Channel length-dependent parasitic bipolar transistor effect in Poly-Si TFTs considering traps at grain boundary

This paper reports channel length-dependent parasitic bipolar transistor (PBT) effect in Poly-Si TFTs considering traps at grain boundary. As verified by the experimentally measured data and simulation results, due to impact ionization (II), the PBT's current gain is large when the channel length is small at a low drain bias; but independent of the channel length at a high drain bias. The trap density at grain boundary affects strongly the channel length-dependent floating-body effect of the poly-si TFTs.