Influence of oxygen flow during sputtering process on the electrical properties of Ga-doped InZnSnO thin film transistor

Abstract

This work presents the electrical properties of amorphous gallium-doped indium zinc tin oxide (Ga-IZTO) thin film transistors (TFTs), as a function of O-2 flow rate (Ar/O-2), during the sputtering process of the channel layer. As the O-2 flow rate increased from 30:0 to 30:7, the saturation mobility (mu SAT ) monotonically degraded from 31.5 cm(2) V-1 s(-1) to 12.0 cm(2) V-1 s(-1), the threshold voltage (V-TH) shifted from 0.8 V to 6.8 V, and the V-TH shift (Delta V-TH) induced by the negative bias stress improved from -7.0 V to -2.8 V. X-ray diffraction analysis indicated that the microstructure of all the films is amorphous, which is independent of O-2 flow rate. Transmittance spectra reflected that the average transmittance of the thin film is sensitive to the O-2 flow rate and decreases as the O-2 flow rate increases. XPS analysis revealed that the density of oxygen vacancies is reduced, and the oxygen lattices are enhanced as the O-2 flow rate increases. The Hall effect measurements indicated that the carrier concentration (n) was reduced with increasing O-2 flow rate. These results show that the electrical properties of Ga-IZTO TFTs can be easily tuned by the O-2 flow rate during the sputtering process. The related mechanism for the variations of electrical properties of Ga-IZTO TFT has been discussed in detail.