Simulation of twin boundary effect on TFT characteristics

The influence of twin boundary on the characteristics of single grain TFT has been analysed by ISE 3-D simulator. It has been found that the orientation and the position of the twin boundary could affect the field effect mobility, the leakage current and the kink effect of the device. The field effect mobility increases with the decrease of the angle between the twin boundary and the channel direction, which is consistent with the experiment results. The twin boundary in contact with the drain leads to higher leakage current because electron-hole generation is enhanced by the trap states in the twin boundary. The simulation indicates that the local electric field near a twin boundary is very high, thus inducing strong impact ionization. The smaller the distance between the twin boundary and the drain the higher the kink effect.