In this contribution we report on the application of the sublimation molecular beam epitaxy (MBE) method to grow efficient light emitting Si:Er structures as well the extension of this method to grow waveguiding Si1-xGex layers. The formation processes of optically active Er centers in sublimation MBE grown materials and their properties are discussed. We distinguish the following optically effective Er centers in these materials: the oxygen-related Er-1 center, specific for sublimation MBE layers, a carbon- related center, SiO2-precipitate like centers and a variety of oxygen-related centers with low symmetry. The effect of the increase of photoluminescence efficiency in selectively doped structures, namely, in periodic multilayer Si-Si:Er/Si structures, has been discovered.