Berlin 2005 – scientific programme

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SYOO: Organic Optoelectronics and Photonics

SYOO 6: Poster

SYOO 6.29: Poster

Monday, March 7, 2005, 18:00–20:00, Poster TU A

Parasitic Capacitances in Organic Field-Effect Transistors and their Influence on the cut-off Frequency — •I. Hörselmann and S. Scheinert — Festkörperelektronik, TU Ilmenau, 98693 Ilmenau

Organic field-effect transistors (OFETs) are promising elements for low-cost electronics. Many processes presented for OFET mass production will lead to parasitic capacitances resulting in reduction of the cut-off frequency. These capacitances are mostly caused by the overlap of the gate and source/drain contacts. In particular, for comb-like structures the overlap is very large and consequently a critical parameter for the design. Furthermore, for commercial applications supply voltages smaller 10V are necessary. This requires thin organic insulator layers resulting in higher parasitic capacitances. We performed ac simulations to determine the cut-off frequency for different OFET designs. Simulations have been carried out for various gate overlaps. Mobility, channel length, and insulator thickness have been chosen as parameters. The results show indeed, that the overlap in the comb-like structure is the limiting factor for the cut-off frequency. Most promising for reducing parasitic capacitances is the self-alignment technique. In this case the cut-off frequency is determined solely by the channel length and the mobility of the semiconductor material.