Transport properties of single-crystal tetracene field-effect transistors with silicon dioxide gate dielectric

Single-crystal organic field-effect transistors (SX-OFETs) with channel lengths of 1 and $100μm$ have been fabricated by adhering thin crystals of tetracene to freshly ashed $SiO2$ substrates containing countersunk gold contacts. The intrinsic transport properties of the tetracene single crystals, corrected for potential contact effects by using a standard four-probe configuration, have been measured from room temperature down to $4.2K$⁠. These OFETs exhibit mobilities as high as $0.1cm2V−1s−1$⁠, subthreshold swings of $<500mV∕decade$⁠, and $Ion∕Ioff$ ratios in excess of $109$⁠. The larger devices $(L=100μm,W=1000μm)$ show thermally activated mobilities over the temperature range $200K<T<300K$⁠, but thermally induced cracks in the crystal prevent this analysis from being extended to lower temperatures. The smaller devices have a greater probability of surviving to low temperatures without a crack permeating the active channel, and representative devices have been investigated over the full range $4.2K<T<300K$⁠. The transport mechanism in these smaller devices can be varied from thermally activated to nearly temperature invariant by the application of drain fields $>105V∕cm$⁠.