Effects of Channel Type and Doping on Hysteresis in Low-Temperature Poly-Si Thin-Film Transistors

The influence of channel type and doping on hysteresis in the current-voltage characteristics of poly-Si thin-film transistors (TFTs) has been investigated using p-/n- and intrinsic/B-doped channel TFTs. The hysteresis is greater in the p-channel than the n-channel and decreases in the p-channel but increases in the n-channel as the channel is doped with B. The energy profiles of the border trap density show asymmetry, in which the trap density is greater in the lower half of the bandgap. The border trap density increases as the channel is doped with B. The difference in border trap density between the near bandedge and near midgap energy levels is greater in the p-channel than the n-channel and decreases in the p-channel but increases in the n-channel as the channel is doped with B. The results show good agreement between the hysteresis effect and the energy profiles of border trap density.