Effects of channel length and gate dielectric material on electrical properties of an IGZO TFT

In this paper, the variation of threshold voltage, transconductance, and on/off current ratio of bottom-gate InGaZnO (IGZO) thin-film transistors (TFTs) with different channel lengths and gate dielectric substrate has been investigated. Bottom gate configuration was simulated using SILVACO TCAD Software. Electrical parameters such as threshold voltage, transconductance, and on/ off current ratio were analyzed with an active layer thickness of 30 nm and the variation of length of channel from 5 μm to 25 μm and gate dielectric substrate of high dielectric constant. Threshold voltage increased and transconductance decreased with the increase of the channel length but there was no big change in IOn/IOff ratio. The threshold voltage around 0.64 V, transconductance around 44.2 μs, and On/Off current ratio around 8.13x108 were observed at a channel length of 5 μm. When the dielectric material SiO2 was replaced by Si3N4, the threshold voltage was 0.76 V, transconductance was 85.64, and On/Off current ratio was 1.58x109 and for Al2O3 threshold voltage was 0.77 V transconductance was 199.8 μs and On/Off current ratio was 4.3x109.Transconductance, Threshold voltage, and On/Off current ratio were increased for high K gate dielectric materials.