Low Operating Voltage N-channel Organic Field Effect Transistors using Photoresist/LiF Bilayer Gate Dielectric

We report a low temperature processed, low voltage operable n-channel Organic Field Effect Transistors (OFETs) using N, N'-Dioctyl-3, 4, 9, 10-perylenedicarboximide (PTCDI-C₈) organic semiconductor and high-k HPR-504 photoresist gate dielectric. We have studied the effect of the addition of LiF buffer dielectric on the OFET performance in comparison to the single layer photoresist dielectric devices. The single layer dielectric device showed substandard performance than the double layer gate dielectric device primarily due to the high amount leakage current flowing in the device because of the poor insulating property of the photoresist. The gate leakage was effectively reduced by the addition of a thin layer of LiF dielectric below the photoresist and resulted in higher drain current for bilayer devices. The bilayer OFET devices had a low threshold voltage (V_t) of the order of 2.8 V. The typical values of saturation electron mobility (μ_s), on/off ratio and inverse sub-threshold slope (S) for the devices made were estimated to be 8.6×10^-5 cm²/Vs, 54, and 12.5 V/decade respectively.