A narrow process window for the fabrication of p-type semiconductors is one of the major challenges in implementing tin oxide (SnOx) in thin film transistor applications. The SnOx 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 SnOx 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 SnOx 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. (C) 2017 Elsevier B.V. All rights reserved.