A theory of the relaxation of hot quasi-two-dimensional excitons in quantum wells is presented. Based on this theory, we derive analytical expressions for the decay rates of excitons as functions of the initial exciton momentum. We take into account the penetration of electron and hole wave functions into the barrier region, an effect which becomes increasingly significant at narrow well widths. Decay rates are calculated for well widths ranging from 25 to 150 Å at low temperatures for GaAs/Al0.3Ga0.7As single quantum wells. Our results indicate a notable increase of the decay rates with the initial momentum of excitons. Our results also show that the decay probabilities of the heavy-hole excitons are higher than that of the light-hole excitons at a fixed temperature and exciton energy. Good agreement is obtained when we compare the calculated results with available experimental data.
