Channel Defect Profiling and Passivation for ZnO Thin-Film Transistors.

Area of Science:

• Materials Science
• Semiconductor Physics
• Device Engineering

Background:

• Zinc oxide (ZnO) is a promising semiconductor for thin-film transistors (TFTs).
• Oxygen vacancies in ZnO can significantly influence its electrical properties and device performance.
• Understanding these defects is crucial for optimizing ZnO TFTs.

Purpose of the Study:

• To investigate the impact of oxygen vacancies on the electrical characteristics of ZnO thin-film transistors.
• To determine the energy level and role of oxygen vacancies in device operation.
• To evaluate the effectiveness of oxygen annealing in passivating these defects and improving performance.

Main Methods:

• Electrical characterization of ZnO thin-film transistors before and after vacuum treatment.
• Analysis of trap-assisted tunneling and Schottky barrier lowering mechanisms.
• Post-fabrication annealing of ZnO in an oxygen ambient.

Main Results:

• Oxygen vacancies were identified near the conduction band of ZnO, facilitating trap-assisted tunneling at low gate voltages.
• Annealing in oxygen ambient successfully passivated the oxygen vacancies.
• Negative bias stress induced trap-related Schottky barrier lowering, reducing the drain barrier.
• Field-effect mobility increased from 8.5 to 8.9 m² V⁻¹·s⁻¹.
• On-current showed an approximate 13% enhancement.

Conclusions:

• Oxygen vacancies play a critical role in the electrical behavior of ZnO TFTs, particularly at low gate voltages.
• Passivation of oxygen vacancies through oxygen annealing is an effective strategy to improve ZnO TFT performance.
• The findings provide insights into defect management for advanced ZnO-based electronic devices.