Global Potential Energy Surface Exploration of In–Ga–Zn–O (IGZO) Reveals Ga-Rich Layered Channel Material

C-axis aligned crystalline indium-gallium-zinc oxides (CAAC-IGZOs) with layered phase are widely utilized as functional tunnel material for thin-film transistors (TFTs). Their performance, i.e., stability or mobility etc., of IGZO strongly depends on the indium:gallium:zinc (In:Ga:Zn) ratio, yet most of reports limit to the simplest 1:1:1 ratio for the great difficulty to explore comprehensively the quaternary IGZO material at all possible contents. Herein by developing a quaternary In-Ga-Zn-O global neural network potential, we searched for the full energy landscape with 137 compositions for IGZO, based on which the thermodynamic stable composition range is revealed to be in a general formula of (In_<i>x</i>Ga_2-<i>x</i>ZnO₄)_<i>m</i>(ZnO)_<i>n</i> with 0.5 < <i>x</i> < 1.5, <i>m</i> > 1 and <i>n</i> as a non-negative integer. Importantly, 15 stable CAAC-IGZO candidates are screened out with favorable thermal and optical stability. Their electrical properties and device simulation are verified by density functional theory (DFT) calculations. Our results showed that apart from IGZO(1:1:1), a Ga-rich IGZO(3:5:4) phase can also have similar electrical properties (bandgap ∼ 2.8 eV, effective mass ∼ 0.26 <i>m</i>₀) and favorable properties with subthreshold swing being 82 meV/dec in a simulated 6 nm device, respectively, superior to IGZO(1:1:1) 88 meV/dec.