THE STOKES SHIFT IN GOOD QUALITY QUANTUM-WELL STRUCTURES

The origin of the red shift of the excitonic luminescence with respect to the absorption peak (Stokes shift) in good quality quantum wells, usually ascribed to exciton trapping, is explained in terms of a therm al population of the inhomogeneous distribution of excitonic states. W ithin this new picture the Stokes shift turns out to be quadratic on t he absorption linewidth and inversely proportional to the excitonic te mperature. The predictions are found to be in good agreement with care ful measurements in a set of GaAs/AlGaAs single quantum well structure s.