Highly Robust Spray‐Pyrolyzed Al₂O₃ Gate Insulator for Flexible a‐IGZO Thin‐Film Transistors for Low‐Power Displays

Thin‐film transistor (TFT) is a key element in flexible display technology for energy‐efficient wearable electronics. A systematic analysis is performed to demonstrate the high‐quality high‐ k Al 2 O 3 gate insulator (GI) by low‐cost spray pyrolysis on a polyimide (PI) substrate for low‐power flexible displays. The spray‐pyrolyzed Al 2 O 3 film deposited at 375 °C shows an amorphous phase, smooth surface roughness, and higher metal‐oxygen bonding states. Additionally, one‐cycle Ar/O 2 plasma treatment on Al 2 O 3 enhances the dielectric properties, exhibiting a lower leakage current density of 6.1 × 10 −6 A cm −2 (@6.0 MV cm −1 ), higher breakdown electric field of 9.7 MV cm −1 , and negligible frequency dependence in capacitance curves. The high‐performance and robust amorphous InGaZnO TFTs are fabricated using Al 2 O 3 GI on a PI substrate, demonstrating a field‐effect mobility of 13.4 cm 2 V −1 s −1 , threshold voltage of −0.7 V, subthreshold swing of 0.305 V dec −1 , I ON / I OFF ratio of ≈10 9 , gate leakage current of ≈0.1 pA, zero hysteresis voltage, and stable operation against electrical and mechanical stresses. Finally, a high‐speed ring oscillator operating at an oscillation frequency of 2.63 MHz, along with a gate driver exhibiting rising and falling times of 655 and 576 ns, are presented using spray‐pyrolyzed Al 2 O 3 /a‐IGZO TFTs on a PI substrate.