Structural and Electrical Properties of Solution-Processed Gallium-Doped Indium Oxide Thin-Film Transistors

We fabricated solution-processed gallium-doped indium oxide (GIO) thin-film transistors (TFTs). The electrical property, crystallinity, and transmittance were investigated as a function of gallium content. Varying the gallium/indium ratio is found to have a significant effect on structural and electrical properties of thin films. The shrinkage of the lattice of a GIO film originates from substitution of Ga on In sites in the In 2 O 3 lattice, which was verified by X-ray diffraction (XRD) analysis. By increasing the gallium ratio of the channel material, the GIO film shows an amorphous phase. The optimized GIO film ($\text{Ga/In}= 0.35$) has an electron mobility of 3.59 cm 2 V -1 s -1 , a threshold voltage of 0.1 V, an on/off current ratio of $8.2\times 10^{7}$, and a subthreshold slope of 0.9 V/decade, and is highly transparent (${\sim}92$%) in the visible region.