The structural, optical and electrical properties of Y-doped SnO thin films and their p-type TFT application

Unintentionally doped and Y-doped SnO thin films were prepared and characterized by x-ray diffraction, spectroscopic ellipsometry, and Hall-effect measurements. SnO-based thin-film transistors were also fabricated and investigated. Preferred (0 0 l) grain orientation present in the undoped films is alleviated by Y doping, inducing the deterioration of crystallinity as well as the decrease in Hall-effect and saturation field-effect mobilities. However, both the films and the transistor devices always possess p-type characteristics in this study. As the Y content increases, the optical band gap, the real part of the dielectric constant of the films and the on/off current ratio of the devices increase. Moreover, the threshold voltage was observed to shift towards the positive direction as more yttrium content is introduced. These results give evidence that the yttrium element is incorporated into the SnO lattice successfully and higher hole concentration can be generated.