The Influence of ZnO Layer Thickness on the Performance and Electrical Bias Stress Instality in ZnO Thin Film Transistors

Date

2020-01-23

Advisors

Journal Title

Journal ISSN

ISSN

Volume Title

Publisher

Institute of Physics

Type

Article

Peer reviewed

Yes

Abstract

Thin Film Transistors (TFTs) are the active elements for future large area electronic applications, in which low cost, low temperature processes and optical transparency are required. Zinc oxide (ZnO) thin film transistors (TFTs) on SiO2/n+-Si substrate are fabricated with the channel thicknesses ranging from 20 nm to 60 nm. It is found that both the performance and gate bias stress related instabilities of the ZnO TFTs fabricated were influenced by the thickness of ZnO active channel layer. The effective mobility was found to improve with increasing ZnO thickness by up to an order in magnitude within the thickness range investigated (20 – 60 nm). However, thinner films were found to exhibit greater stability in threshold voltage and turn-on voltage shifts with respect to both positive and negative gate bias stress. It was also observed that both the turn on voltage (Von) and the threshold voltage (VT) decrease with increasing channel thickness. Moreover, the variations in subthreshold slope (S) with ZnO thickness as well as variations in VT and Von suggest a possible dependence of trap states in the ZnO on the ZnO thickness. This is further correlated by the dependence of VT and Von instabilities with gate bias stress.

Description

University of Buea supported the first author during the writing of this manuscript Open access article

Keywords

Thin Film Transistors, ZnO, instability

Citation

Ngwashi, D.K., Mih, T.A. and Cross, R.B.M. (2020). The influence of ZnO layer thickness on the performance and electrical bias stress instability in ZnO thin film transistors. Materials Research Express. ‌

Rights

Research Institute

Institute of Engineering Sciences (IES)