STRUCTURAL CHARACTERIZATION OF II-VI SEPARATE-CONFINEMENT HETEROSTRUCTURE LASERS WITH ZN1-XMGXSYSE1-Y CLADDING LAYERS

We have investigated the structural characteristics of II-VI separate confinement heterostructure lasers grown on GaAs substrates and contai ning Zn1-xMgxSySe1-y quaternary cladding layers, ZnSe or ZnSySe1-y gui ding layers and Zn(1-z)Cd(z)e quantum well active layers. The study wa s performed with a combination of transmission electron microscopy and high resolution x-ray diffraction techniques. We found that the quate rnary cladding layers remain pseudomorphic to the GaAs substrate altho ugh they can be lattice mismatched up to 0.1%. When the 0.5-mu m-thick optical guiding layer contains ZnSe, there is partial relaxation of t he laser structure by misfit dislocations at the lower cladding-guidin g layer interface and the threading dislocation density in the Zn1-zCd zSe quantum well active region is about 10(7) cm(-2). However, when la ttice matched (to GaAs)ZnSySe1-y is used as the guiding layer the enti re laser structure is pseudomorphic and the threading dislocation dens ity is <10(6) cm(-2) The combination of low defect density and enhance d carrier and optical confinement by using Zn1-xMgxSySe1-y quaternary cladding layers has produced significant improvement in the room tempe rature threshold current (500 A/cm(2)) and maximum operating temperatu re (394 K).