High-Speed Pseudo-CMOS Circuits Using Bulk Accumulation a-IGZO TFTs

We propose a way to achieve high-speed circuits with dual-gate (DG) bulk-accumulation back-channel-etched (BCE) amorphous indium-gallium-zinc-oxide (a-IGZO) thin-film transistors (TFTs) using the pseudo-CMOS structure. The DG BCE a-IGZO TFTs exhibit field-effect mobility (mu(FE)), threshold voltage (V-th), and subthreshold swing of 30 +/- 3 cm(2)/Vs, 2 +/- 0.5 V, and 120 +/- 30 mV/decade, respectively. For input voltage (V-DD) of 20 V, seven-stage pseudo-CMOS ring oscillators implemented with the BCE bulk-accumulation a-IGZO TFTs show oscillation frequency of 6.51 MHz, which corresponds to a propagation delay time of 11 ns/stage and is faster than the 17 ns/stage delay of the fastest single-gate-driven ratioed coplanar a-IGZO TFT circuits.