Influence of mechanical bending and temperature on the threshold voltage instability of a-Si:H thin-film transistors under electrical stress

This paper studies the electrical characteristics of hydrogenated amorphous silicon thin-film transistors (a-Si:H TFTs) under flat and bending situations after AC/DC stress at different temperatures. Stress temperature was varied from 77 K to 400 K, and threshold voltage shifts were extracted to analyze degradation mechanisms. It was found that high temperature and mechanical bending played important roles under AC stress, with an enhanced stress effect resulting in a more serious degradation. This study also discusses the dependence between the accumulated sum of bias rising and falling time and the threshold voltage shifts under AC stress.

► The Vt shifts of bended a-Si:H TFT were found to relate with AC stress frequency.
► At high temperature, the bended a-Si:H TFT exhibits the largest Vt shift.
► Both thermal energy and mechanical bending will reduce the Si–Si bond strength.
► Hydrogen reacts with weak Si–Si bonds causing the degradation of Vt.
► Electrons act to break weak Si–Si bonds in the drain/source depletion region.