Local bonding geometry of oxygen implanted in GaN: a depth-dependent study

Area of Science:

• Materials Science
• Solid State Physics
• Surface Science

Background:

• Gallium Nitride (GaN) is a crucial semiconductor for optoelectronic and high-power applications.
• Understanding oxygen incorporation is vital for controlling GaN properties.
• Implantation of oxygen ions creates defects and alters the GaN lattice structure.

Purpose of the Study:

• To elucidate the bonding environment of oxygen implanted in GaN.
• To determine the influence of implantation fluence on oxygen's lattice site and bonding.
• To correlate structural changes with spectroscopic observations.

Main Methods:

• Near Edge X-ray Absorption Fine Structure (NEXAFS) spectroscopy at the O-K edge.
• High-energy ion implantation (70 keV O ions) with varying fluences (1x10^15 to 1x10^17 cm^-2).
• Spectra simulation using the FEFF8 code with defect models and lattice disorder analysis.

Main Results:

• Oxygen initially occupies interstitial sites, particularly in channels along the c-axis and Ga-planes.
• At higher fluences (1x10^16 cm^-2), oxygen substitutes nitrogen atoms.
• At the highest fluence (1x10^17 cm^-2), mixed GaOxNy phases form, with N/O ratio decreasing with depth.

Conclusions:

• The bonding environment of implanted oxygen in GaN is strongly dependent on implantation fluence.
• Oxygen's lattice location transitions from interstitial to substitutional and finally to mixed phase formation.
• These findings provide critical insights for tailoring GaN properties through ion implantation.