Influence of the channel layer thickness on electrical properties of indium zinc oxide thin-film transistor

Thin-film transistors (TFTs) were fabricated on SiO2/n+–Si substrates using amorphous binary In2O3–ZnO (a-IZO) films with different thickness for active channel layers deposited by the rf magnetron sputtering at room temperature. The performance of devices was found to be thickness dependent. With the active layer thickness from 33 to 114 nm, the field-effect mobility μFE increased from 1.60 to 4.59 cm2/V s, the threshold voltage VTH decreased from 62.26 to 20.82 V, and the subthreshold voltage swing S decreased from 4.06 V/decade to 1.30 V/decade. Further, the dependence of TFTs’ electrical properties on active layer thickness was investigated in detail on the basis of free carrier density and interface scattering.