Optical properties of cubic GaN grown on SiC/Si substrates

The optical properties of MBE cubic GaN layers grown on SiC/Si substrates were studied by photoreflectance and photoluminescence. From 9 K PR measurements, we derive the two excitons energies at 3.268 and 3.283 eV. We evidence that the PL excitonic transition observed at 3.265 eV is a combination of both donor-bound and free excitonic recombinations. Two overlapped PL components 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 attribution to the D–A and e–A recombinations. Their relative intensity strongly depends on the V/III ratio.