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HL: Fachverband Halbleiterphysik

HL 9: Poster 1

HL 9.91: Poster

Montag, 23. März 2009, 14:30–17:00, P2

Temperature-dependent bias stress effects in organic thin-film transistors — •Nicole Killat, Ingo Hörselmann, Susanne Scheinert, and Gerhard Gobsch — TU Ilmenau, 98684 Ilmenau, PF 100565, Germany

An investigation of the stability of organic thin-film transistors (OTFT) was carried out by bias stress measurements. OTFTs with bottom- and top- source/drain-contacts (W/L=1000/30) were fabricated with 30nm SiO₂ as gate dielectric and the polythiophene P3HT or the polyvinylene TPD(4M)-MEH-PPV as active layer. The transfer characteristics after each stress sequence as well as the time-dependent drain-current at constant gate bias were measured in the linear regime at a constant temperature between 240K and 340K and in nitrogen atmosphere. For both polymers a negative gate bias caused a negative threshold voltage shift during stress time, which increased with higher temperatures. In contrast to P3HT, PPV showed no complete reversibility of the negative threshold voltage shift after applying a positive gate bias, which is not affected by heating. However, the positive threshold voltage shift of a top-contacted transistor with P3HT, caused by a positive gate bias, increased significantly with higher temperatures. Measurements in air enforced the bias stress effect in the PPV-OTFT. In P3HT the acceptor-like doping by oxygen amplified the positive threshold voltage shift during positive bias stress and was hardly compensated by negative bias stress. As a conclusion, the bias stress effect in OTFTs increases with higher temperatures, but principle tendencies are not affected.