Nanoscale Relative Emission Efficiency Mapping Using Cathodoluminescence g⁽²⁾ Imaging

Area of Science:

• Photonics
• Materials Science
• Nanotechnology

Background:

• Cathodoluminescence (CL) imaging offers deep-subwavelength spatial resolution for photonic nanostructures.
• Existing CL methods cannot directly measure spatially resolved excitation and emission probabilities.

Purpose of the Study:

• To develop and demonstrate a new CL mapping methodology for disentangling excitation and emission rates.
• To analyze excitation and emission rate variations in InGaN/GaN quantum wells within GaN nanowires.

Main Methods:

• Mapping the cathodoluminescence autocorrelation function (g(2)) alongside CL spectral distribution.
• Utilizing InGaN/GaN quantum wells in GaN nanowires (200-500 nm diameter) as a model system.

Main Results:

• The new g(2) mapping method successfully disentangles excitation and emission rates at each position.
• Significant differences in excitation and emission rates were observed both between and within individual nanowires.
• Spatial variations in CL intensity within nanowires correlate with nanoscale geometry-dependent excitation rates.

Conclusions:

• The developed g(2) mapping technique provides spatially resolved measurements of excitation and emission rates.
• CL intensity variations in nanostructures are influenced by both emission efficiency and excitation efficiency.
• This has significant implications for interpreting CL data from nanostructured materials.