We have observed In out diffusion from strained InxGa1-xAs quantum wells into the adjacent GaAs barriers in degraded 980-nm-wavelength strained quantum-well lasers. A previous calculation on misfit stress-induced compositional instability indicates that this material system is stable with respect to misfit strain. Therefore, the out diffusion of In from an InxGa1-xAs quantum well is mainly driven by the compositional discontinuity across the well/barrier heterointerfaces, and is believed to be activated by the nonradiative recombination of injected carriers. (C) 2001 American Institute of Physics.