Performance and stability of amorphous In-Ga-Zn-O thin film transistors involving gate insulators synthesized at low temperatures

This study consists of an investigation on the electrical characteristics of amorphous In-Ga-Zn-O (a-IGZO) thin-film-transistors (TFTs) using SiO₂ and Al₂O₃ gate insulators deposited at temperatures lower than 200 °C. The SiO₂ and Al₂O₃ layers were synthesized by radio-frequency magnetron sputtering and atomic layer deposition (ALD). The a-IGZO TFTs involving stacked Al₂O₃/SiO₂ gate insulators exhibit relatively high performance compared to those based on single SiO₂ dielectrics. The maximum field effect mobility and subthreshold swing (SS) values obtained were 6.96 cm²/Vs and 0.28 V/decade, respectively. The threshold voltage shift (ΔV_th) under negative bias stress (NBS), negative bias illumination stress (NBIS) and positive bias stress (PBS) were −0.38V, −2.05 V and 1.98 V, respectively. Here it is suspected that the defect content in sputtered SiO₂ is reduced when it is grown onto ALD Al₂O₃, thus enhancing the device performance and stability.