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<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\cdot $ </tex-math></inline-formula> s, fantastic <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">on</small>-/<sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">off</small>-ratio of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$10^{{10}}$ </tex-math></inline-formula>, 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.