Electron energy-loss spectroscopy characterization of pyramidal defects in metalorganic vapor-phase epitaxy Mg-doped GaN thin films

In the present letter, Mg-doped GaN thin films grown by metalorganic vapor-phase epitaxy were studied using parallel electron energy-loss spectroscopy in a transmission electron microscope. A microstructural characterization of such thin films showed the presence of pyramidal defects (PDs) with a density of about $1018 cm−3.$ Comparison of energy-loss spectra recorded outside a PD and from the PD showed a significant change in the energy-loss near-edge structure strongly reflecting the presence of inclusions (Mg-based), the electronic properties of which differ from those of GaN. Considering, however, their relatively high density $(∼1018 cm−3),$ one can expect that the optical properties of such inclusions may interfere with those of GaN and, therefore, be at the origin of the frequently obtained blue emission at 2.8–2.9 eV in heavily doped samples.