• Journal of the Korea Institute of Information and Communication Engineering
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• v.21 no.9
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• pp.1627-1634
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• 2017

In this work, a junctionless transistor with different film thickness of amorphous InGaZnO has been fabricated and it's instability has been analyzed with different film thickness under positive and negative gate stress as well as light illumination. It was found that the threshold voltage shift and the variation of drain current have been increased with decrease of film thickness under the condition of gate stress and light illumination. The reasons for the observed results have been explained by stretched-exponential model and device simulation. Due to the reduced carrier trapping time with decrease of film thickness, electrons and holes can be activated easily. Due to the increase of vertical channel electric field reaching the back interface with decrease of film thickness, more electrons and holes can be accumulated in back interface. When one decides the film thickness for the fabrication of junctionless transistor, the more significant device instability with decrease of film thickness should be consdered.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.22 no.1
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• pp.117-124
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• 2018

Junctionless amorphous InGaZnO thin film transistors with different film thickness have been fabricated. Their device performance parameters were extracted and gate oxide breakdown voltages were analyzed with different film thickness. The device performances were enhanced with increase of film thickness but the gate oxide breakdown voltages were decreased. The device performances were enhanced with increase of temperatures but the gate oxide breakdown voltages were decreased due to the increased drain current. The drain current under illumination was increased due to photo-excited electron-hole pair generation but the gate oxide breakdown voltages were decreased. The reason for decreased breakdown voltage with increase of film thickness, operation temperature and light intensity was due to the increased number of channel electrons and more injection into the gate oxide layer. One should decide the gate oxide thickness with considering the film thickness and operating temperature when one decides to replace the junctionless amorphous InGaZnO thin film transistors as BEOL transistors.

• 한국정보디스플레이학회:학술대회논문집
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• 2009.10a
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• pp.1002-1004
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• 2009

Solution-processed indium-gallium-zinc-oxide thin-film transistors were fabricated by sol-gel method. By a combinatorial study of InGaZnO multi-component system, optimum molar ratio of In, Ga, and Zn has been selected. By adjusting the In:Ga:Zn molar ratio, TFTs with field-effect mobility of 0.5 ~ 1.5 $cm^2$/V-s, threshold voltage of -5 ~ 5 V, and subthreshold slope of 1.5 ~ 2.5 V/decade were achieved.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2010.05a
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• pp.693-694
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• 2010

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.29 no.2
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• pp.69-74
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• 2016

In this study, we proposed an a-IGZO (amorphous In-Ga-Zn-O) TFT (thin-film transistor) with off-planed source/drain structure. Furthermore, two different electrode materials (ITO and Ti) were applied to the source and drain contacts for performance improvement of a-IGZO TFTs. When the ITO with a large work-function and the Ti with a small work-function are applied to drain electrode and source contact, respectively, the electrical performances of a-IGZO TFTs were improved; an increased driving current, a decreased leakage current, a high on-off current ratio, and a reduced subthreshold swing. As a result of gate bias stress test at various temperatures, the off-planed S/D a-IGZO TFTs showed a degradation mechanism due to electron trapping and both devices with ITO-drain or Ti-drain electrode revealed an equivalent instability.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.08a
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• pp.256-256
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• 2012

Oxide semiconductors such as zinc tin oxide (ZTO) or indium gallium zinc oxide (IGZO) have attracted a lot of research interest owing to their high potential for application as thin film transistors (TFTs) [1,2]. However, the instability of oxide TFTs remains as an obstacle to overcome for practical applications to electronic devices. Several studies have reported that the electrical characteristics of ZnO-based transistors are very sensitive to oxygen, hydrogen, and water [3,4,5]. To improve the reliability issue for the amorphous InGaZnO (a-IGZO) thin-film transistor, back channel passivation layer is essential for the long term bias stability. In this study, we investigated the instability of amorphous indium-gallium-zinc-oxide (IGZO) thin film transistors (TFTs) by the back channel contaminations. The effect of back channel contaminations (humidity or oxygen) on oxide transistor is of importance because it might affect the transistor performance. To remove this environmental condition, we performed vacuum seasoning before the deposition of hybrid passivation layer and acquired improved stability. It was found that vacuum seasoning can remove the back channel contamination if a-IGZO film. Therefore, to achieve highly stable oxide TFTs we suggest that adsorbed chemical gas molecules have to be eliminated from the back-channel prior to forming the passivation layers.

• Journal of Sensor Science and Technology
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• v.28 no.2
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• pp.133-138
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• 2019

The a-InGaZnO (a-IGZO) thin film transistor (TFT) has the advantages of larger mobility than that of amorphous silicon TFTs, acceptable reliability and uniformity over a large area, and low process cost. A capacitive-type touch sensor was studied with an a-IGZO TFT that can be used on the front side of a display due to its transparency. A capacitive sensor detects changes of capacitance between the surface of the finger and the sensor electrode. The capacitance varies according to the distance between the sensor plate and the touching or non-touching of the sensing electrode. A capacitive touch sensor using only one a-IGZO TFT was developed with the reduction of two bus lines, which made it easy to reduce the pixel pitch. The proposed sensor circuit maintained the amplification performance, which was investigated for various drive conditions.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.16 no.6
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• pp.1266-1272
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• 2012

An InGaZnO thin film transistor with different gate lengths and widths have been fabricated and their device degradations with device sizes have been also performed after negative gate bias stress. The threshold voltage and subthreshold swing have been decreased with decrease of gate length. However, the threshold voltages were increased with the decrease of gate lengths. The transfer curves were negatively shifted after negative gate stress and the threshold voltage was decreased. However, the subthreshold swing was not changed after negative gate stress. This is due to the hole trapping in the gate dielectric materials. The decreases of the threshold voltage variation with the decrease of gate length and the increase of gate width were believed due to the less hole injection into gate dielectrics after a negative gate stress.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.11a
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• pp.146-147
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• 2008

In this paper we report upon an investigation into the effect of sputter RF power on the electrical properties of Gallium doped zinc oxide (ZnO:Ga) film. Structural, electrical and optical properties of the ZnO:Ga films were investigation in terms of the sputtering power. Working pressure fixed in 5 mtorr and RF powers the variable did with 50~100 W. The result, We were able to without substrate temperature obtain resistivity of $9.3\times10^{-4}{\Omega}cm$ and optical transmittance of 90%.

• Korean Journal of Materials Research
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• v.33 no.12
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• pp.511-516
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• 2023

Amorphous In-Ga-Zn-O (a-IGZO) thin film transistors (TFTs) with a coplanar structure were fabricated to investigate the feasibility of their potential application in large size organic light emitting diodes (OLEDs). Drain currents, used as functions of the gate voltages for the TFTs, showed the output currents had slight differences in the saturation region, just as the output currents of the etch stopper TFTs did. The maximum difference in the threshold voltages of the In-Ga-Zn-O (a-IGZO) TFTs was as small as approximately 0.57 V. After the application of a positive bias voltage stress for 50,000 s, the values of the threshold voltage of the coplanar structure TFTs were only slightly shifted, by 0.18 V, indicative of their stability. The coplanar structure TFTs were embedded in OLEDs and exhibited a maximum luminance as large as 500 nits, and their color gamut satisfied 99 % of the digital cinema initiatives, confirming their suitability for large size and high resolution OLEDs. Further, the image density of large-size OLEDs embedded with the coplanar structure TFTs was significantly enhanced compared with OLEDs embedded with conventional TFTs.