Achieving nearly 70 cm2/V·s field-effect mobility in single amorphous Ga-In-ZnO thin-film transistors deposited by sputtering process via intermediate patterned metal layer insertion

• The study presents a novel approach to significantly improve the field-effect mobility of amorphous Ga-In-Zn-O (a-GIZO) thin-film transistors (TFTs) by incorporating patterned metal layers, specifically aluminum (Al) and gold (Au). • he insertion of an Al layer increased mobility from 16.22 to 40.15 cm 2 /V·s. When both Al and Au layers were used, mobility further increased to 69.46 cm 2 /V·s. • This improvement is attributed to Al’s role in creating oxygen vacancies and Au’s ability to prevent oxidation, thereby enhancing electron mobility without compromising device stability. • The devices with patterned metal layers exhibited improved stability under positive bias stress (PBS) conditions. In this study, we introduce a novel method for enhancing the mobility of amorphous Ga-In-Zn-O (a-GIZO) thin-film transistors (TFTs) by incorporating a patterned metal layer within the a-GIZO single channel. The patterned metal layer comprises either a single layer of aluminum or a combination of aluminum and gold as the bottom and top layers, respectively. TFTs with a single aluminum layer achieved a field-effect mobility of 40.15 cm 2 /V∙s, significantly higher than the 16.22 cm 2 /V∙s of standard a-GIZO TFTs. This enhancement is attributed to aluminum’s low Gibbs free energy, which increases oxygen vacancies in the a-GIZO layer and thus improves carrier mobility. Furthermore, when a patterned dual-metal layer consisting of aluminum as the bottom layer and gold as the top layer is used, a field-effect mobility of 69.46 cm 2 /V∙s is achieved. This improvement is attributed to the low electrical resistivity of gold, which prevents oxidation between the upper gold layer and the a-GIZO layer deposited by sputtering process. Furthermore, this mechanism facilitates the enhancement of the reaction with a lower a-GIZO layer. The unique characteristics of gold prevent oxidation between the a-GIZO and gold interface, thereby promoting favorable interactions between Al and the underlying a-GIZO layer. Our findings demonstrate that strategically inserted patterned metal layers can significantly boost mobility of a single a-GIZO TFT while maintaining device stability, offering a promising approach for advanced display technologies.