RbNO₃ Wet Chemical Treatment for Contact Engineering and Enhanced Performance of a-IGTO TFTs with Improved Stability

Amorphous indium gallium tin oxide (a-IGTO) has emerged as a promising channel material for next-generation oxide thin-film transistors (TFTs) owing to its superior carrier transport properties and compatibility with low-temperature processing. However, high contact resistance is observed at the metal/semiconductor interface, and instability is caused by bulk and interface defects, which hinder device performance and reliability. In this study, we proposed a simple and effective rubidium nitrate wet chemical treatment (WCT) for the first time to address the existing challenges in amorphous oxide semiconductor devices. The optimized WCT process improves the surface morphology and promotes Rb cation diffusion at the Al/a-IGTO interface, thereby reducing the contact and channel resistivity by four and seven times, respectively. This, in turn, effectively enhances the field-effect mobility from 10.1 to 22.54 cm 2 /V·s as well as subthreshold swing from 0.37 to 0.14 V/dec and shifts the threshold voltage from −3.9 to 0.1 V at most. Furthermore, the treated devices significantly improve the stability under positive/negative bias stress, negative bias illumination stress, and positive bias temperature stress, which is attributed to the formation of stable Rb–O bonds that suppress the oxygen vacancies. The synergistic effects of surface morphology improvement, controlled Rb surface doping, and bulk Rb incorporation enable the development of high-performance, reliable oxide TFTs, paving the way for their integration into future electronic applications.