The Al2O3 gate insulator modified by SiO2 film to improve the performance of IGZO TFTs

•The Al2O3 gate insulator was fabricated by ALD.•A SiO2 film is used to modify the Al2O3 gate insulator.•The effect of SiO2 interlayer on performance of IGZO TFT is studied.•The SiO2 interlayer improves the performance of IGZO TFT.

High-performance thin-film transistors (TFTs) using atomic layer deposited (ALD) Al2O3 as gate insulator and radio frequency (RF) sputtering In–Ga–Zn Oxide (IGZO) as channel layer were fabricated in this work. A SiO2 buffer layer was applied between IGZO and Al2O3 to prevent the picked-up defects when the samples were switched from ALD to RF sputtering. Contrasting to the TFTs without buffer layer, the SiO2 buffer layer improved the TFTs performances greatly, such as: the field effect mobility increases from 5.2 cm2/V s to 6.1 cm2/V s, the threshold voltage downshifts from 4.9 V to 1.7 V, the Ion/Ioff ratio increases from 2.8 × 107 to 9.6 × 107, the sub-threshold swing decreased from 0.76 V/dec to 0.6 V/dec. The maximum density of surface states at the channel–insulator interface decreased from 2.1 × 1012 cm−2 to 1.53 × 1012 cm−2.