Contribution in exciton, donor and acceptor energy determining in a high-purity ZnS vapor-deposited layer

• High quality ZnS grown on a GaAs (001) substrate by MOCVD at 350°C. • Free excitons Ex and Ex(n = 2) and impurities levels (donor and acceptor) bounded to excitons are determined using photoluminescence and reflictivity. • Using the theory developed by Hopfield and by Sharma and Rodriguez to determine excitons and impurities bounded to excitons level. • Two electron satellite (TES) level is found to be at 3.7592 eV in our ZnS sample. A thin layer of a high quality ZnS grown on a GaAs (001) substrate by MOCVD at 350°C and characterized by photoluminescence (PL) at 20 K and reflectivity (at 20 K) allowed us to determine the energy of free and bound excitons as well as those of the impurities present in our ZnS. By reflectivity we obtained two free excitons Ex and Ex(n = 2) respectively at 3.8017 and 3.8245 eV, showing a high quality of our layer. The energy levels of the impurities are assigned to bound excitons (D 0 X; A 0 X; eA 0 ) and phonon replicas. Using the theory developed by Hopfield and by Sharma and Rodriguez, the transition at 3.7592 eV is attributed to a two electrons satellite (TES), using the hydrogenoid model. Taking the hydrogen model, we determined the value of the gap energy, Eg = 3.8321 eV.