Phonon-assisted exciton formation and relaxation in GaAs/${\mathrm{Al}}_{\mathrm{x}}$${\mathrm{Ga}}_{1\mathrm{-}\mathrm{x}}$As quantum wells

A microscopic analysis of exciton formation and relaxation in photoexcited quantum wells is presented. The theoretical approach is based on a Monte Carlo simulation of the coupled free-carrier and exciton dynamics, and includes various mechanisms contributing to exciton formation and relaxation. Our investigation clarifies the origin of excitonic luminescence in time-resolved experiments. In particular, we address the problem of the relative efficiencies of exciton formation assisted by either LO phonons or acoustic phonons, respectively.