The Study on the Lasing Modes Modulated by the Dislocation Distribution in the GaN-Based Microrod Cavities

Area of Science:

• Optoelectronics
• Materials Science
• Semiconductor Physics

Background:

• Gallium nitride (GaN)-based materials are crucial for optoelectronic devices.
• Fabricating high-performance GaN micro-lasers is challenging due to defects like threading dislocations (TDs).
• Patterned sapphire substrates (PSS) are used to improve GaN crystal quality.

Purpose of the Study:

• To demonstrate low-threshold lasing in GaN microrod cavities at room temperature.
• To investigate the influence of threading dislocation distribution on lasing properties.
• To understand the relationship between lasing modes and material defects.

Main Methods:

• Fabrication of GaN microrod cavities on PSS.
• Confocal micro-photoluminescence spectroscopy (μ-PL) to analyze lasing properties.
• Finite-difference time-domain (FDTD) simulations to study whispering gallery modes (WGMs).

Main Results:

• Achieved low-threshold lasing (minimum threshold ~0.3 kW/cm²) in 2 μm-diameter GaN microrod cavities.
• Observed that strongest lasing WGMs preferentially occur in regions with fewer TDs.
• Correlated lasing mode distribution with dislocation density variations.

Conclusions:

• The distribution of lasing modes in GaN microrod cavities is directly influenced by threading dislocation density.
• Minimizing TDs in specific regions can enhance lasing efficiency.
• This study provides insights for developing high-efficiency, low-threshold GaN micro-lasers.