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

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°C). Evaluated using Au/PVP/p⁺-Si structures, the dielectric strength of PVP films cured at 175°C was superior to those of the other PVP films cured at different temperatures. Although the field mobility (∼0.13cm²/Vs) obtained from a TFT with PVP film cured at 200°C appeared higher than that (∼0.07cm²/Vs) from the device with 175°C-cured polymer film, the TFT prepared at 200°C revealed a low on/off current ratio of less than 10⁴ 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.