DEPENDENCE OF EXCITON FORMATION ON ITS CENTER-OF-MASS MOMENTUM IN QUANTUM WELLS

Abstract

We present a comprehensive study of the process of exciton formation due to exciton-phonon interaction. Using the exciton-phonon interaction arising from deformation potential, piezoelectric, and polar couplings, we have calculated the rate of formation of an exciton as a function of carrier densitiies, temperatures, and center-of-mass momentum ( K ‖) in quantum wells. Our results show that excitons are dominantly formed at non-zero K ‖, which agrees very well with experiments. The formation of an exciton due to emission of longitudinal optical phonon is found to be more efficient at relatively small values of K ‖, and that due to acoustic phonon emission is more efficient at relatively large K ‖ values for carrier temperature Te-h≲50 K.