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The electrical characteristics and stability of dual-gate (DG) coplanar homojunction amorphous indium-gallium-zinc-oxide thin-film transistors (a-IGZO TFTs) on glass substrates are described herein. In this device structure, both top gate (TG) and bottom gate are defined by lithography, allowing independent biasing when adjacent TFTs are present. The DG a-IGZO TFT demonstrates excellent electrical performance with subthreshold swing (SS) of 99 mV/dec, field-effect mobility of 15.1 , and on- off current ratio of . By applying various bias voltages on the TG electrode, it is found that the TFT threshold voltage can be controlled without any change of the SS and off current. Under conditions of negative bias temperature stress (BTS), the transfer curves of the TFT exhibit negligible shifts after 10 000 s. Larger shifts are observed under conditions of a positive BTS. Finally, the application of this DG device to active-matrix organic light-emitting displays is suggested.