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

Abstract

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 (ΔVth) 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.