Low-voltage pentacene thin-film transistors with Ta2O5 gate insulators and their reversible light-induced threshold voltage shift

Abstract

We have fabricated pentacene thin-film transistors using Ta 2 O 5 films prepared by magnetron reactive sputtering as gate insulators. These transistors exhibit good electrical characteristics at an operating voltage as low as 5 V, with a field-effect mobility of 0.32 cm 2 ∕ Vs , an on∕off ratio of 10 4 , and a subthreshold slope of 0.5 V ∕ decade . We have also investigated the optical properties of these transistors and observed a reversible light-induced threshold voltage shift. Under illumination, the threshold voltage shifts towards the positive direction while the field-effect mobility and on∕off ratio remain almost unchanged. In the dark, however, the threshold voltage can slowly be restored to its original state. At a gate voltage of − 5 V , the transistors show a broadband responsivity of 3.7 A ∕ W after illumination at 60 μ W ∕ cm 2 for 10 min.