Defect creation in the accumulation layer of a-Si: H thin-film transistors

Abstract

Metastable changes in a-Si: H/a-SiN _x : H TFTs caused by prolonged application of high gate voltages and by light exposure are studied by measurements of the transfer characteristics and by a transient current spectroscopy (TCS). Voltage stress leads to a strong shift of the threshold voltage due to charge trapping in the nitride and also to the creation of metastable defects in the accumulation layer. This voltage-induced defect generation is thermally activated with an energy near 0·7 eV and therefore, at room temperature, is less effective than defect creation by light soaking.