Fabrication of Schottky Barrier Oxide Transistors to Reduce Subthreshold Swing Close to the Theoretical Limits

Abstract

The nature of the contact between the semiconductor channel and metal electrodes have a great influence on the functionality of a thin film transistor (TFT). A Schottky barrier of such contact can originate a ‘thermionic emission and thermionic field emission’ limited current transport that can reduce the sub-threshold swing of a TFT largely. This attribution has been dealt with using an asymmetric work-function source-drain (S-D) electrode of a low operating voltage TFT. Furthermore, the performance of the device can be optimized by incorporating a suitable interface layer with an optimal thickness in the asymmetric work-function S-D electrode configuration. In this study, a ZnO TFT has been fabricated by using a LiInSnO<inf>4</inf> gate dielectric that reduces its operating voltage to 2 V due to the high areal capacitance of the ionic gate dielectric. In this TFT, LiF/Al serves as the source electrode, while MoO<inf>3</inf>/Ag works as the drain electrode with variable thickness of the MoO<inf>3</inf> layer. Notably, by adjusting the thickness of the MoO<inf>3</inf> layer within the MoO<inf>3</inf>/Ag electrode, the subthreshold swing of the TFT achieved 66 mV/decade, which is close to the theoretical limit of subthreshold swing for oxide TFTs. © 2025 Wiley-VCH GmbH.