Impact of the Gate Dielectric on Contact Resistance in High‐Mobility Organic Transistors. (14th March 2019)

• Record Type: Journal Article
• Authors: Paterson, Alexandra F.; Mottram, Alexander D.; Faber, Hendrik; Niazi, Muhammad R.; Fei, Zhuping; Heeney, Martin; Anthopoulos, Thomas D.
• Is Part Of: Advanced Electronic Materials. Volume 5:Number 5(2019)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2019-03-14
• Subjects: contact resistance -- dielectric -- mobility overestimation -- organic thin‐film transistors -- small molecule polymer blends; Materials -- Electric properties -- Periodicals; Materials science -- Periodicals; Magnetic materials -- Periodicals; Electronic apparatus and appliances -- Periodicals; 537
• DOI: 10.1002/aelm.201800723
• Languages: English
• ISSNs: 2199-160X

Abstract

Abstract: The impact of the gate dielectric on contact resistance in organic thin‐film transistors (OTFTs) is investigated using electrical characterization, bias‐stress stability measurements, and bandgap density of states (DOS) analysis. Two similar dielectric materials, namely Cytop and poly[4, 5‐difluoro‐2, 2‐bis(trifluoromethyl)‐1, 3‐dioxole‐ co ‐tetrafluoroethylene] (Teflon AF2400), are tested in top‐gate bottom‐contact OTFTs. The contact resistance of Cytop‐based OTFTs is found to be greater than that of the AF2400‐based devices, even though the metal/OSC interface remains identical in both systems. The Cytop devices are also found to perform worse in bias‐stress stability tests which, along with the DOS calculations, suggests that charge trapping at the OSC/dielectric interface is more prevalent with Cytop than AF2400. This increased charge trapping at the Cytop OSC/dielectric interface appears to be associated with the higher contact resistance in Cytop OTFTs. Differences in the molecular structure between Cytop and AF2400 and the large difference in the glass transition temperature of the two polymers may be responsible for the observed difference in the transistor performance. Overall, this study highlights the importance of the gate dielectric material in the quest for better performing OTFTs and integrated circuits. Abstract : The type of gate dielectric in organic transistors is found to influence the contact resistance and bias stability of the devices. Both parameters are shown to vary between two different fluoropolymer dielectric materials, namely Cytop and AF2400. Charge trapping at the interface between the dielectric and the organic semiconductor is argued to be the primary cause for this observation.