Influence of the Contact Thickness on Electrical Performance of Staggered and Planer p-Channel Organic Field Effect Transistors

The influence of contact thickness on electrical performance of bottom gate Organic Field Effect Transistor (BG-OFET) with staggered and planer structures is studied in this paper. Two dimensional device simulation is performed with identical dimensions for both devices which show a good agreement between simulated and measured results. Contact thickness is varied from 0nm to 20nm for planer and staggered structures. The electrical characteristics are strongly affected by the contact thickness variation. With increasing contact thickness, the threshold voltage shifts from negative to positive. The simulation results indicate that saturation current value of staggered structure is higher than that of planer. Although the current does not increase in staggered structure due to its increasing contact thickness, while the current in planer structure increases up to three times. However, current in planer is still below the current in staggered structure. The extracted field effect mobility and current on-off ratio at 20nm electrode thickness for staggered structure is 0.67 cm2/V.s and 108, respectively. It has been observed that the field effect mobility, threshold voltage, sub-threshold slope, transconductance and current on-off ratio can be modified by varying contact thickness. Analysis of the results clearly demonstrates the significance of controlling the contact thickness in planer and staggered OFETs. It even offers a way to control OFETs parameters.