Subthreshold Swing Control in IGZO TFTs Using Floating‐Gate Engineering for AMOLED Displays

Achieving uniform low‐gray luminance in high‐resolution active‐matrix organic light‐emitting diode (AMOLED) displays remains a critical challenge. As pixel density increases, driving transistors are forced to operate in the deep subthreshold regime, where the steep subthreshold swing (SS) of conventional oxide thin‐film transistors (TFTs) makes the drain current highly sensitive to threshold voltage variations and noise. To address this, we propose a novel indium‐gallium‐zinc‐oxide (IGZO) floating‐gate TFT architecture capable of precise and wide‐range SS modulation. By engineering the layout‐defined gate coupling ratio (GCR), specifically through the adjustment of floating gate width and the introduction of a source‐overlapped floating gate (SO‐FG) structure, the SS can be linearly tuned with minimal additional fabrication process. Experimental characterization and 3D TCAD simulations confirm that the SS is strictly governed by capacitive coupling ratios, demonstrating a controllable range from 80.5 mV/dec (for switching) to over 499 mV/dec (for driving). Notably, the SO‐FG design enables area‐efficient SS expansion, significantly extending the driving voltage range from 0.5 to 2.4 V. This design facilitates the monolithic integration of high‐speed switches and robust driving transistors, providing a practical solution for enhancing low‐gray uniformity in high‐density pixel circuits.