Influence of threading dislocations on the near-bandedge photoluminescence of wurtzite GaN thin films on SiC substrate

Wurtzite GaN thin films have been grown on the 6H-SiC substrates by plasma-assisted molecular-beam epitaxy. The correlation between crystalline structure and photoluminescence (PL) properties is examined by high-resolution x-ray diffraction and PL measured at different temperatures from 5 to 300 K. At 5 K, the PL spectrum is dominated by two near-bandedge emissions at 3.470 and 3.427 eV. At room temperature, a broad yellow luminescence (YL) centered at 2.16 eV is present in the PL spectrum. The intensities of both the 3.427 eV peak and the YL are found to be strongly related to the threading-dislocation density of the GaN epilayers.