Solution processed high performance ferroelectric Hf_0.5Zr_0.5O₂ thin film transistor on glass substrate

Thin film transistors (TFTs) with a ferroelectric Hf_0.5Zr_0.5O₂ (HZO) gate insulator (GI) have been reported by using the vacuum process for HZO such as sputtering and atomic layer deposition methods. We report in this paper the ZnO TFT with ferroelectric GI using solution processed AlO_x/HZO. AlO_x assists in the initiation of ferroelectricity by applying large mechanical stress and provides a sufficient amount of oxygen vacancy to the underlying HZO. X-ray diffraction and capacitance-voltage, polarization-voltage, and anti-clockwise hystereses in the transfer curve confirm the formation of the ferroelectric phase of HZO. The AlO_x/HZO TFTs exhibited a field-effect mobility of 140 cm²/V s, an on/off current ratio of 10⁹, and a sub-threshold swing of 0.32 V/decade. The TFT shows a good bias-voltage tunable memory window of ∼4.5 V and memory retention characteristics up to 10 000 s for a programing/erasing voltage of ±10 V with a pulse width of 0.5 s. This work demonstrates the fabrication of ferroelectric HZO TFT using the solution process, and the results can be applied to ferroelectric oxide semiconductor TFT electronics.