Water-based processed and alkoxide-based processed indium oxide thin-film transistors at different annealing temperatures

In this study, indium oxide (In₂O₃) thin-film transistors (TFTs) are fabricated by two kinds of low temperature solution-processed technologies (T_a ≤ 300 °C), i.e., water-based (DIW-based) process and alkoxide-based (2-ME-based) process. The thickness values, crystallization properties, chemical structures, surface roughness values, and optical properties of In₂O₃ thin-films and the electrical characteristics of In₂O₃ TFTs are studied at different annealing temperatures. Thermal annealing at higher temperature leads to an increase in the saturation mobility (μ_sat) and a negative shift in the threshold voltage (V_TH). The DIW-based processed In₂O₃-TFT annealed at 300 °C exhibits excellent device performance, and one annealed at 200 °C exhibits an acceptable μ_sat of 0.86 cm²/Vs comparable to that of a-Si:H TFTs, whereas the 2-ME-based TFT annealed at 300 °C exhibits an abundant μ_sat of 1.65 cm²/Vs and one annealed at 200 °C is inactive. The results are attributed to the fact that the DIW-based process induces a higher degree of oxidation and less defect states than the 2-ME-based process at the same temperature. The DIW-based process for fabricating the In₂O₃ TFT opens the way for the development of nontoxic, low-cost, and low-temperature oxide electronics.