Effects of tunneling-based access resistance in layered single-crystalline organic transistors
- PDF / 1,069,404 Bytes
- 14 Pages / 584.957 x 782.986 pts Page_size
- 11 Downloads / 179 Views
INVITED PAPER Effects of tunneling-based access resistance in layered singlecrystalline organic transistors Takamasa Hamaia) and Shunto Arai Department of Applied Physics, The University of Tokyo, Tokyo 113-8656, Japan
Tatsuo Hasegawa Department of Applied Physics, The University of Tokyo, Tokyo 113-8656, Japan; and Flexible Electronics Research Center, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba 305-8565, Japan (Received 12 September 2017; accepted 10 May 2018)
7-Decyl-2-phenyl[1]benzothieno[3,2-b][1]benzothiophene (Ph-BTBT-C10) is a soluble organic semiconductor that can afford high mobility organic thin-film transistors (OTFTs). The material exhibits inherent high layered crystallinity due to the formation of bilayer-type layeredherringbone packing that involves nearly independent p-electron core layers and alkyl-chain layers within the crystals. Here, we discuss that the bottom-gate/top-contact OTFTs composed of single-crystalline Ph-BTBT-C10 channel layers exhibit noticeable effects in the device characteristics caused by the highly insulating nature of the alkyl-chain layers. Notable layer-number (n) dependence was observed in the nonlinear current–voltage characteristics and the device mobility (2–14 cm2/Vs, with TFT ideality factor 15–46%, mainly due to large threshold voltages), which can be clearly ascribed to the tunneling-based interlayer access resistance across the alkyl-chain layers. The gated-four-probe measurements of single-crystalline OTFTs also revealed quite high mobility more than 40 cm2/Vs along the channel semiconducting layer, whereas highly insulating effects due to the alkyl-chain layers were also apparent as the large hysteresis in the gate-off states of OTFTs. We discuss the whole features of the tunneling-based access resistance in the device operations of single-crystalline OTFTs, on the basis of comparison between experimental results and model simulations.
I. INTRODUCTION
In the last decade, considerable progress has been made for organic semiconductor materials, especially for their use in solution-processed organic thin-film transistors (OTFTs).1–3 Some soluble small-molecule organic semiconductors were shown to afford high performance OTFTs whose device mobility of more than 10 cm2/Vs is generally higher than those obtained by vacuum-based thinfilm processing. In most of these materials, p-electron cores, which are responsible for the semiconducting properties, are chemically substituted by alkyl chains (or other substituents) to obtain sufficiently high solubility for their use in the solution processes.4–9 It was shown that the substitution by normal alkyl chains is quite effective and useful, not only for improving the solvent solubility but also for enhancing the layered crystallinity. Particularly, the resultant high layered crystallinity should be most crucial to obtain highperformance OTFTs, as it allows the production of uniform channel semiconductor layers that have flat semiconductor/ insulator interfaces, along which the efficient cha
Data Loading...
