The photoluminescence properties of MgxZn1−xSe solid solution grown on ZnSe substrate by a closed solid-state diffusion technique have been investigated. The depth profiles of the diffusion region shows distinguished surface layer and thick graded layer. The PL. spectra of MgxZn1−xSe side of the sample excited with a wide range of excitation energy shift the edge emission band toward longer wavelengths with decreasing excitation energy. The edge emission spectrum was found to shift toward the shorter wavelength with electric field applied parallel to the compositional gradient ofMgxZn1−xSe-ZnSe heterostructure.