Polarized luminescence of bound excitons in Cu2O single crystal

Photoluminescence was studied for Cu2O (100) single crystal in the 1.2-1.9 eV spectral range under polarized laser excitation 532 nm at low temperature. Polarized luminescence and negative thermal quenching were detected for the emission bands at 1.34, 1.53 and 1.7 eV, assigned to the bound excitons localized at copper vacancies V-Cu and oxygen vacancies V-O(+), V-O(2+), correspondingly. The complex structure of the most intense emission bands 1.34 and 1.7 eV containing spectrally shifted orthogonally polarized subbands was identified. Luminescence polarization degree, intensity and spectral position of the subbands depend on temperature as well as on the excitation light density and vary from point to point. The origin of the polarized luminescence and negative thermal quenching of the bound excitons in Cu2O crystal is discussed.