Hypoeutectic Liquid Metal Printing of 2D Indium Gallium Oxide Transistors

2D native surface oxides formed on low melting temperature metals such as indium and gallium offer unique opportunities for fabricating high-performance flexible electronics and optoelectronics based on a new class of liquid metal printing (LMP). An inherent property of these Cabrera-Mott 2D oxides is their suboxide nature (e.g., In₂O_3-x), which leads high mobility LMP semiconductors to exhibit high electron concentrations (n_e > 10¹⁹ cm^-3) limiting electrostatic control. Binary alloying of the molten precursor can produce doped, ternary metal oxides such as In-X-O with enhanced electronic performance and greater bias-stress stability, though this approach demands a deeper understanding of the native oxides of alloys. This work presents an approach for hypoeutectic rapid LMP of crystalline InGaO_x (IGO) at ultralow process temperatures (180 °C) beyond the state of the art to fabricate transistors with 10X steeper subthreshold slope and high mobility (≈18 cm² Vs^-1). Detailed characterization of IGO crystallinity, composition, and morphology, as well as measurements of its electronic density of states (DOS), show the impact of Ga-doping and reveal the limits of doping induced amorphization from hypoeutectic precursors. The ultralow process temperatures and compatibility with high-k Al₂O₃ dielectrics shown here indicate potential for 2D IGO to drive low-power flexible transparent electronics.