Eutectic Formation, V/III Ratio and Controlled Polarity Inversion in Nitrides on Silicon^[1]

Area of Science:

• Materials Science
• Solid State Physics
• Crystal Growth

Background:

• Crystallographic polarity in aluminum nitride (AlN) films is crucial for device performance.
• Achieving controlled polarity in AlN grown on silicon substrates presents significant challenges.

Purpose of the Study:

• To intentionally invert the crystallographic polarity of AlN films from N-polar to Al-polar.
• To investigate the role of silicon in controlling the polarity inversion boundary.
• To explore methods for producing polarity-engineered nitride structures.

Main Methods:

• Plasma-assisted molecular beam epitaxy (MBE) growth of AlN on Si(111).
• Utilizing a two-step growth process with abrupt changes in Al-rich and N-rich conditions.
• Analyzing the formation and incorporation of an Al-Si eutectic layer.

Main Results:

• Successfully inverted AlN polarity from N-polar to Al-polar at a planar boundary.
• Demonstrated control over the inversion boundary position via growth condition changes.
• Identified silicon incorporation from an Al-Si eutectic as the mechanism for polarity inversion.
• Observed nonuniformity in inversion and formation of narrow, vertical inversion domains due to Si incorporation variations.

Conclusions:

• Intentional silicon incorporation can control AlN crystallographic polarity.
• A two-step growth process involving Al-Si eutectic formation enables polarity inversion.
• Uniform silicon incorporation may lead to controlled polarity-engineered nitride structures.