In/Ga-free, inkjet-printed charge transfer doping for solution-processed ZnO.

Area of Science:

• Materials Science
• Semiconductor Physics
• Nanotechnology

Background:

• Zinc oxide (ZnO) is a promising semiconductor for thin-film transistors (TFTs).
• Traditional doping methods often involve indium (In) or gallium (Ga), which can be costly or environmentally concerning.
• Developing efficient, In/Ga-free doping techniques is crucial for advancing ZnO-based electronics.

Purpose of the Study:

• To demonstrate an Indium/Gallium-free doping method for zinc oxide (ZnO) using printable charge transfer doping layers (CTDL).
• To investigate the effect of CTDL on the electrical properties of ZnO thin-film transistors (TFTs).
• To explore the applicability of this doping method in fabricating ZnO-based electronic devices like inverters.

Main Methods:

• Utilized self-assembled (3-aminopropyl)triethoxysilane (APS) molecules as a printable CTDL on ZnO thin films.
• Investigated the n-type doping mechanism attributed to the electron-donating amine group in APS.
• Tuned TFT performance by varying APS grafting density and ZnO film thickness.
• Fabricated depletion load ZnO inverters using selective CTDL deposition via inkjet printing.

Main Results:

• Achieved n-type doping of ZnO and effective filling of shallow electron traps.
• Demonstrated tunability of threshold voltage and mobility in ZnO TFTs.
• Optimized ZnO TFTs exhibited high electron mobility (4.2 cm²/Vs), a threshold voltage of 10.5 V, and an on/off current ratio >10⁷.
• Successfully fabricated high-performance depletion load ZnO inverters using inkjet printing.

Conclusions:

• The printable CTDL method offers an effective In/Ga-free approach for n-type doping of ZnO.
• This technique allows for precise control over ZnO TFT characteristics.
• The developed method is compatible with simple inkjet processes, paving the way for low-cost, high-performance ZnO electronics.