Effects of argon flow rate on electrical properties of amorphous indium gallium zinc oxide thin-film transistors

• IGZO thin films RF-sputtered on glass substrates under various Ar to oxygen flow rates
• The electrical performances and thin film quality of a-IGZO TFT were characterized.
• High mobility 27.7 cm2/V·s and very small sub-threshold voltage 0.11 V/decade obtained.
• Simple and low cost electron-beam deposited SiO2 used as gate dielectric.
• Ohmic behavior of source–drain with channel material has been achieved.

In this report, amorphous indium gallium zinc oxide (a-IGZO) thin films were deposited on glass substrates using different argon flow rates (AFRs). The impact on the electrical properties of the a-IGZO thin-film transistors with various AFRs during film growth has been carefully investigated. The AFR varied 20–60 sccm while the oxygen flow rate was maintained at 1 sccm. All a-IGZO films achieved transmittance higher than 80% in the wavelength range of 350–1000 nm, and it increased slightly with increasing AFR in the higher wavelength region. The rise in partial pressure due to increased AFR could affect the performance, in particular by increasing the current on/off ratio, and changes in electron mobility, sub-threshold swing voltage and threshold voltage. The optimal results were attained at AFR of 50 sccm. The field effect mobility, sub-threshold swing, ratio of on-current to the off-current, interfacial trap density and threshold voltage are 27.7 cm2/V·s, 0.11 V/dec, 2.9 × 108, 1.1 × 1012 cm− 2 eV− 1 and 0.84 V, respectively. In addition, good electrical properties were achieved using dielectric SiO2 prepared by simple, low-cost electron beam evaporator system.