Hyun Jae Kim
Yonsei University
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Featured researches published by Hyun Jae Kim.
Applied Physics Letters | 2008
Byung Du Ahn; Hyun Soo Shin; Hyun Jae Kim; Jin-Seong Park; Jae Kyeong Jeong
We proposed a homojunctioned amorphous InGaZnO (a-IGZO) thin film transistor (TFT) and compared its performance to that of a conventional structured TFT. The source/drain regions were formed in the a-IGZO channel layer using Ar and H2 plasma treatments, respectively. Hydrogen itself was found to act as a carrier of donors with H2 plasma treatment, which had effects to a depth of 50 nm. Our TFT had a field-effect mobility of 7.27 cm2/V s, an on/off ratio of 1.2×107, a threshold voltage of 0.96 V, and a subthreshold swing of 0.49 V/decade.
Applied Physics Letters | 2009
Gun Hee Kim; Byung Du Ahn; Hyun Soo Shin; Woong Hee Jeong; Hee-Jin Kim; Hyun Jae Kim
The effects of the indium content on characteristics of nanocrystalline InGaZnO (IGZO) films grown by a sol-gel method and their thin film transistors (TFTs) have been investigated. Excess indium incorporation into IGZO enhances the field effect mobilities of the TFTs due to the increase in conducting path ways and decreases the grain size and the surface roughness of the films because more InO2− ions induce cubic stacking faults with IGZO. These structural variations result in a decrease in density of interfacial trap sites at the semiconductor-gate insulator interface, leading to an improvement of the subthreshold gate swing of the TFTs.
Applied Physics Letters | 2010
Gun Hee Kim; Woong Hee Jeong; Byung Du Ahn; Hyun Soo Shin; Hee-Jin Kim; Hyun Jae Kim; Myung-kwan Ryu; Kyung-Bae Park; Jong-Baek Seon; Sangyoon Lee
We have fabricated high-performance and high-stability sol-gel-processed MgInZnO thin films transistors with varying Mg content. As the Mg content was increased, the turn-on-voltage increased and the off-current decreased. This is because the incorporation of Mg (with low standard electrode potential and high optical band gap, Eopt, when oxidized) causes reduction in the oxygen vacancy, acting as a carrier source, and an increase in Eopt of the film. This results in reduction in carrier concentration of the film. Small grains and smooth morphology by varying the Mg content lead to an improvement of the mobility, on-current, and subthreshold gate swing.
Applied Physics Letters | 2010
You Seung Rim; Dong Lim Kim; Woong Hee Jeong; Hyun Jae Kim
Thin-film transistors (TFTs) with a ZrZnSnO (ZZTO) channel layer were fabricated using a solution process. As-prepared ZnSnO (ZTO) TFTs had a large off-current. However, as the content of Zr ions increased in ZTO, the threshold voltage shifted, and the off-current in the TFTs decreased. Because Zr has a lower standard electrode potential, it is more readily oxidized than Sn or Zn. Thus, Zr acted as an effective carrier suppressor in the ZTO system and a ZZTO TFT with a high mobility of a 4.02 cm2 V−1 s−1 and a large on/off ratio of over 106 was achieved.
Applied Physics Letters | 2010
Woong Hee Jeong; Gun Hee Kim; Hyun Soo Shin; Byung Du Ahn; Hyun Jae Kim; Myung-kwan Ryu; Kyung-Bae Park; Jong-Baek Seon; Sang Yoon Lee
The effects of adding Hf into a InZnO (IZO) system, particularly the electrical characteristics of their thin film and thin film transistors (TFTs), were investigated as a function of atomic concentration from 0 to 10 at. % of Hf and Ga/Zn. Because Hf has a high affinity for oxygen in IZO system, the Hf suppresses carrier generation more effectively than does Ga. At 10 at. % of Hf/Zn atomic concentration, the HfInZnO TFTs showed wider on-to-off ratios than those of GaInZnO TFTs due to the low standard-electrode-potential of Hf and sharp subthreshold swings due to low trap density.
