7.8-GHz flexible thin-film transistors on a low-temperature plastic substrate

RF flexible thin-film transistors (TFTs) with a new speed record of cut-off frequency (fT) of 2.04 GHz and maximum oscillation frequency (fmax) of 7.8 GHz were realized using single-crystal Si nanomembrane as an active channel layer on a low-temperature plastic substrate. We report the detailed device layout design considerations for optimizing the frequency response of the flexible RF TFTs, supported by accurate small-signal equivalent circuit modeling. It is indicated that, by properly considering the tradeoff between the parasitic source/drain resistances and the parasitic source-to-gate/drain-to-gate capacitances, fT and fmax of the single-crystal-Si TFTs can be optimized separately in order to meet the requirements of certain potential RF applications.