Localized Tail States and Electron Mobility in Amorphous ZnON Thin Film Transistors

Sungsik Lee; Arokia Nathan; Yan Ye; Yuzheng Guo; John Robertson

doi:10.1038/srep13467

Localized Tail States and Electron Mobility in Amorphous ZnON Thin Film Transistors

Sci Rep. 2015 Aug 25:5:13467. doi: 10.1038/srep13467.

Authors

Sungsik Lee¹, Arokia Nathan¹, Yan Ye², Yuzheng Guo¹, John Robertson¹

Affiliations

¹ Department of Engineering, University of Cambridge, Cambridge CB2 1PZ, United Kingdom.
² Display and SunFab Solar Business Group, Applied Materials, Santa Clara, California 95054, USA.

Abstract

The density of localized tail states in amorphous ZnON (a-ZnON) thin film transistors (TFTs) is deduced from the measured current-voltage characteristics. The extracted values of tail state density at the conduction band minima (N(tc)) and its characteristic energy (kT(t)) are about 2 × 10(20) cm(-3)eV(-1) and 29 meV, respectively, suggesting trap-limited conduction prevails at room temperature. Based on trap-limited conduction theory where these tail state parameters are considered, electron mobility is accurately retrieved using a self-consistent extraction method along with the scaling factor '1/(α + 1)' associated with trapping events at the localized tail states. Additionally, it is found that defects, e.g. oxygen and/or nitrogen vacancies, can be ionized under illumination with hv ≫ E(g), leading to very mild persistent photoconductivity (PPC) in a-ZnON TFTs.