Strain effects in lattice-mismatched InxGa1-xAs/InyAl1-yAs coupled double quantum wells

Transmission electron microscopy (TEM) and Raman scattering spectroscopy measurements were performed to investigate strain effects in lattice-mismatched InxGa1-xAs/InyAl1-yAs modulation-doped coupled double quantum wells. The high-resolution TEM images showed that a 100-Angstrom In0.8Ga0.2As deep quantum well and. a 100-Angstrom In0.53Ga0.47As shallow quantum well were separated by a 30-Angstrom In0.25Ga0.75As embedded potential barrier. The selected-area electron-diffraction pattern obtained from TEM measurements on the InxGa1-xAs/InyAl1-yAs double quantum well showed that the InxGa1-xAs active layers were grown pseudomorphologically on the InP buffer layer. The values of the strain and the stress of the InxGa1-xAs layers were determined from the electron-diffraction pattern. Based on the TEM results, a possible crystal structure for the InxGa1-xAs/InyAl1-yAs coupled double quantum well is presented. (C) 1998 American Institute of Physics.