DLTS study of defect creation in amorphous-silicon thin-film transistors

Abstract

The metastable changes in a-Si:H/a-SiN x:H TFTs caused by prolonged application of high gate voltages and light irradiation have been studied for the first time by transient current spectroscopy, a DLTS technique. We find that the effective density of interface states, N i, which most likely is determined by a spatially non-uniform distribution of states in the a-Si:H film, increases during voltage stress by up to a factor of 2. The energy distribution of ΔN i suggests that the defects created are Si-dangling bonds with an areal density of approximately 10 12 cm −2. We find that ΔN i depends appreciably stronger on the stress temperature than the density of light-induced defects, indicating that voltage-induced defect creation is energetically less favorable than the light-induced effect.