Electron energy-loss spectroscopy characterization of pyramidal defects inmetalorganic 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 de nsity of about 10(18) cm(-3). Comparison of energy-loss spectra recorded ou tside a PD and from the PD showed a significant change in the energy-loss n ear-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 (similar to 10(18) cm(-3)), one ca n expect that the optical properties of such inclusions may interfere with those of GaN and, therefore, be at the origin of the frequently obtained bl ue emission at 2.8-2.9 eV in heavily doped samples. (C) 2000 American Insti tute of Physics. [S0003-6951(00)00740-3].