Abstract
In this report, an amorphous indium gallium zinc oxide (a-IGZO) thin-film was fabricated by DC-sputtering at different oxygen partial pressure values. The transmittance of the thin films could be enhanced by treated with oxygen during sputtering and greater than 90% at 300～700 nm. It has been found that the oxide semiconductor properties are highly dependent on oxygen content, because oxygen vacancies provide the needed free carriers for electrical conduction. Therefore, the conductivity could be controlled by adjusting the flux of the mixture oxygen during film deposition. With the increasing amount of oxygen, the IGZO thin film would change from conductor to semiconductor, and finally become an insulator. During this tunable characteristic, one can adjust the resistivity according to different kinds of IGZOs, such as InGaZnO4, In1.1Ga1.1Zn0.9O4, In1.5Ga1.5Zn0.5O5, and In2Ga2Zn1O7. In the case of In2Ga2Zn1O7, we can get an amorphous, transparent thin film with the mobility around 6 cm2/V-s and the resistivity around 106 ohm when the oxygen to argon ratio is 0.66%.
