Regensburg 2002 – wissenschaftliches Programm

Bereiche | Tage | Auswahl | Suche | Downloads | Hilfe

SYOH: Organische Halbleiter

SYOH 3: Organic Field-Effect Transistors

SYOH 3.4: Vortrag

Montag, 11. März 2002, 12:45–13:00, H37

Modulation spectroscopy and electrical characterization of organic field effect transistors — •V. Wagner¹, T. Muck¹, J. Rudolph¹, T. Borzenko¹, F. Biscarini², and J. Geurts¹ — ¹Physikalisches Institut, Experimentelle Physik III, Universität Würzburg, Am Hubland, D-97074 Würzburg — ²CNR-Istituto di Spettroscopia Molecolare, Via P. Gobetti 101, I-40129 Bologna

Organic semiconductor devices suffer from low carrier mobility due to grain boundaries (GB). Our concept to overcome this problem is a reduction of the channel length to the dimension of organic crystallite size (sub-µ region). For this purpose field effect transistors were manufactured from oxidized n-doped silicon wafers by lateral structured gold contacts using e-beam lithography and subsequent deposition of the active organic layer (channel length down to 300 nm). The carrier mobility was determined by electrical measurements in the linear regime. We found for quaterthiophene (α-4T) and sexithiophene (α-6T) layers values of 1.2 · 10⁻⁶ cm²/(Vs) and 1·10⁻⁴cm²/(Vs), respectively, for not yet optimized substrate/film interfaces. To obtain further information in addition to the electrical data we applied electromodulation spectroscopy. In organic FETs using perylene tetracarboxylic dianhydride (PTCDA) as active material we can observe charge-transfer-excitons, whose signatures show a strong temperature dependence and vanish at lower temperatures (77K). Furthermore, the relative intensity within the experimental signature is dependent on the modulating field orientation, i.e. if the modulated electric field is either parallel or perpendicular to the organic layer. These results are compared with the electrical characterization.