An atomic-scale model for the kinetics of intermixing of GaAs/AlGaAs, quantum confined heterostructures is presented. It quantifies the effects of the statistical nature of defect diffusion through heterostructures on the Ga/Al interdiffusion across such an interface. The model has been validated by successfully predicting the observed amounts of quantum well intermixing induced by a hydrogen plasma induced defect layer intermixing process. Agreement within 30&percent; of the measurements was obtained for values of the surface releasevelocity>1 &mgr;m s1.©1997 American Institute of Physics.