Continuous Grain Growth of High Band Gap InGaO on Crystalline In_0.7Ga_0.3O for 0.3 µm Channel Length Thin Film Transistors

Abstract In‐based crystalline oxides have been of increasing interest for thin film transistors (TFTs) due to their high mobility and excellent stability. In₂O₃ TFTs suffer from inferior stability so a stabilizer such as gallium (Ga) is necessary for stable crystalline(c‐) TFTs. However, excess dopants can disrupt the crystal structure of indium oxide, resulting in degraded TFT performance. In this study, continuous crystal growth of high Ga InGaO (IGO) on low Ga IGO by spray pyrolysis (SP) is investigated. IGO with higher Ga concentration grain grows by following the seed IGO. The In_0.5Ga_0.5O (In:Ga = 5:5) and In_0.4Ga_0.6O (In:Ga = 4:6) are grown on In_0.7Ga_0.3O for TFT applications, exhibiting the field‐effect mobility of 28.9 and 25.1 cm² V s⁻¹, respectively. Note that the field‐effect mobility of a single layer of In_0.7Ga_0.3O (In:Ga = 7:3) is 33.8 cm² V s⁻¹. The TFTs with 0.3 µm channel length are demonstrated with c‐In_0.4Ga_0.6O on c‐In_0.7Ga_0.3O layer. The c‐IGO with a high Ga concentration top layer has a lower carrier concentration and reduced oxygen vacancies, resulting in accumulation mode IGO TFT. The study proposes the application of short‐channel crystalline oxide TFTs for high‐resolution, active‐matrix organic and inorganic light‐emitting diode displays.