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-channeletched (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 (μ_FE), threshold voltage (Vth), and subthreshold swing of 30 ± 3 cm²/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.