Numerical analysis of effects of back channel interfacial states on characteristics of amorphous InGaZnO thin-film transistors

The effects of back channel interfacial states (N_bit) that can be generated by passivation layer deposition for amorphous indium gallium zinc oxide thin-film transistors (a-IGZO TFTs) by using an ATLAS 2D device simulator are analysed. As N_bit is increased, the positive shift of threshold voltage (V_TH) is observed for thin and thick active layer TFTs due to the acceptor-like characteristics of interfacial states. However, as N_bit is further increased, the V_TH shift of the thick active layer TFT is eventually saturated, while that of the thin active layer TFT is continuously increased. This is because the characteristics of the a-IGZO TFT with a thin active layer are strongly affected by N_bit, which can be used for optimising the performance of a-IGZO TFTs.