The top-gate structure is currently adopted in various flat-panel displays because of its diverse advantages such as passivation from the external environment and process compatibility with industries. However, the mobility of the currently commercialized top-gate oxide thin-film transistors (TFTs) is insufficient to drive ultrahigh-resolution displays. Accordingly, this work suggests metal-capped Zn-Ba-Sn-O transistors with top-gate structures for inducing mobility-enhancing effects. The fabricated top-gate device contains para-xylylene (PPx), which is deposited by a low-temperature chemical vapor deposition (CVD) process, as a dielectric layer and exhibits excellent interfacial and dielectric properties. A technology computer-aided design (TCAD) device simulation reveals that the mobility enhancement in the Al-capped (Zn,Ba)SnO3 (ZBTO) TFT is attributed not only to the increase in the electron concentration, which is induced by band engineering due to the Al work function but also to the increased electron velocity due to the redistribution of the lateral electric field. As a result, the mobility of the Al-capped top-gate ZBTO device is 5 times higher (∼110 cm2/Vs) than that of the reference device. These results demonstrate the applicability of top-gate oxide TFTs with ultrahigh mobility in a wide range of applications, such as for high-resolution, large-area, and flexible displays.
Keywords: Zn−Ba−Sn−O; chemical vapor deposition; para-xylylene; thin-film transistors; top-gate transistors.