Strain Release in GaN Epitaxy on 4° Off-Axis 4H-SiC

Area of Science:

• Materials Science
• Semiconductor Physics
• Power Electronics

Background:

• Hybrid field-effect transistors (HyFETs) offer superior performance for power electronics by combining gallium nitride (GaN) and silicon carbide (SiC).
• Epitaxial growth challenges, particularly substrate mismatch (GaN on-axis vs. SiC off-axis), hinder HyFET development.

Purpose of the Study:

• To present a high-quality GaN-based heterostructure grown on a standard off-axis 4H-SiC substrate.
• To demonstrate a viable approach for fabricating GaN-based high-electron-mobility transistors (HEMTs) for HyFETs.
• To investigate a novel two-step biaxial strain-relaxation process.

Main Methods:

• Epitaxial growth of GaN-based heterostructures on 4° off-axis 4H-SiC substrates.
• Comprehensive material characterizations to assess structural and electronic properties.
• Development and analysis of a two-step strain-relaxation technique.

Main Results:

• Successful epitaxial growth of a high-quality GaN-based heterostructure on a conventional off-axis SiC substrate.
• Demonstrated suitability for fabricating GaN-based HEMTs.
• Characterization of a unique two-step biaxial strain-relaxation process.

Conclusions:

• The developed epitaxial method provides a practical route for realizing advanced HyFETs.
• The findings suggest a promising strategy for integrating GaN and SiC for next-generation power electronics.
• The proposed strain-relaxation technique is crucial for high-quality epitaxial growth.