Impact of Gate Metal Workfunction on Device Performance of Organic Thin Film Transistor

In this paper we have presented the simulation and analysis of the impact of the work function of the gate metal on the parameters and performance of the organic thin film transistor (OTFT). The bottom contact transistor, which is made from pentacene active material, paryelene dielectric and gold source/drain electrodes, has been used for our simulation. The simulations have been performed using Silvaco's Atlas device simulator. The Poole-Frenkel transport model was used in the pentacene active material. To simulate the gate leakage current we have used the Fowler-Nordheim and the hot carrier tunneling models. The results of the simulation have shown an impact of the gate metal work function on the threshold voltage, the gate leakage current and the on/off ratio of the device. The simulations were done for different values of the gate electrode work function, ranging from 4.0 eV to 5.4 eV. The threshold voltage has changed from -3.5 V to -2.3 V by changing the work function in the indicated range. The simulation has shown an increase in both the gate leakage and the drain currents with increasing gate work function. In addition there was an observed decrease in an ON/OFF ratio of the devices as gate work functions increased. The probed electric field at the interface between pentacene and parylene has also shown a slight increase as the gate electrode workfunction increased. Physical arguments supporting the trends observed have been discussed.