Si-doping effect on solution-processed In-O thin-film transistors

In this work, silicon-doped indium oxide thin-film transistors (TFTs) have been fabricated for the first time by a solution processing method. By varying the Si concentration in the In₂O₃-SiO₂ binary oxide structure up to 15 at%, the thicknesses, densities, and crystallinity of the resulting In-Si-O (ISO) thin films were investigated by x-ray reflectivity (XRR) and x-ray diffraction techniques, while the produced TFTs were characterized by a conventional three-probe method. The results of XRR analysis revealed that the increase in the content of Si dopant increased the thickness of the produced film and reduced its density, and that all the Si-doped ISO thin films contained only a single amorphous phase even after annealing at temperatures as high as 800 C. The manufactured ISO TFTs exhibited a reduction in the absolute value of threshold voltage V _T close to 0 V and low current in the off-state, as compared to those of the non-doped indium oxide films, due to the reduced number of oxygen defects, which was consistent with the behavior of ISO TFTs fabricated by a sputtering method. The ISO TFT with a Si content of 3 at% annealed at 400 C demonstrated the smallest subthreshold swing of 0.5 V/dec, V _T of -5 V, mobility of 0.21 cm² V^-1s^-1, and on/off current ratio of about 2 10⁷.