ZnSe and ZnSSe epitiaxial layers were grown on GaAS(100) substrate under Se-rich conditions at a substrate temperature of $300^{circ}C$ by molecular beam epitaxy. We have investigated the heterostructures of Zn(S, Se)/GaAs by Raman spectroscopy. In these layers, GaAs-LO, ZeSe-LO, ZnS-LO, ZmSe-TO, and phonon-plasmon coupled modes were observed. To investigate crystal quality with in-depth, a slope beveled structure was obtained from ZnSe/GaAs by mechanical angle lapping.