Advanced Materials | 2014
You Seung Rim; Huajun Chen; Xiaolu Kou; Hsin-Sheng Duan; Huanping Zhou; Min Cai; Hyun Jae Kim; Yang Yang
Novel structure-engineered amorphous oxide semiconductor thin-film transistors using a solution process to overcome the trade-off between high mobility and other parameters (i.e., on/off ratio, sub-threshold voltage swing, threshold voltage, and so on) are proposed. High performance confining structure-engineered AOS TFTs are successfully demonstrated, which utilize a specially designed layer with ultra-high density and high electron mobility.
Japanese Journal of Applied Physics | 2014
Si Joon Kim; Seokhyun Yoon; Hyun Jae Kim
In this review, we summarize solution-processed oxide thin-film transistors (TFTs) researches based on our fulfillments. We describe the fundamental studies of precursor composition effects at the beginning in order to figure out the role of each component in oxide semiconductors, and then present low temperature process for the adoption of flexible devices. Moreover, channel engineering for high performance and reliability of solution-processed oxide TFTs and various coating methods: spin-coating, inkjet printing, and gravure printing are also presented. The last topic of this review is an overview of multi-functional solution-processed oxide TFTs for various applications such as photodetector, biosensor, and memory.
Applied Physics Letters | 2008
Won Jun Park; Hyun Soo Shin; Byung Du Ahn; Gun Hee Kim; Seung Min Lee; Kyung Ho Kim; Hyun Jae Kim
Ga-doped ZnO (GZO) thin film transistors (TFTs) were fabricated based on the solution-processed method and GZO TFTs were investigated according to the variation of the Ga doping concentration [Ga∕Zn (%)]. A field-effect mobility of 1.63cm2∕Vs and a drain current on/off ratio of 4.17×106 were observed in the 5.4 % Ga-doped TFT. This result shows good agreement with its structural properties and electrical properties of the GZO channel layer. It is believed that the optimal and desirable electrical properties of the TFTs can be obtained by adjusting the Ga doping concentration.
Journal of Materials Chemistry | 2012
You Seung Rim; Woong Hee Jeong; Dong Lim Kim; Hyun Soo Lim; Kyung Min Kim; Hyun Jae Kim
High-pressure annealing (HPA) affected the thermodynamics of the formation of a solution-processed oxide film through the simultaneous modification of thermal decomposition and compression, and enabled the use of lower annealing temperatures, which was favourable for device implementation. HPA also reduced the film thickness and decreased the porosity, resulting in enhanced device characteristics at low temperature. Surface and depth profile characterization using X-ray reflectivity (XRR), X-ray photoelectron spectroscopy (XPS), time-of-flight secondary ion mass spectrometry (TOF-SIMS), and ellipsometry suggested that the HPA process supported the effective decomposition of commercial metal-nitrate and/or -salt precursors and strong bonding between oxygen and the metal ions, ultimately reducing the amount of organic residue. The as-optimized HPA process allowed for high-performance solution-processed flexible InZnO (IZO) TFTs on a polymeric substrate at 220 °C with low sub-threshold voltage swing (as low as 0.56 V dec−1), high on–off ratio of over 106, and field-effect mobility as high as 1.78 cm2 V−1 s−1, respectively. These results demonstrate that this is a simple and efficient promising approach for improving the performance of solution-processed electronic devices at low temperatures.
IEEE Electron Device Letters | 2010
Kyung-Bae Park; Jong-Baek Seon; Gun Hee Kim; Mino Yang; Bonwon Koo; Hyun Jae Kim; Myung-kwan Ryu; Sangyoon Lee
We developed thin-film transistors (TFTs) that use solution-processed amorphous indium zinc oxide for the channels in an all-photolithographic process. The transistors, which operate in depletion mode, have excellent transfer characteristics, including saturation mobility of 6.57 cm2/ V·s, threshold voltages of - 0.30 V, turn-on voltages of -1.50 V, on/off ratios of 109, and inverse subthreshold slopes of 0.15 V/dec. We measured the time, temperature, gate voltage, and drain-voltage dependence of the threshold voltage shift, which was 2.16 V under stress conditions. This is nearly the same as that of conventional amorphous silicon TFTs.