Critical Assessment of the High Carrier Mobility of Bilayer In ₂ O ₃ /IGZO Transistors and the Underlying Mechanisms

Abstract High‐performance bilayer In 2 O 3 /IGZO thin‐film transistors (TFTs) fabricated by pulsed laser deposition are reported. The TFTs exhibit an on/off current ratio of 10 9 , a reversed subthreshold slope (ss) of 0.08 V dec −1 , and a high saturation mobility of 47.9 cm 2 V −1 s −1 . The reliability of the mobility values is critically validated and assessed by four‐probe measurements, the transfer‐length method, and the temperature‐dependence. X‐ray photoelectron spectra are combined with C–V measurements to characterize the interface, and the results show that a two‐dimensional electron gas (2DEG)‐like state accumulates at the In 2 O 3 /IGZO interface. However, this state only forms in the subthreshold region and does not cause the high carrier mobility in the region above the threshold. Instead, the enhanced carrier mobility results from the intrinsic high mobility of the In 2 O 3 , the smooth surface, and the low‐defect states in the In 2 O 3 /IGZO bilayer with a good percolation transport path.