High-performance C60 n-channel organic field-effect transistors through optimization of interfaces

High-performance C-60 organic field-effect transistors (OFETs) have been obtained by engineering the essential electrode/semiconductor and dielectric/semiconductor interfaces. By using calcium (Ca) as the source and drain electrodes, the width-normalized contact resistance (RCW) at the electrode/semiconductor interface for devices with channel lengths ranging from 200 down to 25 mu m could be reduced to a constant value of 2 k Omega cm at a gate-source voltage (V-GS) of 2.6 V, leading to electrical properties that are dominated by gate-modulated resistance of the channel as in conventional metal-oxide-semiconductor field-effect transistors. Channel length scaling of the source-drain current and transconductance is observed. Average charge mobility values of 2.5 cm(2)/V s extracted at V-GS < 5 V are found independent of channel length within the studied range. Besides high mobility, overall high electrical performance and stability at low operating voltages are demonstrated by using a 100-nm-thick high-kappa gate dielectric layer of aluminum oxide (Al2O3) fabricated by atomic layer deposition and modified with divinyltetramethyldisiloxane-bis (benzocyclobutene). The combined operating properties of these OFETs, obtained in a N-2-filled glovebox, are comparable to the best p-channel OFETs and outperform those of amorphous silicon thin-film transistors.