The effects of AlAs wet oxidation on overlayers were investigated using InGaAs/GaAs strained-layer superlattice structures grown on an AlAs layer. The superlattice partially relaxes towards its equilibrium spacing as the result of the oxidation of the underlying AlAs layer. Double-crystal x-ray diffraction measurements were used to determine the degree of strain relaxation. Larger relaxation is observed for the sample with a higher indium composition and a thicker AlAs layer. ©1998 American Institute of Physics.