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HL: Fachverband Halbleiterphysik

HL 5: Organic semiconductors I (joint session HL/CPP)

HL 5.3: Vortrag

Montag, 16. März 2020, 10:00–10:15, POT 112

Self-alignment OTFT structures — •Jörn Vahland, Hans Kleemann, and Karl Leo — TU Dresden, IAP

Organic thin film transistor (OTFT) parameters have significantly improved in regard to static transistor performance, e.g. contact resistance and mobility. The dynamic performance, though, is mainly governed by the device capacitance. A large device capacitance restricts the switching frequency and might ultimately lead to inefficient circuits. Historically, this limitation has been overcome in inorganic device architectures by employing a so-called self-aligned gate structure, which allows structuring of source- and drain-electrode with virtually no overlap to the gate, yielding low overlap capacitance.

The transfer to OTFTs is not trivial, since subtractive process steps such as etching need to be selective to various materials within a typical device stack i.e. the semiconductor and the gate dielectrics. First implementations of self-alignments for OTFTs employ process steps which are unfortunately not scalable (such as through-plane exposure or lift-off), effectively prohibiting such devices in actual circuits.

We propose a coplanar OTFT in top gate configuration where selective etching processes and additional passivation layers are used in order to form a truely self-aligned organic transistor. We discuss the scaling of the overlap capacitance and highlight the potential of such self-aligned devices for high-frequency operation. Furthermore, we discuss the influence of etching process on the channel properties, and describe how charge carrier mobility and on/off ratio of the transistor can be preserved.