Dresden 2009 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 52: Organic semiconductors II

HL 52.6: Talk

Friday, March 27, 2009, 11:45–12:00, POT 51

Prediction of Dynamical Properties of Organic Field-Effect Transistors from DC Transistor Parameters — •Benedikt Gburek and Veit Wagner — Jacobs University Bremen, School of Engineering and Science, Campus Ring 1, 28759 Bremen, Germany

Dynamical properties of Organic Field-Effect Transistors (OFETs) are of crucial importance for almost any application. However, not direct AC data but DC measurements are usually used to optimize transistor performance. Here we present a systematic study to which extent DC parameters can actually be used to predict AC performance and AC limits of transistors. The standard FET theory for long channel devices predicts a maximum device bandwidth of ω_B = µ V / L². However, this holds only for ideal situations, e.g. without parasitic capacitances, and not too high frequencies. Furthermore, as was recently shown [1], contact resistances can pose severe additional high-frequency limits to the AC performance. To check the AC limit of a given transistor directly we perform a frequency scan up to the frequency where the gate current equals the drain current, which defines the true bandwidth of the device. The frequency-scanned AC voltage is applied at the gate while the drain contact is kept at a constant voltage. A model which defines a correction factor to the ideal µ V / L² behaviour is proposed in order to predict the measured bandwidth from DC transistor parameters correctly. The model takes into account contact resistances and parasitic capacitances among others.

[1] V. Wagner, P. Wöbkenberg, A. Hoppe, J. Seekamp, Appl. Phys. Lett. 89 (2006) 243515