Electrical characteristics of InGaZnO thin film transistor prepared by co-sputtering dual InGaZnO and ZnO targets

A co-sputtering of dual InGaZnO and ZnO targets, abbreviated by ZnO co-sputtered IGZO, is used to fabricate a high performance indium gallium zinc oxide (IGZO) thin film transistor in this work. The ZnO co-sputtered IGZO thin film exhibits a smooth (R_rms ∼ 0.29 nm), featureless, and amorphous structure with high carrier density (n ∼4.29 × 10¹⁷ cm^-3). The performance and stability of ZnO co-sputtered IGZO TFT has been investigated and compared with the counterparts fabricated by a single ZnO and a-IGZO target respectively. Highest linear field effect mobility of 16.1 cm² V^-1 s^-1 with an I_on/I_off ratio of 1.04 × 10⁷, saturation drain current of 3.8 μA at 5 V, and the lowest threshold voltage of 2.0 V with sub-threshold swing of 0.21 V per decade have been obtained for the ZnO co-sputtered IGZO TFT. Furthermore, the ZnO co-sputtered IGZO TFT exhibited only a threshold voltage shift (ΔV_th) of 2.75 V under negative biased illuminated stress conditions for 2500 s, whereas the IGZO and ZnO based TFTs suffered from a huge threshold voltage shift (ΔV_th > 6 V) under the same conditions. The obtained performance and stability of TFTs with ZnO co-sputtered IGZO film is very promising for low voltage display applications.