Micro Raman and micro photoluminescence study of cubic GaN grown on 3C-SiC(001) substrates by metalorganic vapor phase epitaxy

We have investigated metalorganic vapor phase epitaxy-grown GaN grains on a 3C-SiC(0 0 1) substrate using micro Raman and micro photoluminescence spectroscopy. Polarized micro Raman spectra clearly showed that horizontal flat facets and inclined facets of the rectangular GaN grains correspond to cubic phase regions and hexagonal phase regions, respectively. To examine the photoluminescence properties of "pure" cubic GaN, micro photoluminescence was performed by focusing a laser beam on the horizontal flat facet. A strong photoluminescence line with the full-width at half-maximum of 5 meV was observed, which is the smallest value to date and shows that the crystal quality of the cubic phase region is excellent. We could clearly identify free exciton, donor bound exciton and acceptor bound exciton emissions in the cubic GaN. (C) 1998 Elsevier Science B.V. All rights reserved.