• 한국정보통신학회논문지
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• 제11권2호
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• pp.330-336
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• 2007

본 논문에서는 디지털 의료 영상 및 진단 분야 그리고 산업용으로도 활용 가능한 싱글 포톤 계수형 영상센서를 $0.18{\mu}m$ triple-well CMOS(Complementary Metal Oxide Semiconductor) 공정을 사용하여 설계하였다. 설계된 Readout 칩용 싱글 픽셀은 디지털 X-ray 이미지 센서모듈을 간단화 하기 위해 단일 전원전압을 사용하였으며, Preamplifier의 출력 전압인 signal voltage(${\Delta}Vs$)를 크게 하기 위해 Folded Cascode CMOS OP amp를 이용한 Preamplifier를 설계하였으며, 기존의 Readout 칩 외부에서 인가하던 threshold voltage를 Readout 칩 내부에서 생성해 줄 수 있도록 Externally Tunable Threshold Voltage Generator 회로를 새롭게 제안하였다. 그리고, Photo Diode에서 발생하는 Dark Current Noise를 제거하기 위한 Dark Current Compensation 회로를 제안하였으며, 고속 counting이 가능하고, layout 면적이 작은 15bit LFSR(Linear Feedback Shift Resister) Counter를 설계하였다.

• ETRI Journal
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• 제28권5호
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• pp.555-560
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• 2006

A PIN photodiode having a low dark current of 1.35 nA and a high external quantum efficiency of 95.3% fabricated for a passive optical network receiver. As the current was increased under a high voltage of 38 V and a temperature of $190^{\circ}C$, it was observed that there is a threshold current at 11 mA which induces a junction failure. Experimental data suggest that the junction failure occurs due to the crystal breaking at the end facet as a result of thermal heat or energetic carriers. This threshold behavior of junction failure is a valuable observation for the safe treatment of photodiodes. As long as the current is limited below the threshold currents, we have not observed failure events of our photodiodes.

• 한국광학회:학술대회논문집
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• 한국광학회 2004년도 제15회 정기총회 및 동계학술발표회
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• pp.288-289
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• 2004

The performance of the InGaAs/InP avalanche photodidodes operated in Geiger-mode was investigated for 1550nm wavelengths at room temperature. We find the optimal operating points where the high quantum detection efficiency and low dark current are achieved. For the optical pulse detection, the gated-mode is used to reduce the dark current.

• E2M - 전기 전자와 첨단 소재
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• 제8권4호
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• pp.426-433
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• 1995

Effect of boron in GaAs have been investigated by photo induced current transient spectroscopy(PICTS). The starting material was undoped liquid encapsulated Czochralski(LEC) semi insulating GaAs and boron ion implantation at 150keV energy was conducted with dose of 10$\^$12/ and 10$\^$13/ions/cm$\^$2/. In ion implanted samples, the peaks related arsenic vacancy(V$\_$As/) were decreased but complex lattice defect was increased with annealing temperature. U band was observed at ion implanted(10$\^$13/ ions/cm$\^$2/) and thermally treated(550.deg. C) sample. More negative peak was detected after annealing at temperature between 600 and 700.deg. C. The measurement of dark current showed that the formation of B$\_$GA/-V$\_$As/, complex defect and complex lattice defect by ion implantation were a reasonable explanation for the decrease in dark current.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2002년도 하계학술대회 논문집 Vol.3 No.2
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• pp.813-816
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• 2002

We investigate the junction between CdZnTe and a variety of metals with the aim of determining whether the choice of metal can improve the performance of X-ray image detectors, in particular minimizing the dark current. The samples consist of $5{\mu}m$ thick CdZnTe with top electrodes formed from In, Al, and Au. For each metal, current transients following application of valtages from -10V to 10V are measured for up to 1 hour. We find that dark currents depending on the metal used. The current is controlled by hole injection at the metal-CdZnTe junction and there is consistent trend with the metal's work function possibly and it seems that metal to CdZnTe layer junction is ohmic contact.

