High-Performance Self-Aligned Top-Gate Amorphous InGaZnO TFTs With 4 nm-Thick Atomic-Layer-Deposited AlOx Insulator

Electrical characteristics of self-aligned top-gate (SATG) amorphous InGaZnO (a-IGZO) thin-film transistors (TFTs) with 4 nm-thick atomic-layer-deposited (ALD) AlO_x gate insulator (GI) are investigated. It is demonstrated that the SATG a-IGZO TFTs present high-performance metrics including a near-ideal subthreshold swing (SS) of 60.9 mV/dec, a low off-state current below 10⁻¹² A, a positive ${V}_{\text{th}}$ of 0.1 V, and a decent mobility of 14.1 cm²/ $\text{V}\,\cdot $ s. In addition, the TFTs exhibit negligible ${V}_{\text{th}}$ shifts less than 0.02 V against electrical bias stresses. Both high performance and excellent stability are thus simultaneously achieved for the ultrathin GI of amorphous oxide semiconductor (AOS) TFTs.