Berlin 2005 – scientific programme

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HL: Halbleiterphysik

HL 57: Poster IIa

HL 57.6: Poster

Tuesday, March 8, 2005, 16:30–19:00, Poster TU E

Dynamic behaviour and scaling properties of OFETs with channel lengths between 50 µ m and 100 nm — •Jörg Seekamp, Tobias Muck, Arne Hoppe, Torsten Balster, and Veit Wagner — School of Engineering and Science, International University Bremen, 28759 Bremen, Germany

A major demand to organic field effect transistors (OFETs) is the improvement of their dynamic properties. The maximum operating frequency of the transistor follows from the gradual channel approximation: f_t=µ V_ds′/2 π L²; V_ds′:=min(V_gs−V_t, V_ds). For this frequency the input current, i.e. I_gate, is equal to the output current, i.e. I_drain. At higher frequencies a given stage of an electronic circuit is no longer able to drive a following stage of the same type. For an OFET with L=100 nm,µ=0.01 cm²/Vs, V_ds′=1.7 V this results in f_t=27 MHz. In this contribution transit frequencies for the small signal case and the switching behaviour of OFETs with channel lengths between 50 µ m and 100 nm are presented. For a common gate bottom electrode device geometry f_t from 100 Hz to 10 kHz were measured for channel length between 50 µ m and 1 µ m. Geometry effects are accounted for by introducing a geometry factor: f_t=aµ V_ds′/2 π L². Further deviations of measured f_t with respect to the expected values are discussed in terms of the organic material properties and interfaces to the gate isolator and electrodes.