Transmission electron microscopy (TEM) and Raman scattering spectroscopy measurements were performed to investigate strain effects in lattice-mismatchedInxGa1−xAs/InyAl1−yAsmodulation-doped coupled double quantum wells. The high-resolution TEM images showed that a 100-ÅIn0.8Ga0.2Asdeep quantum well and a 100-ÅIn0.53Ga0.47Asshallow quantum well were separated by a 30-ÅIn0.25Ga0.75Asembedded potential barrier. The selected-area electron-diffraction pattern obtained from TEM measurements on theInxGa1−xAs/InyAl1−yAsdouble quantum well showed that theInxGa1−xAsactive layers were grown pseudomorphologically on the InP buffer layer. The values of the strain and the stress of theInxGa1−xAslayers were determined from the electron-diffraction pattern. Based on the TEM results, a possible crystal structure for theInxGa1−xAs/InyAl1−yAscoupled double quantum well is presented. ©1998 American Institute of Physics.