• Transactions on Electrical and Electronic Materials
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• 제18권6호
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• pp.316-319
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• 2017

A new approach to improving the electrical characteristics and optical response of a polysilicon-based metal-semiconductor-metal (MSM) photodetector is proposed. To understand the cause of current restriction in the MSM photodetector, modified trap mechanisms are suggested, which include interfacial electron traps at the metal/polysilicon interface and silicon dangling bonds between silicon crystallite grains. Those traps were passivated using hydrogen ion implantation with subsequent post-annealing. Photodetectors that were ion-implanted under optima conditions exhibited improved photoconductivity and reduced dark current instability, implying that the hydrogen bonds in the polysilicon influence the simultaneous decreases in the density of dangling bonds at grain boundaries and the trapped positive charges at the contact interface.

• 한국전기전자재료학회논문지
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• 제33권4호
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• pp.255-262
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• 2020

Grain boundaries play a major role in determining device performance, particularly of polysilicon-based photodetectors. Through the post-annealing of as-deposited polysilicon and then, the analysis of electric behavior for a metal-polysilicon-metal (MSM) photodetector, we were able to identify the influence of grain boundaries. A modified model of polysilicon grain boundaries in the MSM structure is presented, which uses a crystalline-interfacial layer-SiO_x layer- interfacial layer-crystalline system that is similar to the Si-SiO₂ system in MOS device. Hydrogen passivation was achieved through a hydrogen ion implantation process and was used to passivate the defects at both interfacial layers. The thin SiO_x layer at the grain boundary can enhance the photosensitivity of an MSM photodetector by decreasing the dark current and increasing the light absorption.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2013년도 제45회 하계 정기학술대회 초록집
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• pp.224.2-224.2
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• 2013

본 연구에서는 CIGS박막 태양전지의 온도 및 시간 인가에 따른 전기적 특성 변화를 분석하였다. 실험에서는 온도 스트레스를 $25^{\circ}C$, $50^{\circ}C$, $100^{\circ}C$, $150^{\circ}C$, $200^{\circ}C$에서 각각 10시간씩 인가한 후에 Dark I-V와 C-V측정을 통해 전기적 특성 변화를 분석하였다. $25^{\circ}C$일 때를 초기 온도로 하여 특성을 측정한 것과 온도별로 노출시킨 후에 측정한 것을 비교했을 때 소자의 효율은 $100^{\circ}C$에서 감소하기 시작하였고, 인가한 온도가 높을수록 점점 많이 감소하는 모습이 나타났다. 이와 비슷하게 I-V그래프와 C-V그래프의 모습도 초기 값과 비교해서 변화하는 모습이 나타났고, 온도가 높아질수록 점점 변화하는 양이 증가하였다. I-V그래프에서 Diode ideality factor는 온도변화에 따라 초기 값 대비 증가하는 모습이 나타났다. 온도에 노출되기 전보다 노출된 후에 current와 capacitance가 감소하는 경향을 보이는데, 이는 온도의 영향으로 인해 소자의 결함이 증가하여 전하들의 반응에 영향을 주었기 때문으로 판단된다.

• Current Optics and Photonics
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• 제5권2호
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• pp.129-133
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• 2021

This study observed the performance of an InAs/GaSb type-II superlattice photodiode with a p-i-n structure for mid-wavelength infrared detection. The 10 ML InAs/10 ML GaSb type-II superlattice photodiode was grown using molecular beam epitaxy. The cutoff wavelength of the manufactured photodiode with Si3N4 passivation on the mesa sidewall was determined to be approximately 5.4 and 5.5 ㎛ at 30 K and 77 K, respectively. At a bias of -50 mV, the dark-current density for the Si3N4-passivated diode was measured to be 7.9 × 10-5 and 1.1 × 10-4 A/㎠ at 77 K and 100 K, respectively. The differential resistance-area product RdA at a bias of -0.15 V was 1481 and 1056 Ω ㎠ at 77 K and 100 K, respectively. The measured detectivity from a blackbody source at 800 K was calculated to be 1.1 × 1010 cm Hz1/2/W at zero bias and 77 K.

