Transfer characteristics of a-IGZO thin film transistors prepared with different RF powers

We investigated the effects of RF power on the properties of amorphous indium gallium zinc oxide (a-IGZO) thin films and the transfer characteristics of a-IGZO thin film transistors (TFTs). The TFTs were fabricated using the a-IGZO thin film as the n-channel active layer deposited by RF-magnetron sputtering. The carrier concentration of the a-IGZO was controlled via the oxygen pressure during the sputtering process. The roughness of a-IGZO film decreased from 12.2 to 6.5 A and the density increased from 6.0 to 6.1 g/cm³ as the RF power increased from 75 to 150 W. The a-IGZO thin films were transparent (>85%) in the visible region, and the optical band gap slightly decreased with increasing RF power. The threshold voltage increased from 0.9 to 7 V, and the subthreshold slope increased from 0.3 to 0.8 (V/decade) as the RF power increased. However, the mobility increased from 11 to 19 cm²/V s with the increase in RF power.