Effect of annealing temperature on the optoelectronic properties of quinary amorphous oxide semiconductor IGZTO thin films

In this study, novel quinary InGaZnSnO (IGZTO) oxide thin films deposited on glass substrates using a high purity IGZTO (In:Ga:Zn:Sn:O=1:0.5:1.5: 0.25:x, atomic ratio) ceramic target via RF magnetron sputtering were air annealed in the temperature of RT to 450°C. The effects of annealing temperatures on the microstructure, electrical, and optical properties of thin films were systematically investigated. Both the as-deposited and the annealed IGZTO films exhibit amorphous structures. The film annealed at 150 °C demonstrated the best electrical performance with a carrier concentration of 3.06 × 10¹⁹ cm⁻³, mobility of 35.68 cm²/(V·s), and resistivity of 5.70 × 10⁻3 Ω·cm, while the one annealed at 350 °C has a carrier concentration of 3.58×1017 cm-3 and the smoothest surface, with the lowest RMS and Ra roughness of 0.384 nm and 0.278 nm, respectively. As the annealing temperatures increasing from 150°C to 450°C, the optical energy gaps (Eg) changes from 3.52 eV to 3.56 eV, and Urbach energy (EU) enhances from 170 to 274 meV, indicating that the increased disorder and more defects generated after annealing. Oxygen vacancies (Vo) are found to the main origin for the conductivity of IGZTO films, and its concentration gets the minimum value for the 350 °C-annealed film. The TFT with the 350°C-annealed IGZTO thin film as the active layer exhibits a favorable field-effect mobility (μFE) of 20.17 cm²/(V·s), which is higher than that of most of the reported IGZO TFT. Our films are grown by a single-target sputtering and their optoelectronic properties are regulated easily by annealing temperatures, so this work provide a facile and convenient method to get IGZTO films with appropriate electrical properties and high-performance IGZTO TFTs.