Origin of the improved mobility and photo-bias stability in a double-channel metal oxide transistor

This study examined the performance and photo-bias stability of double-channel ZnSnO/InZnO (ZTO/IZO) thin-film transistors. The field-effect mobility (μ FE ) and photo-bias stability of the double-channel device were improved by increasing the thickness of the front IZO film ( t int ) compared to the single-ZTO-channel device. A high-mobility (approximately 32.3 cm 2 /Vs) ZTO/IZO transistor with excellent photo-bias stability was obtained from Sn doping of the front IZO layer. First-principles calculations revealed an increase in the formation energy of O vacancy defects in the Sn-doped IZO layer compared to the IZO layer. This observation suggests that the superior photo-bias stability of the double-channel device is due to the effect of Sn doping during thermal annealing. However, these improvements were observed only when t int was less than the critical thickness. The rationale for this observation is also discussed based on the oxygen vacancy defect model.