Potential solution-induced HfAlO dielectrics and their applications in low-voltage-operating transistors and high-gain inverters

Abstract

Recently, much attention has been paid to the investigation of solution-driven oxides for application in thin film transistors (TFTs). In current study, a fully solution-based method, using 2-methoxyethanol as solvent, has been adopted to prepare InZnO thin films and HfAlO_x gate dielectrics. Amorphous HfAlO_x thin films annealed at 600 °C have shown a high transparency (>85%), low leakage current density (6.9 × 10⁻⁹ A cm⁻² at 2 MV cm⁻¹), and smooth surface. To verify the potential applications of HfAlO_x gate dielectrics in oxide-based TFTs, fully solution-induced InZnO/HfAlO_x TFTs have been integrated. Excellent electrical performance for InZnO/HfAlO_x TFTs annealed at 450 °C has been observed, including a low operating voltage of 3 V, a saturated mobility of 5.17 cm² V⁻¹ s⁻¹, a high I_on/I_off of ∼10⁶, a small subthreshold swing of 87 mV per decade, and a threshold voltage shift of 0.52 V under positive bias stress (PBS) for 7200 s, respectively. In addition, time dependent threshold voltage shift under PBS could be described by a stretched-exponential model, which can be due to charge trapping in the semiconductor/dielectric interface. Finally, to explore the possible application in logic operation, a resistor-loaded inverter based on InZnO/HfAlO_x TFTs has been built and excellent swing characteristic and well dynamic behavior have been obtained. Therefore, it can be concluded that fully solution-driven InZnO/HfAlO_x TFTs have demonstrated potential application in nontoxic, eco-friendly and low-power consumption oxide-based flexible electronics.