Enhanced mobility and bias stability of SnO₂ thin-film transistors enabled by Ga₂O₃ passivation-induced two-dimensional electron gas

This study presents a method to achieve both high performance and electrical stability in SnO₂ thin-film transistors (TFTs) fabricated by a sol–gel process. Sol–gel–processed Ga₂O₃ passivation layers are introduced onto the SnO₂ active channel layers to address bias instabilities. The Ga₂O₃ films passivate the back channel by compensating dangling bonds and isolating the channel from H₂O and O₂, which improves bias stability. Structural, optical, chemical, and device-level properties were systematically analyzed. When Ga₂O₃ is deposited on SnO₂, electrons redistribute to maintain thermal equilibrium and become confined in the potential well of SnO₂, forming a quasi two-dimensional electron gas that increases the free carrier concentration. This effect results in a 1.5-fold enhancement in field-effect mobility (from ∼10 cm²/Vs to ∼15 cm²/Vs) together with improved bias stability. The proposed SnO₂–Ga₂O₃ passivation method offers a promising route toward bias-stable, high-performance metal oxide films for applications in TFTs, solar cells, transparent conducting electrodes, and resistive random-access memory (ReRAM).