Spatially resolved imaging of the spectral emission characteristic of an InGaN/GaN-multi quantum well- light-emitting diode by scanning electroluminescence microscopy

The microscopic spectral emission characteristic of an InGaN/GaN multi quan tum 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 especiall y 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 mu m spatial resolution. Indium concentrations varying from around 0.09 to 0.11 are found in the active InGaN-region of the near ultraviolet diode emi tting at 404 nm with a FWHM of 20 nm. At high current density a 4 nm redshi ft of emission wavelength due to ohmic heating is observed. Whereas the mes a electroluminescence intensity mapping of the front side becomes uniform f or higher current densities, the backside electroluminescence still shows e lectroluminescence intensity fluctuations.