Eco-Friendly Fully Water-Driven HfGdO ${_{x}}$ Gate Dielectrics and Its Application in Thin-Film Transistors and Logic Circuits

In this work, HfGdO
_x
gate dielectric thin films have been prepared via a nontoxic and environmental-friendly fully water-driven (WD) method. An in-depth investigation has been conducted to reveal the evolution of physical properties in the as-prepared HfGdO
_x
thin films as a function of annealing temperature. Based on the measurements of electrical parameters of the HfGdO
_x
thin films, it is observed that the 500 °C-annealed HfGdO
_x
thin films have shown optimized properties, including a smooth surface, lower leakage current density, and a larger areal capacitance. To validate the feasibility of the HfGdOx gate dielectrics in thin-film transistors (TFTs), In
₂
O
₃
/HfGdO
_x
TFTs have been constructed. The optimized In
₂
O
₃
/HfGdO
_x
TFT exhibited excellent electrical performances, including high field-effect mobility of 11.2 cm
²
V
^-1
s
^-1
, a high ON-/OFF-state current ratio of 4.1 × 10
⁶
, a small subthreshold swing of 105.2 mV/decade, and a threshold voltage shift of 0.58 V after 7200-s bias stress, respectively. Finally, based on the In
₂
O
₃
/HfGdO
_x
TFT, an inverter is assembled by connecting an external 3-MΩ resistor. High gain of 8.73 and excellent swing characteristics have been obtained. As a result, it can be inferred that fully WD In
₂
O
₃
/HfGdO
_x
TFTs with high performance will pave the way for achieving low-power-consumption, low-cost, and large-area electronics.