In–Si–O thin-film transistors with atomic layer deposition-grown Al₂O₃ gate insulator

In this work, indium silicon oxide (ISO) active channel layers were deposited at room temperature using radio frequency (RF) magnetron sputtering. Aluminium oxide (Al₂O₃), deposited via atomic layer deposition (ALD) over a p-type crystalline (100) silicon (p-Si) substrate, served as the dielectric and gate electrode respectively, for the construction of thin-film transistors (TFTs). A molybdenum (Mo) metal contact was deposited as the source and drain using RF sputtering at room temperature. The maskless photolithography process was employed for patterning the active channel layer and source/drain contacts with various channel widths (W) and lengths (L). The average capacitance per unit area (C_i) and the dielectric constant (κ) of the Mo/Al₂O₃/p-Si metal–insulator-semiconductor (MIS) structure were calculated to be 56.05 nF/cm² and 6.33, respectively. The ISO TFT, post-annealed at 200 °C, with a length (L) of 100 µm and a width (W) of 200 µm, exhibited a saturation mobility (µ_sat) of 20.24 cm²/V·s, an on–off drain current ratio (I_ON/I_OFF) of 1 × 10⁹, a turn-on voltage (V_ON) of − 2 V, and a sub-threshold swing (SS) of 0.52 V/dec.