BAND-EDGE PHOTOLUMINESCENCE OF CUGASE2 FILMS GROWN BY MOLECULAR-BEAM EPITAXY

Slightly Cu-rich CuGaSe2 films were grown on [001] oriented GaAs subst rates by molecular beam epitaxy. Photoluminescence of the films showed a remarkable emission peaked at 1.71 eV at low temperature, which is attributed to recombination of free excitons and bound excitons. The d issociation energy of free excitons and their localization energy to a center are found to be 16.2 and 3.3 meV, respectively. The band-gap e nergy E(g), is estimated to be 1.7310 eV at low temperature. It is sug gested that the temperature variation of E(g) is dominated by interact ion with phonons of 26 meV which corresponds to the mean energy of the optical phonons in CuGaSe2. (C) 1996 American Institute of Physics.