A Simulation Study of Carrier Transport Affected by Local Defects in Amorphous InGaZnO Thin-Film Transistors

This paper investigates effects of local defects on performances of amorphous-InGaZnO (a-IGZO) thin-film transistors (TFTs) by numerical simulation. For systematic study, the local defects are represented by acceptorlike tail and acceptorlike deep-level defect states. TFT performance dependences on these local defects locating at source region, near source region, in the middle of channel region, near drain region, and at drain region are quantitatively explored. The thicknesses of the a-IGZO layers and defect regions are 10-70 nm. Different a-IGZO layer or defect-region thicknesses lead to distinct TFT performances. Compared with the defects in the source/drain regions, defects in the channel region will lead to severe mobility degradation. The mobility degradation caused by the defects in the drain region is strongly drain-bias dependent. Transfer curves, linear and saturation mobilities, energy band diagrams, conduction current distributions, as well as electric field distributions are investigated to explore the corresponding physical mechanisms.