Enhanced Ferromagnetism in Nanoscale GaN:Mn Wires Grown on GaN Ridges

Area of Science:

• Materials Science
• Condensed Matter Physics
• Semiconductor Spintronics

Background:

• Weak magnetism has limited the practical applications of magnetic semiconductors.
• The underlying magnetic mechanisms in gallium nitride (GaN)-based magnetic semiconductors remain a subject of extensive scientific debate.
• Developing materials with robust ferromagnetic properties is crucial for advancing spintronic devices.

Purpose of the Study:

• To investigate methods for enhancing ferromagnetism in GaN-based magnetic semiconductors.
• To elucidate the relationship between material structure, composition, and magnetic properties in GaN:Mn.
• To explore the role of defects in the magnetism of GaN:Mn.

Main Methods:

• Growth of nanoscale GaN:Mn wires on GaN ridges using metalorganic chemical vapor deposition (MOCVD).
• Characterization of magnetic properties using a superconducting quantum interference device (SQUID) magnetometer.
• Elemental composition analysis via secondary ion mass spectrometry (SIMS) and energy dispersive spectroscopy (EDS).
• Microstructural analysis using transmission electron microscopy (TEM) and EDS mapping.
• Investigation of material properties using micro-Raman spectroscopy.

Main Results:

• Significantly enhanced ferromagnetism was observed in the fabricated GaN:Mn nanowires.
• A notable increase in manganese (Mn) composition was detected in the nanowire regions compared to the GaN ridges.
• Transmission electron microscopy and EDS mapping revealed a strong correlation between abundant stacking faults (SFs) and high Mn doping concentrations.
• Micro-Raman spectroscopy provided further insights into the material's properties.

Conclusions:

• The enhanced ferromagnetism in GaN:Mn is attributed to increased Mn composition and the presence of stacking faults.
• The study suggests that magnetism in GaN:Mn is influenced by Mn concentration, intrinsic defects, and stacking faults.
• These findings offer a pathway to overcome the challenge of weak magnetism in magnetic semiconductors and contribute to understanding their fundamental mechanisms.