• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.19 no.12
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• pp.1140-1143
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• 2006

We report on the fabrication of P3HT-based thin-film transistors (TFTs) for liquid crystal display that consist of $NiO_x$, poly-vinyl phenol (PVP), and Ni for the source-drain (S/D) electrodes, gate dielectric layer, and gate electrode, respectively The $NiO_x$ S/D electrodes of which the work function is well matched to that of P3HT are deposited on a P3HT channel by electron-beam evaporation of NiO powder. The maximum saturation current of our P3HT-based TFT is about $15{\mu}A$ at a gate bias of -30 V showing a high field effect mobility of $0.079cm^2/Vs$ in the dark, and the on/off current ratio of our TFT is about $10^5$. It is concluded that jointly adopting $NiO_x$ for the S/D electrodes and PVP for gate dielectric realizes a high-quality P3HT-based TFT.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.61 no.6
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• pp.817-820
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• 2012

We studied p-type capacitance characteristics of ZnO thin-film transistors (TFT's), grown by metal organic chemical vapor deposition (MOCVD). We compared two ZnO TFT's: one grown at $450^{\circ}C$ and the other grown at $350^{\circ}C$. ZnO grown at $450^{\circ}C$ showed smooth capacitance profile with electron density of $1.5{\times}10^{20}cm^{-3}$. In contrast, ZnO grown at $350^{\circ}C$ showed a capacitance jump when gate voltage was changed to negative voltages. Current-voltage characteristics measured in the two samples did not show much difference. We explain that the capacitance jump is related to p-type ZnO layer formed at the $SiO_2$ interface. Current-voltage and capacitance-voltage data support that p-type characteristics are observed only when background electron density is very low.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.258-258
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• 2016

최근 디스플레이 산업의 발전에 따라 고성능 디스플레이가 요구되며, 디스플레이의 백플레인 (backplane) TFT (thin film transistor) 구동속도를 증가시키기 위한 연구가 활발히 진행되고 있다. 트랜지스터의 구동속도를 증가시키기 위해 높은 이동도는 중요한 요소 중 하나이다. 그러나, 기존 백플레인 TFT에 주로 사용된 amorphous silicon (a-Si)은 대면적화가 용이하며 가격이 저렴하지만, 이동도가 낮다는 (< $1cm2/V{\cdot}s$) 단점이 있다. 따라서 전기적 특성이 우수한 산화물 반도체가 기존의 a-Si의 대체 물질로써 각광받고 있다. 산화물 반도체는 비정질 상태임에도 불구하고 a-Si에 비해 이동도 (> $10cm2/V{\cdot}s$)가 높고, 가시광 영역에서 투명하며 저온에서 공정이 가능하다는 장점이 있다. 하지만, 차세대 디스플레이 백플레인에서는 더 높은 이동도 (> $30cm2/V{\cdot}s$)를 가지는 TFT가 요구된다. 따라서, 본 연구에서는 차세대 디스플레이에서 요구되는 높은 이동도를 갖는 TFT를 제작하기 위하여, amorphous In-Ga-Zn-O (a-IGZO) 채널하부에 화학적으로 안정하고 전도성이 뛰어난 SnO2 채널을 얇게 형성하여 TFT를 제작하였다. 표준 RCA 세정을 통하여 p-type Si 기판을 세정한 후, 열산화 공정을 거쳐서 두께 100 nm의 SiO2 게이트 절연막을 형성하였다. 본 연구에서 제안된 적층된 채널을 형성하기 위하여 5 nm 두계의 SnO2 층을 RF 스퍼터를 이용하여 증착하였으며, 순차적으로 a-IGZO 층을 65 nm의 두께로 증착하였다. 그 후, 소스/드레인 영역은 e-beam evaporator를 이용하여 Ti와 Al을 각각 5 nm와 120 nm의 두께로 증착하였다. 후속 열처리는 퍼니스로 N2 분위기에서 $600^{\circ}C$의 온도로 30 분 동안 실시하였다. 제작된 소자에 대하여 TFT의 전달 및 출력 특성을 비교한 결과, SnO2 층을 형성한 TFT에서 더 뛰어난 전달 및 출력 특성을 나타내었으며 이동도는 $8.7cm2/V{\cdot}s$에서 $70cm2/V{\cdot}s$로 크게 향상되는 것을 확인하였다. 결과적으로, 채널층 하부에 SnO2 층을 형성하는 방법은 추후 높은 이동도를 요구하는 디스플레이 백플레인 TFT 제작에 적용이 가능할 것으로 기대된다.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.16 no.1
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• pp.26-32
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• 2003

