Effects of Ga ₂ O ₃ deposition power on electrical properties of cosputtered In-Ga-Zn-O semiconductor films and thin-film transistors

In this study, we have successfully fabricated In-Ga-Zn-O (IGZO) thin-film transistors (TFTs) with various Ga₂O₃ deposition powers prepared using a two radio-frequency (RF) (ceramics targets: In ₂O₃ and Ga₂O₃) and one direct-current (DC) (metallic target: Zn) magnetron cosputtering system at room temperature. The carrier concentration for the IGZO films decreases to less than 3 × 10¹⁶ cm^-3 when the Ga₂O₃ deposition power is 175 W and Hall mobility decreases from 12.8 cm² V^-1 s^-1 and saturates at 4.6 cm² V^-1 s^-1 with increasing Ga₂O₃ deposition power. The increase in the resistivity of the cosputtered films correlates with the decrease in the crystallinity of the InGaZn₇O₁₀ phase and the phase transformation from InGaZn₇O₁₀ to InGaZn ₂O₅ with increasing Ga₂O₃ deposition power. With an optimum Ga₂O₃ deposition power of 150W, cosputtered IGZO TFTs with a higher, saturated drain current of 4.5 μA, good saturation mobility, μ_sat of 4.92 cm² V^-1 s^-1, I_on/I_off of 10⁹, a low subthreshold swing (SS) of 0.27V/decade, and R_SD of 30kΩ have been successfully fabricated.