The effect of channel length on turn-on voltage in pentacene-based thin film transistor

We report on the influence of channel length on transfer characteristics of pentacene-based thin film transistor (TFT). As the channel length is reduced from 50 to 5 μm, turn-on voltage (Vturn-on) is shifted to more positive values, regardless of surface treatments and gate insulators. Especially in case of relatively short channel TFTs having the channel length of below 10 μm, multi-channel operation behavior has been observed and resulted in hump-shaped transfer characteristics. The positive shift behavior of Vturn-on is similar to the threshold voltage reduction behavior by drain induced barrier lowering in Si devices and multi-channel operation can be explained by the channel length variation inevitably obtained after lift-off patterning of Au/Ti source–drain metal in relatively short channel TFTs.