The influence of low indium composition ratio on sol-gel solution-deposited amorphous zinc oxide thin film transistors

In this work, we examined the influence of In doping on the morphological and structural characteristics of ZnO active layers grown by the spin coating and the electrical performance of ZnO-based thin film transistors. XRD results indicated that the active layers were amorphous due to the absence of any sharp peaks. XPS analysis was carried out to determine indium amounts as an atomic percentage in ZnO and oxidation state of In. AFM images indicated that the roughness of the active layers decreased with increasing indium concentration in ZnO. The indium doping has dramatically improved the electrical parameters of ZnO-based transistors. The field-effect mobility of undoped TFT increased similar to 157 times by adding %3 In content. The highest field-effect mobility (mu(sat)) of 12.9 cm(2)V(-1) s(-1)was obtained for %3 In-doped ZnO TFT (IZO3). Also IZO3 has a 6.96 V threshold voltage (V-th), 10(6)I(on)/I-off ratio, 1.98 V/dec subthreshold slope (SS), and a high on-current of 4.6 mA. We ascribed the performance enhancement of devices with In doping due to increasing carrier concentration of channel. These results show that the low concentration of indium incorporation is very crucial to change the morphological properties of ZnO active layers and to obtain high-performance solution-processed TFTs.