Dependence of device behaviours on oxygen vacancies in ZnSnO thin-film transistors

ZnSnO thin-film transistors (TFTs) were fabricated by pulsed laser deposition in different oxygen partial pressures. It is found that the oxygen vacancy (V-O) contents in ZnSnO films can be readily modified by the oxygen pressures in the growth process. The dependence of behaviors of ZnSnO films and TFTs on relative V-O concentration was studied in detail. The relative V-O concentration was determined by XPS spectra. The optical band-gap energies of ZnSnO films showed a negative correlation with V-O concentration. The strong relation can also be identified for the electrical performances of ZnSnO TFTs. The threshold voltage, subthreshold swing, and density of interfacial trap states increased with the V-O concentration in general. The field-effect mobility had a maximum value of 23.6cm(2)V(-1)s(-1) at oxygen pressure of 6Pa, which is ascribed to the competitive factors of V-O at different chemical states. It is expected that this work would gain a better understanding of oxygen vacancy in ZnSnO TFTs for practical applications.