The optical emission properties of a-plane GaN layers, grown onto r-plane sapphire by metalorganic chemical vapor deposition, were studied. Together with the typical band edge exciton emission, the photoluminescence spectra revealed 3 low-energy emissions which peaked at 3.42, 3.34 and 3.29eV. These were related to structural defects. Temperature- and excitation-dependent stationary photoluminescence and time-resolved photoluminescence were used to clarify the exact origin of these emissions. The 3.42 and 3.34eV emissions were found to be of intrinsic origin and were associated with carriers localized at stacking faults. The emission at 3.29eV exhibited a donor–acceptor pair behavior which suggested that impurities attached to structural defects; which were most likely to be partial dislocations terminating stacking faults.

Structural Defect-Related Emissions in Nonpolar a-Plane GaN. P.P.Paskov, R.Schifano, T.Paskova, T.Malinauskas, J.P.Bergman, B.Monemar, S.Figge, D.Hommel: Physica B, 2006, 376-377, 473-6