Optical properties of cubic GaN grown on SiC Si substrates

The optical properties of MBE cubic GaN layers grown on SiC/Si substrates w ere studied by photoreflectance and photoluminescence. From 9 K PR measurem ents, we derive the two excitons energies at 3.268 and 3.283 eV. We evidenc e that the PL excitonic transition observed at 3.265 eV is a combination of both donor-bound and free excitonic recombinations. Two overlapped PL comp onents are observed at about 3.13 and 3.15 eV. The analysis of these lines behaviour as a function of temperature and excitation power allows their at tribution to the D-A and e-A recombinations. Their relative intensity stron gly depends on the V/III ratio. (C) 1999 Elsevier Science S.A. All rights r eserved.