Study of Local Band Bending in n-Channel In₂O₃ Thin-Film Transistors under Gate and Drain Voltage Stress Using...

In this study, we analyze In₂O₃ thin-film transistors (In₂O₃-TFT) using synchrotron-based hard X-ray photoelectron spectroscopy (HAXPES) in operando conditions. A bottom-gate In₂O₃-TFT with a high-k Al₂O₃ gate dielectric, grown on thermally oxidized silicon (SiO₂/p⁺-Si), was examined while operating at varying V_GS and V_DS. The results reveal that the In 3d core level binding energy varies along the horizontal channel length, driven by the potential gradient induced by V_DS. Furthermore, the polarity of V_GS under positive V_DS significantly affects the channel structure, and V_DS influences the vertical electrostatic potential in the buried gate dielectric and the gate electrode. Analysis suggests that the primary source of drain-source leakage current (I_DSS) arises from high intrinsic electron and defect/trap levels associated with oxygen vacancies (V_O²⁺). Additionally, investigation beneath the Au/Ti drain and source electrodes under different bias voltages reveals substantial In₂O₃ reduction, leading to significant indium metal (In⁰) formation. Schematic models of carrier transport mechanisms are proposed to explain these findings.