Photoluminescence and Raman spectra of the ordered vacancy compound CuGa5Se8

We studied the photoluminescence (PL) and Raman properties of the ordered defect compound CuGa5Se8. Twelve peaks were detected from the room-temperature Raman spectra with the A1 mode around 160 cm−1. Due to the stress in the polycrystalline thin film the corresponding frequencies of the Raman modes of a CuGa5Se8 single crystal were slightly shifted. One broad asymmetric PL band at 1.788 and 1.765 eV was observed at 10 K in the PL spectra of CuGa5Se8 single crystal and polycrystalline layer, respectively. The temperature and laser power dependencies of the PL spectra were also studied. The shape and properties of the PL band assure the presence of potential fluctuations and the analyses of the PL data suggest that the emission is due to band-to-tail (BT) or band-to-impurity (BI) recombination.