Ultrahigh On/Off Ratio Oxide Transistors via Noncoplanar Schottky–Ohmic Contacts

Abstract

Abstract Simultaneously balancing high mobility and ultra-low leakage current is a major challenge for metal-oxide thin-film transistors (TFTs) in ultra-low-power applications. Herein, we construct a high-performance InGaZnO/InGaO/InGaZnO tri-layer TFT based on a noncoplanar Schottky–Ohmic hybrid contact architecture. Remarkably, despite utilizing identical ITO electrodes, differential interfacial engineering explicitly decouples carrier transport: the bottom interface forms a 670 meV Schottky barrier to strictly suppress off-state leakage, while the top interface ensures low-resistance Ohmic extraction. Furthermore, a deep quantum potential well (ΔEc = 0.20 eV) formed between the high-impedance InGaZnO cladding layers and the highly conductive InGaO core strongly localizes carriers within the inner layer, constructing an ultra-low-scattering two-dimensional transport pathway. The device achieves an ultrahigh on/off current ratio exceeding 1010, together with a high field-effect mobility of 28 cm2/V s and a steep subthreshold swing of 120 mV/dec. The TFT also exhibits excellent bias stability, with a VTH shift of only 0.8 V under ± 20 V gate stress for 3600 s. Unipolar depletion-load inverters based on this architecture deliver full-swing operation and a maximum voltage gain of 55. These findings establish noncoplanar Schottky–Ohmic contacts as a powerful strategy to break the long-standing mobility–leakage trade-off, offering a scalable pathway toward low-power, high-performance oxide electronics for advanced display backplanes and large-area integrated circuits.