• E2M - 전기 전자와 첨단 소재
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• 제11권11호
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• pp.37-45
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• 1998

In this paper, present status of super high-efficiency tandem solar cells has been reviewed and key issues for realizing super high-efficiency have also been discussed. In addition, the terretrial R&D activities of tandem cells, in the New Sunshine Program of MITI(Ministry of International Trade and Industry) and NEDO(New Energy and Industrial Technology Development Organization) in Japan are reviewed briefly. The mechanical stacked 3-junction cells of monolithically grown InGaP/GaAs 2-junction cells and InGaAs cells have reached the highest efficiency achieved in Japan of 33.3% at 1-sun AM1.5. This paper also reports high-efficiency InGaP/GaAs 2-junction solar cells with a world-record efficiency of 26.9% at AM0, 28$^{\circ}C$ and radiation damage recovery phenomena of the tandem cell performance due to minority-carrier injection under light illumination or forward bias, which causes defect annealing in InGaP top cells. Future prospects for realizing super-high efficiency and low-cost tandem solar cells are also described.

• 한국시뮬레이션학회논문지
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• 제9권4호
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• pp.67-75
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• 2000

Often system analysts are interested in the estimation of percentile for system performance. For instance, in PERT network system, the percentile that the project. Typically the control variate method is used to reduce the variability of mean response using the correlation between the response and the control variates with a little additional cost during the course of simulation. In the same spirit, we apply this method to estimate the percentile of project completion time in PERT system, and evaluate the efficiency of the controlled estimator for its percentile.1 Simulation results indicate that the controlled estimators are more effective in reducing the variances of estimators than the simple estimators, however those tend to a little underestimate the percentiles for some critical values. We need more simulation experiments to examine such a kind of bias problem. We expect this research presents a step forward in the area of variance reduction techniques of stochastic simulation.

• 전자공학회논문지A
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• 제33A권4호
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• pp.106-111
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• 1996

Schottky diodes are fabricated on laser annealed and unannealed polysilicon substrate and their electrical characteristics are studied and analyzed. Current of laser annealed devices are larger than that of unannealed devices because of grain growth, decrease of grain boundary and trap density, lowering of grain boundary barrier height, decrease of dopant segregation. At low forward bias (<0.7V), currents of unanealed devices are larger. Soft breakdown voltages of laser annealed devices are larger than that of unannealed devices.

• Transactions on Electrical and Electronic Materials
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• 제3권1호
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• pp.38-41
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• 2002

We have investigated current-voltage-luminance characteristics of organic light-emitting diodes based on TPD/Alq$_3$organics depending on the application of forward-backward bias voltage. Luminance-voltage characteristics and luminous efficiency were measured at the same time when the current-voltage characteristics were measured. We have observed that the current-voltage characteristics shows a reversible current maxima at low voltage, which is possibly not related to the emission from Alq$_3$. Current-voltage-luminance characteristics imply that the conduction luminance mechanism at low voltage is different from that of high voltage one.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2001년도 추계학술대회 논문집
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• pp.130-132
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• 2001

We have investigated current-voltage(I-V) characteristics of organic light-emitting diodes based on TPD/Alq$_3$ organics depending on the application of forward-reverse bias voltage. Luminance-voltage characteristics and luminous efficiency were measured at the same time when the I-V characteristics were measured. We have observed that the I-V characteristics shows a current mxima at low voltage, which is possibly not related to the emission from Alq$_3$.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2004년도 하계학술대회 논문집 Vol.5 No.1
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• pp.17-19
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• 2004

The electrical properties of gate oxides grown in two different processes, which are in 10% nitrous oxide($N_2O$) and in dry oxygen, have been experimentally investigated and compared. It has been observed that the $SiC-SiO_2$ interface-trap density(Dit) measured in nitrided gate oxide has been tremendously reduced, compared to the density obtained from gate oxide grown in dry oxygen. The beneficial effects of nitridation on gate oxides also have been demonstrated in the values of total near interface-trap density and of forward-bias breakdown field. The reasons of these improvements have been explained.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2004년도 하계학술대회 논문집 Vol.5 No.2
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• pp.1050-1053
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• 2004

Many organic materials have been synthesized and extended efforts have been made to obtain high performance electroluminescence(EL) devices, since the first report of the light-emitting diodes based on Alq3. BECCP[bis(3-N-ethylcarbazolyl)cyanoterephthalidene] is a new luminescent material having cyano as an electron acceptor part and carbazole moiety as an electron donor part. The BECCP material shows blue PL and EL spectra of the device at about 480nm and in the ITO/BECCP/Al device shows typical rectifying diode characteristics. We have introduced Alq3 between the electrode and BECCP, and obtained more intensive rectifying diode characteristics in forward and reverse bias.

