Nitrogen solubility and induced defect complexes in epitaxial GaAs:N.

Area of Science:

• Materials Science
• Solid State Physics
• Semiconductor Research

Background:

• Thermodynamic calculations indicate low equilibrium nitrogen (N) solubility in bulk gallium arsenide (GaAs:N) due to nitrogen chemical potential limitations.
• In epitaxial growth, a fully relaxed GaN phase is prevented by spontaneous N-rich layer formation on the surface, further limiting N incorporation.

Purpose of the Study:

• To investigate methods for significantly increasing nitrogen solubility in GaAs during epitaxial growth.
• To understand the role of nitrogen chemical potential in overcoming thermodynamic barriers for N incorporation in GaAs.

Main Methods:

• Utilizing first-principles total-energy calculations to model nitrogen behavior in epitaxial GaAs.
• Comparing theoretical predictions with experimental results at specific temperatures and compositions.

Main Results:

• Demonstrated that increasing the maximum nitrogen chemical potential (μmax(N)) in the epitaxial regime, without forming a N-rich layer, enhances [N] by 8 orders of magnitude.
• Achieved approximately 4% nitrogen solubility in GaAs at 650°C, aligning with experimental observations.
• Identified that dominant defects in GaAs:N are qualitatively different at high nitrogen concentrations compared to low concentrations.

Conclusions:

• Epitaxial growth offers a pathway to significantly enhance nitrogen solubility in GaAs beyond equilibrium bulk limits.
• Controlling nitrogen chemical potential during growth is crucial for achieving high-performance dilute nitride semiconductors.
• The findings provide fundamental insights into defect formation and solubility limits in semiconductor alloys.