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CPP: Chemische Physik und Polymerphysik

CPP 21: SYMPOSIUM Functional Organic Thin Films II

CPP 21.1: Hauptvortrag

Donnerstag, 30. März 2006, 14:00–14:30, ZEU Lich

Recent Advances in Charge Transport in Organic Field effect Transistors — •Ananth Dodabalapur, Liang Wang, Lawrence Dunn, and Debarshi Basu — Microelectronics Research Center, The University of Texas at Austin

This presentation will focus on two recent advances in studying charge transport in organic thin-film field-effect transistors with pentacene active semiconductor layers. With the help of electron-beam lithography we have fabricated transistors with short channel lengths. This, combined with careful surface treatments to improve hole injection, has enabled the fabrication of devices which are not seriously injection limited with channel lengths in the range between 250 nm and 5 microns. The electric-field dependence of carrier mobility has been measured in the range 104 - 6 x 105 V/cm and between 60-300 K by analyzing the transistor DC characteristics. The field dependence of the mobility more closely follows a Frenkel-type dependence than a polaronic dependence.

A new method to measure charge carrier mobility in organic field-effect has been developed in which the drift mobility of injected carriers (generated with a step voltage pulse) is measured. This permits the measurement of the velocity and mobility of the fastest carriers. The mobility evaluated in this manner is generally found to be higher than that obtained by the conventional technique based on an analysis of DC currents in a transistor. Extensions of our new method to measure the distribution of velocities or mobilities will also be described.