SL 29

ORGANIC CMOS INVERTERS THROUGH DIELECTRIC INTERFACE MODIFICATION OF OFETS

N. Benson, M. Schidleja, C. Melzer, H. von Seggern

Darmstadt University of Technology, Institute of Materials Science, Electronic Materials Division, Petersenstra├če 23, D-64287 Darmstadt, Germany (seggern@e-mat.tu-darmstadt.de)

Textov├ę pole:  
Fig.1 Organic pentacene CMOS inver-ter with UV modified dielectric layer
For the overall success of Organic Electronics the realization of a simple CMOS technology is essential. In the present talk we demonstrate a method for conversion of p- to n-type and n- to p-type field-effect transistors by interface modification of the dielectric gate insulator prior to the deposition of the organic semiconductor. In case of utilizing SiO2 dielectric gate oxides a deposition of traces of calcium is shown to alter the transport characteristics of a pentacene OFET from p- to n-type and the reverse process is shown for UV treated polymeric gate insulators. In addition, it will be demon-strated that both p- and n-type transistors can be fabricated by using a single metal for all source and drain electrodes. It will be shown that the barrier lowering at the source electrode, necessary to inject holes from calcium into pentacene, will be manifested through trapping of electrons in the transistor channel. Such trapped charges result in a large threshold voltage shift which finally allows for hole injection across an injection barrier of more than 2 eV. In the talk the physical mechanisms for the conversion will be highlighted and the device properties of the individual transistors as well as the resulting CMOS inverters (see exemplary Fig.1) will be presented.