Wafer-scale AA-stacked hexagonal boron nitride grown on a GaN substrate

Area of Science:

• Materials Science
• Condensed Matter Physics
• Nanotechnology

Background:

• The stacking sequence of two-dimensional hexagonal boron nitride (hBN) dictates its polytypes and physical properties.
• The thermodynamically stable AA' stacking is common, but achieving alternative configurations like AA stacking has been challenging.

Purpose of the Study:

• To demonstrate the scalable synthesis of hexagonal boron nitride (hBN) with an unprecedented AA stacking sequence.
• To explore the potential of engineered hBN polytypes for applications requiring unique optical properties.

Main Methods:

• Epitaxial growth of hBN on a two-inch single-crystalline gallium nitride wafer.
• Utilized metal-organic chemical vapour deposition (MOCVD) technique.
• Employed comprehensive structural and optical characterizations, supported by theoretical modeling.

Main Results:

• Successfully synthesized multilayer hBN with the previously elusive AA stacking configuration.
• Identified that hBN nucleation on a vicinal gallium nitride surface promotes unidirectional layer alignment.
• Demonstrated the critical role of electron doping in stabilizing the AA stacking.

Conclusions:

• The study provides a scalable pathway for synthesizing engineered hBN polytypes.
• The achieved AA-stacked hBN exhibits unique properties, including significant optical nonlinearity.
• Findings offer new insights into controlling hBN stacking for advanced material applications.