  Scanning tunneling electroluminescence microscopy is performed on a
3-nm-thick InGaN/GaN quantum well with x = 0.23 such that the main light
emission occurs in the green. The technique is used to map the local
recombination properties at a scale of ~10 nm and to correlate them with the
surface topography imaged by scanning tunneling microscopy. A 500 nm x 500 nm
area around a 150-nm large and 2.5-nm deep hexagonal defect is probed,
revealing emission at higher energies close to the defect edges, a feature
which is not visible in the macro-photoluminescence spectrum of the sample. Via
a fitting of the local tunneling electroluminescence spectra, quantitative
information on the fluctuations of the intensity, energy, width and phonon
replica intensity of the different spectral contributions are obtained,
revealing information about carrier localization in the quantum well. This
procedure also indicates that carrier diffusion length on the probed part of
the quantum well is approximately 40 nm.
