Performance Modulation in All-Solution-Driven InCaOₓ/HfGdOₓ Thin-Film Transistors and Exploration in Low-Voltage-Operated Logic Circuits

Abstract

In current work, InCaO x thin films with different Ca-doping concentrations were prepared via solution-processed method. A systematic investigation was conducted to reveal the variation in the physical properties of InCaO x thin films as a function of Ca-doping concentration by using various characteristic measurements. Results not only demonstrate that Ca-doping can change the optical properties, microstructure, and surface roughness of In2O3 thin films but also indicate that Ca-doping can effectively decrease oxygen vacancies in In2O3 thin films. By measuring the electrical properties of InCaO x /HfGdO x thin-film transistors (TFTs) at a low operating voltage of 5 V, it is noteworthy that Ca-doping can improve the deteriorated performance of In2O3/HfGdO x TFT caused by excessive oxygen vacancies. As Ca-doping concentration reaches 0.5%, InCaO x /HfGdO x TFT manifests superior performances, including a larger $\mu _{\text {FE}}$ of 15.1 cm2V−1s−1 and a higher ${I}_{ \mathrm{\scriptscriptstyle ON}}/{I}_{ \mathrm{\scriptscriptstyle OFF}}$ of $2.3\times \vphantom {{1}^{\frac {{1}}{{2}}}}\,\,10^{{7}}$ . Furthermore, the stability of In2O3/HfGdO x TFTs under positive bias stress is improved after Ca-doping. Finally, an inverter with a high gain of 6.0 is assembled on the basis of InCaO x /HfGdO x TFT. More importantly, these excellent performances of InCaO x /HfGdO x TFTs are achieved at a low operating voltage, which marks a giant step toward the achievement of low cost and low power consumption electrical devices.