High-performance metal-oxide thin-film transistors based on inkjet-printed self-confined bilayer heterojunction channels

Abstract

The use of a semiconductor heterojunction channel layer has been explored as a method of improving the performance of metal-oxide thin-film transistors (TFTs). Construction of such a heterojunction bilayer is easy using a vacuum sputtering deposition process but difficult using inkjet printing deposition. Some attempts in this direction have not shown significant improvement compared to single channel layer TFTs, and the present work systematically studied inkjet printing of In₂O₃/IGZO heterojunction channel TFTs. It was found that the bilayer alignment is the most critical factor for obtaining high-performance TFTs. A simple UV/ozone treatment on an inkjet-printed In₂O₃ layer can be effective in achieving perfect alignment for IGZO printed on the In₂O₃ pattern area. The mechanism of alignment is not due to the difference in surface energy between the In₂O₃ layer and SiO₂ dielectric layer, but due to the topography of the In₂O₃ layer sidewall. With well-aligned heterojunction channels, the embedded In₂O₃ front channel layers transform the carrier transport from the main trap-limited charge (TLC) transport process to the PC-dominated process. Therefore, the maximum mobility of 14.5 cm² V⁻¹ s⁻¹ was achieved for inkjet-printed In₂O₃/IGZO TFTs, which is an unattainable result that only increases the proportion of In atoms in IGZO. The average mobility of the In₂O₃/IGZO TFTs is twice that of single-layer In₂O₃ TFTs or IGZO TFTs. Furthermore, the In₂O₃/IGZO TFTs show superior bias stress stability.