• 한국진공학회지
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• 제19권2호
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• pp.134-140
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• 2010

Metal-organic chemical vapour deposition (MOCVD)법으로 성장된 $In_{0.5}(Ga_{1-x}Al_x)_{0.5}P$/GaAs 이중 이종접합 구조의 특성을 contactless electroreflectance (CER) 분광법으로 조사하였다. CER 측정은 변조전압($V_{ac}$), 온도 및 dc 바이어스 전압($V_{bias}$)의 함수로 수행하였다. 상온에서는 5개의 신호가 관측되었는데, 이 신호들은 각각 GaAs, $In_{0.5}Ga_{0.5}P$, $In_{0.5}(Ga_{0.73}Al_{0.27})_{0.5}P$, $In_{0.5}(Ga_{0.5}Al_{0.5})_{0.5}P$ 및 $In_{0.5}(Ga_{0.2}Al_{0.8})_{0.5}P$ 전이에 관련된 것이다. CER 스펙트럼의 온도 의존성으로부터 Varshni 계수 및 평탄인 자를 구하였다. 그리고 인가전압에 따른 신호의 진폭은 순방향 바이어스 전압 인가시 점차로 감소하나, 역방향 바이어스 전압 인가시에는 반대의 경향을 보였다.

• 대한전자공학회논문지SD
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• 제39권10호
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• pp.25-34
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• 2002

본 논문에서는 코발트 실리사이드가 형성된 얕은 p+-n과 n+-p 접합의 전류-전압 특성을 분석하여 silicidation에 의해 형성된 Schottky contact 면적을 구하였다. 역방향 바이어스 영역에서는 Poole-Frenkel barrier lowering 효과가 지배적으로 나타나서 Schottky contact 효과를 파악하기가 어려웠다. 그러나 Schottky contact의 형성은 순방향 바이어스 영역에서 n+-p 접합의 전류-전압 (I-V) 동작에 영향을 미치는 것으로 확인되었다. 실리사이드가 형성된 n+-p 다이오드의 누설전류 증가는 실리사이드가 형성될 때 p-substrate또는 depletion area로 코발트가 침투퇴어 Schottky contact을 형성하거나 trap들을 발생시켰기 때문이다. 분석결과 perimeter intensive diode인 경우에는 silicide가 junction area까지 침투하였으며, area intensive junction인 경우에는 silicide가 비록 공핍층이나 p-substrate까지 침투하지는 않았더라도 공핍층 근처까지 침투하여 trap들을 발생시켜 누설전류를 증가시킴을 확인하였다. 반면 p+-n 다이오드의 경우 Schottky contact이발생하지 않았고 따라서 누설전류도 증가하지 않았다. n+-p 다이오드에서 실리사이드에 의해 형성된 Schottky contact 면적은 순방향 바이어스와 역방향 바이어스의 전류 전압특성을 동시에 제시하여 유도할 수 있었고 전체 접합면적의 0.01%보다 작게 분석되었다.

• 전자공학회논문지
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• 제54권1호
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• pp.33-38
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• 2017

본 논문에서는 채널 당 3.125-Gb/s 동작 속도를 갖는 4-채널 공통-캐소드 VCSEL 다이오드 드라이버 어레이 칩을 구현하였다. 스위칭 동작하는 메인 드라이버의 동작속도 향상을 위해, 액티브 인덕터를 사용한 전치증폭단과 이퀄라이저 기능을 탑재한 입력버퍼단으로 구성하였다. 특히 개선된 입력버퍼단의 경우, 주파수 영역의 피킹으로 대역폭 증대뿐 아니라 비교적 적은 전류로 동작하도록 설계하였다. 본 논문에서 사용한 VCSEL 다이오드는 2.2 V 순방향 전압과 $50{\Omega}$ 기생저항 및 850 fF 기생 캐패시턴스를 갖는다. 또한, 3.0 mA 변조전류 및 3.3 mA 바이어스 전류로 동작하므로, 두 개의 독립적인 전류소스로 구동 가능한 current steering 기반의 메인 드라이버를 설계하였다. 제안한 4-채널 광 송신기 어레이 칩은 $0.11-{\mu}m$ CMOS 공정을 이용하여 제작하였다. 칩 코어의 면적은 $0.15{\times}0.18{\mu}m^2$ 이며, 채널 당 22.3 mW 전력소모를 갖는다.