Abstract
The microscopic spectral emission characteristic of an InGaN/GaN multi quantum well light-emitting diode is directly imaged by highly spectrally- and spatially-resolved scanning electroluminescence microscopy under operation as a function of injection current density from both, contact and substrate side. The mono- and panchromatic luminescence intensity maps and especially the peak-wavelength scanning images provide access to the optical quality of the final device and yield direct images of the In fluctuations with 1 µm spatial resolution. Indium concentrations varying from around 0.09 to 0.11 are found in the active InGaN-region of the near ultraviolet diode emitting at 404 nm with a FWHM of 20 nm. At high current density a 4 nm redshift of emission wavelength due to ohmic heating is observed. Whereas the mesa electroluminescence intensity mapping of the front side becomes uniform for higher current densities, the backside electroluminescence still shows electroluminescence intensity fluctuations.
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