Dresden 2006 – scientific programme

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HL: Halbleiterphysik

HL 31: Organic semiconductors

HL 31.16: Talk

Wednesday, March 29, 2006, 18:30–18:45, POT 51

In situ stability studies of long-life organic field-effect transistors — •M. Michelfeit, M. Leufgen, G. Schmidt, J. Geurts, and L. W. Molenkamp — Physikalisches Institut der Universität Würzburg, Experimentelle Physik III

In spite of numerous investigations, degradation of organic field effect transistors (OFETs) due to contamination, ageing and voltage stressing remains a hot issue. We report on stability studies, performed in situ in UHV in order to avoid extrinsic contamination effects. For this purpose we fabricated high-performance OFETs with UHV deposited dihexylquaterthiophene (DH4T) as active material. Using UHV-processed Au/Ti electrodes, mobility values of 0,12 cm²/Vs are achieved and the in-situ performance data show negligible ageing effects on a time scale of at least several weeks. Thus they allow age independent measurements of the effect of applied voltage stress (both at gate/source and drain/source) on the OFET performance. We discover the carrier mobility to be independent of the voltages and the time of their application. In contrast, the threshold voltage exhibits a strong dependence on these parameters, although its shift turns out to be almost reversible. We explain this behaviour by the existence of traps at the organic/insulator interface.