Improvement in the photon-induced bias stability of Al-Sn-Zn-In-O thin film transistors by adopting AlOx passivation layer

This study examined the impact of the passivation layer on the light-enhanced bias instability of Al-Sn-Zn-In-O (AT-ZIO) thin film transistors. The suitably passivated device exhibited only a threshold voltage (V-th) shift of 0.72 V under light-illuminated negative-thermal stress conditions, whereas the device without a passivation layer suffered from a huge negative V-th shift of >11.5 V under identical conditions. The photocreated hole trapping model could not itself explain this behavior. Instead, the light-enhanced V-th instability of the unpassivated device would result mainly from the photodesorption of adsorbed oxygen ions after exposing the AT-ZIO back-surface in an ambient atmosphere. (C) 2010 American Institute of Physics. [doi:10.1063/1.3432445]