Highly spatially resolved electron energy-loss spectroscopy in the bandgap regime of GaN

The possibilities of obtaining information about interband scattering processes in the bandgap regime of GaN from electron energy-loss spectra, taken in a dedicated scanning transmission electron microscope (STEM), are investigated. With the help of precise simulations of the zero-loss peak it is feasable to process, extract and analyse data in the extreme low-loss regime of a few electronvolts. The accuracy of the results is restricted predominantly by instrumental broadening functions. By modelling these accurately, it is possible to eliminate the effects of the tail of the zero-loss peak. and to extract the low-loss spectrum together with the correct value for the bandgap of GaN. Furthermore, differences in the shapes of the low-loss spectra can be revealed, depending on the microstructural features, probed at different beam locations.