High-Performance In-Sn-Zn-O Vertical Thin-Film Transistors with Al₂O₃ Tunneling Layer

To address performance degradation caused by the drain-induced barrier lowering (DIBL) effect in short-channel vertical thin-film transistors (VTFTs), this work proposes an ultrathin tunneling layer (TL) modification strategy. A 2 nm Al₂O₃ TL with low roughness, narrow bandgap, and low barrier height is fabricated at the drain-spacer sidewall-source interface, forming a TL-VTFT based on an In-Sn-Zn-O active layer (AL). This design overcomes the trade-off between DIBL suppression and performance enhancement. The TL increases the contact barrier, enabling space-charge-limited conduction (SCLC) at low electric fields and Fowler-Nordheim tunneling at medium-high fields, achieving a DIBL of only 0.045 V/V. Additionally, it optimizes the back-channel interface, reducing charge scattering and enhancing carrier transport. For short-channel devices (width 2000 nm and length 200 nm), a saturation mobility of 30.22 cm²/V ˙ s, subthreshold swing of 67.3 mV/dec, and current drivability of 16.58 μ A/μ m (R_ds =0.5 V) are achieved. This work offers new insights for designing high-performance, low-DIBL short-channel VTFTs.