Reducing the contact resistance of bottom-contact pentacene thin-film transistors by employing a MoOx carrier injection layer

We report on the reduced contact resistance in bottom-contact (BC) pentacene thin-film transistors (TFTs) with a molybdenum oxide (MoO(x)) carrier injection layer. MoO(x) layers were placed between the gate insulator and the source-drain (S-D) electrodes instead of the conventional adhesive layer such as Cr or Ti. The performance of the BC pentacene-TFT with the MoO(x) injection layer was significantly improved at low operating voltages. The contact resistance of the MoO(x)/Au S-D electrodes, estimated using the gated-transmission line method, was nearly two orders of magnitude smaller than that of conventional Cr/Au electrodes at the gate voltage of -10 V. The highest performance was obtained with a MoO(x) injection layer a few nanometers thick, which was comparable to the effective channel thickness of the pentacene-TFT on the gate insulator. This result indicated the importance of the direct connection between the MoO(x) injection layer and the effective channel to reduce the contact resistance. (c) 2008 American Institute of Physics.