Accuracy of the calculated unoccupied states in GaN phases as tested by high-resolution electron energy-loss spectroscopy

The electronic structures of cubic and hexagonal phases of GaN have been investigated by high-resolution electron energy-loss spectroscopy in a monochromated transmission electron microscope. Both the Ga-L2,3 and N K-edges were measured. The data are compared to the latest versions of two different calculation schemes: band structure and multiple-scattering calculations. We have found that both methods are capable of giving results that can be compared quantitatively to the experiment. Small discrepancies with experiment could be eliminated by future developments in the implementation of these methods.