Regensburg 2007 – wissenschaftliches Programm

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SYOE: Symposium Organic Thin Film Electronics: From Molecular Contacts to Devices

SYOE 4: Organic Transistors

SYOE 4.3: Vortrag

Dienstag, 27. März 2007, 10:30–10:45, H1

Electric field induced gap states in pentacene — •Dietmar Knipp¹, Amare Benor¹, Arne Hoppe¹, Veit Wagner¹, and Armin Völkel² — ¹International University Bremen, School of Engineering and Science , 28759 Bremen, Germany — ²Palo Alto Research Center, Electronic Materials and Device Laboratory, Palo Alto, California, USA

Despite the realization of pentacene transistors with high mobility the electronic transport is not fully understood. In particular the creation of gap states and the influence of gap states on the charge transport are still under investigation. To study the creation of electronic defects electrical in-situ measurements of pentacene TFTs were carried out. The devices with hole mobilities ranging from 0.2-0.5cm²/Vs were exposed to oxygen and moisture to study the influence on the device characteristic. Exposing the transistor to oxygen does not lead to a change of the transistor characteristic. Only if an electric field is applied while exposing the devices to oxygen a change of the device characteristic is observed. Applying voltages to the device leads to a shift of the onset of the drain current towards positive gate voltages. As a consequence the subthreshold slope is destinclty increased. The threshold voltage and the mobility are not affected by the oxygen contamination. Numerical simulations of the device charateristic reveal that the onset of the drain current is caused by acceptor-like defect states deep in the bandgap. A good agreement between the simulation and the experiment was observed by using a Gaussian distribution of defect states.