• 한국방사선학회논문지
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• 제3권3호
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• pp.27-35
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• 2009

본 연구에서는 적층 구조를 이용하여 누설전류를 저감 시키는 기술을 적용하여 PIB(Particle-In-Binder) 법을 이용한 방사선 영상 센서의 변환 물질을 개발하였다. 이는 디지털 방사선 영상 검출기의 두 가지 방식 중 하나인 직접방식에 사용되는 핵심 소자로 기존의 a-Se을 대체하여 더욱 효율이 높은 후보 물질들이 연구되어지는 가운데 태양전지와 반도체 분야에서 이미 많이 사용되어온 이종접합을 이용해 누설 전류를 저감 시키는데 그 목적이 있다. 본 연구에서 사용되는 PIB 제작 방법은 검출 물질 제작이 용이하고 높은 수율과 대면적의 검출기 제작에 적합하나 높은 누설 전류가 의료 영상에 있어서 문제가 되어 오고 있다. 이러한 단점을 보완하기 위해 적층 구조를 이용하여 누설 전류를 저감시킨다면 PIB법을 이용하여 간편하게 향상된 효율의 디지털 방사선 검출기를 제작 할 수 있다고 사료 되어 진다. 본 연구에서는 누설 전류와 민감도에 대한 전기적 신호를 측정하여 제작된 적층 구조의 방사선 검출 물질의 특성 평가가 이루어 졌다.

• 한국진공학회지
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• 제15권2호
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• pp.216-222
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• 2006

InGaAs/GaAs 양자 우물 내에 삽입된 InAs 양자점으로 구성된 5층의 흡수층과 $Al_{0.3}Ga_{0.7}As/GaAs$ SL (superlattice) 암전류 장벽층을 갖는 QDIP (quantum dot infrared photodetector) 구조에 대한 수소 RF 플라즈마에 의한 수소화 처리가 QDIP의 전기적. 광학적 특성에 미치는 영향에 대해 연구하였다. RF 플라즈마 수소화 처리는 양자점의 밴드구조에 영향을 미치지 않았으며 $Al_{0.3}Ga_{0.7}As/GaAs$ SL 암전류 장벽층 내의 결함 제거 및 QDIP 구조 내 결함 생성을 동시에 유도함으로써 QDIP의 전기적 특성 향상은 수소 플라즈마 처리시간의 함수임을 알았다. 20 W의 수소 RF 플라즈마를 사용했을 때, 10분간의 플라즈마 조사가 가장 좋은 전기적 특성을 제공하여 높은 암전류 때문에 원시료에서는 측정 할 수 없었던 광전류 신호를 측정 할 수 있었다.

• 대한의용생체공학회:학술대회논문집
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• 대한의용생체공학회 1997년도 춘계학술대회
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• pp.457-460
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• 1997

The photoconductive gain mechanism in various types of hydrogenated amorphous silicon devices, such as p-i-n, n-i-n and n-i-p-i-n structures was investigated in connection with applications to radiation detection. We measured the photoconductive gain in two time scales: one for short pulses of visible light $(<1{\mu}sec)$ which simulate the transit of energetic charged particles, and the other for rather long pulses of light $(\sim1msec)$ which simulate x-ray exposure in medical imaging. We used two definitions of photoconductive gain: current gain and charge gain which is an integration of the current gain. We found typical charge gains of $3\sim9$ for short pulses and a few hundred for long pulses at a dark current density level of $10mA/cm^2$.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2003년도 춘계학술대회 논문집 센서 박막재료 반도체 세라믹
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• pp.71-74
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• 2003

Photoconductor for direct detection fiat-panel imager present a great materials challenge, since their requirement include high X-ray absorption, ionization and charge collection, low leakage current and large area deposition, CdTe is practical material. We report studies of detector sensitivity, That is an CdTe with $5{\mu}m$ thickness on glass. That is hybrid layer of depositting ZnS:AgCl phosphor with $100{\mu}m$ on CdTe. The leakage current of hybrid is similar to it of a-Se, but photocurrent is larger than a-Se. Both of them have high spatial resolution, but hybrid has higher sensitivity than a-Se at comparable bias voltage.

