Enhancement of electrical stability of a-IGZO TFTs by improving the surface morphology and packing density of active channel

a-IGZO films were deposited on Si substrates by d.c sputtering technique with various working power densities (pd) in the range of 0.74–2.22 W/cm2. The correlation between material properties and their effects on electrical stability of a-IGZO thin-film transistor (TFTs) was studied as a function of pd. At a pd of 1.72 W/cm2 a-IGZO film had smoothest surface roughness (0.309 nm) with In-rich and Ga-poor cation compositions as a channel. This structurally ordered TFTs exhibited a high field effect mobility of 9.14 cm2/Vs, a sub-threshold swing (S.S.) of 0.566 V/dec, and an on–off ratio of 107. Additionally, the Vth shift in hysteresis loop is almost eliminated. It was shown that the densification of the a-IGZO film resulted in the reduction of its interface trap density (1.83 × 1012 cm−2), which contributes for the improvement in the electrical and thermal stability.