• Current Optics and Photonics
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• 제4권3호
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• pp.193-199
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• 2020

In this paper we propose a dark-field digital holographic microscopy system based on 360-degree oblique illumination. This setup is constructed without using a dark-field objective. The principle of 360-degree oblique illumination of vortex beam and dark-field digital holographic microscopy are introduced theoretically and experimentally. By analyzing the reconstructed image of a dark-field digital hologram of a USAF 1951 target, it is proved that the imaging resolution can be improved by this method. And also, comparison and analysis are made on the reconstructed image of a bright-dark field digital hologram of a pumpkin stem slice, the result shows that the imaging contrast is also enhanced with this method, and it is effective for dark-field digital holographic microscopy imaging of large transparent biological samples.

• 전자공학회논문지A
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• 제29A권9호
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• pp.56-64
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• 1992

Because of a small bandgap energy, a high doping density, and a low operating temperature, the dark current in HgCdTe photodiode is almost composed of a tunneling current. The tunneling current is devided into an indirect tunneling current via traps and a band-to-band direct tunneling current. The indirect tunneling current dominates the dark current for a relatively high temperature and a low reverse bias and forward bias. For a low temperature and a high reverse bias the direct tunneling current dominates. In this paper, to verify the tunneling currents in HgCdTe photodiode, the new tunneling-recombination equation via trap is introduced and tunneling-recombination current is calculated. The new tunneling-recombination equation via trap have the same form as SRH (Shockley-Read-Hall) generation-recombination equation and the tunneling effect is included in recombination times in this equation. Chakrabory and Biswas's equation being introduced, band to band direct tunneling current are calculated. By using these equations, HgCdTe (mole fraction, 0.29 and 0.222) photodiodes are analyzed. Then the temperature dependence of the tunneling-recombination current via trap and band to band direct tunneling current are shown and it can be known what is dominant current according to the applied bias at athe special temperature.

• Transactions on Electrical and Electronic Materials
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• 제10권6호
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• pp.189-192
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• 2009

The leakage current in a CMOS image sensor (CIS) can have various origins. Leakage current investigations have focused on such things as cobalt-salicide, source and drain scheme, and shallow trench isolation (STI) profile. However, there have been few papers examining the effects on leakage current of nitride stringers that are formed by gate sidewall etching. So this study reports the results of a series of experiments on the effects of a nitride stringer on real display images. Different step heights were fabricated during a STI chemical mechanical polishing process to form different nitride stringer sizes, arsenic and boron were implanted in each fabricated photodiode, and the doping density profiles were analyzed. Electrons that moved onto the silicon surface caused the dark leakage current, which in turn brought up the speckle defect on the display image in the CIS.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2006년도 하계학술대회 논문집 Vol.7
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• pp.75-76
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• 2006

In this paper, the polycrystalline silicon photodiodes utilizing vertically directed current path are investigated. The location of electrodes is considered with the grain direction and the current path. The relationships between grain boundaries and characteristics of photodiode are simulated to apply the vertically grown polycrystalline silicon to photodiodes. From the results, the vertically grown polycrystalline silicon photodiode is a potential candidate for CMOS image sensor. However, the increment of dark current related to grain boundaries should be reduced.

• Journal of information and communication convergence engineering
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• 제5권2호
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• pp.116-120
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• 2007

In this paper, the image sensor using the a-Si:H TFT is proposed. The optimum amorphous silicon thin film is deposited using plasma enhanced chemical vapor deposition (PECVD). TFT and photodiode both with the thin film are fabricated and form image sensor. The photodiode shows that $I_{dark}\;is\;{\sim}10^{-13}\;A,\;I_{photo}\;is\;{\sim}10^{-9}\;A\;and\;I_{photo}/I_{dark}\;is\;{\sim}10^4$, respectively. In the case of a-Si:H TFT, it indicates that $I_{on}/I_{off}\;is\;10^6$, the drain current is a few ${\mu}A\;and\;V_{th}\;is\;2{\sim}4$ volts. For the analysis on the fabricated image sensor, the reverse bias of -5 volts in ITO of photodiode and $70 {\mu}sec$ pulse in the gate of TFT are applied. The image sensor with good property was conformed through the measured photo/dark current.