High-Mobility Indium Native Oxide Transistors via Liquid-Metal Printing in Air

Oxide semiconductors have emerged as common channel materials in transistors and hold promise for next-generation electronics, yet achieving high mobility typically requires costly vacuum-based techniques. Here, ultrathin (5 nm) indium native oxide (InO_x) prepared by ambient-air liquid-metal printing (LMP) at a low temperature (250 °C) is applied as a semiconducting channel in a field-effect transistor (FET). The resulting InO_x is found to be polycrystalline, with large lateral grains that extend vertically throughout the film thickness. InO_x FETs in a transfer length method configuration demonstrate a high conductivity mobility (μ_CON) of 125 cm² V^-1 s^-1, with systematic analysis of contact resistance confirming the potential for channel length scaling. Integration with atomic-layer-deposited gate dielectrics further reveals excellent compatibility; for instance, an InO_x FET integrated with HfO₂ exhibits a high field-effect mobility (μ_FE) of 107 cm² V^-1 s^-1, an on/off current ratio (I_ON/I_OFF) of >10⁷, a subthreshold swing (SS) of 204 mV dec^-1, and a gate leakage of <10^-6 A cm^-2, while maintaining stable performance over 10⁴ endurance cycles without degradation. Postfabrication oxygen plasma treatment is applied to achieve enhancement-mode operation, and a depletion-load inverter is demonstrated, exhibiting a voltage gain of 69.8 V/V. These results demonstrate the great potential of LMP InO_x as a semiconducting channel in high-performance and power-efficient transistors for next-generation oxide electronics.