Significant Performance Enhancement of Very Thin InGaZnO Thin-Film Transistors by a Self-Assembled Monolayer Treatment
Wensi Cai, Joshua Wilson, Jiawei Zhang, Joseph Brownless, Xijian Zhang, Leszek A. Majewski, Aimin Song
Abstract
The use of amorphous InGaZnO (IGZO) has become more and more popular especially in display technologies because of its high mobility, excellent large area uniformity, and low-temperature processability. However, unlike Si-based thin-film transistors (TFTs), the top channel surface of IGZO TFTs is extremely sensitive to air, resulting in a degraded device performance, particularly when a very-thin channel layer is used. To avoid such detrimental effects and improve the device performance, a top surface treatment such as encapsulation is necessary. In this work, very thin, 1 V IGZO TFTs with top surface modified by a self-assembled monolayer (SAM) were studied. The electrical performance of the presented TFTs was significantly enhanced after the SAM modification because of a much reduced desorption–adsorption effect on the IGZO surface. The importance of top surface condition on TFTs with ultrathin channel layers was discussed. TFTs with a 5 nm thick IGZO channel layer showed a carrier mobility almost tripled plus an 18% decrease of total trap density after the SAM treatment. The treated devices also showed a superb air stability with negligible change of electrical performance after being stored in ambient air for a year. Considering the high cost of indium, this approach has a high potential to significantly reduce the manufacturing cost of IGZO-based electronics.