Mobility overestimation due to gated contacts in organic field-effect transistors

• DOI: 10.1038/ncomms10908
• Publication Date: 2016-03-10T10:32:50Z
• Authors: Emily G. Bittle; James I. Basham; Thomas N. Jackson; Oana D. Jurchescu; David J. Gundlach
• Keywords: Naphthacenes; Transistors, Electronic; Science; Dielectric Spectroscopy; Q; Materials Testing; Silicon Dioxide; 01 natural sciences; Article; 0104 chemical sciences

AbstractParameters used to describe the electrical properties of organic field-effect transistors, such as mobility and threshold voltage, are commonly extracted from measured current–voltage characteristics and interpreted by using the classical metal oxide–semiconductor field-effect transistor model. However, in recent reports of devices with ultra-high mobility (>40 cm2 V−1 s−1), the device characteristics deviate from this idealized model and show an abrupt turn-on in the drain current when measured as a function of gate voltage. In order to investigate this phenomenon, here we report on single crystal rubrene transistors intentionally fabricated to exhibit an abrupt turn-on. We disentangle the channel properties from the contact resistance by using impedance spectroscopy and show that the current in such devices is governed by a gate bias dependence of the contact resistance. As a result, extracted mobility values from d.c. current–voltage characterization are overestimated by one order of magnitude or more.