Fabrication of an organic thin-film transistor by direct deposit of a pentacene layer onto a silicon substrate

Abstract

Contrary to the conventional bottom-contact and top-contact structure, a new organic thin-film transistor structure has been developed in this work based on good crystallinity of the pentacene layer and on large grain sizes. Both these characteristics are obtained when the material is deposited directly onto a silicon substrate. In addition to depositing the pentacene layer at the bottom of the transistor, we adopted an HfO 2 and Si 3N 4 stack as the gate dielectric using sputtering to lower the operation voltage and to reduce the gate leakage current. This proposed organic thin-film transistor shows an acceptable carrier mobility of 0.21 cm 2 V −1 s −1 and a threshold voltage of −7 V. Because the gate dielectric is placed on top of the pentacene active layer, the new structure has a five-fold life-time improvement when compared with a conventional organic thin-film transistor without a passivation layer.