Influence of oxygen partial pressure in In-Sn-Ga-O thin-film transistors at a low temperature

We examined the electrical properties of low-temperature-processed top-gate In-Sn-Ga-O (ITGO) thin-film transistors (TFTs) by rf/dc-sputtering with different oxygen partial pressures (PO₂). As PO₂ changed from 0 to 50.0%, the ITGO TFT showed various electrical characteristics such as from conductor-like behavior to transfer curves with positive-shifted threshold voltages (V_th). The TFT at PO₂ of 25.0% afforded the best performance, exhibiting field-effect mobility of 14.8 cm²V⁻¹s⁻¹, V_th of 0.56 V, and subthreshold slope of 0.16 Vdec⁻¹ with reasonable electrical stability for gate bias stress. From various analysis techniques, we found that the TFT characteristics and the electrical stability strongly depended on the metal-oxygen surface states of the ITGO films influenced by PO₂ during the sputtering process.