Electrical performance enhancement of p-type tin oxide channel thin film transistor using aluminum doping

A narrow process window for the fabrication of p-type semiconductors is one of the major challenges in implementing tin oxide (SnO_x) in thin film transistor applications. The SnO_x lattice was doped with Al to widen the process window and enhance the p-type channel thin film transistor performance with co-sputtering process. A change in the growth orientation direction with the presence of Al in SnO_x thin films was observed in the grazing-incidence X-ray diffraction data. The changes in the oxidation states of Sn ions were determines by X-ray photoelectron spectroscopy. With increasing Al concentration, the ratio of Sn⁴⁺ in the Sn peaks decreases indicating that the SnO_x film has improved p-type properties. These changes led to an improvement of the electrical properties such as output characteristic, field effect mobility, subthreshold swing, and positive shift of threshold voltage. - Highlights: • Co-sputtering process with metal targets was used to deposit Al doped SnO_x thin film. • The changes of orientation growth and oxidation states with various Al contents were observed. • Electrical performances were improved at optimum Al atomic percentage utilizing TFT structure.