Field-induced degradation of organic field-effect transistors under vacuum condition

Organic field effect transistors (OFETs) are widely known to suffer from exposure to environmental factors such as humidity and air. OFETs are also degraded under electrical bias stress test performed in the atmosphere. However, electric-field-induced degradation should be distinguished from atmosphere-induced degradation to evaluate the stability and the reliability of OFETs properly. In order to investigate the degradation characteristics under various electric field distributions preventing ambient-related degradation, we performed electrical stress tests with different bias schemes in a vacuum chamber. All measurements before and after stress tests were performed and compared under a vacuum condition. The results revealed that the vertical electric field across the gate insulator between the gate and the source (or drain) under hole accumulation was a critical degradation agent. We also investigated the dependence of the threshold voltage (V (th) ) on the temperature under constant bias stress in a vacuum. Larger shifts of the threshold voltage were observed from the devices stressed at elevated temperature.