Characterization of pentacene organic thin film transistors fabricated on SiN_x films by non-photolithographic processes

Non-photolithographic organic thin film transistors (OTFTs) were fabricated using pentacene and SiN_x films on p-Si (100) at room temperature to investigate both the effects of their device structure (two different types of OTFTs, top-electrode and bottom-electrode) and the pentacene film deposition-rate on their current-voltage characteristics. OTFTs of the top-electrode type were prepared by thermal evaporation at various deposition rates of 1, 3, 5 and 7 Å/s. The top-electrode OTFTs exhibited 40 times higher amount of currents than the bottom-electrode OTFTs at the same bias conditions. An optimum OTFT was obtained using 5 Å/s and exhibited the saturation current, I_D of approximately 4 μA at a gate bias of -40 V along with the field effect mobility of ∼0.046 cm²/Vs and the on/off current ratio of ∼10⁵.