Relationship between Detrapping of Electrons and Negative Gate Bias during Recovery Process in a-InGaZnO Thin Film Transistors

Abstract

The relationship between detrapping of electrons and negative gate bias in amorphous InGaZnO thin film transistors (a-IGZO TFTs) is investigated. In these devices, positive gate-bias stress (PBS) traps electrons at the gate insulator (GI) or at the interface between the channel and the GI, and creates acceptor-like states, which the authors speculate may be oxygen interstitials or zinc vacancies. In contrast, negative gate-bias stress (NBS) increases donor-like states, which are speculated as ionized oxygen vacancies, near the interface. When subsequent negative gate bias (SNB) is applied to a TFT after PBS, electrons are detrapped and donor-like states are increased simultaneously. Measurements with various SNB and PBS conditions suggests that SNB accelerates detrapping of electrons, and that those detrapped electrons interrupts the increase of donor-like states.