Photoluminescence depth-profiling of epitaxial films which had been grown onto c-plane sapphire using metalorganic chemical vapor deposition was carried out. Reflectivity and photoluminescence spectra were measured before and after reactive ion etching. The photoluminescence measurements showed that both the near-bandedge and yellow luminescence remained fairly constant up to a film thickness of about 700nm. A large drop was observed in the ratio, of near-bandedge to yellow emission intensity, when the film was thinner than about 300nm. It was showed that the yellow luminescence emitters were confined mainly to the near-interface region. This supported the suggestion that the yellow luminescence was due to native defects rather than impurities.

Yellow Luminescence Depth Profiling of GaN Epifilms. L.W.Tu, Y.C.Lee, S.J.Chen, I.Lo, D.Stocker, E.F.Schubert: Applied Physics Letters, 1998, 73[19], 2802-4