Balanced Performance Improvement of a-InGaZnO Thin-Film Transistors Using ALD-Derived Al₂O₃-Passivated High-k HfGdO_x Dielectrics

High-speed operation and low-power-consumption requirements have accelerated the development of thin-film transistors (TFTs) with exploration of gate dielectrics. In this work, the integration of all-sputtering-derived HfGdO high-k gate dielectrics with amorphous InGaZnO (a-InGaZnO) films has been reported, yielding significant improvements in the performance of a-InGaZnO TFTs. By adjusting the multilayer dielectric sequence, TFT device performance can be precisely manipulated. It has been detected that a-InGaZnO TFTs with an optimized Al2O3/HfGdO dielectric configuration have demonstrated superior electrical performance, including a high field-effect mobility (μFE) of 23.3 cm2·V–1·S–1, a large on/off current ratio of 1.2 × 107, a low subthreshold swing of 0.09 V/dec, and good stability under bias stress. Finally, a low-voltage-operated resistor-loaded unipolar inverter has been assembled on the base of Al2O3/HfGdO/a-InGaZnO TFTs, demonstrating full swing characteristics and high gain of ∼20. All of the experimental results indicate promising potentials for all-sputtering-derived Al2O3/HfGdO laminated dielectrics toward the achievement of low-cost, low-power-consumption, and large-area all-oxide optoelectronics.