Synergistic Enhancement of Mobility and Stability in TiO ₂ /ITZO Heterostructure TFTs via Quasi-2DEG and Interfacial Passivation

Abstract This study addresses the insufficient stability of ITZO-based thin-film transistors (TFTs) by designing and fabricating a heterostructured oxide TFT with an ITZO front-channel and an ultra-thin TiO 2 back-channel. After introducing the TiO 2 layer, the field-effect mobility (μ FE ) is improved from 7.6 to 18.4 cm 2 V -1 s -1 . Under 3600 s bias stress, the threshold voltage shift (ΔV TH ) under positive bias stress (PBS) is reduced from 5.73 to 1.78 V (a reduction of 68.9%), and under negative bias stress (NBS) from -3.95 to -0.78 V (an 80.3% reduction in absolute value), demonstrating significantly enhanced stability. Mechanistic analysis shows that the conduction band offset between TiO 2 and ITZO drives electron accumulation at the heterointerface, forming a high-concentration quasi-two-dimensional electron gas (quasi-2DEG) and boosting carrier transport. Meanwhile, the TiO 2 layer acts as an efficient self-passivation barrier by reducing oxygen vacancies, suppressing charge trapping, and passivating interface defects, thus greatly improving stability. This work provides an effective strategy for enhancing the stability of ITZO-based TFTs and offers new pathways for developing high performance oxide electronic devices.