Highly Robust Flexible Oxide Thin-Film Transistors by Bulk Accumulation

We report the achievement of flexible oxide thin-film transistors (TFTs) that are highly robust under mechanical bending stress. Fabricated on solution-processed polyimide, the oxide TFTs employ the dual-gate structure with an amorphous-indium-gallium-zinc oxide (a-IGZO) semiconductor, silicon dioxide gate insulators, and molybdenum gate and source/drain electrodes. High mechanical stability is achieved by shorting the two gates together to induce bulk accumulation (BA)-a condition in which the channel accumulation layer of electrons extends the entire depth of the active layer. It is shown experimentally that the BA a-IGZO TFTs exhibit better stability under bending stress compared with single gate-driven TFTs. From TCAD simulations, the immunity to slight variations in carrier concentration under tensile strain is found to be a result of the high gate-drive intrinsic of the BA TFTs.