COMPOSITION MODULATION IN LATTICE-MATCHED ZN1-XMGXSYSE1-Y ZNSE BUFFERLAYER GAAS HETEROSTRUCTURES

[100] composition modulation as well as [101] and [1BAR01] tweed strai n contrast were observed in lattice matched Zn1-xMg(x)S(y)Se1-y epitax ial films grown on ZnSe buffer layers. The composition modulation corr esponds to regions with different S and Mg concentration in a directio n perpendicular to the growth direction. Very high quality lattice mat ched Zn1-xMg(x)S(y)Se1-y films with a ZnSe quantum well were grown on As stabilized GaAs substrates exposed to Zn for a short time. The dens ity of defects in these samples was less than 5 x 10(4)/cm2. Other sam ples showed rough interfaces and high densities of Frank partial dislo cations. The roughness is believed to result from an As-rich GaAs surf ace produced after the desorption of oxide under As overpressure.