Titanium induced polarity inversion in ordered (In,Ga)N/GaN nanocolumns

Area of Science:

• Materials Science
• Semiconductor Physics
• Nanotechnology

Background:

• Ordered (Indium,Gallium)Nitride/GalliumNitride nanocolumns are vital for advanced electronic and optoelectronic devices.
• Controlling crystal polarity is essential for predictable material properties and device performance.
• Plasma-assisted molecular beam epitaxy (P-MBE) is a key technique for nitride semiconductor growth.

Purpose of the Study:

• To investigate the formation of polarity inversion in (In,Ga)N/GaN nanocolumns.
• To understand the role of Titanium (Ti) masking in inducing polarity inversion.
• To elucidate the impact of polarity inversion on indium incorporation.

Main Methods:

• Plasma-assisted molecular beam epitaxy (P-MBE) for nanocolumn growth.
• High-resolution transmission electron microscopy (HR-TEM) for structural analysis.
• Electron energy-loss spectroscopy (EELS) for elemental and chemical state analysis.
• Density functional theory (DFT) calculations for atomic-level understanding.

Main Results:

• A stacking fault-like planar defect at the GaN interface, caused by Ti incorporation, was identified.
• This defect triggers the generation of N-polar domains within Ga-polar nanocolumns.
• DFT calculations confirmed Ti monolayer occupation on the GaN (0002) plane and the inversion mechanism.
• Polarity inversion resulted in enhanced indium incorporation in the (In,Ga)N segment.

Conclusions:

• Ti incorporation via masking is a critical factor for inducing polarity inversion in (In,Ga)N/GaN nanocolumns.
• The identified defect mechanism provides a pathway for controlled selective area growth.
• This work deepens the understanding of Ti's role in nitride nanostructure fabrication and property tuning.