This paper presents for the first time photo-assisted Metalorganic vapor phase epitaxial (MOVPE) growth of ZnMgS on Si (100) substrates. The growth was done using dimethylzinc (DMZn), bismethylcyclo-pentadienyl-magnesium ((MeCP)2Mg), and diethylsulfhide (DES) as zinc, magnesium, and sulfur precursors. Epitaxial characterization by X-ray Photoelectron Spectroscopy (XPS), and low - angle X-ray Diffraction (XRD) results are presented. Mg solid phase incorporation is estimated to vary from 0 to 60 percent. The epitaxial nature of the ZnMgS layers has been verified using the low-angle X-ray diffraction eliminating any interference from the Si substrate. It can be shown with this technique that the change in the ZnMgS peak position changes from 27.35 degrees to 26.5 degrees with an increase in Mg incorporation, compared with a Si control sample peak at 27.4 degrees. XRD results obtained have been verified with XPS data. Chlorine doping of the ZnMgS layer was also studied. Concentrations up to 3 × 1015 cm−3 were observed in the ZnMgS layer. Results of the n (ZnMgS:Cl) – p (Si) diodes fabricated are also presented.