Reliability and Stability Issues in Bi₂O₂Se/β-Bi₂SeO₅ Field-Effect Transistors.

Area of Science:

• Materials Science
• Condensed Matter Physics
• Semiconductor Physics

Background:

• Bismuth oxychalcogenide (Bi2O2Se) is a promising semiconductor for nanoelectronics due to its high electron mobility, suitable bandgap, and air stability.
• It forms a high-κ native oxide, Bi2SeO5, crucial for device functionality.
• Intrinsic point defects in both Bi2O2Se and Bi2SeO5 can significantly affect electronic properties and device reliability.

Purpose of the Study:

• To investigate the electronic structure, formation energies, and trap levels of native defects in Bi2O2Se and β-Bi2SeO5 using density functional theory.
• To correlate theoretical defect findings with experimental measurements in Bi2O2Se/β-Bi2SeO5 field-effect transistors.
• To elucidate the role of defects in device reliability issues like hysteresis and bias temperature instability.

Main Methods:

• Density Functional Theory (DFT) calculations to determine defect properties.
• Investigation of electronic structure, formation energies, trap levels, and relaxation energies.
• Experimental characterization of a prototype Bi2O2Se/β-Bi2SeO5 field-effect transistor using scanning transmission electron microscopy (STEM).

Main Results:

• Selenium and oxygen vacancies in Bi2O2Se act as shallow donors, contributing to n-type conductivity.
• Oxygen vacancies in β-Bi2SeO5 create deep-level trap states, potentially limiting device performance.
• Theoretical defect identification was successfully correlated with experimental device measurements.

Conclusions:

• Native defects, particularly vacancies, play a critical role in the electronic behavior and reliability of Bi2O2Se/β-Bi2SeO5 heterostructures.
• Understanding these defects is essential for mitigating performance limitations and improving device stability.
• The findings provide crucial input for reliability modeling and defect engineering strategies for future nanoelectronic applications.