Improvement of sub-threshold current models for a-Si:H thin-film transistors

The improved sub-threshold drain–source current models of a-Si:H thin-film transistors (TFTs) is demonstrated in this paper. The current–voltage (I–V) characteristics of a-Si:H TFTs are revealed in both forward and reverse sub-threshold region. The I–V characteristics exhibit a strong dependence on the gate–source voltage (VGS) and the drain–source voltage (VDS). The effects of weak electron distribution and a lateral component of the electric field on the a-Si:H TFT characteristics, which are induced by VDS at both front and back interface, are considered in current model. This strong dependence of the sub-threshold current on VDS is attributed to the channel length, drain–gate overlap vicinity, and process condition. Simulated results based on the model exhibit a good agreement with measured experimental data. The proposed model and the modeling process will be very useful for practical TFTs simulation.