Regensburg 2002 – wissenschaftliches Programm

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SYOH: Organische Halbleiter

SYOH 3: Organic Field-Effect Transistors

SYOH 3.2: Vortrag

Montag, 11. März 2002, 12:15–12:30, H37

Subthreshold characteristics of P3AT-based field effect transistors using different gate insulators — •S. Scheinert¹, G. Paasch², M. Schrödner³, H.-K. Roth³, S. Sensfuß ³ und T. Doll¹ — ¹TU Ilmenau — ²IFW Dresden — ³TITK Rudolstadt

Organic field effect transistors using thin films (d ≤ 50nm) of regioregular poly-3-alkylthiophene (P3AT) have been prepared. An organic gate insulator made from poly-4-vinylphenol (P4VP) has been used in the case of P3DDT and silicon oxid in that one of P3OT. The mobilities of 5 · 10⁻³ cm²/Vs for P3DDT and 3· 10⁻⁵ cm²/Vs for P3OT have been estimated from the active region of the transfer characteristics. These curves show a very high inverse subthreshold slope of S ≈ 7 V/dec using P3DDT on P4VP and the subthreshold current depends on the drain voltage. But in the case of the organic/inorganic interface the value of S is low (200 mV/dec) and there is no drain voltage dependency in this region. To clarify these peculiarities we carried out 2D simulations of the transfer characteristics. It turns out that both the high inverse subthreshold slope and the drain voltage dependency can be explained by assuming the presence of rechargable traps either at the interface or in the bulk. Because of the low inverse slope using an inorganic insulator we suppose that interface traps are the reason. But, alone from the current characteristics it is not possible to determine without ambiguity the exact material parameters because there are too many influences on the subthreshold region.