Modeling the Short-Channel Effects in Coplanar Organic Thin-Film Transistors

• Published in: IEEE transactions on electron devices Vol. 69; no. 3; pp. 1099 - 1106
• Main Authors: Pruefer, Jakob, Leise, Jakob, Borchert, James W., Klauk, Hagen, Darbandy, Ghader, Nikolaou, Aristeidis, Iniguez, Benjamin, Gneiting, Thomas, Kloes, Alexander
• Format: Journal Article
• Language: English
• Published: New York IEEE 01.03.2022; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: CAD; Computer aided design; Coordinates; Coplanar device architecture; Current voltage characteristics; drain-induced barrier lowering (DIBL); Electric potential; Electrodes; Geometry; Integrated circuit modeling; Logic gates; Mathematical models; modeling; organic thin-film transistors (TFTs); Semiconductor devices; short-channel effects; Thin film transistors; Threshold voltage; threshold-voltage shift; Transistors
• ISSN: 0018-9383; 1557-9646
• DOI: 10.1109/TED.2022.3145779

We have developed models for three different short-channel effects [subthreshold-swing degradation, threshold-voltage roll-off, and drain-induced barrier lowering (DIBL)] in coplanar organic thin-film transistors (TFTs) and verified them against the measured current-voltage characteristics of TFTs having channel lengths as small as <inline-formula> <tex-math notation="LaTeX">0.5 \mu \text{m} </tex-math></inline-formula>. To derive the models, the Schwarz-Christoffel transformation was applied to obtain a complex mapping function that links the coplanar device geometry to an equivalent geometry in a different coordinate system in order to solve Laplace's equation of the 2-D potential problem. The solution to this potential problem serves as the basis for the definition of the short-channel models, which can be incorporated into any compact dc models for coplanar TFTs that use the TFTs' threshold voltage and subthreshold swing as input parameters. To verify the model, the channel-length-dependent effects were extracted from technology computer-aided design (TCAD) simulations (transfer characteristics and surface-potential profile) and from measurements performed on organic p-channel TFTs fabricated using high-resolution stencil lithography.