An Energy-Band Model for Dual-Gate-Voltage Sweeping in Hydrogenated Amorphous Silicon Thin-Film Transistors

Abstract

This paper clarifies the correct transmission mechanism, misattributed in the previous research, of a hydrogenated amorphous silicon thin-film transistor (a-Si:H TFT) device. Complete drain current-gate voltage (I-D-V-G) transfer characteristics including the forward and backward gate sweeps (gate voltage carried out in the OFF-state -> on-state and the ON-state -> OFF-state) are performed, and the physics models of an energy-band schematic are clearly explained. This paper reveals that the I-D-V-G curve stretch-out behavior of the subthreshold region is due to the leakage of the Poole-Frenkel region. At the Poole-Frenkel regions, electrons transfer to the drain terminal, and holes remain in the valance band of the a-Si:H bulk. The remaining holes represent the positive voltage and cause the electron barrier height lowering. This causes an increase in subthreshold current of the subthreshold region. Finally, three experiments are performed to prove the correctness of these models, and the a-Si TFTs device improvement methods will be proposed to enhance the stability and performance of product of the a-Si TFTs.