Influence of the InGaZnO channel layer thickness on the performance of thin film transistors

• The Al2O3 gate insulator is fabricated by ALD.
• The effect of channel thickness on performance of TFT is studied.
• The proper channel thickness enhances the performance of TFT.
• 58 nm will be a proper channel thickness for IGZO TFT.

We report on the electrical properties of bottom-gate InGaZnO (IGZO) thin film transistors (TFTs) with different channel layer thicknesses. The IGZO channel layer with thickness varied from 25 to 120 nm were deposited by radio frequency sputtering. Al2O3 films were deposited on highly-doped n-Si substrate by atomic layer deposition (ALD) as gate insulator in this work. The influence of the IGZO channel layer thickness on the performance of TFTs is studied. The performance of devices is found to be thickness dependent. The best performance of devices is obtained from a 58 nm thick IGZO TFT, which shows a field-effect mobility in the saturation region of 6.2 cm2/Vs, a threshold voltage of 2.1 V, an Ion/Ioff ratio of approximately 6.4 × 107, and a subthreshold swing of 0.6 V/dec.