• Journal of the Korean Institute of Telematics and Electronics
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• v.18 no.4
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• pp.49-61
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• 1981

A generally applicable computer simulation program for diffused silicon solar cells has been developed on the basis of the experimental results. The program can be easily used to obtain the spectral response and I-V characteristics for N+P, P+N N+PP+, P+NN+cells by changing various input parameters. The insolated spectra can be taken from AMI and constant intensity and GE - ELH lamp light sources. The options for AR coating are Si3N4 film and materials with constant reflectance including zero reflectance for ideal case. The computer simulation demonstrates successful results compared with the measured values for the short circuit current, open circuit voltage, efficiency, spectral response, quantum efficiency, I-V characteristics, etc. This program was used to optimize doping concentration, cell thickness, light concentration, junction depth, and to obtain the limit values for front surface recornbination velocity, effective carrier life time in the depletion regions and shunt resistance, and also to drive the changing rate in conversion efficiency depending on operation temperature, series resistance and electric field strength in N+P+ bulk regions.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.11a
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• pp.94-94
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• 2008

We have performed simulation for Junction Field Effect Transistor(JFET) using Silvco to improve its electrical properties. The device structure and process conditions of Si-control JFET(Si-JFET) were determined to set its cut off voltage and drain current(at Vg=0V) to -0.5V and $300{\mu}A$, respectively. From electrical property obtained at various implantation energy, dose, and drive-in conditions of p-gate doping, we found that the drive in time of p-type gate was the most determinant factor due to severe diffusion. Therefore we newly designed SiGe-JFET, in which SiGe layer is to epitaxial layers placed above and underneath of the Si-channel. The presence of SiGe layer lessen the p-type dopants (Boron) into the n-type Si channel the phenomenon would be able to enhance the structural consistency of p-n-p junction. The influence of SiGe layer will be discussed in conjunction with boron diffusion and corresponding I-V characteristics in comparison with Si-control JFET.

• Korean Chemical Engineering Research
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• v.48 no.5
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• pp.654-659
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• 2010

We have investigated the effect of rubrene-doped CuPc hole transport layer on the performance of p-i-n type bulk hetero-junction photovoltaic device with a structure of ITO/PEDOT:PSS/CuPc: rubrene/CuPc:C60(blending ratio 1:1)/C60/BCP/Al and have evaluated the current density-voltage(J-V) characteristics, short-circuit current($J_{sc}$), open-circuit voltage($V_{oc}$), fill factor(FF), and energy conversion efficiency(${\eta}_e$) of the device. By rubrene doping into CuPc hole transport layer, absorption intensity in absorption spectra decreased. However, the performance of p-i-n organic type bulk hetero-junction photovoltaic device fabricated with crystalline rubrene-doped CuPc was improved since rubrene shows higher bandgap and hole mobility compared to CuPc. Increased injection currents have effected on the performance improvement of the present device with energy conversion efficiency(${\eta}_e$) of 1.41%, which is still lower value compared to silicone solar cell and many efforts should be made to improve organic photovoltaic devices.

• Journal of Satellite, Information and Communications
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• v.9 no.3
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• pp.15-21
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• 2014

An electrostatic discharge (ESD) protection device, so called, N-type embedded silicon controlled rectifier (NESCR), was analyzed for high voltage operating I/O applications. A conventional NESCR standard device shows typical SCR-like characteristics with extremely low snapback holding voltage, which may cause latch-up problem during normal operation. However, our modified NESCR_CPS_PPW device with proper junction/channel engineering such as counter pocket source (CPS) and partial P-well structure demonstrates highly latch-up immune current-voltage characteristics with high snapback holding voltage and on-resistance.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.204-205
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• 2011

In thin film silicon solar cells, p-i-n structure is adopted instead of p/n junction structure as in wafer-based Si solar cells. PECVD is a most widely used thin film deposition process for a-Si:H or ${\mu}c$-Si:H solar cells. For best performance of thin film silicon solar cell, the dopant profiles at p/i and i/n interfaces need to be as sharp as possible. The sharpness of dopant profiles can easily achieved when using multi-chamber PECVD equipment, in which each layer is deposited in separate chamber. However, in a single-chamber PECVD system, doped and intrinsic layers are deposited in one plasma chamber, which inevitably impedes sharp dopant profiles at the interfaces due to the contamination from previous deposition process. The cross-contamination between layers is a serious drawback of a single-chamber PECVD system in spite of the advantage of lower initial investment cost for the equipment. In order to resolve the cross-contamination problem in single-chamber PECVD systems, flushing method of the chamber with NH3 gas or water vapor after doped layer deposition process has been used. In this study, a new plasma process to solve the cross-contamination problem in a single-chamber PECVD system was suggested. A single-chamber VHF-PECVD system was used for superstrate type p-i-n a-Si:H solar cell manufacturing on Asahi-type U FTO glass. A 80 MHz and 20 watts of pulsed RF power was applied to the parallel plate RF cathode at the frequency of 10 kHz and 80% duty ratio. A mixture gas of Ar, H2 and SiH4 was used for i-layer deposition and the deposition pressure was 0.4 Torr. For p and n layer deposition, B2H6 and PH3 was used as doping gas, respectively. The deposition temperature was $250^{\circ}C$ and the total p-i-n layer thickness was about $3500{\AA}$. In order to remove the deposited B inside of the vacuum chamber during p-layer deposition, a high pulsed RF power of about 80 W was applied right after p-layer deposition without SiH4 gas, which is followed by i-layer and n-layer deposition. Finally, Ag was deposited as top electrode. The best initial solar cell efficiency of 9.5 % for test cell area of 0.2 $cm^2$ could be achieved by applying the in-situ plasma cleaning method. The dependence on RF power and treatment time was investigated along with the SIMS analysis of the p-i interface for boron profiles.

• Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
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• 2002.02a
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• pp.127-130
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• 2002

Step-edge dc SQUID magnetometers have been fabricated on sapphire substrate. Ce$O_{2}$ buffer layer and $YBa_{2}$$Cu_{3}$ $O_{7}$(YBCO) films were deposited in-situ on the low angle (~$35^{\circ}$)steps formed on the substrates. Typical 5-$\mu$m-wide junction has $R_{N}$ of 4 $\Omega$ and $I_{c}$ of 60 $\mu$A with $I_{c}$$R_{N}$ product of 240 $\mu$V at 77 K. According to applied bias current, depth of voltage modulation was changed and maximum voltage was measured 100~300 fT/$\checkmark$ Hz at 100 Hz, and about 1.5 pT/$\checkmark$ Hz at 1 Hz. For ac bias reversal method, field noise was decreased in the 1/f region. The QRS peak of magneto-cardiogram was measured 50 pT in the magnetically shielded room.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.29A no.10
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• pp.29-34
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• 1992

JFET's with gate lengths ranging from 1$\mu$m to 8.3$\mu$m are successfully fabricated on InP substrate where the long haul (1.3$\mu$m~8.3$\mu$m) OEIC's(OptoElectronic Integrated Circuits) have been made. The pn junction of InP JFET's is made by co-implantation and RTA process. JFET's have etched-mesa-gate structure and the maximum gm larger than 90mS/mm was measured and this is the highest record in JFET's of such structure without S/D n$^{+}$ ion implantation. To maintain maximum g$_m$ should be well controlled the overetch of n-layer which inevitably occurs during etching off the unused p-layer. The I-V characteristic is checked during p-layer etch, for this purpose. A dc voltage gain of 11 is obtained from a preamplifier circuit thus fabricated.

• Journal of IKEEE
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• v.17 no.2
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• pp.182-188
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• 2013

Using a ceramic target ZnO:In with In doping concentration of 2%, hetero-junctions of n-ZnO:In/p-Si and p-ZnO:(In, N)/n-Si were fabricated by depositing Indium doped n - type ZnO (ZnO:In or IZO) and Indium-nitrogen co-doped p - type ZnO (ZnO:(In, N)) films on wafers of p-Si (100) and n-Si (100) by DC magnetron sputtering, respectively. These films with the best electrical and optical properties were then obtained. The micro-structural, optical and electrical properties of the n-type and p-type semiconductor thinfilms were characterized by X-ray diffraction (XRD), RBS, UV-vis; four-point probe resistance and room-temperature Hall effect measurements, respectively. Typical rectifying behaviors of p-n junction were observed by the current-voltage (I-V) measurement. It shows fairly good rectifying behavior with the fact that the ideality factor and the saturation current of diode are n=11.5, Is=1.5108.10-7 (A) for n-ZnO:In/p-Si hetero-jucntion; n=10.14, Is=3.2689.10-5 (A) for p-ZnO:(In, N)/n-Si, respectively. These results demonstrated the formation of a diode between n-type thin film and p-Si, as well as between p-type thin film and n-Si..

• Proceedings of the KIEE Conference
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• 2002.07c
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• pp.1587-1589
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• 2002

Photovoltaics is considered as one of the most promising new energy technology, because its energy source is omni present, pollution-free and inexhaustive. It is agreed that these solar cells must be thin film type because thin film process is cost-efficive in the fact that it uses much less raw materials and can be continuous. The defect chalcopyrite material $CuIn_3Se_5$ has been identified as playing an essential role in efficient photovoltaic action in $CuInSe_2$-based devicesm It has been reported to be of n-type conductivity, forming a p-n junction with its p-type counterpart CuInSe2. Because the most efficient cells consist of the $Cu(In,Ga)Se_2$ quarternary, knowledge of some physical properties of the Ga-containing defect chalcopyrite $Cu(In,Ga)_3Se_5$ may help us better understand the junction phenomena in such devices.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.429-429
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• 2012

본 연구에서는 분자선 박막 성장법(MBE)으로 성장된 GaAs single junction solar cell의 광학적 특성 변화를 photoreflectance (PR)을 이용하여 연구하였다. 본 연구에 사용된 태양전지 구조는 n+-GaAs (100)기판 위에 n+-GaAs buffer를 200 nm 성장 후 그 위에 i-GaAs 250 nm와 p+-GaAs 200 nm 성장 하였다. 상온에서 PR 측정 결과, 변조빔 세기가 증가할수록 Franz-Keldysh oscillation (FKO)의 주파수가 증가하는 현상이 관측되었다. 이는 변조빔의 세기가 강해질수록 광케리어수의 증가로 인한 스크리닝 효과에 기인한 것으로 사료된다. 아울러 Fast Fourier transform (FFT) 결과, 변조빔의 세기가 약할 때는 세 개의 주된 피크가 나타났으며, 이러한 현상은 GaAs에서 가전자대의 heavy hole (HH)과 light hole (LH)의 전이로 인해 나타나는 FKO 신호가 중첩되어 HH과 LH 피크가 HH과 HH-,LH과 LH-로 나뉘어진 것으로 사료된다. 여기광의 세기가 $1.40mW/cm^2$ 이상일 때는 주된 세 개 피크 이외에 부가적인 피크가 상대적으로 고 주파수 영역에서 관측되었다. 이러한 고주파수 영역에서의 나타나는 FKO 주파수는 시료의 내부전기장이 여기광의 세기가 증가할수록 감소하는 결과로 사료된다.