Effect of Atmosphere Dependent Annealing on the Electrical Characteristics of a-In $_{\text{2}}$ O $_{\text{3}}$ Thin-film Transistors

In $_{\text{2}}$ O $_{\text{3}}$ has been recognized as a wide-gap transparent semiconductor oxide with high mobility, in which the oxygen plays an important role in its electronic properties. Here, we investigate the effects of air, O $_{\text{3}}$ and N $_{\text{2}}$ annealing on the electrical characteristics of a-In $_{\text{2}}$ O $_{\text{3}}$ thin film transistors (TFTs) by analyzing the behavior of weakly bonded oxygen (O $_{\text{wb}}$ ), excess oxygen (O $_{\text{ex}}$ ), and oxygen vacancy (V $_{\text{O}}$ ) in the channel layer. X-ray diffraction (XRD) result indicates an amorphous phase of In $_{\text{2}}$ O $_{\text{3}}$ layer after annealing. The oxygen behavior and bonding information before and after annealing of the In $_{\text{2}}$ O $_{\text{3}}$ films are investigated via X-ray photoelectron spectroscopy (XPS) measurements. The a-In $_{\text{2}}$ O $_{\text{3}}$ TFTs with field-effect mobility of 50–60 cm $^{\text{2}}$ /Vs and enhanced reliability are achieved by optimizing channel thickness and annealing conditions in air. The large threshold voltage shifting, reduced mobility, and low ON/OFF ratio of O $_{\text{3}}$ -annealed In $_{\text{2}}$ O $_{\text{3}}$ TFT are attributed to the existence of O $_{\text{ex}}$ . The hump-effect observed in N $_{\text{2}}$ -annealed In $_{\text{2}}$ O $_{\text{3}}$ TFT is attributed to the creation of a parasitic channel with high V $_{\text{O}}$ level above the main channel. The results reveal that O $_{\text{wb}}$ can be removed by thermal treatment, and V $_{\text{O}}$ can be partially filled and stabilized without introducing O $_{\text{ex}}$ by annealing the as-deposited In $_{\text{2}}$ O $_{\text{3}}$ TFTs in air at appropriate condition.