Channel length variation effect on performance parameters of organic field effect transistors

This research paper analyzes, finite element based two dimensional device simulations for top and bottom contact organic field effect transistors (OFETs) by considering uniform and non-consistent mobility regions. To model the morphological disorder in bottom contact structure, some calibrated standards for simulation is developed viz. by considering variable low mobility regions near the contacts. An analytical model is developed, by considering contact resistance and field dependent mobility. The effect of channel length variation (5–40 μm) on performance parameters is highlighted for both the structures. Subsequently, results shows only 1% change in current for bottom contact with 0.5 μm and 1 μm low mobility region near the contacts, due to dominant contact resistance, whereas, linear dependency is observed for other simulated structures. The top contact device shows 0.43 cm2/V s saturation mobility at 5 μm and 13% decrease up to 20 μm and afterwards constant behavior is noticed, whereas low mobility is extracted in bottom contact devices and shows 10–20% increase in both the mobilities for increasing channel length from 5 to 40 μm. For top and bottom devices, total 65% and 62% decrease in contact resistance is observed for increasing gate voltage from −1.8 V to −3 V and this percentage reduces for increasing the length of low mobility region. Further, we have evaluated 13%, 40% and 78% increase in the trap density, while proceeding for 0.25 μm, 0.5 μm and 1 μm low mobility region in the bottom contact structure.