2D C-Axis-Aligned Crystalline In─S─O Transistors Processed from Aqueous Solution

Abstract

There is a growing interest in exploring nanometer-thin 2D oxide semiconductor transistors for future scaled and multifunctional (e.g., ultraflexible and high transparency) devices. However, further development is hindered due to the degraded device performance with nanometer-thin 2D oxide semiconductor channels and the use of costly vacuum-based techniques. Here, 2D (2.7 nm thick) c-axis-aligned crystalline In─S─O channel material processed from aqueous solution is reported. The 2D In─S─O transistors based on Si/SiO₂ substrates exhibit high mobility (µ) of 22.15 cm² V⁻¹ s⁻¹, on/off current ratio (I_on/I_off) of ≈10⁷, and good bias stress stability. Detailed investigations show that this achievement is attributed to the highly c-axis-aligned crystalline structure, well-designed In─S─O channel material, and atomically smooth surface. Furthermore, the 2D In─S─O channel is integrated with an aqueous sol-gel-derived 6 nm thick high-k ZrO₂ insulator. The all-aqueous-solution-based quasi-2D In─S─O/ZrO₂ devices show high µ of 15.65 cm² V^─1 s^─1, I_on/I_off of ≈10⁶, and low operating voltage of 1.5 V. This 2D c-axis-aligned crystalline wide-bandgap oxide semiconductor channel material opens tremendous opportunities for multifunctional, ultra-scaled and low-cost electronics.