Comprehensive Optimization Strategies for InSnZnO Grade-Channel Thin-Film Transistors via Atomic Layer Deposition

The amorphous oxide semiconductors (AOSs) have been widely explored for thin-film transistors (TFTs). However, a tradeoff persists between high field-effect mobility and low threshold voltage attributed to percolation conduction, necessitating comprehensive optimization. Herein, the grade-channel InSnZnO (ITZO) TFTs with enhanced performance synthesized by atomic layer deposition (ALD) were investigated by the stoichio-metric and structure optimization in channel. The relationship between stoichiometric of channel and electrical transport property has been investigated in single-layer-channel ITZO TFTs. Then, we investigated the influence of vertical stoichiometric distribution on performance enhancement in bilayer-channel and grade-channel ITZO TFTs. The ITZO TFTs based on grade channel exhibit superior characteristics, including remarkable mobility of 65.88 cm2/V $\cdot $ s, fantastic on-/off-ratio of $10^{{10}}$ , and excellent subthreshold swing (SS) of 72.85 mV/dec, which weaken the tradeoff. Furthermore, the positive bias stress (PBS) instability test indicates that the grade-channel structure also enhances PBS stability beyond mobility improvement. These findings are promising for the performance enhancement of high-mobility AOS TFTs.