Compositional dependence of Raman scattering and photoluminescence emission in CuxGaySe2 thin films

Raman scattering and photoluminescence (PL) emission of CuxGaySe2 thin films, grown by metalorganic chemical vapor deposition (MOCVD) on GaAs (100) and by physical vapor deposition (PVD) on Glass/Mo substrates, were studied at room and low temperatures as a function of composition. Line width changes of Raman bands in the temperature range 20–300 K indicate the formation of a more disordered CuxGaySe2 phase with increasing Ga content. It is most likely that Raman bands observed at 193 and 199 cm−1 in the Ga-rich samples at low temperatures are associated with defect-related interface modes. The intensity increase of these bands and the photoluminescence intensity enhancement may be correlated to an increase in defect concentration in the Ga-rich phase. The radiative recombination in defect-rich Ga-rich samples with a higher degree of disorder apparently supports the PL emission. The observed changes are more pronounced in MOCVD than in PVD grown films.