STRAIN EFFECTS IN LATTICE-MISMATCHED INXGA1-XAS INYAL1-YAS COUPLED DOUBLE-QUANTUM WELLS/

Transmission electron microscopy (TEM) and Raman scattering spectrosco py measurements were performed to investigate strain effects in lattic e-mismatched InxGa1-xAs/InyAl1-yAs modulation-doped coupled double qua ntum wells. The high-resolution TEM images showed that a 100-Angstrom In0.8Ga0.2As deep quantum well and. a 100-Angstrom In0.53Ga0.47As shal low quantum well were separated by a 30-Angstrom In0.25Ga0.75As embedd ed potential barrier. The selected-area electron-diffraction pattern o btained from TEM measurements on the InxGa1-xAs/InyAl1-yAs double quan tum well showed that the InxGa1-xAs active layers were grown pseudomor phologically on the InP buffer layer. The values of the strain and the stress of the InxGa1-xAs layers were determined from the electron-dif fraction pattern. Based on the TEM results, a possible crystal structu re for the InxGa1-xAs/InyAl1-yAs coupled double quantum well is presen ted. (C) 1998 American Institute of Physics.