Conduction instability of amorphous InGaZnO thin-film transistors under constant drain current stress

Conduction characteristics of amorphous InGaZnO thin-film transistors were investigated by applying constant drain current with gate bias (V_GS) modulation. Constant drain current in the off-current (I_off) level from the transfer characteristic was applied to the drain electrode and the measured drain voltage with the gate bias sweep. The normalized channel conductance (G_d) characteristics were extracted from transfer characteristics and the gate bias modulated drain voltage characteristics with constant drain current stress were compared with the characteristics. The drain voltage induced by the constant drain current stress showed simultaneous transition from off-state with generation current dominant region with increasing drain bias (V_DS) to the turn-on state. The high electric field at the drain electrode edge was observed at the threshold voltage (V_TH), which can affect the instability characteristics of TFTs.