Lattice mismatch and atomic structure studies on In Ga AsrIn Al As coupled double-step quantum wells

Lattice mismatch and atomic structure studies of In Ga AsrIn Al As coupled double-step quantum wells have x 1yx y 1yy been performed by transmission electron microscopy TEM.and electron-diffraction pattern measurements. The high-resolu- tion TEM image of the In Ga AsrIn Al As coupled double-step quantum well showed that two sets of a 60-A° x 1yx y 1yyIn0.65Ga0.35As deep quantum well and a 60-A° In0.53Ga0.47As shallow step quantum wells bounded by two thick In0.52Al0.48As barriers are separated by a 38-A° In0.52 Al0.48As embedded potential barrier. The selective-area electron-diffraction pattern obtained from TEM measurements on the In Ga AsrIn Al As double-step quantum well showed that x 1yx y 1yy In Ga As active layers were grown pseudomorphologically on the InP buffer layer. The value of the lattice mismatch x 1yx between the In0.53Ga0.47As and the In0.65Ga0.35As layers obtained from the high-resolution TEM measurements is 1.6%. A possible crystal structure for the In Ga AsrIn Al As coupled double-step quantum well is presented based on the x 1yx y 1yy TEM results. These results can help improve understanding of the structural properties for the applications of strained In Ga AsrIn Al As coupled double-step quantum wells in new kind of the optoelectronic devices. q2000 Elsevier x 1yx y 1yy Science B.V. All rights reserved