Nearly fully transparent InGaZnO thin film transistors with Mo-InGaZnO electrodes: The possibility of homogeneous InGaZnO based thin film transistors

In this letter, we demonstrate high performance and highly transparent InGaZnO thin film transistors (IGZO-TFTs) with nearly metal-free Mo doped IGZO source/drain (S/D) electrodes by co-sputtering. The electrical parameters such as filed effect mobility, on/off ratio and subthreshold swing are 15.9 cm²/V sec, 3.82×10⁷ and 300 mV/decade, respectively. The electrical performance and reliability of the IGZO-TFTs with Mo-IGZO S/D electrodes are comparable with the conventional IGZO-TFTs with Mo electrodes. Besides, the transparency is remarkably improved. With the optimized condition, the transmittance of the IGZO-TFTs with Mo-IGZO S/D electrodes can be >70%. From XPS material analysis, the addition of Mo can change the oxygen bonding states in IGZO, which may be the reason for the observed conductor behavior of IGZO. Hence, the formation of Mo-IGZO S/D electrodes with co-sputtering is a simple, cost effective and low temperature method for achieving fully transparent IGZO-TFTs with high electrical performance and well reliability.