Effects of silicon doping on the performance of tin oxide thin film transistors

Thin film transistors (TFTs) with silicon-doped tin oxide (TSO) as channel layer were prepared by radio frequency magnetron sputtering. The decreased defect-state-related peak in photoluminescence (PL) excitation spectra and oxygen-vacancy-related O 1s peak in X-ray photoelectron spectroscopy (XPS) with increasing Si content, accompanied by the decreased off-state current and positive shift of turn-on voltage, confirms that silicon can be a good carrier suppressor. The optimum TFT performance after annealing at 300 °C was achieved at Si content 5.4 at.%, with saturation mobility of 5.3 cm2 V−1 s−1, turn-on voltage of −0.2 V, and on-off current ratio of 3.3 × 106, respectively. Increasing the annealing temperature is useful to improve the mobility, but the polycrystalline structure formed above 350 °C goes against the uniformity of oxide TFTs.