Improving resistance to gate bias stress in pentacene TFTs with optimally cured polymer dielectric layers

Abstract

We report on the insulator charging effects of poly-4-vinylphenol (PVP) gate dielectric on the reliabilities of pentacene thin-film transistors (TFTs). Our PVP films were prepared by spin coating and subsequent curing at various temperatures (155, 175, and 200 degrees C). Evaluated using Au/PVP/p(+)-Si structures, the dielectric strength of PVP films cured at 175 degrees C was superior to those of the other PVP films cured at different temperatures. Although the field mobility (similar to 0.13 cm(2)/V s) obtained from a TFT with PVP film cured at 200 S C appeared higher than that (similar to 0.07 cm(2)/V s) from the device with 175 degrees C-cured polymer film, the TFT prepared at 200 degrees S revealed a low on/off current ratio of less than 10(4) due to its high off-state current and a higher sensitivity to gate bias stress. The unreliable behavior is due to the dielectric charging caused by gate electron injection. We thus conclude that there are some optimal PVP-curing conditions to improve the reliability of pentacene TFT. (c) 2005 The Electrochemical Society.