We have grown MgS bp MBE in the zinc blende crystal structure on GaAs(1 0 0) substrates using a novel technique where the sources are Mg and ZnS. Layers up to 134 nm thick have been grown without any degradation in the crystal structure. The lattice constant was found to be 0.5619 +/- 0.0001 run anti Poisson's ratio was estimated to be 0.425. PL and reflection spectra obtained from ZnSe quantum wells showed sharp signals indicating less than 1 hit fluctuations on the well widths. A binding energy of 43.9 meV has been obtained from excitons confined in a 5 nm wide ZnSe well.