Amorphous semi-insulating Al-doped In₂O₃ growth by atomic layer deposition for thin-film transistors

In₂O₃-based metal-oxide-semiconductor channel materials are attractive for thin-film transistors and novel back-end-of-line (BEOL) compatible devices and have attracted intensive research activities in recent years. However, several challenges remain, such as the ultrahigh electron density and the nature of polycrystalline films. To overcome these issues, here in this work, we demonstrated an in situ semi-insulating doping method of In₂O₃ via atomic layer deposition and fabricated the indium-aluminum-oxide (IAO) transistors. The controllable concentration of Al enables an on-current of 1.8 μA/μm with the cycle ratio at In₂O₃:Al₂O₃ (10:1), mobility, and subthreshold swing of the transistor are 8.7 cm²/V s, and 203 mV/dec. The threshold voltage (V_t) is adjustable by varying Al concentrations, shifting to negative bias with a higher concentration of Al. The IAO-based transistor presents many advantages, including excellent on/off ratio and high mobility, making it ideal for many applications, such as display panels and low-power BEOL integrations.