• Current Photovoltaic Research
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• 제2권3호
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• pp.135-139
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• 2014

Different power output of solar cells can be observed at high-temperature regions such as desert areas. In this study, performance dependence on operating temperature of crystalline silicon solar cells with different emitter types was analyzed. Based on the light current-voltage (LIV) measurement, temperature coefficients of short-circuit current density ($J_{SC}$), open-circuit voltage ($V_{OC}$), fill factor (FF) and power conversion efficiency were measured and compared for two groups of crystalline silicon solar cells with different emitter types. One group had homogeneously doped (conventional) emitter and another selectively doped (selective) emitter. Varying the operating temperature from 25 to 40, 60, and $80^{\circ}C$, LIV characteristics of the cells were measured and the properties of saturation current densities ($J_0$) were extracted from dark current-voltage (DIV) curve. From the DIV data, effect of temperature on the performance of the solar cells with different electrical structures for the emitter was analyzed. Increasing the temperature, both emitter structures showed a slight increase in $J_{SC}$ and a rapid degradation of $V_{OC}$. FF and power conversion efficiency also decreased with the increasing temperature. The degrees of $J_{SC}$ increase and $V_{OC}$ degradation for two groups were compared and explained. Also, FF change was explained by series and shunt resistances from the LIV data. It was concluded that the degradation of solar cells shows different values at different temperatures depending on the emitter type of solar cells.

• 한국표면공학회:학술대회논문집
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• 한국표면공학회 2014년도 추계학술대회 논문집
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• pp.273-273
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• 2014

Quantum-dot sensitized solar cells (QDSCs) are an emerging class of solar cells owing to their easy fabrication, low cost and material diversity. Despite of the fact that the maximum conversion efficiency of QDSCs is still far less than that of Dye-Sensitized Solar Cells (>12 %), their unique characteristics like Multiple Exciton Generation (MEG), energy band tune-ability and tendency to incorporate multiple co-sensitizers concurrently has made QDs a suitable alternative to expensive dyes for solar cell application. Lead Sulfide (PbS) Quantum dot sensitized solar cells are theoretically proficient enough to have a photo-current density ($J_{sc}$) of $36mA/cm^2$, but practically there are very few reports on photocurrent enhancement in PbS QDSCs. Recently, $Hg^{2+}$ incorporated PbS quantumdots and Cadmium Sulfide (CdS) co-sensitized PbS solarcells are reported to show an improvement in photo-current density ($J_{sc}$). In this study, we explored the efficacy of $In_2S_3$ as an interfacial layer deposited through SILAR process for PbS QDSCs. $In_2S_3$ was chosen as the interfacial layer in order to avoid the usage of hazardous CdS or Mercury (Hg). Herein, the deposition of $In_2S_3$ interfacial layer on $TiO_2$ prior to PbS QDs exhibited a direct enhancement in the photo-current (Isc). Improved photo-absorption as well as interfacial recombination barrier caused by $In_2S_3$ deposition increased the photo-current density ($J_{sc}$) from $13mA/cm^2$ to $15.5mA/cm^2$ for single cycle of $In_2S_3$ deposition. Increase in the number of cycles of $In_2S_3$ deposition was found to deteriorate the photocurrent, however it increased $V_{oc}$ of the device which reached to an optimum value of 2.25% Photo-conversion Efficiency (PCE) for 2 cycles of $In_2S_3$ deposition. Effect of Heat Treatment, Normalized Current Stability, Open Circuit Voltage Decay and Dark IV Characteristics were further measured to reveal the characteristics of device.