The performance of polymer thin film transistors, made of different semiconducting polymers, depends mostly on the type of polymer and its deposition conditions. For these polymer field-effect transistors (PFETs), the current transport is limited by the carrier injection from the source electrode into the polymer. The disordered polymer molecules near the injection interface randomize and decrease the injection barrier, resulting in a large variation of the PFET characteristics, such as threshold voltage, leakage current, and mobility. The PFET current-voltage characteristics degrade at temperatures higher than 40 degreesC and the low frequency noise increases by 0.3 dB/degreesC. (C) 2004 American Vacuum Society.