Effect of high conductivity amorphous InGaZnO active layer on the field effect mobility improvement of thin film transistors

High mobility thin film transistors (TFTs) with a high conductivity amorphous InGaZnO (a-IGZO) active layer were successfully fabricated. The operation of the high-carrier-IGZO thin film transistor with a Schottky barrier (SB) was proposed and clearly experimentally explained. The switching characteristic of SB-TFT does not rely on the accumulation process but due to the Schottky barrier height control. Leakage current can be reduced by Schottky contact at the source/drain (S/D), while it was as high as the on current so that the switch properties could not achieve in ohmic ones. The a-IGZO SB-TFTs with Ag S/D contact express the high performance with μ_FE of 20.4 cm² V^-1 s^-1, V_th of 5.8 V, and I_ON/I_OFF of 2 × 10⁷ @ VD = 1V. The introduction of operating mechanism for TFTs using high conductivity a-IGZO promises an expansion study for other active layer materials.