Thin film transistor having semiconductor active layer

1. A thin film transistor, comprising:

a substrate;

an IGZO active layer on the substrate, the IGZO active layer, an atomic % of In in the IGZO active layer being between 55 atomic % and 75 atomic %, and an atomic % of Ga in the IGZO active layer being at least 10 atomic %, and the IGZO active layer including a channel region, a source region, and a drain region;

a gate electrode overlapping the channel region and insulated from the IGZO active layer by a gate insulator; and

source and drain electrodes contacting the source and drain regions, respectively,

wherein the IGZO active layer is formed by:

depositing ions including In, Ga, and Zn from a first target including In, Ga, and Zn; and

depositing ions including In from a second target having a different atomic composition from the first target, the second target including InZnO, and

controlling the deposition of ions from the second target so as to adjust an atomic % of In in the IGZO active layer to be between 55 atomic % and 75 atomic %.

2. The thin film transistor as claimed in claim 1 , wherein the IGZO active layer has a relative ratio of In:Ga:Zn that varies across the IGZO active layer in a direction parallel to the IGZO active layer.

3. The thin film transistor as claimed in claim 1 , wherein the thin film transistor has a field-effect mobility μ FE of from about 18.60 to 26.64 cm2/Vs.

4. The thin film transistor as claimed in claim 1 , wherein a bias power applied to the second target is from about 400 W to 600 W during the forming of the IGZO active layer.

5. The thin film transistor as claimed in claim 3 , wherein the atomic % of In in the IGZO active layer and the field-effect mobility μ FE of the thin film transistor are controlled by a bias power applied to the second target of from about 400 W to 600 W.