Clarification of the origin of high electron mobility for ultra-high-definition display materials —A big step toward realizing ultra-high mobility transparent oxide thin film transistors exceeding 100 cm²/Vs—

POINT

• Clarification of the origin of high electron mobility in ultra-high-definition display materials.
• Analysis of the operating mechanism of a transistor using a unique thermoelectric field modulation method.
• Major progress toward realization of ultra-high mobility transparent oxide thin film transistors exceeding 100 cm²/Vs.

A research group led by Visiting Scholar Hui Yang, Professor Yasutaka Matsuo, Assistant Professor Yusaku Magari, and Professor Hiromichi Ohta at the Research Institute for Electronic Science, Hokkaido University has clarified the origin of the high electron mobility in ultra-high-definition display materials. The transparent oxide semiconductor In-Sn-Zn-O (ITZO) exhibits a high mobility (>50 cm²/Vs) that is more than five times that of the transparent oxide semiconductor In-Ga-Zn-O (IGZO, electron mobility: about 10 cm²/Vs), which is currently applied to organic EL televisions, it is expected to be used as a material for ultra-high-definition displays, but the origin of the high electron mobility has not been clarified. In this study, Yang et al. measured and analyzed the thermopower of the ITZO thin films and the ITZO thin film transistors using the electric field thermopower modulation method. As a result, the following things were found. (1) the effective mass of carrier electrons in ITZO is about 30% lighter than that of IGZO, (2) the carrier relaxation time of ITZO is four times longer than that of IGZO, and (3) the effective thickness of the conductive layer is more than 10 nm. This is a great step toward the realization of ultra-high-mobility transparent oxide thin-film transistors with electron mobilities exceeding 100 cm²/Vs.

The results of this research were published in ACS Applied Electronic Materials on September 29, 2022 (Thursday).

Hui Yang^*, Yuqiao Zhang, Yasutaka Matsuo, Yusaku Magari, and Hiromichi Ohta^*, “Thermopower Modulation Analyses of High-mobility Transparent Amorphous Oxide Semiconductor Thin-Film Transistors”, ACS Appl. Electron. Mater. XX, XXXX-XXXX (2022). (September 29, 2022) (DOI: 10.1021/acsaelm.2c01210)