Enhancement in Performance and Reliability of Transparent IGZO Thin-Film Transistors by ITO/Ti Stacked Source/Drain Contacts

Enhancement in performance and reliability of transparent IGZO thin-film transistor (TFT) was achieved by adopting a laminated structure with a thin ITO layer and an ultrathin Ti layer as the source/drain (S/D) contacts. Compared with the transparent TFT with pure ITO S/D contacts, the transparent TFT with the ITO/Ti S/D contacts showed three times of enhancement in field-effect mobility from 4.75 to 12.10 cm 2 /Vs, two times of enhancement in on/off current ratio from 7.0 × 10 7 to 1.54 × 10 8 , three times of reduction in contact resistance from 15.74 to 4.64 kΩ, and a decrease in threshold voltage from 3.11 V to 2.80 V. The TFT with the ITO/Ti S/D contacts also maintained an extremely low leakage current at zero gate bias (for the device with channel width/channel length of 40 μ m/5 μ m, the leakage current was ∼1 × 10 −13 A). In addition, the TFT with the ITO/Ti S/D contacts showed a hump-free transfer curve and a smaller shift in threshold voltage under negative bias illumination stress. The enhancement in performance and reliability makes the transparent TFT with the ITO/Ti S/D contacts very promising in transparent display applications.