Simulation of the effect of deep defects created by hydrogen on the performance of amorphous indium gallium zinc oxide thin film transistor (a-IGZO TFT)

Amorphous indium gallium zinc oxide (a-IGZO) are promising for developing thin film transistors (TFTs) because of their large electron mobility, small threshold voltage (Vth), and low temperature fabrication process. In this study, we have investigated the effect of near valance band defects on the output parameters of a-IGZO TFTs by using two-dimensional TCAD numerical simulation. It was found that donor defects near the valance band have no effect. The degradation of the mobility also causes degradation in the TFT performance. Acceptor defects states near valance band is the reason of positive Vth shift. It is therefore concluded that near valance band defects are not donor defects but acceptor defects with a Gaussian distribution which can also degrade the mobility.