Berlin 2008 – wissenschaftliches Programm
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SYSA: Symposium Tayloring Organic Interfaces: Molecular Structures and Applications
SYSA 5: Poster Session SYSA
SYSA 5.32: Poster
Dienstag, 26. Februar 2008, 14:30–20:00, Poster A
Switching behaviour of organic field effect transistors — •Ingo Hörselmann, Andrei Herasimovich, and Susanne Scheinert — TU Ilmenau, Germany
We prepared an organic field effect transistor with source/drain electrodes self-alligned to the bottom gate contact, resulting in a low parasitic gate-drain capacitance of 6 pF/cm. As gate insulator we used a 200 nm silicon nitride layer grown by chemical vapor deposition (CVD). The active semiconductor material is spincoated Poly(3-hexylthiophene) P3HT. The channel length is 2 µ m, the measured transconductance cut-off frequency is 2.4 kHz at VGS=VDS=-20 V.
To investigate the transient behavior of the transistor, we switched the drain and gate potential with rectangle pulses and recorded the transient response of the source and drain currents. Because of the low parasitic capacitance it is possible to record the delay between switching the potential and the current flow through the transistor channel. Hysterese effects were investigated by variation the duty factor of gate potential pulses, resulting in different on-currents.
We compare the measured switching behaviour with two dimensional device simulations. The simulation describes the tendency of the measurement. During switch on by decreasing the gate potential, the source current is greater than the drain current because the carriers are mostly injected from the soure contact to build up the channel. During switch off the currents at source and drain are similar, because the holes flow from the accumulation channel to both contacts.