Pit assisted oxygen chemisorption on GaN surfaces

Area of Science:

• Materials Science
• Surface Science
• Semiconductor Physics

Background:

• Epitaxial gallium nitride (GaN) films are crucial for electronic devices.
• Understanding surface oxide formation is vital for device performance and stability.
• Chemisorption of oxygen impacts GaN surface properties and electronic structure.

Purpose of the Study:

• To comprehensively analyze oxygen chemisorption on GaN films grown at various temperatures.
• To investigate the relationship between surface morphology, oxide formation, and electronic structure.
• To determine the role of surface pits in oxygen adsorption.

Main Methods:

• Radio frequency-molecular beam epitaxy (RF-MBE) for GaN film growth.
• X-ray Photoelectron Spectroscopy (XPS) and Ultraviolet Photoelectron Spectroscopy (UPS) for electronic structure analysis.
• Field Emission Scanning Electron Microscopy (FESEM) and Atomic Force Microscopy (AFM) for surface morphology characterization.

Main Results:

• Lower growth temperatures resulted in reduced surface oxide on GaN films.
• Increased oxide coverage led to shifts in core level and valence band maximum positions, indicating downward band bending.
• Hexagonal surface pits were identified as preferential sites for oxygen adsorption, with density and depth correlating with oxide coverage.

Conclusions:

• Surface morphology, specifically the presence and characteristics of hexagonal pits, significantly influences oxygen chemisorption on GaN.
• Growth temperature is a critical factor controlling both surface oxide formation and pit structure, thereby affecting oxygen adsorption.
• The findings provide insights into managing surface oxidation and improving GaN device reliability.