Effect of channel thickness on electrical performance of amorphous IGZO thin-film transistor with atomic layer deposited alumina oxide dielectric

We have investigated the electrical performance of amorphous indium–gallium–zinc oxide (α-IGZO) thin-film transistors with various channel thicknesses. It is observed that when the α-IGZO thickness increases, the threshold voltage decreases as reported at other researches. The intrinsic field-effect mobility as high as 11.1 cm²/Vs and sub threshold slope as low as ∼0.2 V/decade are independent on the thickness of α-IGZO channel, which indicate the excellent interface between α-IGZO and atomic layer deposited Al₂O₃ dielectric even for the case with α-IGZO thickness as thin as 10 nm. However, the source and drain series resistances increased with increasing of α-IGZO channel thickness, which results in the apparent field-effect mobility decreasing. The threshold voltage shift (ΔV_th) under negative bias stress (NBS) and negative bias illumination stress (NBIS) were investigated, also. The hump-effect in the sub threshold region under NBS and threshold voltage shift to negative position under NBIS were enhanced with decreasing of α-IGZO channel thickness, owing to the enhancement of vertical electrical field in channel.