Exciton-phonon interaction and energy transfer of nitrogen-bound excitons in GaP

Heat-pulse and time-resolved-luminescence experiments are performed on bound excitons in dilute GaP:N. A prominent broad luminescent band called the V band, is shown to arise from both zero-phonon and phonon-assisted recombination of excitons from the lower bound exciton state. A quantitative explanation of the shape of the V band is given in terms of resonantly enhanced second-order phonon-assisted recombination involving the upper bound exciton state, taking due account of the averaging of the phonon-induced strain over the exciton wave function. From the time-resolved luminescence experiments we derive a time of 300 ns for exciton energy transfer to disturbed sites.