Investigation on mechanism for instability under drain current stress in amorphous Si-In-Zn-O thin-film transistors

Abstract

The mechanism for instability against positive bias stress (PBS) in amorphous Si-In-Zn-O (SIZO) thin-film transistors has been investigated by analyzing the subgap density of states (DOSs), which was extracted from multi-frequency method using direct capacitance-voltage measurements. It was found that DOSs including shallow tail states and deep trap states are constant in density as PBS time increases. It indicates that the bulk traps in the SIZO channel layer and the channel/dielectric interfacial traps are not created during the PBS duration. Therefore, the instability against PBS in SIZO thin-film transistors is attributed to the charge trapping by the acceptor-like DOSs. (C) 2012 Elsevier B. V. All rights reserved.