Stability of pentacene transistors under concomitant influence of water vapor and bias stress

Operational stability of bottom gate pentacene based organic field effect transistors (OFETs) under concomitant influence of water vapor and gate bias stress was examined. Two different gate dielectric materials, namely SiO2 and poly-methylmetacrylate (PMMA), were compared. When a positive gate bias stress was applied while the device was maintained under controlled relative humidity (RH), electrical characteristics were drastically affected, especially hysteresis direction and magnitude of ID–VG transfer characteristics. Characteristics evolution was specific to combined influence of bias stress and RH and were at variance to what observed when only RH or bias stress was applied to the sample. Devices with SiO2 and PMMA gate dielectric exhibited radically opposite behaviors indicating of a strong influence of the pentacene/gate dielectric interface on traps formation.