High-performance calcium-doped zinc oxide thin-film transistors fabricated on glass at low temperature

High-performance calcium-doped zinc oxide thin-film transistors (Ca-ZnO TFTs) have been successfully fabricated on transparent glass at low temperature by RF magnetron sputtering. To study the effects of calcium doping on zinc oxide thin-film transistors, the characteristics of Ca-ZnO TFTs and ZnO TFTs are compared and analyzed in detail from different perspectives, including electrical performance, surface morphology, and crystal structure of the material. The results suggest that the incorporation of calcium element can decrease the root-mean-square roughness of the material, suppress growth of a columnar structure, and improve device performance. The TFTs with Ca-ZnO active layer exhibit excellent electrical properties with the saturation mobility (mu(sat)) of 147.1 cm(2)V(-1)s(-1), threshold voltage (V-t) of 2.91V, subthreshold slope (SS) of 0.271V/dec, and I-on/I-off ratio of 2.34 x 108. In addition, we also study the uniformity of the devices. The experimental results show that the Ca-ZnO TFTs possess good uniformity, which is important for large-area application. (C) 2016 The Japan Society of Applied Physics