Si/Ge multilayer structures formed by the embedding of relatively small amounts of germanium (less then the critical thickness for 3D island formation via Stranski-Krastanow growth mode) in a silicon matrix are obtained by submonolayer molecular beam epitaxy. Structural and optical properties of the grown structures are investigated. The formation of relatively small Ge clusters at appropriate growth conditions is observed. Possible growth mechanism responsible for the formation of Ge nanostructures is discussed.