Hysteresis effect in bottom-gate polymorphous silicon thin-film transistors

The hysteresis effect observed in the transfer characteristics of n-channel bottom-gate hydrogenated polymorphous silicon (pm-Si:H) thin-film transistors (TFTs) is investigated in terms of the channel width. Such phenomenon is observed in devices of wide channel (>20 μm), whereas it diminishes in devices of narrow channel. The hysteresis of wide channel TFTs is mainly due to charges injected from the channel, trapped in the gate dielectric. As the channel width is reduced the edge effect becomes more significant and the effect of carrier injection from the channel is eliminated, which is balanced by the effect of charge injection from the gate electrode.