Cathodoluminescence imaging and temperature-dependent cathodoluminescence spectroscopy were used to probe the spatial distributions and energies of electronic defects near to GaN/Al2O3 interfaces grown using hydride vapor-phase epitaxy. Cross-sectional secondary electron microscopy imaging, cathodoluminescence spectroscopy and cathodoluminescence imaging revealed systematic variations in defect emissions for a wide range of hydride vapor-phase epitaxial GaN/sapphire electronic properties. These data, together with electrochemical capacitance-voltage profiling and secondary ion mass spectrometry results, provided a consistent picture of near-interface doping by O out-diffusion from Al2O3 and into GaN, over hundreds of nm. Low-temperature cathodoluminescence spectra exhibited a new donor level, at 0.003447eV, near to the interfaces of such samples. This was characteristic of O impurities spatially localized at the nanoscale interface. Cathodoluminescence spectroscopic emissions indicated the formation of amorphous Al–N–O complexes at 3.8eV; extending into the Al2O3 near to the GaN/sapphire interface. The cathodoluminescence spectroscopic and cathodoluminescence images also revealed emissions which were due to excitons bound to stacking faults and cubic GaN. The temperature dependence of the various optical transitions, at 10 to 300K, provided additional information for identifying near-interface defects and impurity doping.

Depth-Dependent Investigation of Defects and Impurity Doping in GaN/Sapphire using Scanning Electron Microscopy and Cathodoluminescence Spectroscopy. X.L.Sun, S.H.Goss, L.J.Brillson, D.C.Look, R.J.Molnar: Journal of Applied Physics, 2002, 91[10], 6729-38