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Next Generation Oxide Semiconductor TFT and deformable display
Flexible and transparent displays
Flexible and transparent displays have attracted much attention because they can be applied to various environments such as wearable device, glass of transportation or buildings, mirrors for everyday life and so on. We realize flexible and transparent oxide TFTs by using peel-off methods
[1] J. B. Ko et al. "Ultrathin, Flexible, and Transparent Oxide Thin-FIlm Transistors by Delamination and Transfer methods for Deformable DIsplays", Adv Mater Tech, 2021
[2] "Skin-Like Oxide Thin-FIlm Transistors for Transparent Displays", Adv Functional Mater, 2016
Vertical TFT
Recently, new technologies represented by VR (Virtual Reality) and AR (Augmented Reality) are getting much attention as the killer application for the next-generation display. Many devices such as Oculus lift,Gear VR and Hololens have already shown us the possibilities of the realization of those new technologies. However, there still remain several critical issues, and one of them is the resolution of display. For example, the latest high-end smartphone displays on the market usually offers 500~600 ppi (pixels per inch) of pixel density, and it is not enough to give the sense of reality to the VR or AR users. To solve this problem, higher resolution and pixel density of several thousands ppi are expected to be desired for the next-generation display. In that point, oxide semiconductor based vertical structure thin-film transistor (VTFT) can be a good candidate for the backplane of future display. Due to its vertical channel structure, it gives smaller footprint than the conventional BCE structure TFT. Therefore, it is able to reduce the size of pixels and offer more pixels within a display panel. Moreover, it is possible to downsize the channel length under 1um by using the existing photolithography equipments. This can give us enhanced current drivability, and higher on-current level.
[1] J. Kim et al. "Channel-Shortening Effect Suppression of a High-Mobility Self-Aligned Oxide TFT using Trench Structure", IEEE Electron Device Letters, 2021
Self-Aligned TFT
Displays with large size and high resolution are required in many electronic devices. In recent years, 8k ultra-high-definition (UHD) display has been developed. Oxide thin film transistors using amorphous indium-tin-zinc oxide (a-ITZO) have been attracted considerable attention for their potential applications in large area and high resolution display because its good uniformity, low off current and high mobility. Top gate coplanar self-align TFT is crucial in realizing high resolution display because of the advantages that can reduce parasitic capacitance between S/D and gate electrodes. However, oxide TFTs suffer from channel shortening effect due to lateral carrier diffusion. the origin of channel shortening effect is known to be the combined effects of the Vo generation in the SD region by the exposure of Ar or He plasma, reaction between S/D metal and active layer beneath the SD electrode, and H diffusion from gate insulator to the active layer. We will primarily focus on investigating the origin of channel shortening effect and finding new electrode compositions, novel semiconductors, and new dielectric materials. dd
[1] W. Jeong et al. "Suppressing Channel Shortening Effect of Self-Aligned Coplanar Al-doped In-Sn-Zn-O TFTs Using Mo-Al Source/Drain Electrodes as Cu Diffusion Barrier", Journal of Alloys and Compounds, 2021
[2] S.-I. Cho et al. "Remarkably Stable High Mobility Self-Aligned Oxide TFT by Investigating the Effect of Oxygen Plasma Time during PEALD of SiO2 Gate Insulator", Journal of Alloys and Compounds, 2022
[3] J. Kim et al. "Channel-Shortening Effect Suppression of a High-Mobility Self-Aligned Oxide TFT using Trench Structure", IEEE Electron Device Letters, 2021
Highly stable high mobility oxide TFT
Recently, display has been rapidly developed to ultra-high resolution to provide realistic image. We realize highly stable high mobility oxide TFTs for the next-generation displays by tailoring the channel of the oxide TFTs.
[1] J. B. Ko et al. "Interface tailoring through the supply of optimized oxygen and hydrogen to semiconductors for highly stable top-gate-structured high-mobility oxide thin-film transistors", RSC Adv, 2020
[2] K. W. Park et al. "Effects of Hydroxly Group in AlOx Gate Insulator on the Negative Bias Illumination Instability of In-Ga-Zn-O Thin Film Transistors", PSSA, 2019
[3] J. B. Ko et al. "Plasma-Enhanced Atomic Layer Deposition Processed SiO2 Gate Insulating Layer for High Mobility Top-Gate Structured Oxide Thin-Film Transistors", IEEE Electron Device Letters, 2016
[4] S.-I. Cho et al. "Remarkably Stable High Mobility Self-Aligned Oxide TFT by Investigating the Effect of Oxygen Plasma Time during PEALD of SiO2 Gate Insulator", Journal of Alloys and Compounds, 2022
Thin Film Encapsulation
Organic light emitting diode (OLED) is attracting attention as a light emitting technology to realize flexible display because of low price, low power consumption, and vivid color. OLED is composed of anode, organic emitting material and cathode. Each component is deteriorated when exposed to water and oxygen, making it difficult to use for a long time. Therefore, it is essential to develop a thin film encapsulation technology that effectively blocks the external environment for long-term use in OLED-based mobile and TV. We are currently focusing on nitride, alumina-based thin film encapsulation technology that is thin and high-performance for barrier.
[1] K. W. Park et al. "High-Performance Thin H:SiON OLED Encapsulation Layer Deposited by PECVD at Low Temperature", RSC Adv, 2019
[2] J. Kim et al. "Effect of H2 Addition during PECVD on the Moisture Barrier Property and Environmental Stability of Thin H:SiNx Passivation Film", Journal of American Ceramic Society, 2021
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