Tuning the contact resistance in nanoscale oligothiophene field effect transistors Available to Purchase

Nanoscale organic transistors for high frequency applications are often limited by contact resistances. We report on tuning of those resistances by shifting the transport level for dihexyl-$n$-thiophene $(DHnT)$ semiconductors by variation of the number of thiophenes $n$ from 4 to 7. The intrinsic mobility as well as contact resistance were determined from individual transfer curves of bottom-contact transistors with channel lengths down to $50nm$⁠. Best values were found for DH7T with $μ=0.12cm2∕Vs$ and $Rc=1kΩcm$⁠. While the contact resistance remains fairly constant for a given $n$ as expected, the intrinsic mobility still decreases with decreasing channel length.