Then-channel poly-Si thin-film transistors (poly-Si TFT's) formed by solid phase crystallization (SPC) method on glass were measured to obtain the electrical parameters such as of I-V characteristics, mobility, leakage current, threshold voltage, and subthreshold slope. Then, devices were analyzed to obtain the reliability and appliability on TFT-LCD with large-size and high density. In n-channel poly-Si TFT with 5$\mu\textrm{m}$/2$\mu\textrm{m}$, 8$\mu\textrm{m}$, 30$\mu\textrm{m}$ devices of channel width/length, the field effect mobilities are 111, 116, 125 $\textrm{cm}^2$/V-s and leakage currents are 0.6, 0.1, and 0.02 pA/$\mu\textrm{m}$, respectively. Low threshold voltage and subthreshold slope, and good ON-OFF ratio are shown, as well. Thus. the poly-Si TFT's used by SPC are expected to be applied on TFT-LCD with large-size and high density, which can integrate the display panel and peripheral circuit on a targe glass substrate.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.31 no.6
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• pp.372-376
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• 2018

The effects of off-state bias stress on the characteristics of p-type poly-Si TFT were investigated. To reduce the gate-induced drain leakage (GIDL) current, the off-state bias stress was changed by varying Vgs and Vds. After application of the off-state bias stress, the Vgs causing GIDL current was dramatically increased from 1 to 10 V, and thus, the Vgs margin to turn off the TFT was improved. The on-current and subthreshold swing in the aged TFT was maintained. We performed a technology computer-aided design (TCAD) simulation to describe the aged characteristics. The aged-transfer characteristics were well described by the local charge trapping. The activation energy of the GIDL current was measured for the pristine and aged characteristics. The reduced GIDL current was mainly a thermionic field-emission current.

• 한국정보디스플레이학회:학술대회논문집
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• 2008.10a
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• pp.239-242
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• 2008

We have investigated the reliability of short channel ($L=1.5{\mu}m$) p-type ELA poly-Si TFTs under hot carrier stress. Threshold voltage of short channel TFT was significantly more shifted to positive direction than that of long channel TFT under the same stress. This result may be attributed to electron trapping at the interface between poly-Si film and gate oxide layer.

• 한국정보디스플레이학회:학술대회논문집
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• 2006.08a
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• pp.1111-1114
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• 2006

We have developed a 2 inch LTPS-TFT AMOLED display with a top emission structure on a $50-{\mu}m-thick$ metal foil. The Active matrix back planes were fabricated with the p-channel LTPS TFT with a conventional pixel circuit consisting of 2 transistors and 1 capacitance. The p-channel TFTs on the metal foil exhibited the field-effect mobility of $22cm^2/Vs$. Finally, a images from prototype monochrome AMOLED displays are successfully presented, with $64{\times}88$ pixels and 56-ppi resolution.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.8 no.4
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• pp.738-742
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• 2007

The variations in the device characteristics of hydrogenated amorphous thin-film transistors (a-Si:H TFTs) were studied according to the processes of pixel electrode fabrication to make active-matrix flat-panel displays. The off-state current was about 1 pA and the switching ratio was over $10^6$ before fabrication of pixel electrodes; however, the off-state current increased over 10 pA after fabrication of pixel electrodes. Surface treatment on SiNx passivation layers using plasma could improve the off-state characteristics after pixel electrode process. $N_2$ plasma treatment gave the best result. Charge accumulation on the SiNx passivation layer during the deposition of transparent conducting layer might cause the increase of off-state current after the fabrication of pixel electrodes.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.61 no.2
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• pp.93-96
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• 2012

We have designed high performance prism light-guide plate (LGP) in 17 inch TFT-LCD. In test result to embody high brightness BLU in case of LGP of base and upper surface with 17 inch, thickness 8mm adding prism construct. Using optical simulation, we forecast the brightness and uniformity in LGP with prism structure. And we adopted novel injection mold method and Nickel stamper to make actual evolution sample. Novel injection mold process has steady heating time zone in heat cycle time of injection mold process. For this novel heat cycle control, we achieved above 90[%] height prism structure as our design. It is superior brightness improvement than previous that of printing form about some 20[%] and in this course to embody actual material it succeeded prism LGP production by 17 inch injection form process.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.58 no.4
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• pp.495-498
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• 2009

To improve the efficiency of the high voltage cable for BLU(backlight unit) of TFT-LCD(Thin Film Transistor-Liquid Crystal Display), the analysis for the trial products(UL3239, UL3633) is conducted by using SEM(scanning electron microscope) and EDX(Energy Dispersive X-ray Spectroscopy). The result that it is possible to accumulate the know-how to about stranding pitch through effective improvement of stranding process. The troubles which are the badness of withstanding voltage and tensile strength etc. are solved by development of excellent material. Furthermore, phenomenon of conductor unfasten in the harness work is solved by improvement of the stranding wire process.