AC characterization of organic thin-film transistors with asymmetric gate-to-source and gate-to-drain overlaps

This paper presents S-parameter characterization and a corresponding physics-based small-signal equivalent circuit for organic thin-film transistors (OTFTs). Furthermore, the impact of misalignment between the source/drain contacts and the patterned gate on the dynamic TFT performance is explored and a simple method to estimate the misalignment from the measured S-parameters is proposed. An excellent fit between theoretical and experimental S-parameters is demonstrated. For this study, OTFTs based on the air-stable organic semiconductor dinaphtho[2,3-b:2',3'-f]thieno[3,2-b]thiophene (DNTT) having a channel length of 1 mu m and a gate-to-contact overlap of 5 or 20 mu m and being operated at a supply voltage of 3 V are utilized. The intentional asymmetry between gate-to-source and gate-to-drain overlaps is precisely controlled by the use of high-resolution silicon stencil masks. (C) 2013 Elsevier B. V. All rights reserved.