Dresden 2003 – wissenschaftliches Programm
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HL: Halbleiterphysik
HL 25: Organische Halbleiter II
HL 25.7: Vortrag
Dienstag, 25. März 2003, 16:45–17:00, BEY/81
Short channel effects in nano-size organic Field Effect Transistors — •V. Wagner1,2, T. Muck2, M. Leufgen2, J. Geurts2, A. Lebib2, T. Borzenko2, G. Schmidt2, and L.W. Molenkamp2 — 1School of Engineering and Science, International University of Bremen, Campus Ring 8, D-28759 Bremen — 2Experimentelle Physik III, Universität Würzburg, Am Hubland, D-97074 Würzburg
Reduction of the channel length of organic field effect transistors (OFETs) results in faster switching speeds due to reduced capacitances. Furthermore, channel lengths below the average grain size of the organic film allow for devices with beneficial single grain transport properties. We investigate the limits for ultra short channels. Therefore we have systematically reduced the organic channel length down to <100 nm for OFETs manufactured by e-beam lithography. Thiophenes are used as active material in the OFETs because of their possible high carrier mobility values. The thiophenes were deposited on SiO2/n+-Si-substrates with structured gold source and drain finger contacts by vacuum evaporation. We expect deviations of the standard FET characteristics (short channel effects) for a channel length L comparable with the junction width of the electrodes and/or with the gate insulator thickness. Standard characteristics were observed for devices with a channel length L > 2 µm. Degradation of the saturation regime were found for L < 1 µm. Finally, for channel lengths of 400 nm or below the on/off ratio strongly deteriorates. The latter channels already have lengths similar to the SiO2 gate insulator thickness of 200 nm. The observed effects will be discussed in comparison with short channel effects known from inorganic devices.