Investigation of intrinsic channel characteristics of hydrogenated amorphous silicon thin-film transistors by gated-four-probe structure

We use a new hydrogenated amorphous silicon (a-Si:H) device structure, the gated-four-probe a-Si:H thin-film transistor (TFT), to investigate the intrinsic channel characteristics of inverted-staggered a-Si:H TFTs without the influence of source/drain series resistances. The experimental results have shown that, for the conventional a-Si:H TFT structure, the field-effect mobility, threshold voltage, and field-effect channel conductance activation energy have a strong dependence on a-Si:H thickness and TFT channel length. On the other hand, for the gated-four-probe a-Si:H TFT structure, these values are a-Si:H thickness and TFT channel length independent, clearly indicating that this new a-Si:H TFT structure can be effectively used to measure the channel intrinsic properties of a-Si:H TFTs.