께 전류-전압 (I-V)의 이상인자 (ideality factor)가 커짐으로서 FF와 효율이 급격히 감소한 결과로 분석된다. 현재 전산모사를 통한 자세한 분석을 진행하고 있으며, 본 결과는 효율 극대화를 위한 최적 층구조 및 도핑 밀도 설계에 활용할 수 있을 것으로 판단된다.

• Magazine of the Korean Society of Agricultural Engineers
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• v.41 no.3
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• pp.33-40
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• 1999

Variations in the discharge rates of drip emittes were examined to find the effects of operation pressure and the tube length and to evaluate performance of the emitters. Several point-source emitters were selected such as pressure compensated, anti-leak pressure compensated, turbulent flow regulated, flow regulated, ready-made dripper, and spaghetti. Combination of operation pressure and tube length were compared. The microirrigatioon system was operated at pressures of 0.5 , 1.0 , 1.5 and 2.0 bar. The discharge from emitters wer collected at every ten meters along the lateral tube and weighted. In order to evaluate the drip emitters performance coeffcient of discharge variation , statistical uniformity, and emission uniformity were calculated. No significant variation in discharge along drip tube resulted with all emitters. There is no trend of variatiiono of discharge rate from pressure compensated emitters with increase in operation pressures. But discharge rate from other types of emitters increased with increase in operation pressures. The nominal discharge of each emitter was secured at pressure of 1.0 bar, Evaluation using statiscal and emission uniformity coefficients indicated that most of the emitters excepts tubulent flow regulated emitter and ready-made dripper performed at excellent level.